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WO2024131392A1 - 逆变器及其控制方法 - Google Patents

逆变器及其控制方法 Download PDF

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Publication number
WO2024131392A1
WO2024131392A1 PCT/CN2023/131924 CN2023131924W WO2024131392A1 WO 2024131392 A1 WO2024131392 A1 WO 2024131392A1 CN 2023131924 W CN2023131924 W CN 2023131924W WO 2024131392 A1 WO2024131392 A1 WO 2024131392A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitor
circuit
inverter
voltage
bus
Prior art date
Application number
PCT/CN2023/131924
Other languages
English (en)
French (fr)
Inventor
高深
陆丰隆
刘帅
石磊
Original Assignee
华为数字能源技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to EP23899091.5A priority Critical patent/EP4432545A1/en
Publication of WO2024131392A1 publication Critical patent/WO2024131392A1/zh

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4833—Capacitor voltage balancing

Definitions

  • the inverter circuit in the inverter converts the DC power of the power supply into AC power and supplies it to the load.
  • some three-level inverter circuits for example, neutral point clamped (NPC) inverter circuits
  • NPC neutral point clamped
  • a three-level inverter circuit that is, an inverter circuit
  • the series connection point of the two sets of capacitors is the midpoint of the inverter circuit, and each switch bridge arm includes multiple switch tubes.
  • the charge (or discharge) of the two groups of capacitors connected in series in the inverter circuit is not equal, resulting in unequal voltages of the two groups of capacitors connected in series in the inverter circuit (that is, the midpoint voltage of the inverter circuit is unbalanced, or the voltage of the positive and negative DC bus is unbalanced), which can cause distortion of the output voltage (or output current) of the inverter circuit and even damage power components in the system.
  • the present application provides an inverter and a control method thereof, which can adjust the output current of the inductor through a balancing circuit to charge the target capacitor when the terminal voltage difference between the two groups of capacitors in the inverter circuit is large, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the present application provides an inverter, the inverter may include an inverter circuit, a collection circuit, a balancing circuit and an inductor, the inverter circuit may include at least one switch bridge arm and a first capacitor and a second capacitor connected in series, and the balancing circuit may include multiple switch tubes.
  • one end of the inverter circuit can be used to connect the power supply through the positive DC bus and the negative DC bus
  • the other end of the inverter circuit can be used to connect the load
  • the first capacitor and the second capacitor are connected in series with at least one switch bridge arm in parallel between the positive DC bus and the negative DC bus
  • the collection circuit connects the positive DC bus, the negative DC bus, the series connection point of the first capacitor and the second capacitor and the balancing circuit
  • the balancing circuit connects the series connection point of the first capacitor and the second capacitor through the inductor.
  • the collection circuit here can detect the DC bus voltage to obtain the terminal voltage value of the first capacitor and the second capacitor.
  • the balancing circuit here can be used to control the conduction or shutdown of multiple switch tubes when the terminal voltage value of the target capacitor is less than or equal to the first voltage threshold, so as to adjust the current charged to the target capacitor through the inductor to reduce the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors, wherein the target capacitor is the capacitor with the smaller terminal voltage value in the first capacitor and the second capacitor.
  • the power supply can be connected to the inverter circuit through the positive DC bus and the negative DC bus, and the inverter circuit can convert the DC power provided by the power supply into AC power and provide it to the load.
  • the inverter circuit can charge and discharge the capacitors (for example, the first capacitor and the second capacitor) in the inverter circuit respectively by turning on and off different switch tubes, and convert the DC power provided by the power supply into AC power and transmit it to the load.
  • the acquisition circuit can obtain the DC bus voltage of the inverter circuit (for example, the positive DC bus voltage and/or the negative DC bus voltage, and the voltage of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit)) to obtain the terminal voltage of the target capacitor.
  • the target capacitor can be the capacitor with the smaller terminal voltage value among the first capacitor and the second capacitor.
  • the terminal voltage value of the target capacitor is less than or equal to At a certain voltage threshold (for example, the first voltage threshold), it can be considered that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, or the positive and negative DC bus voltages of the inverter circuit are in an unbalanced state.
  • the balancing circuit needs to charge the capacitor (for example, the target capacitor).
  • the first voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor or the second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the first voltage threshold can be a voltage value less than 1/2 of the bus voltage, and the bus voltage is the voltage difference between the positive DC bus voltage and the negative DC bus voltage), which can be set according to the application scenario.
  • the first voltage threshold here can be a voltage value, can be multiple voltage values, and can be a voltage interval composed of multiple voltage values.
  • the balancing circuit can determine whether the target capacitor needs to be charged in a variety of ways, and comparing the terminal voltage of the target capacitor with the first voltage threshold is only one of them.
  • the balancing circuit can also determine whether the capacitor of the inverter circuit needs to be charged in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is greater than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is greater than or equal to a certain threshold, the balancing circuit can determine that the capacitor of the inverter circuit needs to be charged at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the first voltage threshold to determine whether the capacitor of the inverter circuit needs to be charged as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can charge the target capacitor through an inductor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit includes multiple switching tubes, and the balancing circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the positive DC bus voltage and the negative DC bus voltage of the balanced inverter circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the inverter when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit, balancing the positive and negative bus voltages, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the balancing circuit can also be used to control multiple switch tubes to remain off when the terminal voltage value of the target capacitor is greater than or equal to the second voltage threshold to stop charging the target capacitor.
  • a certain voltage threshold for example, the second voltage threshold
  • the balancing circuit does not need to charge the capacitor (for example, the target capacitor).
  • the second voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor or the second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the second voltage threshold can be a voltage value less than 1/2 bus voltage and greater than or equal to the first voltage threshold), which can be set according to the application scenario.
  • the second voltage threshold here can be a voltage value, can be multiple voltage values, and can be a voltage interval composed of multiple voltage values.
  • the second voltage threshold can be greater than or equal to the first voltage threshold.
  • the inverter can avoid repeatedly starting and stopping charging the target capacitor through the balancing circuit when the terminal voltage of the target capacitor is not stably greater than the first voltage threshold.
  • the inverter can determine that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, or determine that the positive DC bus voltage and the negative DC bus voltage of the inverter circuit are in a balanced state, after the terminal voltage of the target capacitor is stabilized (for example, stably greater than the first voltage threshold), and then stop charging the target capacitor through the balancing circuit.
  • the balancing circuit can determine whether to stop charging the target capacitor in a variety of ways, and comparing the terminal voltage of the target capacitor with the second voltage threshold is only one of them.
  • the balancing circuit can also determine whether to stop charging the capacitor of the inverter circuit in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is less than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is less than or equal to a certain threshold, the balancing circuit can determine that it is not necessary to charge the capacitor of the inverter circuit at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the second voltage threshold to determine whether it is necessary to stop charging the capacitor of the inverter circuit as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can stop charging the target capacitor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit can control each switch tube in the balancing circuit to remain turned off to stop charging the target capacitor, thereby saving energy and reducing costs.
  • the inverter can stop charging the target capacitor through the balancing circuit when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, thereby reducing the power consumed by the balancing circuit, reducing costs, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the balancing circuit may include a control A circuit and at least one balanced bridge arm, one balanced bridge arm may include two switch tubes connected in series, the control circuit is connected to the inductor through at least one balanced bridge arm, and the acquisition circuit is connected to the control circuit.
  • the acquisition circuit here can also obtain a half-bus voltage value based on the DC bus voltage.
  • the control circuit here can generate a balanced modulation signal based on the terminal voltage value and the half-bus voltage value of the target capacitor, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • the balancing circuit includes at least one balancing bridge arm.
  • the balancing circuit may include a half-bridge circuit with two series-connected switch tubes as a balancing bridge arm, or may include a full-bridge circuit with four switch tubes as two balancing bridge arms.
  • the acquisition circuit may obtain the positive DC bus voltage and the negative DC bus voltage of the inverter circuit, and obtain the half-bus voltage value (that is, 1/2 bus voltage value) based on the positive DC bus voltage and the negative DC bus voltage.
  • control circuit for example, a voltage regulation loop (for example, a proportional integral regulation circuit) and a drive control circuit, or other circuits with voltage regulation and drive control functions
  • the control circuit may generate a balanced modulation signal based on the terminal voltage value of the target capacitor and the half-bus voltage value to control the conduction or shutdown of the switch tube in the balancing circuit.
  • the control circuit may generate a pulse width modulation, a PWM wave or other signal as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • control circuit can use discontinuous pulse width modulation (DPWM) as a balanced modulation signal, and can also use other PWM waves (for example, sinusoidal pulse width modulation (SPWM), third harmonic injection pulse width modulation (THIPWM), carrier-based space vector pulse width modulation (CBPWM)) waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals, which are widely applicable to scenarios and have good control effects.
  • PWM discontinuous pulse width modulation
  • SPWM sinusoidal pulse width modulation
  • THIPWM third harmonic injection pulse width modulation
  • CBPWM carrier-based space vector pulse width modulation
  • the acquisition circuit may also be used to obtain the output current value of the series connection point of the first capacitor and the second capacitor and the input current value of the series connection point of the first capacitor and the second capacitor.
  • the control circuit here may also generate a voltage regulation instruction based on the terminal voltage value and the half-bus voltage value of the target capacitor, generate a balanced modulation signal based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor, and control the conduction or disconnection of the switch tube in at least one balanced bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • the acquisition circuit can obtain the output current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit) and the input current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit).
  • the output current value of the series connection point of the first capacitor and the second capacitor can be determined by adding the current values output by the series connection point of the first capacitor and the second capacitor to each switch bridge arm of the inverter circuit, or it can be determined by other methods.
  • the input current value of the series connection point of the first capacitor and the second capacitor can be determined by the output current of the inductor connected to the series connection point of the first capacitor and the second capacitor, or it can be determined by other methods.
  • the reference direction of the output current and input current of the series connection point of the first capacitor and the second capacitor can be determined according to the target capacitor.
  • the output current flowing from the target capacitor to the series connection point of the first capacitor and the second capacitor is the positive direction of the output current of the series connection point of the first capacitor and the second capacitor
  • the input current flowing from the series connection point of the first capacitor and the second capacitor to the target capacitor is the positive direction of the input current of the series connection point of the first capacitor and the second capacitor.
  • the control circuit (for example, a voltage regulation loop or other circuit with a voltage regulation function) can generate a voltage regulation instruction based on the terminal voltage value of the target capacitor and the half bus voltage value.
  • control circuit for example, a current regulation loop and a drive control circuit, or other circuits with a current regulation function and a drive control function
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the control circuit can generate a balanced modulation signal (for example, a balanced modulation signal such as a PWM wave) based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the balanced modulation signal can control the output current of the balancing circuit, the output current of the balancing circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM wave as a balanced modulation signal, and can also use other PWM waves (for example, SPWM wave, THIPWM wave, CBPWM wave, etc.) as a balanced modulation signal. It has a wide range of applicable scenarios and good control effects.
  • the balancing circuit may further include a control circuit and at least one balancing bridge arm, one balancing bridge arm may include two switching tubes connected in series, the control circuit is connected to the inductor through at least one balancing bridge arm, and the acquisition circuit is connected to the control circuit.
  • the acquisition circuit here can also obtain a half-bus voltage value based on the DC bus voltage, and obtain an output current value of the series connection point of the first capacitor and the second capacitor and an input current value of the series connection point of the first capacitor and the second capacitor.
  • the control circuit here can also generate a balanced modulation signal based on the terminal voltage value of the target capacitor, the half-bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor, and control the conduction or shutdown of the switching tube in at least one balancing bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • control circuit for example, the prediction control circuit and the drive control circuit
  • a control circuit e.g., a current regulation loop and a drive control circuit, or other circuits with a predictive control function and a drive control function
  • control circuit e.g., a current regulation loop and a drive control circuit, or other circuits with a current regulation function and a drive control function
  • the control circuit can generate a balanced modulation signal based on the half-bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor to control the conduction or shutdown of the switch tube in the balancing circuit.
  • the control circuit can generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balancing circuit, the output current of the balancing circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals. It has a wide range of application scenarios and good control effects.
  • the inverter may further include a filter circuit, which connects the switch bridge arm and the load in the inverter circuit.
  • the filter circuit may be an LC filter circuit or an LCL filter circuit composed of an inductor and a capacitor, or other circuits with a filtering function.
  • the filter circuit here can filter out the clutter components (for example, high-frequency components with higher frequencies) contained in the output current (or output voltage) of the inverter circuit, thereby improving the power supply stability.
  • the present application provides a power supply system, which may include a power supply and an inverter.
  • the inverter may include an inverter circuit, a collection circuit, a balancing circuit and an inductor.
  • the inverter circuit may include at least one switch bridge arm and a first capacitor and a second capacitor connected in series.
  • the balancing circuit may include multiple switch tubes.
  • One end of the inverter circuit here can be used to connect the power supply through a positive DC bus and a negative DC bus, and the other end of the inverter circuit can be used to connect the load.
  • the two groups of capacitors of the inverter circuit are connected in series and connected in parallel with at least one switch bridge arm between the positive DC bus and the negative DC bus.
  • the collection circuit connects the positive DC bus, the negative DC bus, the series connection point of the first capacitor and the second capacitor of the inverter circuit, and the balancing circuit.
  • the balancing circuit connects the series connection point of the first capacitor and the second capacitor through an inductor.
  • the inverter when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit, balancing the positive and negative bus voltages, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the power supply system may further include a combiner box, and the power supply is connected to the inverter through the combiner box.
  • the power supply system may further include a DC bus, the power supply is connected to the DC bus via a combiner box, and the DC bus is connected to the inverter.
  • the load is a power grid
  • the power supply system may further include an on-grid and off-grid wiring device
  • the inverter is connected to the power grid through the on-grid and off-grid wiring device.
  • composition of the functional modules in the power supply system is diverse and flexible, which can adapt to different power supply environments, improve the diversity of application scenarios of the power supply system, and enhance the adaptability of the power supply system.
  • the present application provides a control method for an inverter, which can be applied to an inverter, wherein the inverter may include an inverter circuit, a collection circuit, a balancing circuit and an inductor, wherein the inverter circuit may include at least one switch bridge arm and a first capacitor and a second capacitor connected in series, and the balancing circuit may include multiple switch tubes.
