JP2017153184A - Power conversion device and power conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device and a power conversion method capable of inexpensively and accurately detecting currents flowing from a power conversion device to a storage.SOLUTION: A power conversion device 1 comprises: a power conversion circuit 201; a first measurement circuit 204; a second measurement circuit 206; and a control circuit 202 for, when a difference between a voltage of a first power source 4 and a voltage of a second power source 5 is equal to or more than a predetermined value, obtaining estimated currents flowing to a second resistance element R2 by using first currents obtained on the basis of a measurement result of the first measurement circuit 204, and for obtaining a correction coefficient by using second currents obtained on the basis of a measurement result of the second measurement circuit 206 and the estimated currents, and for, when the difference is less than the predetermined value, correcting the second currents by using the correction coefficient.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power conversion device and a power conversion method.

  In recent years, vehicles equipped with a regenerative energy storage system that stores regenerative energy in a storage when decelerating have become widespread. For example, such a regenerative energy storage system includes an alternator, a battery, a power conversion device, a storage, a starter, and the like. A power conversion device used in this regenerative energy storage system includes a bidirectional buck-boost type DC-DC converter including a power conversion circuit (full bridge circuit: H bridge circuit) connected between a battery and a storage. It is.

  There exists patent document 1 as a related technique.

JP 2005-229756 A

  However, when charging the storage from the battery side via the power conversion device using the power conversion device, the current flowing from the power conversion device to the storage is accurately detected, and based on the detected current It is required to control the current. Therefore, conventionally, a current detection method using a current sensor has been employed in order to detect current with high accuracy.

  In the current detection method (A) using a current sensor, a current sensor using a Hall element is provided on a wiring connecting the power conversion device and the storage to detect the current. However, the current detection method (A) using the current sensor can detect the current with high accuracy, but there is a problem that the current sensor using the Hall element is expensive. Therefore, a current detection method (B) using a shunt resistor has been proposed as a current detection method that is cheaper than the current detection method (A) using a current sensor.

  In the current detection method (B), a shunt resistor is connected between the power conversion device and the storage, the voltage at both ends of the shunt resistor is amplified using an amplifier circuit such as an operational amplifier, and based on the amplified voltage. Detect current. Thus, in the current detection method (B), since inexpensive parts such as a shunt resistor and an operational amplifier are used, current detection can be performed at a lower cost than the current detection method (A) using the current sensor. However, when the current detection method (B) is used, there is a problem that the voltage variation is large because the shunt resistor is connected between the power conversion device and the storage, and it depends on the characteristics of the amplifier circuit. Therefore, another current detection method (C) using a shunt resistor has been proposed.

  According to the current detection method (C), the shunt resistor is connected between the ground side terminal of the switch element of the lower arm of the power conversion circuit provided in the power converter and the ground, and the voltage across the shunt resistor is Amplification is performed using an amplifier circuit such as an operational amplifier, and the current flowing from the power converter to the storage is estimated using the amplified voltage. Then, in the current detection method (C), since one terminal of the shunt resistor is connected to the ground, the terminals at both ends of the shunt resistor are connected to the power converter and the storage as in the current detection method (B). Since the voltage fluctuation can be made smaller than the case, the current detection accuracy can be improved as compared with the current detection method (B).

  However, in the current detection method (C), a time during which no current flows through the shunt resistor is generated depending on the switching timing of the switch element. Therefore, the power conversion device does not depend on the switching timing of the switch element as in the current detection method (B). The current that flows from the storage to the storage cannot be detected. Therefore, in the current detection method (C), the time during which no current flows through the shunt resistor must estimate the current flowing from the power converter to the storage based on past measurements.

  Furthermore, in the current detection method (C) using the shunt resistor, when the difference between the battery voltage VB and the storage voltage VC is smaller than a predetermined value (when VB≈VC), the time during which the current flows through the shunt resistor is shortened. Therefore, when the time is shorter than the response time of the amplifier circuit, the current cannot be detected accurately.

