JP5963960B2 - Inverter control device and inverter control method - Google Patents

Description

  The present invention relates to an inverter control device and an inverter control method.

  A ripple current is superimposed on an alternating current output from a pulse width modulation (PWM) control type inverter circuit to an alternating current motor (AC motor). When the ripple current is large, the iron loss and electromagnetic noise in the AC motor increase, and the motor efficiency decreases. Moreover, since the ripple current is also superimposed on the return current from the AC motor to the substation, the possibility of inductive failure is increased.

  The magnitude of the ripple current is determined by the frequency of the switching pulse supplied to the switching element (hereinafter referred to as switching frequency). The higher the switching frequency, the closer the alternating current output from the inverter circuit is to a sine wave, and the ripple current decreases. Patent Document 1 discloses a motor drive system that controls the frequency of a carrier wave (carrier frequency) used for pulse width modulation control based on a comparison between a ripple current width and a reference value of the ripple current width.

International Publication No. 2009/001738

  When the switching frequency is increased, the ripple current is decreased. However, since the switching frequency of the switching element increases, the temperature of the inverter circuit rises. Since the switching element has an upper limit of operating temperature, the switching frequency cannot be increased without limit.

  Generally, the switching frequency is set to a frequency at which the temperature of the inverter circuit does not exceed the upper limit temperature even when the AC motor is used under the worst possible usage conditions. For example, the switching frequency is set to a frequency at which the temperature of the inverter circuit does not exceed the upper limit temperature even if the motor is operated for 24 hours at a predetermined rotation speed and torque when the ambient temperature of the inverter circuit is 90 ° C. The

  The worst use conditions are very severe because they assume all cases. In particular, an AC motor used in a vehicle such as a train or a car is different from an AC motor used in home appliances or the like, and its usage environment is greatly changed by movement. Therefore, the worst use conditions of the AC motor that moves the vehicle must be extremely strict. When the switching frequency is determined in consideration of the worst use condition, the switching frequency is inevitably lowered, and as a result, the ripple current superimposed on the output current is increased.

  The present invention has been made in view of such a problem, and an object thereof is to provide an inverter control device in which a ripple current superimposed on an output current is small.

An inverter control device according to the present invention includes an inverter control unit that outputs a switching pulse for PWM control to a switching element included in an inverter circuit that is a circuit that drives an AC motor that moves a vehicle, and a temperature measurement that measures the temperature of the inverter circuit And a section. The inverter control unit has a frequency calculated by the carrier frequency calculation unit and a carrier frequency calculation unit that calculates the frequency of the carrier wave used for generating the switching pulse based on the temperature information of the inverter circuit acquired from the temperature measurement unit. A pulse generation unit that compares the carrier wave with a signal wave that is a fundamental wave and generates a switching pulse that is output to the switching element. The carrier frequency calculation unit acquires the frequency of the carrier wave that does not exceed the predetermined upper limit temperature as the reference frequency even if the AC motor is used under the worst possible usage conditions that can be assumed, and the acquired reference frequency and The frequency of the carrier wave is calculated based on the temperature of the inverter circuit measured by the temperature measuring unit, and the inverter control unit changes the frequency of the switching pulse based on the temperature of the inverter circuit measured by the temperature measuring unit.

  According to the present invention, since the frequency of the switching pulse is changed based on the temperature of the inverter circuit measured by the temperature measuring unit, the frequency of the switching pulse can be increased. As a result, the inverter control device can reduce the ripple current superimposed on the output current.

It is a figure which shows the inverter control apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the inverter control apparatus which concerns on embodiment of this invention. It is a figure which shows a mode that a gate pulse signal is produced | generated based on the comparison of a carrier wave and a signal wave. It is a figure which shows the structure of an inverter control part. It is a figure which shows the structure of a carrier frequency calculating part. It is a figure which shows a carrier frequency table. It is a figure which shows a carrier frequency gain table. It is a figure which shows a mode that the carrier frequency calculated in a carrier frequency calculating part changes with the temperature of an inverter circuit, and the speed of a train.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference numerals.

  The inverter control device 100 according to the embodiment of the present invention is a device that drives an AC motor 200 that moves a train. Here, the train means a vehicle that travels on a track such as a train or a train. The train includes not only a train with a plurality of cars but also a single train with a car. In addition, the train includes a tram that travels on a road surface, a monorail that travels on one rail, a tire traveling vehicle that travels on a track with rubber tires, and a linear motor car that travels on a track. Trains also include electric trains that run by turning a generator with an engine and driving a motor with the electric power.