  • one end of the inverter circuit may be used to connect a power source through a positive DC bus and a negative DC bus
  • the other end of the inverter circuit may be used to connect a load
  • the first capacitor and the second capacitor are connected in series and connected in parallel with at least one switch bridge arm between the positive DC bus and the negative DC bus
  • the collection circuit connects the positive DC bus, the negative DC bus, the series connection point of the first capacitor and the second capacitor and the balancing circuit
  • the balancing circuit connects the series connection point of the first capacitor and the second capacitor through an inductor
  • the DC bus voltage is detected to obtain the terminal voltage values of the first capacitor and the second capacitor.
  • the on or off of the multiple switch tubes are controlled to adjust the current of the inductor charging the target capacitor to reduce the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors, wherein the target capacitor is the capacitor with the smaller terminal voltage value among the first capacitor and the second capacitor.
  • the acquisition circuit can obtain the DC bus voltage of the inverter circuit (for example, the positive DC bus voltage and/or the negative DC bus voltage, and the voltage of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit)) to obtain the terminal voltage of the target capacitor.
  • the target capacitor can be the capacitor with the smaller terminal voltage value between the first capacitor and the second capacitor.
  • a certain voltage threshold for example, the first voltage threshold
  • the balancing circuit needs to charge the capacitor (for example, the target capacitor).
  • the first voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor or the second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the first voltage threshold can be a voltage value less than 1/2 of the bus voltage, and the bus voltage is the voltage difference between the positive DC bus voltage and the negative DC bus voltage). It can be set specifically according to the application scenario. It can be understood that the first voltage threshold here can be a voltage value, can be multiple voltage values, can be It is a voltage interval composed of multiple voltage values.
  • the balancing circuit can determine whether the target capacitor needs to be charged in a variety of ways, and comparing the terminal voltage of the target capacitor with the first voltage threshold is only one of them.
  • the balancing circuit can also determine whether the capacitor of the inverter circuit needs to be charged in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is greater than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is greater than or equal to a certain threshold, the balancing circuit can determine that the capacitor of the inverter circuit needs to be charged at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the first voltage threshold to determine whether the capacitor of the inverter circuit needs to be charged as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can charge the target capacitor through an inductor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit includes multiple switching tubes, and the balancing circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the positive DC bus voltage and the negative DC bus voltage of the balanced inverter circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the inverter when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit, balancing the positive and negative bus voltages, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the method may further include:
  • the plurality of switch tubes are controlled to remain turned off to stop charging the target capacitor, and the second voltage threshold is greater than or equal to the first voltage threshold.
  • the terminal voltage value of the target capacitor is greater than or equal to a certain voltage threshold (for example, the second voltage threshold)
  • a certain voltage threshold for example, the second voltage threshold
  • the second voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor or the second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the second voltage threshold can be a voltage value less than 1/2 of the bus voltage and greater than or equal to the first voltage threshold), which can be set according to the application scenario.
  • the second voltage threshold here can be a voltage value, a plurality of voltage values, or a voltage interval composed of a plurality of voltage values.
  • the second voltage threshold can be greater than or equal to the first voltage threshold.
  • the inverter can avoid repeatedly starting and stopping charging the target capacitor through the balancing circuit when the terminal voltage of the target capacitor is not stably greater than the first voltage threshold. That is to say, when the second voltage threshold is greater than the first voltage threshold, the inverter can determine that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, or determine that the positive DC bus voltage and the negative DC bus voltage of the inverter circuit are in a balanced state, after the terminal voltage of the target capacitor is stabilized (for example, stably greater than the first voltage threshold), and then stop charging the target capacitor through the balancing circuit.
  • the balancing circuit can determine whether to stop charging the target capacitor in a variety of ways, and comparing the terminal voltage of the target capacitor with the second voltage threshold is only one of them.
  • the balancing circuit can also determine whether to stop charging the capacitor of the inverter circuit in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is less than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is less than or equal to a certain threshold, the balancing circuit can determine that it is not necessary to charge the capacitor of the inverter circuit at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the second voltage threshold to determine whether it is necessary to stop charging the capacitor of the inverter circuit as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can stop charging the target capacitor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit can control each switch tube in the balancing circuit to remain turned off to stop charging the target capacitor, thereby saving energy and reducing costs.
  • the inverter can stop charging the target capacitor through the balancing circuit when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, thereby reducing the power consumed by the balancing circuit, reducing costs, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the balancing circuit may include a control circuit and at least one balancing bridge arm, one balancing bridge arm may include two switching tubes connected in series, the control circuit is connected to the inductor through at least one balancing bridge arm, the acquisition circuit is connected to the control circuit, and after detecting the DC bus voltage to obtain the terminal voltage values of the first capacitor and the second capacitor, the method may further include:
  • a half bus voltage value is obtained based on the DC bus voltage.
  • a balanced modulation signal is generated based on the terminal voltage value of the target capacitor and the half bus voltage value, and the balanced modulation signal is used to control the on or off of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • the balancing circuit includes at least one balancing bridge arm.
  • the balancing circuit may include a half-bridge circuit with two series-connected switch tubes as a balancing bridge arm, or may include a full-bridge circuit with four switch tubes as two balancing bridge arms.
  • the acquisition circuit may obtain the positive DC bus voltage and the negative DC bus voltage of the inverter circuit, and obtain the half-bus voltage value (that is, 1/2 bus voltage value) based on the positive DC bus voltage and the negative DC bus voltage.
  • control circuit for example, a voltage regulation loop (for example, a proportional integral regulation circuit) and a drive control circuit, or other circuits with a voltage regulation function and a drive control function
  • the control circuit may generate a balanced modulation signal based on the terminal voltage value of the target capacitor and the half-bus voltage value to control the conduction or shutdown of the switch tube in the balancing circuit.
  • the control circuit may generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided by the present application can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals, which has a wide range of application scenarios and good control effects.
  • the method may further include:
  • the output current value of the series connection point of the first capacitor and the second capacitor and the input current value of the series connection point of the first capacitor and the second capacitor are obtained.
  • a voltage regulation instruction is generated based on the terminal voltage value of the target capacitor and the half-bus voltage value, and a balanced modulation signal is generated based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor and the input current value of the series connection point of the first capacitor and the second capacitor, and the balanced modulation signal is used to control the conduction or disconnection of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • the acquisition circuit can obtain the output current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit) and the input current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit).
  • the output current value of the series connection point of the first capacitor and the second capacitor can be determined by adding the current values output by the series connection point of the first capacitor and the second capacitor to each switch bridge arm of the inverter circuit, or it can be determined by other methods.
  • the input current value of the series connection point of the first capacitor and the second capacitor can be determined by the output current of the inductor connected to the series connection point of the first capacitor and the second capacitor, or it can be determined by other methods.
  • the reference direction of the output current and input current of the series connection point of the first capacitor and the second capacitor can be determined according to the target capacitor.
  • the output current flowing from the target capacitor to the series connection point of the first capacitor and the second capacitor is the positive direction of the output current of the series connection point of the first capacitor and the second capacitor
  • the input current flowing from the series connection point of the first capacitor and the second capacitor to the target capacitor is the positive direction of the input current of the series connection point of the first capacitor and the second capacitor.
  • the control circuit (for example, a voltage regulation loop or other circuit with a voltage regulation function) can generate a voltage regulation instruction based on the terminal voltage value of the target capacitor and the half bus voltage value.
  • control circuit for example, a current regulation loop and a drive control circuit, or other circuits with a current regulation function and a drive control function
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the control circuit can generate a balanced modulation signal (for example, a balanced modulation signal such as a PWM wave) based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the balanced modulation signal can control the output current of the balancing circuit, the output current of the balancing circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM wave as a balanced modulation signal, and can also use other PWM waves (for example, SPWM wave, THIPWM wave, CBPWM wave, etc.) as a balanced modulation signal. It has a wide range of applicable scenarios and good control effects.
  • the balancing circuit may further include a control circuit and at least one balancing bridge arm, one balancing bridge arm may include two switching tubes connected in series, the control circuit is connected to the inductor through at least one balancing bridge arm, the acquisition circuit is connected to the control circuit, and after detecting the DC bus voltage to obtain the terminal voltage values of the first capacitor and the second capacitor, the method may further include:
  • a half-bus voltage value is obtained based on the DC bus voltage, and an output current value of a series connection point between the first capacitor and the second capacitor and an input current value of a series connection point between the first capacitor and the second capacitor are obtained.
  • a balanced modulation signal is generated based on a terminal voltage value of a target capacitor, a half-bus voltage value, an output current value of a series connection point between the first capacitor and the second capacitor, and an input current value of a series connection point between the first capacitor and the second capacitor, and the balanced modulation signal is used to control the conduction or disconnection of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • control circuit e.g., a prediction control circuit and a drive control circuit, or other circuits with prediction control functions and drive control functions
  • the control circuit can generate a balanced modulation signal based on the terminal voltage value of the target capacitor, the half bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor.
  • the loop and drive control circuit, or other circuits with current regulation function and drive control function can generate a balanced modulation signal based on the half-bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor to control the conduction or shutdown of the switch tube in the balanced circuit.
  • the control circuit can generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on the PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • control circuit can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals, which are widely applicable to various scenarios and have good control effects.
  • PWM waves for example, SPWM waves, THIPWM waves, CBPWM waves, etc.
  • FIG1 is a schematic diagram of an application scenario of an inverter provided in an embodiment of the present application.
  • FIG2 is a schematic diagram of a structure of an inverter provided in an embodiment of the present application.
  • FIG3 is another schematic diagram of the structure of the inverter provided in an embodiment of the present application.
  • FIG4 is another schematic diagram of the structure of the inverter provided in an embodiment of the present application.
  • FIG5 is another schematic diagram of the structure of the inverter provided in an embodiment of the present application.
  • FIG6 is another schematic diagram of the structure of the inverter provided in an embodiment of the present application.
  • FIG7 is a schematic diagram of the structure of a power supply system provided in an embodiment of the present application.
  • FIG8 is a schematic diagram of a flow chart of a control method provided in an embodiment of the present application.
  • FIG. 9 is another schematic flow chart of the control method provided in an embodiment of the present application.
  • an inverter circuit in an inverter is usually used to convert DC power into AC power so that the power can be transmitted between the power source and the load.
  • three-level inverter circuits e.g., NPC inverter circuits and their extended circuits
  • a three-level inverter circuit includes two sets of capacitors connected in series and multiple switch bridge arms. The series connection point of the two sets of capacitors is the midpoint n of the inverter circuit, and each switch bridge arm includes four switch tubes and two clamping diodes.
  • the inverter circuit can charge and discharge the capacitors in the inverter circuit respectively by turning on and off different switch tubes, and convert the DC power provided by the power supply into AC power and transmit it to the load.
  • the output voltage (or output current) of the inverter is asymmetric (for example, different switch tube models, different losses, asymmetric loads, or affected by factors such as switch dead zones)
  • the positive DC bus voltage and the negative DC bus voltage of the inverter circuit will be unbalanced, or in other words, there is a large difference in the terminal voltages of the two groups of capacitors in the inverter circuit, which will cause the output voltage (or output current) of the inverter circuit to be distorted and even damage the power components in the system.
  • the present application provides an inverter and a control method thereof, which can adjust the output current of the inductor through a balancing circuit to charge the target capacitor when the terminal voltage difference between the two groups of capacitors in the inverter circuit is large, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the inverter provided in the present application can be applicable to various application fields such as the field of new energy power generation, the field of peak and frequency regulation of traditional power generation, the field of power supply for important equipment, the field of new energy vehicles, etc., which can be specifically determined according to the actual application scenario and is not limited here.
  • the inverter provided in the present application can be applicable to different power supply systems such as energy storage systems, uninterruptible power supply systems, motor drive systems, etc., which can be specifically determined according to the actual application scenario and is not limited here.
  • the inverter provided in the present application can be adapted to different application scenarios, such as the application scenario of controlling the inverter circuit in a solar power supply environment, the application scenario of controlling the inverter circuit in a wind power supply environment, the application scenario of controlling the inverter circuit in a pure energy storage power supply environment, or other application scenarios.
  • the following will take the application scenario of controlling the inverter circuit in a pure energy storage power supply environment as an example for explanation, and will not be repeated below.
  • Figure 1 is a schematic diagram of an application scenario of the inverter provided in an embodiment of the present application.
  • the power supply system includes an inverter 1, a power supply 2 and a load 3, wherein the inverter 1 includes an inverter circuit 11, and the power supply 2 can be connected to the load 3 through the inverter circuit 11.
  • the power supply 2 can supply power to the load 3 through the inverter circuit 11.
  • the power supply 2 provided in the present application is suitable for powering base station equipment in remote areas where there is no mains power or poor mains power, or for powering household appliances (such as refrigerators, air conditioners, etc.) and other application scenarios for powering various types of electrical equipment.
  • the specific application scenario can be determined according to the actual application scenario. No limitation is made.
  • the load 3 in Figure 2 may include a power grid, where the power grid may include power-consuming devices or power transmission devices such as transmission lines, power transfer sites, communication base stations or household appliances.
  • the load 3 here may also include loads (power-consuming devices or power transmission devices) such as motors and rectifiers, where the voltage and current are nonlinearly related during operation (power supply or power consumption).
  • the inverter circuit 11 may be a three-level inverter circuit (for example, an NPC inverter circuit), and the inverter circuit 11 may include two groups of capacitors (for example, a first capacitor C1 and a second capacitor C2) and at least one switch bridge arm.
  • a group of capacitors may be a capacitor or a capacitor composed of multiple capacitors.
  • the inverter circuit 11 may charge and discharge the two groups of capacitors respectively by turning on and off different switch tubes in the switch bridge arm, and convert the DC power provided by the power supply into AC power and transmit it to the load.
  • the output voltage (or output current) of the inverter 1 is asymmetric (for example, the switch tube models are different, the losses are different, the loads are asymmetric, or affected by factors such as the switch dead zone), in a power supply cycle, the amount of charge flowing into and out of the series connection point of the first capacitor C1 and the second capacitor C2 (or, the midpoint of the inverter circuit 11) is not the same.