  An object according to one aspect of the present invention is to provide a power conversion device and a power conversion method capable of accurately detecting a current flowing from a power conversion device to a storage at low cost.

The power converter which is one form which concerns on this invention has a power converter circuit, a 1st measuring circuit, a 2nd measuring circuit, and a control circuit.
In the power conversion circuit, the first terminal of the first switch element is connected to the first power source, the second terminal of the first switch element, the first terminal of the second switch element, and one of the coils. The first terminal of the third switch element is connected to one terminal of the second resistor, the second terminal of the third switch element and the first terminal of the fourth switch element And the other terminal of the coil are connected, and the second terminal of the second switching element and the second terminal of the fourth switching element are connected to one terminal of the first resistance element.

  The first measuring circuit has a first resistor in which one terminal is connected to the second terminal of the second switch element and the second terminal of the fourth switch element, and the other terminal is connected to the ground. An element and a first amplifier circuit that amplifies the voltage across the first resistance element.

  The second measurement circuit includes a second resistance element in which one terminal is connected to the first terminal of the third switch element, and the other terminal is connected to the second power source. A second amplifier circuit that amplifies the voltage at both ends.

  When the difference between the voltage of the first power supply and the voltage of the second power supply is greater than a predetermined value, the control circuit uses the first current obtained based on the measurement result of the first measurement circuit to And calculating a correction coefficient using the second current and the estimated current obtained based on the measurement result of the second measurement circuit, and calculating the voltage of the first power source and the second current. When the difference from the power supply voltage is less than a predetermined value, the second current is corrected using the correction coefficient.

  The current flowing from the power converter to the storage can be detected with low cost and accuracy.

It is a figure which shows one Example of the regenerative energy electrical storage system provided with a power converter device. It is a figure which shows one Example of a structure of a power converter device. It is a flowchart which shows one Example of operation | movement of a power converter device.

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an example of a regenerative energy storage system including a power conversion device 1 (bidirectional step-up / step-down type). The regenerative energy storage system includes a power conversion device 1, an auxiliary device 2, an alternator 3, a battery 4 (first power source), a storage 5 (second power source), a starter 6, and a switch SW. The regenerative energy storage system shown in FIG. 1 is mounted on, for example, a vehicle and supplies power from the alternator 3 to the storage 5 via the power converter 1 when the vehicle decelerates. That is, the storage 5 is charged. Further, when the vehicle is traveling, the power supply from the alternator 3 to the storage 5 is stopped or reduced, and the auxiliary machine 2 is supplied with power from the storage 5 via the power converter 1. That is, the storage 5 is discharged.

The power conversion device 1 is, for example, a bidirectional buck-boost type DC-DC converter including a full bridge circuit.
The auxiliary machine 2 is, for example, a device mounted on the vehicle.

The alternator 3 performs power generation performed by being driven by an unillustrated engine and power generation performed when the vehicle decelerates (power generation that outputs regenerative energy).
The battery 4 is a power storage device including, for example, a lead battery.

The storage 5 is a power storage device including, for example, a lithium ion battery, a lithium ion capacitor, an electric double layer capacitor, or the like.
The starter 6 includes a motor that starts an engine using the battery 4 as a power source.

  The switch SW is connected at the time of initial start for starting the engine by the ignition switch, and is cut off when the engine is restarted. In the example of FIG. 1, power is supplied from the battery 4 to the starter 6 via the switch SW when the engine is initially started.

The configuration of the power conversion device 1 will be described.
FIG. 2 is a diagram illustrating an example of the configuration of the power conversion apparatus 1. In the power conversion device 1 illustrated in FIG. 1, a battery 4 and a storage 5 are connected.

  The power conversion device 1 includes a power conversion circuit 201, a control circuit 202, a measurement circuit 204 (first measurement circuit) having a shunt resistor R1 (first resistance element) and an amplifier circuit 203, and a shunt resistor R2 (second Resistance element), and a measurement circuit 206 (second measurement circuit) including an amplifier circuit 205.

  The configuration of the power conversion circuit 201 shown in FIG. 2 is such that the drain (first terminal) of the switch element S1 (first switch element) and the input / output terminal 207 connected to the positive terminal of the battery 4 are connected. The source (second terminal) of the element S1, the drain (first terminal) of the switch element S2 (second switch element), and one terminal of the coil L are connected, and the switch element S3 (third switch element). ) And a drain (first terminal) of the switch element S3 and a drain (first terminal) of the switch element S4 (fourth switch element). The other terminal of the coil L is connected. The switch elements S1, S2, S3, and S4 are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and the like.

The measurement circuits 204 and 206 are provided for measuring the current flowing from the power conversion device 1 to the storage 5.
The shunt resistor R1 has one terminal connected to the source (second terminal) of the switch element S2 and the source (second terminal) of the switch element S4, and the other terminal connected to the ground.

The amplifier circuit 203 amplifies the voltage across the shunt resistor R1. For example, a circuit configured using an operational amplifier or the like.
The shunt resistor R <b> 2 has one terminal connected to the drain (first terminal) of the switch element S <b> 3 and the other terminal connected to the positive terminal of the storage 5.

The amplifier circuit 205 amplifies the voltage across the shunt resistor R2. For example, the control circuit 202 configured using an operational amplifier or the like uses, for example, a CPU (Central Processing Unit), a multi-core CPU, a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), or the like). It is a circuit configured. The terminal of the control circuit 202 is connected to the gates (control terminals) of the switch elements S1, S2, S3, and S4 by wiring. The other terminal of the control circuit 202 is connected to the output terminals of the amplifier circuits 203 and 205 by wiring.

  The control circuit 202 performs step-up / step-down control (current control). When the voltage VB of the battery 4 is larger than the voltage VC of the storage 5 (voltage VB> voltage VC), when the voltage VB is stepped down, the control circuit 202 performs current control in which current flows from the battery 4 toward the storage 5. The power conversion circuit 201 is executed. In addition, when the voltage VB of the battery 4 is smaller than the voltage VC of the storage 5 (voltage VB <voltage VC), when the voltage VB is boosted, current control is performed so that current flows from the battery 4 toward the storage 5. 202 causes the power conversion circuit 201 to execute.

  In addition, when the voltage VB of the battery 4 is larger than the voltage VC of the storage 5 (voltage VB> voltage VC), when the voltage VC is boosted, current control is performed so that current flows from the storage 5 side toward the battery 4. 202 causes the power conversion circuit 201 to execute. In addition, when the voltage VB of the battery 4 is smaller than the voltage VC of the storage 5 (voltage VB <voltage VC), when the voltage VC is stepped down, current control is performed so that current flows from the storage 5 to the battery 4. 202 causes the power conversion circuit 201 to execute.

  Further, when the difference between the voltage VB of the battery 4 and the voltage VC of the storage 5 is equal to or greater than a predetermined value, the control circuit 202 uses the current I1 (first current) obtained based on the measurement result of the measurement circuit 204. Thus, an estimated current I2 ′ estimated to flow through the shunt resistor R2 is obtained. Here, as a way of expressing the difference between the voltage VB of the battery 4 and the voltage VC of the storage 5, for example, the absolute value Vs (= | voltage VB−VC |) of the difference may be used. When the absolute value Vs is used as the difference, when the voltage VB> the voltage VC or the voltage VB <the voltage VC, and the absolute value Vs of the difference is equal to or greater than the predetermined value VT, the control circuit 202 performs the shunt measurement by the measurement circuit 204. An amplified voltage V1 obtained by amplifying the voltage at both ends of the resistor R1 is obtained, a current I1 is obtained based on the obtained amplified voltage V1, and an estimated current I2 estimated to flow through the shunt resistor R2 according to the obtained current I1. Ask for '. That is, the current I1 is converted into the estimated current I2 ′.