  • the charge (or discharge) of the two groups of capacitors in the inverter circuit 11 is not equal, resulting in unequal voltages of the two groups of capacitors in the inverter circuit 11 (that is, the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 11 are unbalanced, or, the midpoint voltage of the inverter circuit 11 is unbalanced), which will cause the output voltage (or output current) of the inverter 1 to be distorted, and even damage the power components in the system. Therefore, when the inverter circuit is working, it is necessary to control the difference between the terminal voltages of the two groups of capacitors in the inverter circuit 11 so that the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 11 remain balanced.
  • the inverter 1 may further include an acquisition circuit 12, a balancing circuit 13 and an inductor.
  • the acquisition circuit 12 may acquire the DC bus voltage of the inverter circuit 11, for example, the voltage of the positive DC bus voltage or the negative DC bus voltage and the series connection point of the first capacitor C1 and the second capacitor C2 (or the midpoint of the inverter circuit 11), to obtain the terminal voltage of the target capacitor (the first capacitor C1 or the second capacitor C2).
  • the balancing circuit can adjust the current that charges the target capacitor through the inductor to reduce the terminal voltage difference between the two groups of capacitors, thereby keeping the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 11 balanced.
  • the inverter 1 can adjust the output current of the inductor through the balancing circuit 13 to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit 11 and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the inverter provided in the present application and its working principle will be illustrated below with reference to FIG. 2 to FIG. 9 .
  • FIG. 2 is a schematic diagram of a structure of an inverter provided in an embodiment of the present application.
  • the power supply system includes a power supply, an inverter and a load, and the inverter includes an inverter circuit 101, a collection circuit 102, a balancing circuit 103 and an inductor.
  • the inverter circuit 101 may include at least one switch bridge arm and a first capacitor C1 and a second capacitor C2 connected in series, and the balancing circuit 103 may include multiple switch tubes.
  • the inverter circuit 101 may be a multi-level inverter circuit or a topological circuit of a multi-level inverter circuit.
  • a switch bridge arm composed of a switch tube Ta1, a switch tube Ta2, a switch tube Ta3 and a switch tube Ta4, a switch bridge arm composed of a switch tube Tb1, a switch tube Tb2, a switch tube Tb3 and a switch tube Tb4, and a switch bridge arm composed of a switch tube Tc1, a switch tube Tc2, a switch tube Tc3 and a switch tube Tc4.
  • one end of the inverter circuit 101 can be used to connect the power supply through the positive DC bus and the negative DC bus, and the other end of the inverter circuit 101 can be used to connect the load.
  • the first capacitor C1 and the second capacitor C2 can be connected in series and can be connected in parallel with at least one switch bridge arm between the positive DC bus and the negative DC bus.
  • the acquisition circuit 102 can connect the positive DC bus, the negative DC bus, the series connection point of the first capacitor C1 and the second capacitor C2, and the balancing circuit 103 (as shown by the dotted line in Figure 2), and the balancing circuit 103 can connect the series connection point of the first capacitor C1 and the second capacitor C2 through an inductor.
  • the acquisition circuit 102 can detect the DC bus voltage (for example, the positive DC bus voltage, the negative DC bus voltage, and the voltage of the series connection point of the first capacitor C1 and the second capacitor C2) to obtain the terminal voltage value of the target capacitor, wherein the target capacitor is the capacitor with the smaller terminal voltage value among the first capacitor C1 and the second capacitor C2.
  • the balancing circuit 103 here can be used to control the conduction or shutdown of multiple switching tubes when the terminal voltage value of the target capacitor is less than or equal to the first voltage threshold, so as to adjust the current charging the target capacitor through the inductor, so as to reduce the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors.
  • the acquisition circuit 102 can obtain the DC bus voltage (for example, the positive DC bus voltage and/or the negative DC bus voltage) of the inverter circuit 101 and the voltage of the series connection point of the first capacitor C1 and the second capacitor C2 (or the midpoint of the inverter circuit 101) to obtain the terminal voltage of the target capacitor.
  • the target capacitor can be the capacitor with the smaller terminal voltage value between the first capacitor C1 and the second capacitor C2.
  • the balancing circuit 103 needs to charge the capacitor (for example, the target capacitor).
  • the first voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor C1 or the second capacitor C2) in the inverter circuit 101, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the first voltage threshold can be a voltage value less than 1/2 of the bus voltage, and the bus voltage is the voltage difference between the positive DC bus voltage and the negative DC bus voltage), which can be set according to the application scenario. It can be understood that the first voltage threshold here can be a voltage value, multiple voltage values, or a voltage interval composed of multiple voltage values.
  • the balancing circuit 103 can determine whether the target capacitor needs to be charged in a variety of ways, and comparing the terminal voltage of the target capacitor with the first voltage threshold is only one of them. The balancing circuit 103 can also determine whether the capacitor of the inverter circuit 101 needs to be charged in other ways. For example, when the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2 is greater than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor C1 (or the second capacitor C2) and 1/2 of the bus voltage is greater than or equal to a certain threshold, the balancing circuit 103 can determine that the capacitor of the inverter circuit 101 needs to be charged at this time.
  • This application only introduces the example of the balancing circuit 103 comparing the terminal voltage of the target capacitor with the first voltage threshold to determine whether the capacitor of the inverter circuit 101 needs to be charged.
  • Other comparison methods can be set based on specific application scenarios and are also within the scope of the present invention.
  • the balancing circuit 103 determines (for example, by comparing the terminal voltage of the target capacitor with the first voltage threshold) that the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2 is large, or determines that the positive and negative DC bus voltages of the inverter circuit 101 are in an unbalanced state
  • the balancing circuit 103 can charge the target capacitor through the inductor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit 103 includes a plurality of switch tubes, and the balancing circuit 103 can control the conduction or shutdown of each switch tube to adjust the current charged to the target capacitor through the inductor (for example, increase the current charged to the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor C1 and the second capacitor C2), in other words, balancing the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 101.
  • the inverter can adjust the output current of the inductor through the balancing circuit 103 to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit 101, balancing the positive and negative bus voltages, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the balancing circuit 103 can also be used to control multiple switch tubes to remain off when the terminal voltage value of the target capacitor is greater than or equal to the second voltage threshold to stop charging the target capacitor.
  • a certain voltage threshold for example, the second voltage threshold
  • the balancing circuit 103 does not need to charge the capacitor (for example, the target capacitor).
  • the second voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor C1 or the second capacitor C2) in the inverter circuit 101, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the second voltage threshold can be a voltage value less than 1/2 bus voltage and greater than or equal to the first voltage threshold), which can be set according to the application scenario.
  • the second voltage threshold here can be a voltage value, can be multiple voltage values, and can be a voltage interval composed of multiple voltage values.
  • the second voltage threshold may be greater than or equal to the first voltage threshold.
  • the inverter may avoid repeatedly starting and stopping charging the target capacitor through the balancing circuit 103 when the terminal voltage of the target capacitor is not stably greater than the first voltage threshold. That is, when the second voltage threshold is greater than the first voltage threshold, the inverter may determine that the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2 is small after the terminal voltage of the target capacitor is stable (for example, stably greater than the first voltage threshold), or determine that the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 101 are in a balanced state, and then stop charging the target capacitor through the balancing circuit 103.
  • the balancing circuit 103 can determine whether to stop charging the target capacitor in a variety of ways, and comparing the terminal voltage of the target capacitor with the second voltage threshold is only one of them.
  • the balancing circuit 103 can also determine whether to stop charging the capacitor of the inverter circuit 101 in other ways. For example, when the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2 is less than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor C1 (or the second capacitor C2) and 1/2 of the bus voltage is less than or equal to a certain threshold, the balancing circuit 103 can determine that it is not necessary to charge the capacitor of the inverter circuit 101 at this time.
  • the balancing circuit 103 comparing the terminal voltage of the target capacitor with the second voltage threshold to determine whether it is necessary to stop charging the capacitor of the inverter circuit 101.
  • Other comparison methods can be set based on specific application scenarios and are also within the scope of the present invention.
  • the balancing circuit 103 can stop charging the target capacitor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit 103 can control each switch tube in the balancing circuit 103 to remain off to stop charging the target capacitor, save energy, and reduce costs.
  • the inverter when the inverter determines that the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2 is small, the inverter can stop charging the target capacitor through the balancing circuit 103, thereby reducing the power consumed by the balancing circuit 103 and reducing costs, while improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the inverter circuit may be a multi-level inverter circuit of other structures and its topology circuit.
  • FIG. 3 is another schematic diagram of the structure of the inverter provided by an embodiment of the present application.
  • the inverter circuit 201 can be another three-level inverter circuit of another structure, where the inverter circuit 201 may include a first capacitor C1 and a second capacitor C2 connected in series and three switch bridge arms, that is, a switch bridge arm composed of a switch tube Ta1, a switch tube Ta2, a switch tube Ta3, a switch tube Ta4 and two diodes, a switch bridge arm composed of a switch tube Tb1, a switch tube Tb2, a switch tube Tb3, a switch tube Tb4 and two diodes, and a switch bridge arm composed of a switch tube Tc1, a switch tube Tc2, a switch tube Tc3, a switch tube Tc4 and two diodes.
  • the acquisition circuit 202 and the balancing circuit 203 in
  • the inverter provided by the present application can be applied to any inverter circuit and its topological structure including two groups of series capacitors and switch bridge arms.
  • the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, reduce the terminal voltage difference between the two groups of capacitors in the inverter circuit, balance the positive and negative bus voltages, and improve the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the balancing circuit may include a control circuit and at least one balancing bridge arm.
  • Figure 4 is another structural schematic diagram of the inverter provided in an embodiment of the present application.
  • the balancing circuit may include a control circuit 3031 and at least one balancing bridge arm 3032, and the balancing bridge arm 3032 may include two switch tubes connected in series between the positive and negative DC bus bars.
  • the control circuit 3031 may be connected to the inductor through the balancing bridge arm 3032, and the acquisition circuit 302 may be connected to the control circuit 3031.
  • the acquisition circuit 302 here can also obtain a half-bus voltage value based on the positive DC bus voltage and the negative DC bus voltage.
  • the control circuit 3031 here can generate a balanced modulation signal based on the terminal voltage value and the half-bus voltage value of the target capacitor, and control the conduction or shutdown of the switch tube in at least one balancing bridge arm 3032 through the balanced modulation signal to adjust the output current of the inductor.
  • the balancing circuit includes at least one balancing bridge arm 3032.
  • the balancing bridge arm 3032 in the balancing circuit may be a half-bridge circuit including two switching tubes (eg, switching tube T1 and switching tube T2) connected in series.
  • the acquisition circuit 302 can obtain the positive DC bus voltage and the negative DC bus voltage of the inverter circuit 301, and obtain the half bus voltage value (that is, 1/2 bus voltage value) based on the positive DC bus voltage and the negative DC bus voltage.
  • the control circuit 3031 for example, a voltage regulation loop (for example, a proportional integral regulation circuit) and a drive control circuit 3031, or other circuits with voltage regulation functions and drive control functions
  • the control circuit 3031 can generate a pulse width modulation, PWM wave or other signal as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor during discharge can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2, and balancing the positive and negative DC bus voltages.
  • control circuit 3031 can use discontinuous pulse width modulation (DPWM) wave as a balanced modulation signal, or other PWM waves (for example, sinusoidal pulse width modulation (SPWM) wave, third harmonic injection pulse width modulation (THIPWM) wave, carrier based space vector pulse width modulation (CBPWM) wave, etc.) as a balanced modulation signal, and can also use a driving pulse signal generated based on these PWM waves as a balanced modulation signal, which has a wide range of application scenarios and good control effect.
  • PWM discontinuous pulse width modulation
  • SPWM sinusoidal pulse width modulation
  • THIPWM third harmonic injection pulse width modulation
  • CBPWM carrier based space vector pulse width modulation
  • the acquisition circuit 302 can also be used to obtain the output current value of the series connection point of the first capacitor C1 and the second capacitor C2 and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2.
  • the control circuit 3031 here can also generate a voltage adjustment instruction based on the terminal voltage value and the half-bus voltage value of the target capacitor, generate a balanced modulation signal based on the voltage adjustment instruction, the output current value of the series connection point of the first capacitor C1 and the second capacitor C2, and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm 3032 through the balanced modulation signal to adjust the output current of the inductor.
  • the acquisition circuit 302 can obtain the output current value of the series connection point of the first capacitor C1 and the second capacitor C2 (or the midpoint of the inverter circuit 301) and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2 (or the midpoint of the inverter circuit 301).
  • the output current value of the series connection point of the first capacitor C1 and the second capacitor C2 can be determined by adding the current values output by the series connection point of the first capacitor C1 and the second capacitor C2 to each switch bridge arm of the inverter circuit 301, or it can be determined by other methods.
  • the input current value of the series connection point of the first capacitor C1 and the second capacitor C2 can be determined by the output current of the inductor connected to the series connection point of the first capacitor C1 and the second capacitor C2, or it can be determined by other methods.
  • the reference direction of the output current and the input current of the series connection point of the first capacitor C1 and the second capacitor C2 (or the midpoint of the inverter circuit 301) can be determined based on the target capacitance.
  • the output current flowing from the target capacitance to the series connection point of the first capacitor C1 and the second capacitor C2 is the positive direction of the output current of the series connection point of the first capacitor C1 and the second capacitor C2
  • the input current flowing from the series connection point of the first capacitor C1 and the second capacitor C2 to the target capacitance is the positive direction of the input current of the series connection point of the first capacitor C1 and the second capacitor C2.
  • the control circuit 3031 (for example, a voltage regulation loop or other circuit with a voltage regulation function) can be based on the target capacitance.
  • the terminal voltage value of the capacitor and the half bus voltage value generate a voltage regulation instruction.
  • control circuit 3031 for example, a current regulation loop and a drive control circuit, or other circuits with current regulation function and drive control function
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the control circuit 3031 can generate a balanced modulation signal (for example, a balanced modulation signal such as a PWM wave) based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor C1 and the second capacitor C2, and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm 3032 through the balanced modulation signal to adjust the output current of the inductor.
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2, and balancing the positive and negative DC bus voltages.
  • the control circuit 3031 provided in the present application can use DPWM wave as a balanced modulation signal, and can also use other PWM waves (for example, SPWM wave, THIPWM wave, CBPWM wave, etc.) as a balanced modulation signal. It has a wide range of applicable scenarios and good control effects.