  Here, the conversion of the current I1 into the estimated current I2 ′ is performed by, for example, referring to the estimated current information using the current I1 obtained by the control circuit 202, and using the estimated current I2 ′ corresponding to the current I1 as the estimated current information. It is possible to choose from. The estimated current information is an experiment or simulation using a plurality of reference currents I1n (n = 1 to m: m is a positive integer) corresponding to a current I1 assumed to flow through the shunt resistor R1 and a plurality of reference currents I1n. Is associated with a plurality of estimated reference currents I2′n (n = 1 to m: m is a positive integer) corresponding to the estimated current I2 ′ obtained by the above, and is stored in the storage unit of the control circuit 202. is there. The estimated current information may be a calculation formula obtained by experiment or simulation, and the estimated current I2 ′ may be obtained according to the current I1 with the current I1 as a variable. Further, as the estimated current information, information for correcting a change in the estimated current I2 ′ that changes due to the temperature characteristics of the measurement circuit 204 and the measurement circuit 206 is stored in the storage unit, and the estimated current I2 ′ is corrected. Good.

If the absolute value Vs of the difference is equal to or greater than the predetermined value VT, the control circuit 202 causes the power conversion circuit 201 to execute current control using the estimated current I2 ′ obtained according to the current I1.
Furthermore, when the absolute value Vs of the difference is equal to or greater than the predetermined value VT, the control circuit 202 determines the current I2 (second current) that flows through the shunt resistor R2 that is obtained based on the measurement result of the measurement circuit 206 and the estimated current I2. 'Is used to determine a correction coefficient α for correcting the current I2 when the absolute value Vs of the difference is less than the predetermined value VT (when voltage VB≈voltage VC). The reason is that when the absolute value Vs of the difference is less than the predetermined value VT, even when the current flows through the shunt resistor R1, the time during which the current flows through the shunt resistor R1 is shortened. This is because it is difficult to detect the current I1 and the estimated current I2 'cannot be obtained because the current I1 is difficult to detect. Therefore, the estimated current I2' must be obtained by correcting the current I2 which is originally inaccurate. .

  Therefore, when the absolute value Vs of the difference is equal to or larger than the predetermined value VT, that is, in a state where the current detection accuracy is high, the estimated current I2 ′ is obtained from the accurate current I1, and the current I2 having low current detection accuracy is corrected. A correction coefficient α for improving accuracy is obtained in advance.

  Here, the method for obtaining the correction coefficient α refers to the correction coefficient information using, for example, the difference ΔI (= current I2−estimated current I2 ′) between the current I2 obtained by the control circuit 202 and the estimated current I2 ′. The correction coefficient α corresponding to the difference ΔI may be selected from the correction coefficient information. The correction coefficient information includes a plurality of reference differences ΔIn (n = 1 to m: m is a positive integer) corresponding to the assumed difference ΔI and a correction coefficient obtained by experiment or simulation using the plurality of reference differences ΔIn. A plurality of reference correction coefficients αn (n = 1 to m: m is a positive integer) associated with α are associated and stored in the storage unit of the control circuit 202. The correction coefficient information may be a calculation formula obtained by experiment or simulation, and the correction coefficient α may be obtained according to the difference ΔIn using the difference ΔIn as a variable. Alternatively, the correction coefficient α may be obtained according to the difference ΔIn using the current I2 and the estimated current I2 ′ as variables. Further, the correction coefficient information may store information for correcting a change in the correction coefficient α that changes due to the temperature characteristics of the measurement circuit 204 or the measurement circuit 206, and correct the correction coefficient α.

  In addition, when the absolute value Vs of the difference is less than the predetermined value VT (when voltage VB≈voltage VC), the control circuit 202 corrects the estimated current obtained by correcting the current I2 using the correction coefficient α. Convert to I2 ′. In other words, the correction coefficient α obtained in a state with good current detection accuracy can be obtained regardless of the switching timing of the switching element, but the estimated current I2 is obtained by correcting the current I2 obtained in a state with poor current detection accuracy. I2 ′ (corrected current I2).