  • the acquisition circuit 302 may also obtain a half-bus voltage value based on the positive DC bus voltage and the negative DC bus voltage, and obtain the output current value of the series connection point of the first capacitor C1 and the second capacitor C2 and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2.
  • the control circuit 3031 here may also generate a balanced modulation signal based on the terminal voltage value of the target capacitor, the half-bus voltage value, the output current value of the series connection point of the first capacitor C1 and the second capacitor C2, and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm 3032 through the balanced modulation signal to adjust the output current of the inductor.
  • control circuit 3031 may generate a balanced modulation signal based on the terminal voltage value of the target capacitor, the half-bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor.
  • the predictive control circuit here is a circuit that can simulate the inverter structure.
  • the predictive control can predict the operating state of the inverter based on the input parameters of the inverter (for example, the terminal voltage value of the target capacitor, the half-bus voltage value, the output current value and the input current value of the series connection point of the first capacitor and the second capacitor), so as to obtain a balanced modulation signal that can keep the midpoint voltage of the inverter balanced.
  • the input parameters of the inverter for example, the terminal voltage value of the target capacitor, the half-bus voltage value, the output current value and the input current value of the series connection point of the first capacitor and the second capacitor
  • control circuit 3031 (for example, a current regulation loop and a drive control circuit, or other circuits with current regulation function and drive control function) can generate a balanced modulation signal based on the half-bus voltage value, the output current value of the series connection point of the first capacitor C1 and the second capacitor C2, and the input current value of the series connection point of the first capacitor C1 and the second capacitor C2 to control the conduction or disconnection of the switch tube in the balance circuit.
  • the control circuit 3031 can generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor C1 and the terminal voltage of the second capacitor C2, and balancing the positive and negative DC bus voltages.
  • the control circuit 3031 provided in the present application can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals, which has a wide range of application scenarios and good control effects.
  • the balancing circuit may include multiple balancing bridge arms.
  • Figure 5 is another structural schematic diagram of the inverter provided in an embodiment of the present application.
  • the balancing bridge arm 4032 in the balancing circuit can be a full-bridge circuit consisting of two balancing bridge arms composed of four switch tubes (for example, switch tube T1, switch tube T2, switch tube T3 and switch tube T4), and the full-bridge circuit can be connected between the positive and negative DC bus bars.
  • connection mode and working principle of the inverter circuit 401, the acquisition circuit 402 and the control circuit 4031 in the balancing circuit in Figure 5 are the same as those of the inverter circuit 301, the acquisition circuit 302 and the control circuit 3031 in the balancing circuit in Figure 4, and will not be repeated here.
  • the inverter provided by the present application can be applied to any balancing circuit that can adjust the output current of the inductor.
  • the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, reduce the terminal voltage difference between the two groups of capacitors in the inverter circuit, balance the positive and negative bus voltages, and improve the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the inverter may further include a filter circuit.
  • FIG. 6 is another schematic diagram of the structure of the inverter provided in an embodiment of the present application.
  • the filter circuit 504 can connect the switch bridge arm and the load in the inverter circuit 501. It can be understood that the connection mode and working principle of the inverter circuit 501, the acquisition circuit 502, and the control circuit 5031 and the balance bridge arm 5032 in the balancing circuit in FIG. 6 are the same as those of the inverter circuit 401, the acquisition circuit 402, and the control circuit 4031 and the balance bridge arm 4032 in the balancing circuit in FIG. 5, and are not repeated here.
  • the filter circuit 504 can be an LC filter circuit or an LCL filter circuit (not shown in the figure) composed of an inductor and a capacitor, or other circuits with a filtering function.
  • the filter circuit 504 here can filter out the clutter components (for example, high-frequency components with higher frequencies) contained in the output current (or output voltage) of the inverter circuit 501, and improve the power supply stability.
  • FIG. 7 is a schematic diagram of the structure of the power supply system provided in the embodiment of the present application. Intention.
  • the power supply system may include a power supply and an inverter.
  • the inverter here is applicable to the inverter shown in FIG. 1 to FIG. 6 above.
  • FIG. 7 only takes the inverter shown in FIG. 2 as an example for illustration. It can be understood that the connection mode and working principle of the inverter circuit 601, the acquisition circuit 602 and the balancing circuit 603 in FIG. 7 are the same as those of the inverter circuit 101, the acquisition circuit 102 and the balancing circuit 103 in FIG. 2 above, and are not repeated here.
  • a combiner box 604 may also be included, and the power supply may be connected to the inverter through the combiner box 604.
  • the power supply system may also include a DC bus, and the combiner box 604 may be connected to the load through the DC bus and the inverter.
  • the DC bus may include a bus capacitor C or multiple bus capacitors connected in series, which can be used for energy storage.
  • the inverter device can convert the electric energy output by the power supply and stored at both ends of the bus capacitor, and output the corresponding current and voltage to maintain the operation of the power grid.
  • the load can be a power grid
  • the power supply system can also include an on-grid and off-grid wiring device 605.
  • the inverter can power transmission lines, power transfer stations, batteries, communication base stations or household appliances and other power-consuming equipment or power transmission equipment in the power grid through the on-grid and off-grid wiring device 605.
  • any power supply system or inverter shown in Figures 1 to 7 above can charge the target capacitor by adjusting the output current of the inductor through a balancing circuit when the terminal voltage difference between the two groups of capacitors in the inverter circuit is large, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit, improving the stability and power supply efficiency of the inverter, and having a simple structure, a simple method, and strong applicability.
  • the grid-connected control method provided in the embodiment of the present application will be illustrated below with the structure of the inverter shown in Figure 2.
  • Figure 8 is a flow chart of a control method provided by the present application.
  • the control method provided by the present application is applicable to an inverter, including but not limited to any power supply system or an inverter in a power supply system shown in Figures 1 to 7 above.
  • the control method provided by the present application includes the following steps:
  • S702 When the terminal voltage value of the target capacitor is less than or equal to the first voltage threshold, control the on or off of multiple switch tubes to adjust the current used by the inductor to charge the target capacitor, so as to reduce the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors.
  • the acquisition circuit can obtain the DC bus voltage of the inverter circuit (for example, the positive DC bus voltage and/or the negative DC bus voltage, and the voltage of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit)) to obtain the terminal voltage of the target capacitor.
  • the target capacitor can be the capacitor with the smaller terminal voltage value between the first capacitor and the second capacitor.
  • a certain voltage threshold for example, the first voltage threshold
  • the balancing circuit needs to charge the capacitor (for example, the target capacitor).
  • the first voltage threshold can be determined based on the rated terminal voltage value of the capacitor (first capacitor or second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the first voltage threshold can be a voltage value less than 1/2 of the bus voltage, and the bus voltage is the voltage difference between the positive DC bus voltage and the negative DC bus voltage), which can be set specifically according to the application scenario. It can be understood that the first voltage threshold here can be a voltage value, multiple voltage values, or a voltage interval composed of multiple voltage values.
  • the balancing circuit can determine whether the target capacitor needs to be charged in a variety of ways, and comparing the terminal voltage of the target capacitor with the first voltage threshold is only one of them.
  • the balancing circuit can also determine whether the capacitor of the inverter circuit needs to be charged in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is greater than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is greater than or equal to a certain threshold, the balancing circuit can determine that the capacitor of the inverter circuit needs to be charged at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the first voltage threshold to determine whether the capacitor of the inverter circuit needs to be charged as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can charge the target capacitor through an inductor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit includes multiple switching tubes, and the balancing circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the positive DC bus voltage and the negative DC bus voltage of the balanced inverter circuit can control the conduction or shutdown of each switching tube to adjust the current charging the target capacitor through the inductor (for example, increase the current charging the target capacitor), thereby reducing the terminal voltage difference between the target capacitor and the non-target capacitor in the two groups of capacitors (that is, reducing the terminal voltage difference between the first capacitor and the second capacitor).
  • the inverter when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, thereby reducing the terminal voltage difference between the two groups of capacitors in the inverter circuit, balancing the positive and negative bus voltages, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • FIG. 9 is another flow chart of the control method provided by the present application.
  • the balancing circuit (or inverter) may stop charging the target capacitor based on the terminal voltage value of the target capacitor.
  • the control method may include the following steps:
  • the terminal voltage value of the target capacitor is greater than or equal to a certain voltage threshold (for example, the second voltage threshold)
  • a certain voltage threshold for example, the second voltage threshold
  • the second voltage threshold can be determined based on the rated terminal voltage value of the capacitor (the first capacitor or the second capacitor) in the inverter circuit, and can be determined based on the voltage threshold obtained by the inverter through acquisition, collection, reception, detection or storage (for example, the second voltage threshold can be a voltage value less than 1/2 of the bus voltage and greater than or equal to the first voltage threshold), which can be set according to the application scenario.
  • the second voltage threshold here can be a voltage value, a plurality of voltage values, or a voltage interval composed of a plurality of voltage values.
  • the second voltage threshold can be greater than or equal to the first voltage threshold.
  • the inverter can avoid repeatedly starting and stopping charging the target capacitor through the balancing circuit when the terminal voltage of the target capacitor is not stably greater than the first voltage threshold. That is to say, when the second voltage threshold is greater than the first voltage threshold, the inverter can determine that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, or determine that the positive DC bus voltage and the negative DC bus voltage of the inverter circuit are in a balanced state, after the terminal voltage of the target capacitor is stabilized (for example, stably greater than the first voltage threshold), and then stop charging the target capacitor through the balancing circuit.
  • the balancing circuit can determine whether to stop charging the target capacitor in a variety of ways, and comparing the terminal voltage of the target capacitor with the second voltage threshold is only one of them.
  • the balancing circuit can also determine whether to stop charging the capacitor of the inverter circuit in other ways, such as when the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is less than or equal to a certain threshold, or when the voltage difference between the terminal voltage value of the first capacitor (or the second capacitor) and the voltage of 1/2 bus voltage is less than or equal to a certain threshold, the balancing circuit can determine that it is not necessary to charge the capacitor of the inverter circuit at this time.
  • This application only takes the balancing circuit comparing the terminal voltage of the target capacitor with the second voltage threshold to determine whether it is necessary to stop charging the capacitor of the inverter circuit as an example.
  • Other comparison methods can be set based on specific application scenarios and also belong to the scope of the present invention.
  • the balancing circuit can stop charging the target capacitor to increase the terminal voltage value of the target capacitor.
  • the balancing circuit can control each switch tube in the balancing circuit to remain turned off to stop charging the target capacitor, thereby saving energy and reducing costs.
  • the inverter can stop charging the target capacitor through the balancing circuit when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is small, thereby reducing the power consumed by the balancing circuit, reducing costs, and improving the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.
  • the method may further include:
  • a half bus voltage value is obtained based on the DC bus voltage.
  • a balanced modulation signal is generated based on the terminal voltage value of the target capacitor and the half bus voltage value, and the balanced modulation signal is used to control the on or off of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • the balancing circuit includes at least one balancing bridge arm.
  • the balancing circuit may include a half-bridge circuit with two series-connected switch tubes as a balancing bridge arm, or may include a full-bridge circuit with four switch tubes as two balancing bridge arms.
  • the acquisition circuit may obtain the positive DC bus voltage and the negative DC bus voltage of the inverter circuit, and obtain the half-bus voltage value (that is, 1/2 bus voltage value) based on the positive DC bus voltage and the negative DC bus voltage.
  • control circuit for example, a voltage regulation loop (for example, a proportional integral regulation circuit) and a drive control circuit, or other circuits with a voltage regulation function and a drive control function
  • the control circuit may generate a balanced modulation signal based on the terminal voltage value of the target capacitor and the half-bus voltage value to control the conduction or shutdown of the switch tube in the balancing circuit.
  • the control circuit may generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balanced circuit, the output current of the balanced circuit can charge the inductor, and the output current of the inductor during discharge can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals. It has a wide range of application scenarios and good control effects.
  • the method may further include:
  • the output current value of the series connection point of the first capacitor and the second capacitor and the input current value of the series connection point of the first capacitor and the second capacitor are obtained.
  • a voltage regulation instruction is generated based on the terminal voltage value of the target capacitor and the half-bus voltage value, and a balanced modulation signal is generated based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor and the input current value of the series connection point of the first capacitor and the second capacitor, and the balanced modulation signal is used to control the conduction or disconnection of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • the acquisition circuit can obtain the output current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit) and the input current value of the series connection point of the first capacitor and the second capacitor (or the midpoint of the inverter circuit).
  • the output current value of the series connection point of the first capacitor and the second capacitor can be determined by adding the current values output by the series connection point of the first capacitor and the second capacitor to each switch bridge arm of the inverter circuit, or it can be determined by other methods.
  • the input current value of the series connection point of the first capacitor and the second capacitor can be determined by the output current of the inductor connected to the series connection point of the first capacitor and the second capacitor, or it can be determined by other methods.
  • the reference direction of the output current and input current of the series connection point of the first capacitor and the second capacitor can be determined according to the target capacitor.
  • the output current flowing from the target capacitor to the series connection point of the first capacitor and the second capacitor is the positive direction of the output current of the series connection point of the first capacitor and the second capacitor
  • the input current flowing from the series connection point of the first capacitor and the second capacitor to the target capacitor is the positive direction of the input current of the series connection point of the first capacitor and the second capacitor.
  • the control circuit (for example, a voltage regulation loop or other circuit with a voltage regulation function) can generate a voltage regulation instruction based on the terminal voltage value of the target capacitor and the half bus voltage value.
  • control circuit for example, a current regulation loop and a drive control circuit, or other circuits with a current regulation function and a drive control function
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the control circuit can generate a balanced modulation signal (for example, a balanced modulation signal such as a PWM wave) based on the voltage regulation instruction, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor, and control the conduction or shutdown of the switch tube in at least one balanced bridge arm through the balanced modulation signal to adjust the output current of the inductor.
  • a balanced modulation signal for example, a balanced modulation signal such as a PWM wave
  • the balanced modulation signal can control the output current of the balancing circuit, the output current of the balancing circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM wave as a balanced modulation signal, and can also use other PWM waves (for example, SPWM wave, THIPWM wave, CBPWM wave, etc.) as a balanced modulation signal. It has a wide range of applicable scenarios and good control effects.
  • the method may further include:
  • a half-bus voltage value is obtained based on a DC bus voltage (e.g., a positive DC bus voltage and a negative DC bus voltage), and an output current value of a series connection point of a first capacitor and a second capacitor and an input current value of a series connection point of a first capacitor and a second capacitor are obtained.
  • a DC bus voltage e.g., a positive DC bus voltage and a negative DC bus voltage
  • a balanced modulation signal is generated based on a terminal voltage value of a target capacitor, a half-bus voltage value, an output current value of a series connection point of a first capacitor and a second capacitor, and an input current value of a series connection point of a first capacitor and a second capacitor, and a balanced modulation signal is used to control the conduction or disconnection of a switch tube in at least one balanced bridge arm to adjust the output current of the inductor.
  • control circuit for example, a prediction control circuit and a drive control circuit, or other circuits with prediction control functions and drive control functions
  • the control circuit can generate a balanced modulation signal based on the terminal voltage value of the target capacitor, the half bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor.
  • control circuit for example, a current regulation loop and a drive control circuit, or other circuits with current regulation functions and drive control functions
  • the control circuit can generate a balanced modulation signal based on the half bus voltage value, the output current value of the series connection point of the first capacitor and the second capacitor, and the input current value of the series connection point of the first capacitor and the second capacitor to control the conduction or shutdown of the switch tube in the balancing circuit.
  • the control circuit can generate a signal such as a PWM wave as a balanced modulation signal, or generate a drive pulse signal based on a PWM wave as a balanced modulation signal.
  • the balanced modulation signal can control the output current of the balancing circuit, the output current of the balancing circuit can charge the inductor, and the output current of the inductor when discharging can charge the target capacitor, thereby reducing the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor, and balancing the positive and negative DC bus voltages.
  • the control circuit provided in the present application can use DPWM waves as balanced modulation signals, and can also use other PWM waves (for example, SPWM waves, THIPWM waves, CBPWM waves, etc.) as balanced modulation signals, and can also use drive pulse signals generated based on these PWM waves as balanced modulation signals. It has a wide range of application scenarios and good control effects.
  • the inverter when it is determined that the difference between the terminal voltage of the first capacitor and the terminal voltage of the second capacitor is large, the inverter can adjust the output current of the inductor through the balancing circuit to charge the target capacitor, reduce the terminal voltage difference between the two groups of capacitors in the inverter circuit, balance the positive and negative bus voltages, and improve the stability and power supply efficiency of the inverter.
  • the structure is simple, the method is simple, and the applicability is strong.

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Abstract

本申请提供了一种逆变器及其控制方法，该逆变器适用于供电系统，逆变器包括逆变电路、采集电路、平衡电路和电感；采集电路用于检测直流母线电压以获取第一电容和第二电容的端电压值；平衡电路用于当目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节通过电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值。采用本申请，可在逆变电路中两组电容的端电压差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。

Description

逆变器及其控制方法
本申请要求在2022年12月19日提交中国国家知识产权局、申请号为202211630876.5的中国专利申请的优先权，发明名称为“逆变器及其控制方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电力电子技术领域，尤其涉及一种逆变器及其控制方法。
背景技术
在电力电子技术领域中，逆变器中的逆变电路将电源的直流电能转换为交流电能提供给负载。其中，部分三电平逆变电路(例如，中点钳位式(Neutral Point Clamped,NPC)逆变电路)由于安全性高，效率高，损耗少，谐波小等优点被广泛应用。通常三电平逆变电路(也即，逆变电路)包括两组串联的电容和多个开关桥臂，两组电容的串联点为逆变电路的中点，每一个开关桥臂包括多个开关管。在理想状态下，在逆变电路的一个供电周期内，流入和流出逆变电路中点的电荷量相同，也就是说，逆变电路的两组串联的电容的电压相等。然而，在实际应用中，由于逆变电路的开关桥臂中各开关管的工作状态通常是不对称的(例如，开关管型号不同、损耗不同、负载不对称、或者受开关死区等因素影响)，导致在一个供电周期内，流入和流出逆变电路中点的电荷量并不相同，也就是说，逆变电路中两组串联的电容的充电量(或放电量)并不相等，导致逆变电路的两组串联的电容的电压不相等(也即，逆变电路的中点电压不平衡，或者说，正负直流母线的电压不平衡)，这会使得逆变电路输出电压(或者输出电流)产生畸变，甚至损坏系统内的功率元件。
本申请的发明人在研究和实践的过程中发现，在现有技术中，向逆变电路的开关桥臂中注入共模分量平衡中点电压的方法，由于共模分量的平衡能力有限，且会减小开关桥臂的输出功率，导致这种调制中点电压的方法的适应性差，调节能力差，控制效果差。
发明内容
本申请提供了一种逆变器及其控制方法，可在逆变电路中两组电容的端电压差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
第一方面，本申请提供了一种逆变器，逆变器可包括逆变电路、采集电路、平衡电路和电感，逆变电路可包括至少一个开关桥臂和串联的第一电容和第二电容，平衡电路可包括多个开关管。这里，逆变电路的一端可用于通过正直流母线和负直流母线连接电源，逆变电路的另一端可用于连接负载，第一电容和第二电容串联后与至少一个开关桥臂并联于正直流母线和负直流母线之间，采集电路连接正直流母线、负直流母线、第一电容和第二电容的串联连接点和平衡电路，平衡电路通过电感连接第一电容和第二电容的串联连接点。这里的采集电路可检测直流母线电压，以获取第一电容和第二电容的端电压值。这里的平衡电路可用于在目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节通过电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值，其中，目标电容为第一电容和第二电容中端电压值较小的电容。
在本申请中，电源可以通过正直流母线和负直流母线连接逆变电路，逆变电路可以将电源提供的直流电能转换为交流电能提供给负载。在供电过程中，逆变电路可以通过不同的开关管的导通和关断，分别对逆变电路中的电容(例如，第一电容和第二电容)进行充电和放电，将电源提供的直流电能转换为交流电能传输给负载。可以理解，当逆变器的输出电压(或者输出电流)不对称时(例如，开关管型号不同、损耗不同、负载不对称、或者受开关死区等因素影响)，会导致逆变电路的正直流母线电压和负直流母线电压不平衡，或者说，逆变电路的第一电容的端电压和第二电容的端电压存在较大差值，这会使得逆变电路输出电压(或者输出电流)产生畸变，甚至损坏系统内的功率元件。
在本申请中，采集电路可以获取逆变电路的直流母线电压(例如，正直流母线电压和/或负直流母线电压，以及第一电容和第二电容的串联连接点(或者说逆变电路的中点)的电压)，得到目标电容的端电压。这里，目标电容可以是第一电容和第二电容中端电压值较小的电容。当目标电容的端电压值小于或等 于某一电压阈值(例如，第一电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较大，或者说逆变电路的正负直流母线电压处于不平衡状态，此时，平衡电路需要为电容(例如，目标电容)进行充电。这里，第一电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第一电压阈值可以是一个小于1/2母线电压的电压值，母线电压是正直流母线电压和负直流母线电压的电压差值)，具体可根据应用场景设定。可以理解，这里的第一电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。
可以理解，平衡电路可以通过多种方式确定是否需要对目标电容进行充电，将目标电容的端电压与第一电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否需要对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值大于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值大于或等于一定阈值时，平衡电路都可以确定此时需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第一电压阈值进行比较，确定是否需要为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第一电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较大，或者说确定逆变电路的正负直流母线电压处于不平衡状态之后，平衡电路可以通过电感为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路包括多个开关管，平衡电路可以控制各个开关管的导通或者关断，以调节通过电感为目标电容充电的电流(例如增大为目标电容充电的电流)，进而减小两组电容中目标电容和非目标电容的端电压差值(也即，减小第一电容和第二电容的端电压差值)，换句话说，平衡逆变电路的正直流母线电压和负直流母线电压。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
结合第一方面，在第一种可能的实施方式中，平衡电路还可用于在目标电容的端电压值大于或等于第二电压阈值时，控制多个开关管保持关断，以停止对目标电容充电。这里，当目标电容的端电压值大于或等于某一电压阈值(例如，第二电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较小，或者说逆变电路的正负直流母线电压处于平衡状态，此时，平衡电路不需要为电容(例如，目标电容)进行充电。这里，第二电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第二电压阈值可以是一个小于1/2母线电压且大于或等于第一电压阈值的电压值)，具体可根据应用场景设定。可以理解，这里的第二电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。这里，第二电压阈值可以大于或等于第一电压阈值。当第二电压阈值大于第一电压阈值时，逆变器可以避免在目标电容的端电压并没有稳定大于第一电压阈值时，通过平衡电路反复开始和停止为目标电容充电。也就是说，当第二电压阈值大于第一电压阈值时，逆变器可以在目标电容的端电压稳定(例如，稳定大于第一电压阈值)之后，确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正直流母线电压和负直流母线电压处于平衡状态，再停止通过平衡电路为目标电容充电。
可以理解，平衡电路可以通过多种方式确定是否停止对目标电容进行充电，将目标电容的端电压与第二电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否停止对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值小于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值小于或等于一定阈值时，平衡电路都可以确定此时不需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第二电压阈值进行比较，确定是否需要停止为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第二电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正负直流母线电压处于平衡状态之后，平衡电路可以停止为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路可以控制平衡电路中的各个开关管保持关断，以停止为目标电容充电，节约电能，降低成本。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较小时，通过平衡电路停止为目标电容充电，减少平衡电路消耗的电能，降低成本，同时提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
结合第一方面或第一方面第一种可能的实施方式，在第二种可能的实施方式中，平衡电路可包括控制 电路和至少一个平衡桥臂，一个平衡桥臂可包括两个串联的开关管，控制电路通过至少一个平衡桥臂连接电感，采集电路连接控制电路。这里的采集电路还可基于直流母线电压得到半母线电压值。这里的控制电路可基于目标电容的端电压值和半母线电压值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
在本申请中，平衡电路包括至少一个平衡桥臂，例如，平衡电路可以包括由两个串联的开关管作为一个平衡桥臂的半桥电路，也可以包括由四个开关管作为两个平衡桥臂的全桥电路等。这里，采集电路可以获取逆变电路的正直流母线电压和负直流母线电压，并基于正直流母线电压和负直流母线电压得到半母线电压值(也即，1/2母线电压值)。这里，控制电路(例如，电压调节环路(例如，比例积分调节电路)和驱动控制电路，或其他具有电压调节功能和具有驱动控制功能的电路)可以基于目标电容的端电压值和半母线电压值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成脉冲宽度调制Pulse Width Modulation,PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用不连续脉冲宽度调制(Discontinuous Pulse Width Modulation，DPWM)波作为平衡调制信号，也可以采用其他PWM波(例如，正弦脉冲宽度调制(Sinusoidal Pulse Width Modulation，SPWM)波、三次谐波注入脉冲宽度调制(Third Harmonic Injection Pulse Width Modulation，THIPWM)波、基于载波空间矢量脉冲宽度调制(Carrier Based Space Vector Pulse Width Modulation，CBPWM)波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