  Thereby, when the absolute value Vs of the difference is less than the predetermined value VT, the current I2 flowing from the power converter 1 to the storage 5 can be accurately detected even if the time during which the current I1 flows through the shunt resistor R1 is short. . Further, the current I2 can be detected at a lower cost than when a current sensor is used.

  When the absolute value Vs of the difference is less than the predetermined value VT, the control circuit 202 performs power control using the estimated current I2 ′ (corrected current I2) obtained by correcting the current I2 with the correction coefficient α. The conversion circuit 201 is executed.

Operation | movement of the power converter device 1 is demonstrated.
FIG. 3 is a flowchart showing an embodiment of the operation of the power conversion device. In step S <b> 1, the control circuit 202 acquires the voltage VB of the battery 4 and the voltage VC of the storage 5.

  In step S2, the control circuit 202 compares the voltage VB with the voltage VC. That is, the control circuit 202 determines whether the absolute value Vs of the difference between the voltage VB and the voltage VC is greater than or equal to the predetermined value VT, or whether the absolute value Vs of the difference is less than the predetermined value VT. If the absolute value Vs of the difference is equal to or greater than the predetermined value VT, that is, if the voltage VB> the voltage VC or the voltage VB <the voltage VC, and the absolute value Vs of the difference is equal to or greater than the predetermined value VT, the process proceeds to step S3. When the absolute value Vs of the difference is less than the predetermined value VT, that is, when voltage VB≈voltage VC, the process proceeds to step S7.

  In step S3 (when the difference absolute value Vs is equal to or greater than the predetermined value VT), the control circuit 202 obtains currents I1 and I2 flowing in the resistors R1 and R2, respectively. The control circuit 202 acquires the amplified voltage V1 obtained by amplifying the voltage across the shunt resistor R1 measured by the measurement circuit 204, and obtains the current I1 based on the acquired amplified voltage V1. In addition, the control circuit 202 obtains an amplified voltage V2 obtained by amplifying the voltage across the shunt resistor R2 measured by the measurement circuit 206, and obtains a current I2 based on the obtained amplified voltage V2.

  In step S4, the control circuit 202 converts the current I1 into a current I2 ′ flowing through the resistor R2. The control circuit 202 obtains an amplified voltage V1 obtained by amplifying the voltage across the shunt resistor R1 measured by the measurement circuit 204, obtains a current I1 based on the obtained amplified voltage V1, and the shunt resistor according to the obtained current I1. Estimate the estimated current I2 'that will flow through R2. For the conversion from the current I1 to the estimated current I2 ′, for example, the estimated current I2 ′ corresponding to the current I1 can be obtained using the estimated current information described above.

  In step S5, the control circuit 202 obtains the correction coefficient α using the current I2 and the current I2 ′. As a method of obtaining the correction coefficient α, for example, it is considered that the correction coefficient α corresponding to the current I2 and the estimated current I2 ′ is obtained using the current I2 and the estimated current I2 ′ using the correction coefficient information described above. It is done.

In step S6, the control circuit 202 causes the power conversion circuit 202 to execute current control using the current I2 ′ obtained in step S5 or step S8.
In step S7 (when the absolute value Vs of differences is less than the predetermined value VT), the control circuit 202 obtains the current I2 flowing through the resistor R2. The control circuit 202 acquires an amplified voltage V2 obtained by amplifying the voltage across the shunt resistor R2 measured by the measuring circuit 206, and obtains a current I2 based on the acquired amplified voltage V2.

  In step S8, the control circuit 202 corrects the current I2 by the correction coefficient α and converts it to an estimated current I2 ′ (corrected current I2). Thereafter, the process proceeds to step S6, and the control circuit 202 executes current control using the estimated current I2 ′.

Note that the processing from step S1 to step S8 is repeatedly executed when the control circuit 202 performs step-up / step-down control.
By this processing, when the absolute value Vs of the difference is less than the predetermined value VT, the switching element is obtained using the correction coefficient α obtained in a state where the current detection accuracy is high even if the time during which the current I1 flows through the shunt resistor R1 is short. The estimated current I2 ′ (corrected current I2) can be obtained by correcting the current I2 obtained in a state where the current detection accuracy is not good. Therefore, the current I2 flowing from the power conversion device 1 to the storage 5 can be detected with high accuracy. Further, the current I2 can be detected at a lower cost than when a current sensor is used.