结合第一方面第二种可能的实施方式，在第三种可能的实施方式中，采集电路还可用于获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。这里的控制电路还可基于目标电容的端电压值和半母线电压值生成电压调节指令，基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
采用本申请，采集电路可以获取第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流值和第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输入电流值。这里，第一电容和第二电容的串联连接点的输出电流值可以由第一电容和第二电容的串联连接点向逆变电路的各个开关桥臂输出的电流值相加确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点的输入电流值可以由与第一电容和第二电容的串联连接点相连的电感的输出电流确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流和输入电流的参考方向，可以根据目标电容确定。例如，由目标电容流向第一电容和第二电容的串联连接点，为第一电容和第二电容的串联连接点的输出电流的正向，由第一电容和第二电容的串联连接点流向目标电容，为第一电容和第二电容的串联连接点的输入电流的正向。这里，控制电路(例如，电压调节环路或其他具有电压调节功能的电路)可以基于目标电容的端电压值和半母线电压值生成电压调节指令。进而控制电路(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号(例如，PWM波等平衡调制信号)，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，适用场景广泛，控制效果好。
结合第一方面或第一方面任一种可能的实施方式，在第四种可能的实施方式中，平衡电路还可包括控制电路和至少一个平衡桥臂，一个平衡桥臂可包括两个串联的开关管，控制电路通过至少一个平衡桥臂连接电感，采集电路连接控制电路。这里的采集电路还可基于直流母线电压得到半母线电压值，并获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。这里的控制电路还可基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。这里，控制电路(例如，预测控制电路和驱动控 制电路，或其他具有预测控制功能和具有驱动控制功能的电路)可以基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号。进而控制电路(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
结合第一方面第四种可能的实施方式，在第五种可能的实施方式中，逆变器还可包括滤波电路，滤波电路连接逆变电路中的开关桥臂和负载。这里，滤波电路可以是电感和电容组成的LC滤波电路或者LCL滤波电路，或者其他具有滤波功能的电路。这里的滤波电路可以滤除逆变电路的输出电流(或者输出电压)中包含的杂波分量(例如，频率较高的高频分量)，提升供电稳定性。
第二方面，本申请提供了一种供电系统，供电系统可包括电源和逆变器，逆变器可包括逆变电路、采集电路、平衡电路和电感，逆变电路可包括至少一个开关桥臂和串联的第一电容和第二电容，平衡电路可包括多个开关管。这里的逆变电路的一端可用于通过正直流母线和负直流母线连接电源，逆变电路的另一端可用于连接负载，逆变电路的两组电容串联后与至少一个开关桥臂并联于正直流母线和负直流母线之间，采集电路连接逆变电路的正直流母线、负直流母线、第一电容和第二电容的串联连接点和平衡电路，平衡电路通过电感连接第一电容和第二电容的串联连接点。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
结合第二方面，在第一种可能的实施方式中，供电系统还可包括汇流箱，电源通过汇流箱连接逆变器。
结合第二方面第一种可能的实施方式，在第二种可能的实施方式中，供电系统还可包括直流母线，电源通过汇流箱连接直流母线，直流母线连接逆变器。
结合第二方面第二种可能的实施方式，在第三种可能的实施方式中，负载为电网，供电系统还可包括并离网接线装置，逆变器通过并离网接线装置连接电网。
在本申请中，供电系统中功能模块的组成方式多样、灵活，可适应不同的供电环境，提高供电系统的应用场景的多样性，增强供电系统的适应性。
第三方面，本申请提供了一种逆变器的控制方法，该控制方法可适用于逆变器，逆变器可包括逆变电路、采集电路、平衡电路和电感，逆变电路可包括至少一个开关桥臂和串联的第一电容和第二电容，平衡电路可包括多个开关管。这里，逆变电路的一端可用于通过正直流母线和负直流母线连接电源，逆变电路的另一端可用于连接负载，第一电容和第二电容串联后与至少一个开关桥臂并联于正直流母线和负直流母线之间，采集电路连接正直流母线、负直流母线、第一电容和第二电容的串联连接点和平衡电路，平衡电路通过电感连接第一电容和第二电容的串联连接点，方法可包括：
检测直流母线电压，以获取第一电容和第二电容的端电压值。当目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值，其中，目标电容为第一电容和第二电容中端电压值较小的电容。
在本申请中，采集电路可以获取逆变电路的直流母线电压(例如，正直流母线电压和/或负直流母线电压，和第一电容和第二电容的串联连接点(或者说逆变电路的中点)的电压)，以得到目标电容的端电压。这里，目标电容可以是第一电容和第二电容中端电压值较小的电容。当目标电容的端电压值小于或等于某一电压阈值(例如，第一电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较大，或者说逆变电路的正负直流母线电压处于不平衡状态，此时，平衡电路需要为电容(例如，目标电容)进行充电。这里，第一电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第一电压阈值可以是一个小于1/2母线电压的电压值，母线电压是正直流母线电压和负直流母线电压的电压差值)，具体可根据应用场景设定。可以理解，这里的第一电压阈值可以是一个电压值，可以是多个电压值，可以 是多个电压值组成的电压区间。
可以理解，平衡电路可以通过多种方式确定是否需要对目标电容进行充电，将目标电容的端电压与第一电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否需要对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值大于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值大于或等于一定阈值时，平衡电路都可以确定此时需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第一电压阈值进行比较，确定是否需要为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第一电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较大，或者说确定逆变电路的正负直流母线电压处于不平衡状态之后，平衡电路可以通过电感为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路包括多个开关管，平衡电路可以控制各个开关管的导通或者关断，以调节通过电感为目标电容充电的电流(例如增大为目标电容充电的电流)，进而减小两组电容中目标电容和非目标电容的端电压差值(也即，减小第一电容和第二电容的端电压差值)，换句话说，平衡逆变电路的正直流母线电压和负直流母线电压。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
结合第三方面，在第一种可能的实施方式中，在检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
当目标电容的端电压值大于或等于第二电压阈值时，控制多个开关管保持关断，以停止对目标电容充电，第二电压阈值大于或等于第一电压阈值。
这里，当目标电容的端电压值大于或等于某一电压阈值(例如，第二电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较小，或者说逆变电路的正负直流母线电压处于平衡状态，此时，平衡电路不需要为电容(例如，目标电容)进行充电。这里，第二电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第二电压阈值可以是一个小于1/2母线电压且大于或等于第一电压阈值的电压值)，具体可根据应用场景设定。可以理解，这里的第二电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。这里，第二电压阈值可以大于或等于第一电压阈值。当第二电压阈值大于第一电压阈值时，逆变器可以避免在目标电容的端电压并没有稳定大于第一电压阈值时，通过平衡电路反复开始和停止为目标电容充电。也就是说，当第二电压阈值大于第一电压阈值时，逆变器可以在目标电容的端电压稳定(例如，稳定大于第一电压阈值)之后，确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正直流母线电压和负直流母线电压处于平衡状态，再停止通过平衡电路为目标电容充电。
可以理解，平衡电路可以通过多种方式确定是否停止对目标电容进行充电，将目标电容的端电压与第二电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否停止对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值小于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值小于或等于一定阈值时，平衡电路都可以确定此时不需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第二电压阈值进行比较，确定是否需要停止为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第二电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正负直流母线电压处于平衡状态之后，平衡电路可以停止为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路可以控制平衡电路中的各个开关管保持关断，以停止为目标电容充电，节约电能，降低成本。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较小时，通过平衡电路停止为目标电容充电，减少平衡电路消耗的电能，降低成本，同时提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
结合第三方面或第三方面第一种可能的实施方式，在第二种可能的实施方式中，平衡电路可包括控制电路和至少一个平衡桥臂，一个平衡桥臂可包括两个串联的开关管，控制电路通过至少一个平衡桥臂连接电感，采集电路连接控制电路，在检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
基于直流母线电压得到半母线电压值。基于目标电容的端电压值和半母线电压值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
采用本申请，平衡电路包括至少一个平衡桥臂，例如，平衡电路可以包括由两个串联的开关管作为一个平衡桥臂的半桥电路，也可以包括由四个开关管作为两个平衡桥臂的全桥电路等。这里，采集电路可以获取逆变电路的正直流母线电压和负直流母线电压，并基于正直流母线电压和负直流母线电压得到半母线电压值(也即，1/2母线电压值)。这里，控制电路(例如，电压调节环路(例如，比例积分调节电路)和驱动控制电路，或其他具有电压调节功能和具有驱动控制功能的电路)可以基于目标电容的端电压值和半母线电压值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
结合第三方面第二种可能的实施方式，在第三种可能的实施方式中，在基于直流母线电压得到半母线电压值之后，方法还可包括：
获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。基于目标电容的端电压值和半母线电压值生成电压调节指令，基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
采用本申请，采集电路可以获取第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流值和第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输入电流值。这里，第一电容和第二电容的串联连接点的输出电流值可以由第一电容和第二电容的串联连接点向逆变电路的各个开关桥臂输出的电流值相加确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点的输入电流值可以由与第一电容和第二电容的串联连接点相连的电感的输出电流确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流和输入电流的参考方向，可以根据目标电容确定。例如，由目标电容流向第一电容和第二电容的串联连接点，为第一电容和第二电容的串联连接点的输出电流的正向，由第一电容和第二电容的串联连接点流向目标电容，为第一电容和第二电容的串联连接点的输入电流的正向。这里，控制电路(例如，电压调节环路或其他具有电压调节功能的电路)可以基于目标电容的端电压值和半母线电压值生成电压调节指令。进而控制电路(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号(例如，PWM波等平衡调制信号)，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，适用场景广泛，控制效果好。
结合第三方面或第三方面任一种可能的实施方式，在第四种可能的实施方式中，平衡电路还可包括控制电路和至少一个平衡桥臂，一个平衡桥臂可包括两个串联的开关管，控制电路通过至少一个平衡桥臂连接电感，采集电路连接控制电路，在检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
基于直流母线电压得到半母线电压值，并获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
这里，控制电路(例如，预测控制电路和驱动控制电路，或其他具有预测控制功能和具有驱动控制功能的电路)可以基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号。进而控制电路(例如，电流调节 环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
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图1是本申请实施例提供的逆变器的应用场景示意图；
图2是本申请实施例提供的逆变器的一结构示意图；
图3是本申请实施例提供的逆变器的另一结构示意图；
图4是本申请实施例提供的逆变器的另一结构示意图；
图5是本申请实施例提供的逆变器的另一结构示意图；
图6是本申请实施例提供的逆变器的另一结构示意图；
图7是本申请实施例提供的供电系统的结构示意图；
图8是本申请实施例提供的控制方法的一流程示意图；
图9是本申请实施例提供的控制方法的另一流程示意图。
具体实施方式
在电力电子技术领域中，通常利用逆变器中的逆变电路将直流电能转换为交流电能，使得电能可以在电源和负载之间的传输。其中，三电平逆变电路(例如，NPC逆变电路及其扩展电路)由于安全性高，效率高，损耗少，谐波小等优点被广泛应用。通常三电平逆变电路包括两组串联的电容和多个开关桥臂，两组电容的串联点为逆变电路的中点n，每一个开关桥臂包括四个开关管和两个钳位二极管。在工作状态下，逆变电路可以通过不同的开关管的导通和关断，分别对逆变电路中的电容(进行充电和放电，将电源提供的直流电能转换为交流电能传输给负载。可以理解，当逆变器的输出电压(或者输出电流)不对称时(例如，开关管型号不同、损耗不同、负载不对称、或者受开关死区等因素影响)，会导致逆变电路的正直流母线电压和负直流母线电压不平衡，或者说，逆变电路的两组电容的端电压存在较大差值，这会使得逆变电路输出电压(或者输出电流)产生畸变，甚至损坏系统内的功率元件。因此，在逆变电路工作时，需要控制逆变电路中的两组电容的端电压的差值(例如，为逆变电路中的电容充电)，以使得逆变电路的正直流母线电压和负直流母线电压保持平衡。
本申请提供了一种逆变器及其控制方法，可在逆变电路中两组电容的端电压差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
本申请提供的逆变器可以适用于新能源发电领域，传统发电调峰调频领域，重要设备供电领域，新能源汽车领域等多种应用领域，具体可根据实际应用场景确定，在此不做限制。本申请提供的逆变器可适用于储能系统，不间断供电系统，电机驱动系统等不同的供电系统，具体可根据实际应用场景确定，在此不做限制。本申请提供的逆变器可适配于不同的应用场景，比如，对光能供电环境中的逆变电路进行控制的应用场景、风能供电环境中的逆变电路进行控制的应用场景、纯储能供电环境中的逆变电路进行控制的应用场景或者其它应用场景，下面将以对纯储能供电环境中的逆变电路进行控制的应用场景为例进行说明，以下不再赘述。
请参见图1，图1是本申请实施例提供的逆变器的应用场景示意图。在纯储能供电的供电系统中，如图1所示，供电系统包括逆变器1、电源2和负载3，其中，逆变器1包括逆变电路11，电源2可通过逆变电路11与负载3相连。在一些可行的实施方式中，电源2可以通过逆变电路11为负载3供电。可以理解，本申请提供的电源2适用于为在无市电或者市电差的偏远地区的基站设备供电，或者为家用设备(如冰箱、空调等等)供电等为多种类型的用电设备供电的应用场景中，具体可根据实际应用场景确定，在此 不做限制。进一步可以理解，图2中的负载3可以包括电网，这里的电网可以包括传输线、电力中转站点、通信基站或者家用设备等用电设备或电力传输设备。这里的负载3还可以包括电机、整流设备等在运行(供电或者用电)过程中电压和电流为非线性关系的负载(用电装置或者电力传输装置)。在一些可行的实施方式中，逆变电路11可以是三电平逆变电路(例如，NPC逆变电路)，逆变电路11可包括两组电容(例如，第一电容C1和第二电容C2)和至少一个开关桥臂。这里，一组电容可以是一个电容，也可以是多个电容集成组成的电容。在供电过程中，逆变电路11可以通过开关桥臂中不同的开关管的导通和关断，分别对两组电容进行充电和放电，将电源提供的直流电能转换为交流电能传输给负载。可以理解，当逆变器1的输出电压(或者输出电流)不对称时(例如，开关管型号不同、损耗不同、负载不对称、或者受开关死区等因素影响)，在一个供电周期内，流入和流出第一电容C1和第二电容C2的串联连接点(或者说，逆变电路11的中点)的电荷量并不相同。也就是说，逆变电路11中两组电容的充电量(或放电量)并不相等，导致逆变电路11的两组电容的电压不相等(也即，逆变电路11的正直流母线电压和负直流母线电压不平衡，或者说，逆变电路11的中点电压不平衡)，这会使得逆变器1的输出电压(或者输出电流)产生畸变，甚至损坏系统内的功率元件。因此，在逆变电路工作时，需要控制逆变电路11中的两组电容的端电压的差值，以使得逆变电路11的正直流母线电压和负直流母线电压保持平衡。这里，逆变器1还可以包括采集电路12、平衡电路13和电感。这里，采集电路12可以获取逆变电路11的直流母线电压，例如，正直流母线电压或负直流母线电压和第一电容C1和第二电容C2的串联连接点(或者说逆变电路11的中点)的电压，以得到目标电容(第一电容C1或第二电容C2)的端电压。当目标电容的端电压值小于或等于某一电压阈值(例如，第一电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较大，或者说逆变电路的正负直流母线电压处于不平衡状态，此时，平衡电路可以调节通过电感为目标电容充电的电流，以减小两组电容的端电压差值，进而使得逆变电路11的正直流母线电压和负直流母线电压保持平衡。这里，逆变器1可在逆变电路11中两组电容的端电压差值较大时，通过平衡电路13调节电感的输出电流为目标电容进行充电，减小逆变电路11中两组电容的端电压差值，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
下面将结合图2至图9对本申请提供的逆变器及其工作原理进行示例说明。
请参见图2，图2是本申请实施例提供的逆变器的一结构示意图。如图2所示，供电系统包括电源、逆变器和负载，逆变器包括逆变电路101、采集电路102、平衡电路103和电感。其中，逆变电路101可包括至少一个开关桥臂和串联的第一电容C1和第二电容C2，平衡电路103可包括多个开关管。这里，逆变电路101可以是多电平逆变电路或者多电平逆变电路的拓扑电路，图2中所示的逆变电路101只是其中一种三电平逆变电路，包括串联的第一电容C1和第二电容C2和三个开关桥臂，也即，开关管Ta1、开关管Ta2、开关管Ta3和开关管Ta4组成的一个开关桥臂,开关管Tb1、开关管Tb2、开关管Tb3和开关管Tb4组成的一个开关桥臂,以及开关管Tc1、开关管Tc2、开关管Tc3和开关管Tc4组成的一个开关桥臂。这里，逆变电路101的一端可用于通过正直流母线和负直流母线连接电源，逆变电路101的另一端可用于连接负载，第一电容C1和第二电容C2串联后可与至少一个开关桥臂并联于正直流母线和负直流母线之间，采集电路102可连接正直流母线、负直流母线、第一电容C1和第二电容C2的串联连接点和平衡电路103(如图2中虚线所示)，平衡电路103可通过电感连接第一电容C1和第二电容C2的串联连接点。这里的采集电路102可检测直流母线电压(例如正直流母线电压、负直流母线电压和第一电容C1和第二电容C2的串联连接点的电压)，以得到目标电容的端电压值，其中，目标电容为第一电容C1和第二电容C2中端电压值较小的电容。这里的平衡电路103可用于在目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节通过电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值。
可以理解，采集电路102可以获取逆变电路101的直流母线电压(例如，正直流母线电压和/或负直流母线电压)和第一电容C1和第二电容C2的串联连接点(或者说逆变电路101的中点)的电压，得到目标电容的端电压。这里，目标电容可以是第一电容C1和第二电容C2中端电压值较小的电容。当目标电容的端电压值小于或等于某一电压阈值(例如，第一电压阈值)时，可以认为第一电容C1的端电压和第二电容C2的端电压的差值较大，或者说逆变电路101的正负直流母线电压处于不平衡状态，此时，平衡电路103需要为电容(例如，目标电容)进行充电。这里，第一电压阈值可以基于逆变电路101中电容(第一电容C1或第二电容C2)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第一电压阈值可以是一个小于1/2母线电压的电压值，母线电压 是正直流母线电压和负直流母线电压的电压差值)，具体可根据应用场景设定。可以理解，这里的第一电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。
在一些可行的实施方式中，平衡电路103可以通过多种方式确定是否需要对目标电容进行充电，将目标电容的端电压与第一电压阈值进行比较只是其中一种。平衡电路103也可以通过其他方式确定是否需要对逆变电路101的电容进行充电，比如当第一电容C1的端电压和第二电容C2的端电压的差值大于或等于一定阈值时，或者当第一电容C1(或第二电容C2)的端电压值与1/2母线电压的电压差值大于或等于一定阈值时，平衡电路103都可以确定此时需要对逆变电路101的电容进行充电。本申请仅以平衡电路103将目标电容的端电压和第一电压阈值进行比较，确定是否需要为逆变电路101的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路103(例如，通过将目标电容的端电压和第一电压阈值进行比较)确定第一电容C1的端电压和第二电容C2的端电压的差值较大，或者说确定逆变电路101的正负直流母线电压处于不平衡状态之后，平衡电路103可以通过电感为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路103包括多个开关管，平衡电路103可以控制各个开关管的导通或者关断，以调节通过电感为目标电容充电的电流(例如增大为目标电容充电的电流)，进而减小两组电容中目标电容和非目标电容的端电压差值(也即，减小第一电容C1和第二电容C2的端电压差值)，换句话说，平衡逆变电路101的正直流母线电压和负直流母线电压。
采用本申请，逆变器可以在确定第一电容C1的端电压和第二电容C2的端电压的差值较大时，通过平衡电路103调节电感的输出电流为目标电容进行充电，减小逆变电路101中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，平衡电路103还可用于在目标电容的端电压值大于或等于第二电压阈值时，控制多个开关管保持关断，以停止对目标电容充电。这里，当目标电容的端电压值大于或等于某一电压阈值(例如，第二电压阈值)时，可以认为第一电容C1的端电压和第二电容C2的端电压的差值较小，或者说逆变电路101的正负直流母线电压处于平衡状态，此时，平衡电路103不需要为电容(例如，目标电容)进行充电。这里，第二电压阈值可以基于逆变电路101中电容(第一电容C1或第二电容C2)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第二电压阈值可以是一个小于1/2母线电压且大于或等于第一电压阈值的电压值)，具体可根据应用场景设定。可以理解，这里的第二电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。这里，第二电压阈值可以大于或等于第一电压阈值。当第二电压阈值大于第一电压阈值时，逆变器可以避免在目标电容的端电压并没有稳定大于第一电压阈值时，通过平衡电路103反复开始和停止为目标电容充电。也就是说，当第二电压阈值大于第一电压阈值时，逆变器可以在目标电容的端电压稳定(例如，稳定大于第一电压阈值)之后，确定第一电容C1的端电压和第二电容C2的端电压的差值较小，或者说确定逆变电路101的正直流母线电压和负直流母线电压处于平衡状态，再停止通过平衡电路103为目标电容充电。
可以理解，平衡电路103可以通过多种方式确定是否停止对目标电容进行充电，将目标电容的端电压与第二电压阈值进行比较只是其中一种。平衡电路103也可以通过其他方式确定是否停止对逆变电路101的电容进行充电，比如当第一电容C1的端电压和第二电容C2的端电压的差值小于或等于一定阈值时，或者当第一电容C1(或第二电容C2)的端电压值与1/2母线电压的电压差值小于或等于一定阈值时，平衡电路103都可以确定此时不需要对逆变电路101的电容进行充电。本申请仅以平衡电路103将目标电容的端电压和第二电压阈值进行比较，确定是否需要停止为逆变电路101的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路103(例如，通过将目标电容的端电压和第二电压阈值进行比较)确定第一电容C1的端电压和第二电容C2的端电压的差值较小，或者说确定逆变电路101的正负直流母线电压处于平衡状态之后，平衡电路103可以停止为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路103可以控制平衡电路103中的各个开关管保持关断，以停止为目标电容充电，节约电能，降低成本。
采用本申请，逆变器可以在确定第一电容C1的端电压和第二电容C2的端电压的差值较小时，通过平衡电路103停止为目标电容充电，减少平衡电路103消耗的电能，降低成本，同时提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，逆变电路可以是其他结构的多电平逆变电路及其拓扑电路。请参见图3， 图3是本申请实施例提供的逆变器的另一结构示意图。如图3所示，逆变电路201可以是另一种结构的三电平逆变电路，这里的逆变电路201可包括串联的第一电容C1和第二电容C2和三个开关桥臂，也即，开关管Ta1、开关管Ta2、开关管Ta3、开关管Ta4和两个二极管组成的一个开关桥臂,开关管Tb1、开关管Tb2、开关管Tb3、开关管Tb4和两个二级管组成的一个开关桥臂,以及开关管Tc1、开关管Tc2、开关管Tc3、开关管Tc4和两个二极管组成的一个开关桥臂。图3中的采集电路202和平衡电路203与图2中采集电路102和平衡电路103的连接关系和工作原理相同，在此不再赘述。
本申请提供的逆变器，可以适用于任意包含两组串联电容和开关桥臂的逆变电路及其拓扑结构。采用本申请，逆变器都可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，平衡电路可包括控制电路和至少一个平衡桥臂。请参见图4，图4是本申请实施例提供的逆变器的另一结构示意图。如图4所示，平衡电路可包括控制电路3031和至少一个平衡桥臂3032，平衡桥臂3032可包括两个串联于正负直流母线之间的开关管，控制电路3031可通过平衡桥臂3032连接电感，采集电路302可连接控制电路3031。这里的采集电路302还可基于正直流母线电压和负直流母线电压得到半母线电压值。这里的控制电路3031可基于目标电容的端电压值和半母线电压值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂3032中开关管的导通或关断，以调节电感的输出电流。这里，平衡电路包括至少一个平衡桥臂3032，如图4所示，平衡电路中的平衡桥臂3032可以是包括两个串联的开关管(例如，开关管T1和开关管T2)的半桥电路。
在一些可行的实施方式中，采集电路302可以获取逆变电路301的正直流母线电压和负直流母线电压，并基于正直流母线电压和负直流母线电压得到半母线电压值(也即，1/2母线电压值)。这里，控制电路3031(例如，电压调节环路(例如，比例积分调节电路)和驱动控制电路3031，或其他具有电压调节功能和具有驱动控制功能的电路)可以基于目标电容的端电压值和半母线电压值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路3031可以生成脉冲宽度调制Pulse Width Modulation,PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容C1的端电压和第二电容C2的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路3031可以采用不连续脉冲宽度调制(Discontinuous Pulse Width Modulation，DPWM)波作为平衡调制信号，也可以采用其他PWM波(例如，正弦脉冲宽度调制(Sinusoidal Pulse Width Modulation，SPWM)波、三次谐波注入脉冲宽度调制(Third Harmonic Injection Pulse Width Modulation，THIPWM)波、基于载波空间矢量脉冲宽度调制(Carrier Based Space Vector Pulse Width Modulation，CBPWM)波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
在一些可行的实施方式中，采集电路302还可用于获取第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值。这里的控制电路3031还可基于目标电容的端电压值和半母线电压值生成电压调节指令，基于电压调节指令、第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂3032中开关管的导通或关断，以调节电感的输出电流。这里，采集电路302可以获取第一电容C1和第二电容C2的串联连接点(或者说逆变电路301的中点)的输出电流值和第一电容C1和第二电容C2的串联连接点(或者说逆变电路301的中点)的输入电流值。这里，第一电容C1和第二电容C2的串联连接点的输出电流值可以由第一电容C1和第二电容C2的串联连接点向逆变电路301的各个开关桥臂输出的电流值相加确定，也可以通过其他方式确定。这里，第一电容C1和第二电容C2的串联连接点的输入电流值可以由与第一电容C1和第二电容C2的串联连接点相连的电感的输出电流确定，也可以通过其他方式确定。这里，第一电容C1和第二电容C2的串联连接点(或者说逆变电路301的中点)的输出电流和输入电流的参考方向，可以根据目标电容确定。例如，由目标电容流向第一电容C1和第二电容C2的串联连接点，为第一电容C1和第二电容C2的串联连接点的输出电流的正向，由第一电容C1和第二电容C2的串联连接点流向目标电容，为第一电容C1和第二电容C2的串联连接点的输入电流的正向。这里，控制电路3031(例如，电压调节环路或其他具有电压调节功能的电路)可以基于目标 电容的端电压值和半母线电压值生成电压调节指令。进而控制电路3031(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于电压调节指令、第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值生成平衡调制信号(例如，PWM波等平衡调制信号)，并通过平衡调制信号控制至少一个平衡桥臂3032中开关管的导通或关断，以调节电感的输出电流。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容C1的端电压和第二电容C2的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路3031可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，适用场景广泛，控制效果好。
在一些可行的实施方式中，采集电路302还可基于正直流母线电压和负直流母线电压得到半母线电压值，并获取第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值。这里的控制电路3031还可基于目标电容的端电压值、半母线电压值、第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂3032中开关管的导通或关断，以调节电感的输出电流。这里，控制电路3031(例如，预测控制电路和驱动控制电路，或其他具有预测控制功能和具有驱动控制功能的电路)可以基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号。这里的预测控制电路是一种可以模拟逆变器结构的电路，预测控制可以基于逆变器的输入参数(例如，目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和输入电流值)对逆变器的运行状态进行预测，从而得到可以使得逆变器的中点电压保持平衡的平衡调制信号。进而控制电路3031(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于半母线电压值、第一电容C1和第二电容C2的串联连接点的输出电流值和第一电容C1和第二电容C2的串联连接点的输入电流值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路3031可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容C1的端电压和第二电容C2的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路3031可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
在一些可行的实施方式中，平衡电路可以包括多个平衡桥臂。具体请参见图5，图5是本申请实施例提供的逆变器的另一结构示意图。如图5所示，平衡电路中的平衡桥臂4032可以是由四个开关管(例如，开关管T1、开关管T2、开关管T3和开关管T4)组成两个平衡桥臂的全桥电路，该全桥电路可以连接于正负直流母线之间。可以理解，图5中逆变电路401、采集电路402和平衡电路中的控制电路4031与前述图4中逆变电路301、采集电路302和平衡电路中的控制电路3031的连接方式与工作原理相同，在此不再赘述。
可以理解，本申请提供的逆变器，可以适用于任意可以调节电感的输出电流的平衡电路。采用本申请，逆变器都可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，逆变器还可包括滤波电路。具体请参见图6，图6是本申请实施例提供的逆变器的另一结构示意图。如图6所示，滤波电路504可以连接逆变电路501中的开关桥臂和负载。可以理解，图6中逆变电路501、采集电路502和平衡电路中的控制电路5031和平衡桥臂5032与前述图5中逆变电路401、采集电路402和平衡电路中的控制电路4031和平衡桥臂4032的连接方式与工作原理相同，在此不再赘述。这里，滤波电路504可以是电感和电容组成的LC滤波电路或者LCL滤波电路(图中未示出)，或者其他具有滤波功能的电路。这里的滤波电路504可以滤除逆变电路501的输出电流(或者输出电压)中包含的杂波分量(例如，频率较高的高频分量)，提升供电稳定性。
本申请还提供了一种供电系统，具体请一并参见图7，图7是本申请实施例提供的供电系统的结构示 意图。如图7所示，供电系统可包括电源和逆变器，这里的逆变器适用于上述图1至图6所示的逆变器，图7中仅以图2所示的逆变器为例作为说明。可以理解，图7中逆变电路601、采集电路602和平衡电路603与前述图2中逆变电路101、采集电路102和平衡电路103的连接方式与工作原理相同，在此不再赘述。在图7所示的供电系统中，还可以包括汇流箱604，电源可以通过汇流箱604连接逆变器。供电系统中还可以包括直流母线，汇流箱604可通过直流母线和逆变器连接负载。这里，直流母线上可包括一个母线电容C或者相互串联的多个母线电容，可用于储能。逆变装置可将电源输出并存储至母线电容两端的电能进行转换，并输出相应的电流和电压以维持电网工作。请进一步参见图7，这里的负载可以是电网，供电系统中还可以包括并离网接线装置605，逆变器可通过并离网接线装置605为电网中的传输线、电力中转站点、蓄电池、通信基站或者家用设备等用电设备或电力传输设备进行供电。