The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.
In addition, since the circuit itself of the power converter device 1 which concerns on this invention does not depend on the voltage of the battery 4, it can apply also to the power converter device of a different voltage specification.

  In the embodiment, the absolute value Vs (= | voltage VB−voltage VC |) is used as a method of expressing the difference between the voltage VB of the battery 4 and the voltage VC of the storage 5 as a target to be compared with the predetermined value VT. A difference between the voltage VB of the battery 4 and the voltage VC of the storage 5 may be used. That is, instead of using the absolute value Vs of the difference between the voltage VB and the voltage VC, the voltage VB−the voltage VC or the voltage VC−the voltage VB may be simply obtained, and the obtained difference may be compared with a predetermined value. In this case, however, the predetermined value is -VT to VT.

DESCRIPTION OF SYMBOLS 1 Power converter 2 Auxiliary machine 3 Alternator 4 Battery 5 Storage 6 Starter 201 Power conversion circuit 202 Control circuit 203, 205 Amplifier circuit 204, 206 Measurement circuit 207, 208 Input / output terminal L Coils S1, S2, S3, S4 Switch element SW Switch R1, R2 Shunt resistor

Claims (2)

The first terminal of the first switch element is connected to the first power source, and the second terminal of the first switch element, the first terminal of the second switch element, and one terminal of the coil are connected. The first terminal of the third switch element is connected to one terminal of the second resistor, the second terminal of the third switch element, the first terminal of the fourth switch element, and the coil The other terminal of the second switching element is connected, and the second terminal of the second switching element and the second terminal of the fourth switching element are connected to one terminal of the first resistance element When,
A first resistance element having one terminal connected to the second terminal of the second switch element and the second terminal of the fourth switch element and the other terminal connected to the ground; A first amplifying circuit that amplifies the voltage across one resistance element, and a first measurement circuit,
One terminal is connected to the first terminal of the third switch element, the other terminal is connected to the second power source, and the voltage across the second resistor element is amplified. A second amplifier circuit, and a second measurement circuit having
When the difference between the voltage of the first power source and the voltage of the second power source is larger than a predetermined value, the second current is obtained using the first current obtained based on the measurement result of the first measurement circuit. And calculating a correction coefficient using the second current obtained based on the measurement result of the second measurement circuit and the estimated current, and calculating the voltage of the first power source. A control circuit that corrects the second current using the correction coefficient when a difference from the voltage of the second power supply is less than the predetermined value;
A power conversion device comprising: The first terminal of the first switch element is connected to the first power source, and the second terminal of the first switch element, the first terminal of the second switch element, and one terminal of the coil are connected. The first terminal of the third switch element is connected to one terminal of the second resistor, the second terminal of the third switch element, the first terminal of the fourth switch element, and the coil The other terminal of the second switching element is connected, and the second terminal of the second switching element and the second terminal of the fourth switching element are connected to one terminal of the first resistance element When,
A first resistance element having one terminal connected to the second terminal of the second switch element and the second terminal of the fourth switch element and the other terminal connected to the ground; A first amplifying circuit that amplifies the voltage across one resistance element, and a first measurement circuit,
One terminal is connected to the first terminal of the third switch element, the other terminal is connected to the second power source, and the voltage across the second resistor element is amplified. A power conversion device comprising: a second measurement circuit having a second amplification circuit;
When the difference between the voltage of the first power source and the voltage of the second power source is larger than a predetermined value, the second current is obtained using the first current obtained based on the measurement result of the first measurement circuit. And obtaining a correction coefficient using the second current obtained based on the measurement result of the second measurement circuit and the estimated current.
When the difference between the voltage of the first power supply and the voltage of the second power supply is less than the predetermined value, the second current is corrected using the correction coefficient.
The power conversion method characterized by the above-mentioned.

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