在本申请中，逆变器和供电系统中功能模块的组成方式多样、灵活，可适应不同的供电环境，提高供电系统的应用场景的多样性，增强供电系统的适应性。同时，上述图1至图7所示的任一供电系统或者逆变器，都可以在逆变电路中两组电容的端电压差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。为方便描述，下面将以图2所示的逆变器的结构对本申请实施例提供的并网控制方法进行示例说明。
请参见图8，图8是本申请提供的控制方法的一流程示意图。本申请提供的控制方法适用于逆变器，包括但不限于上述图1至图7所示的任一供电系统或者供电系统中的逆变器。如图8所示，本申请提供的控制方法包括如下步骤：
S701：检测直流母线电压，以获取第一电容和第二电容的端电压值。
S702：当目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值。
在本申请提供的实施方式中，采集电路可以获取逆变电路的直流母线电压(例如，正直流母线电压和/或负直流母线电压，和第一电容和第二电容的串联连接点(或者说逆变电路的中点)的电压)，以得到目标电容的端电压。这里，目标电容可以是第一电容和第二电容中端电压值较小的电容。当目标电容的端电压值小于或等于某一电压阈值(例如，第一电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较大，或者说逆变电路的正负直流母线电压处于不平衡状态，此时，平衡电路需要为电容(例如，目标电容)进行充电。这里，第一电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第一电压阈值可以是一个小于1/2母线电压的电压值，母线电压是正直流母线电压和负直流母线电压的电压差值)，具体可根据应用场景设定。可以理解，这里的第一电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。
可以理解，平衡电路可以通过多种方式确定是否需要对目标电容进行充电，将目标电容的端电压与第一电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否需要对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值大于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值大于或等于一定阈值时，平衡电路都可以确定此时需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第一电压阈值进行比较，确定是否需要为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第一电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较大，或者说确定逆变电路的正负直流母线电压处于不平衡状态之后，平衡电路可以通过电感为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路包括多个开关管，平衡电路可以控制各个开关管的导通或者关断，以调节通过电感为目标电容充电的电流(例如增大为目标电容充电的电流)，进而减小两组电容中目标电容和非目标电容的端电压差值(也即，减小第一电容和第二电容的端电压差值)，换句话说，平衡逆变电路的正直流母线电压和负直流母线电压。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，请一并参见图9，图9是本申请提供的控制方法的另一流程示意图。如图9所示，在前述步骤S701中的检测直流母线电压，以获取第一电容和第二电容的端电压值之后，平衡电路(或者逆变器)可以基于目标电容的端电压值停止对目标电容进行充电，该控制方法可包括如下步骤：
S801：检测直流母线电压，以获取第一电容和第二电容的端电压值。
S802：当目标电容的端电压值小于或等于第一电压阈值时，控制多个开关管的导通或关断，以调节电感为目标电容充电的电流，以减小两组电容中目标电容和非目标电容的端电压差值。
S803：当目标电容的端电压值大于或等于第二电压阈值时，控制多个开关管保持关断。
这里，当目标电容的端电压值大于或等于某一电压阈值(例如，第二电压阈值)时，可以认为第一电容的端电压和第二电容的端电压的差值较小，或者说逆变电路的正负直流母线电压处于平衡状态，此时，平衡电路不需要为电容(例如，目标电容)进行充电。这里，第二电压阈值可以基于逆变电路中电容(第一电容或第二电容)的额定端电压值确定，可以基于逆变器通过获取、采集、接收、检测或者存储等方式得到的电压阈值进行确定(例如，第二电压阈值可以是一个小于1/2母线电压且大于或等于第一电压阈值的电压值)，具体可根据应用场景设定。可以理解，这里的第二电压阈值可以是一个电压值，可以是多个电压值，可以是多个电压值组成的电压区间。这里，第二电压阈值可以大于或等于第一电压阈值。当第二电压阈值大于第一电压阈值时，逆变器可以避免在目标电容的端电压并没有稳定大于第一电压阈值时，通过平衡电路反复开始和停止为目标电容充电。也就是说，当第二电压阈值大于第一电压阈值时，逆变器可以在目标电容的端电压稳定(例如，稳定大于第一电压阈值)之后，确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正直流母线电压和负直流母线电压处于平衡状态，再停止通过平衡电路为目标电容充电。
可以理解，平衡电路可以通过多种方式确定是否停止对目标电容进行充电，将目标电容的端电压与第二电压阈值进行比较只是其中一种。平衡电路也可以通过其他方式确定是否停止对逆变电路的电容进行充电，比如当第一电容的端电压和第二电容的端电压的差值小于或等于一定阈值时，或者当第一电容(或第二电容)的端电压值与1/2母线电压的电压差值小于或等于一定阈值时，平衡电路都可以确定此时不需要对逆变电路的电容进行充电。本申请仅以平衡电路将目标电容的端电压和第二电压阈值进行比较，确定是否需要停止为逆变电路的电容充电为例进行介绍，其他比较方法可以基于具体应用场景进行设定，也属于本发明的涵盖范围。这里，在平衡电路(例如，通过将目标电容的端电压和第二电压阈值进行比较)确定第一电容的端电压和第二电容的端电压的差值较小，或者说确定逆变电路的正负直流母线电压处于平衡状态之后，平衡电路可以停止为目标电容进行充电，以提高目标电容的端电压值。这里，平衡电路可以控制平衡电路中的各个开关管保持关断，以停止为目标电容充电，节约电能，降低成本。
采用本申请，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较小时，通过平衡电路停止为目标电容充电，减少平衡电路消耗的电能，降低成本，同时提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
在一些可行的实施方式中，在执行前述步骤S701或者S801中检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
基于直流母线电压得到半母线电压值。基于目标电容的端电压值和半母线电压值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
采用本申请，平衡电路包括至少一个平衡桥臂，例如，平衡电路可以包括由两个串联的开关管作为一个平衡桥臂的半桥电路，也可以包括由四个开关管作为两个平衡桥臂的全桥电路等。这里，采集电路可以获取逆变电路的正直流母线电压和负直流母线电压，并基于正直流母线电压和负直流母线电压得到半母线电压值(也即，1/2母线电压值)。这里，控制电路(例如，电压调节环路(例如，比例积分调节电路)和驱动控制电路，或其他具有电压调节功能和具有驱动控制功能的电路)可以基于目标电容的端电压值和半母线电压值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。 可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
在一些可行的实施方式中，在执行前述步骤S701或者S801中检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。基于目标电容的端电压值和半母线电压值生成电压调节指令，基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
采用本申请，采集电路可以获取第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流值和第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输入电流值。这里，第一电容和第二电容的串联连接点的输出电流值可以由第一电容和第二电容的串联连接点向逆变电路的各个开关桥臂输出的电流值相加确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点的输入电流值可以由与第一电容和第二电容的串联连接点相连的电感的输出电流确定，也可以通过其他方式确定。这里，第一电容和第二电容的串联连接点(或者说逆变电路的中点)的输出电流和输入电流的参考方向，可以根据目标电容确定。例如，由目标电容流向第一电容和第二电容的串联连接点，为第一电容和第二电容的串联连接点的输出电流的正向，由第一电容和第二电容的串联连接点流向目标电容，为第一电容和第二电容的串联连接点的输入电流的正向。这里，控制电路(例如，电压调节环路或其他具有电压调节功能的电路)可以基于目标电容的端电压值和半母线电压值生成电压调节指令。进而控制电路(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于电压调节指令、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号(例如，PWM波等平衡调制信号)，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，适用场景广泛，控制效果好。
在一些可行的实施方式中，在执行前述步骤S701或者S801中检测直流母线电压，以获取第一电容和第二电容的端电压值之后，方法还可包括：
基于直流母线电压(例如，正直流母线电压和负直流母线电压)得到半母线电压值，并获取第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值。基于目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，并通过平衡调制信号控制至少一个平衡桥臂中开关管的导通或关断，以调节电感的输出电流。
这里，控制电路(例如，预测控制电路和驱动控制电路，或其他具有预测控制功能和具有驱动控制功能的电路)可以目标电容的端电压值、半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号。进而控制电路(例如，电流调节环路和驱动控制电路，或其他具有电流调节功能和具有驱动控制功能的电路)可以基于半母线电压值、第一电容和第二电容的串联连接点的输出电流值和第一电容和第二电容的串联连接点的输入电流值生成平衡调制信号，控制平衡电路中开关管的导通或者关断。例如，控制电路可以生成PWM波等信号作为平衡调制信号，或者基于PWM波生成驱动脉冲信号作为平衡调制信号。这里，平衡调制信号可以控制平衡电路的输出电流，平衡电路的输出电流可以为电感充电，电感在放电时的输出电流可以为目标电容进行充电，进而可以减小第一电容的端电压和第二电容的端电压之间的差值，平衡正负直流母线电压。可以理解，本申请提供的控制电路可以采用DPWM波作为平衡调制信号，也可以采用其他PWM波(例如，SPWM波、THIPWM波、CBPWM波等)作为平衡调制信号，还可以采用基于这些PWM波生成的驱动脉冲信号作为平衡调制信号，适用场景广泛，控制效果好。
在本申请中，逆变器可以在确定第一电容的端电压和第二电容的端电压的差值较大时，通过平衡电路调节电感的输出电流为目标电容进行充电，减小逆变电路中两组电容的端电压差值，平衡正负母线电压，提高逆变器的稳定性和供电效率，结构简单，方法简便，适用性强。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (11)

  1. 一种逆变器，其特征在于，所述逆变器包括逆变电路、采集电路、平衡电路和电感，所述逆变电路包括至少一个开关桥臂和串联的第一电容和第二电容，所述平衡电路包括多个开关管；
    所述逆变电路的一端用于通过正直流母线和负直流母线连接电源，所述逆变电路的另一端用于连接负载，所述第一电容和所述第二电容串联后与所述至少一个开关桥臂并联于所述正直流母线和所述负直流母线之间，所述采集电路连接所述正直流母线、所述负直流母线、所述第一电容和所述第二电容的串联连接点和所述平衡电路，所述平衡电路通过所述电感连接所述第一电容和所述第二电容的串联连接点；
    所述采集电路用于检测直流母线电压，以获取所述第一电容和所述第二电容的端电压值；
    所述平衡电路用于在目标电容的端电压值小于或等于第一电压阈值时，控制所述多个开关管的导通或关断，以调节通过所述电感为所述目标电容充电的电流，以减小所述两组电容中所述目标电容和非目标电容的端电压差值，所述目标电容为所述第一电容和所述第二电容中端电压值较小的电容。
  2. 根据权利要求1所述的逆变器，其特征在于，所述平衡电路还用于在所述目标电容的端电压值大于或等于第二电压阈值时，控制所述多个开关管保持关断，以停止对所述目标电容充电，所述第二电压阈值大于或等于所述第一电压阈值。
  3. 根据权利要求1或2所述的逆变器，其特征在于，所述平衡电路包括控制电路和至少一个平衡桥臂，一个所述平衡桥臂包括两个串联的开关管，所述控制电路通过所述至少一个平衡桥臂连接所述电感，所述采集电路连接所述控制电路；
    所述采集电路还用于基于所述直流母线电压得到半母线电压值；
    所述控制电路用于基于所述目标电容的端电压值和所述半母线电压值生成平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
  4. 根据权利要求3所述的逆变器，其特征在于，所述采集电路还用于获取所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值；
    所述控制电路还用于基于所述目标电容的端电压值和所述半母线电压值生成电压调节指令，基于所述电压调节指令、所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值生成所述平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
  5. 根据权利要求1-4任一项所述的逆变器，其特征在于，所述平衡电路还包括控制电路和至少一个平衡桥臂，一个所述平衡桥臂包括两个串联的开关管，所述控制电路通过所述至少一个平衡桥臂连接所述电感，所述采集电路连接所述控制电路；
    所述采集电路还用于基于所述直流母线电压得到半母线电压值，并获取所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值；
    所述控制电路还用于基于所述目标电容的端电压值、所述半母线电压值、所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值生成平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
  6. 根据权利要求5所述的逆变器，其特征在于，所述逆变器还包括滤波电路，所述滤波电路连接所述逆变电路中的开关桥臂和所述负载。
  7. 一种逆变器的控制方法，其特征在于，所述控制方法适用于逆变器，所述逆变器包括逆变电路、采集电路、平衡电路和电感，所述逆变电路包括至少一个开关桥臂和串联的第一电容和第二电容，所述平衡电路包括多个开关管；
    所述逆变电路的一端用于通过正直流母线和负直流母线连接电源，所述逆变电路的另一端用于连接负载，所述第一电容和所述第二电容串联后与所述至少一个开关桥臂并联于所述正直流母线和所述负直流母线之间，所述采集电路连接所述正直流母线、所述负直流母线、所述第一电容和所述第二电容的串联连接 点和所述平衡电路，所述平衡电路通过所述电感连接所述第一电容和所述第二电容的串联连接点，所述方法包括：
    检测直流母线电压，以获取所述第一电容和所述第二电容的端电压值；
    当所述目标电容的端电压值小于或等于第一电压阈值时，控制所述多个开关管的导通或关断，以调节所述电感为所述目标电容充电的电流，以减小所述两组电容中所述目标电容和非目标电容的端电压差值，所述目标电容为所述第一电容和所述第二电容中端电压值较小的电容。
  8. 根据权利要求7所述的控制方法，其特征在于，在所述检测直流母线电压，以获取所述第一电容和所述第二电容的端电压值之后，所述方法还包括：
    当所述目标电容的端电压值大于或等于第二电压阈值时，控制所述多个开关管保持关断，以停止对所述目标电容充电，所述第二电压阈值大于或等于所述第一电压阈值。
  9. 根据权利要求7或8所述的控制方法，其特征在于，所述平衡电路包括控制电路和至少一个平衡桥臂，一个所述平衡桥臂包括两个串联的开关管，所述控制电路通过所述至少一个平衡桥臂连接所述电感，所述采集电路连接所述控制电路，在所述检测直流母线电压，以获取所述第一电容和所述第二电容的端电压值之后，所述方法还包括：
    基于所述直流母线电压得到半母线电压值；
    基于所述目标电容的端电压值和所述半母线电压值生成平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
  10. 根据权利要求9所述的控制方法，其特征在于，在基于所述直流母线电压得到半母线电压值之后，所述方法还包括：
    获取所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值；
    基于所述目标电容的端电压值和所述半母线电压值生成所述电压调节指令，基于所述电压调节指令、所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值生成所述平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
  11. 根据权利要求7-10任一项所述的控制方法，其特征在于，所述平衡电路还包括控制电路和至少一个平衡桥臂，一个所述平衡桥臂包括两个串联的开关管，所述控制电路通过所述至少一个平衡桥臂连接所述电感，所述采集电路连接所述控制电路，在所述检测直流母线电压，以获取所述第一电容和所述第二电容的端电压值之后，所述方法还包括：
    基于所述直流母线电压得到半母线电压值，并获取所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值；
    基于所述目标电容的端电压值、所述半母线电压值、所述第一电容和所述第二电容的串联连接点的输出电流值和所述第一电容和所述第二电容的串联连接点的输入电流值生成平衡调制信号，并通过所述平衡调制信号控制所述至少一个平衡桥臂中开关管的导通或关断，以调节所述电感的输出电流。
PCT/CN2023/131924 2022-12-19 2023-11-16 逆变器及其控制方法 WO2024131392A1 (zh)

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