  As shown in FIG. 1, the inverter control apparatus 100 includes power input terminals P and N, AC output terminals U, V, and W, and information input terminals I1, I2, and I3. The power input terminal P (positive terminal) is connected to the overhead line 500 via the current collector 400, and the power input terminal N (negative terminal) is connected to the rail 700 via the wheel 600. The information input terminals I1 and I2 are connected to the cab 300, and the information input terminal I3 is connected to the AC motor 200. The AC output terminals U, V, and W are connected to the AC motor 200.

  The cab command MC, the vehicle body weight VL, and the speed FM are input to the information input terminals I1 to I3, respectively. The cab command MC is a command related to on / off of power running acceleration, on / off of brake, power running acceleration and brake strength. The vehicle body weight VL is information indicating the current vehicle body weight of the train. The speed FM is the current speed of the train, for example, the current rotation speed of the AC motor 200.

  Hereinafter, the inverter control device 100 will be described in detail.

  The inverter control device 100 includes a power conversion unit 110 that converts DC power supplied from the overhead line 500 into AC power and outputs the AC power to the AC motor 200, a temperature measurement unit 120 that measures the temperature of the power conversion unit 110, and a temperature measurement. The inverter control unit 130 controls the power conversion unit 110 based on the temperature measured by the unit 120.

  As shown in FIG. 2, the power conversion unit 110 includes a reactor 111 and a capacitor 112 that form an LC filter circuit, an inverter circuit 113 that converts DC power output from the LC filter circuit into AC power, and a power conversion unit 110. A current detector 114 that measures the current input to the power converter 110, a voltage detector 115 that measures the voltage input to the power converter 110, and a voltage detector 116 that measures the voltage input to the inverter circuit 113. Is done.

  The reactor 111 and the capacitor 112 are elements constituting an LC filter circuit. The LC filter circuit is connected between the power input terminals P and N and the inverter circuit 113. The LC filter circuit smoothes a ripple component included in the voltage of the overhead line 500 and suppresses a noise current generated by a switching operation of the switching elements 113U to 113Z described later from flowing out to the overhead line 500.

  The inverter circuit 113 is a voltage-type three-phase two-level inverter circuit. The inverter circuit 113 is located at the subsequent stage of the LC filter circuit, and is connected to the AC motor 200 via AC output terminals U, V, and W. The inverter circuit 113 includes six switching elements (switching elements 113U to 113Z). The gate terminals of the switching elements 113U to 113Z are connected to the inverter control unit 130, respectively. Switching elements 113U to 113Z are switched by a switching pulse (gate pulse signal GP) supplied from inverter control unit 130. By this switching, the inverter circuit 113 converts the direct current supplied from the LC filter circuit into an alternating current and outputs the alternating current to the alternating current motor 200.

  The current detector 114 is an ammeter that measures the current supplied from the overhead line 500 to the power conversion unit 110. The current detector 114 is connected between the power input terminal P and the reactor 111. The current detector 114 measures the current flowing through the power input terminal P and the reactor 111 and outputs the measurement result to the inverter control unit 130 as the current detection value IS.

  The voltage detector 115 is a voltmeter that measures the voltage of the overhead line 500. The voltage detector 115 has one end connected to the power input terminal P via the current detector 114 and the other end connected to the power input terminal N. The voltage detector 115 measures the voltage between the power input terminals P and N, and outputs the measurement result to the inverter control unit 130 as the voltage detection value ES.

  The voltage detector 116 is a voltmeter that measures the voltage input to the inverter circuit 113. The voltage detector 115 has one end connected to the power input terminal P side of the capacitor 112 and the other end connected to the power input terminal N side of the capacitor 112. The voltage detector 116 measures the voltage across the capacitor 112 and outputs the measured value to the inverter control unit 130 as the voltage detection value EFC.

  The temperature measurement unit 120 is a thermometer for measuring the temperature of the inverter circuit 113, for example, a thermistor. The temperature measurement unit 120 is installed on the surface of the semiconductor chip constituting the power conversion unit 110 if the power conversion unit 110 is configured from a semiconductor chip. The temperature of the inverter circuit 113 is measured, and the measurement value is output to the inverter control unit 130 as the temperature measurement value TH.

  The inverter control unit 130 is a device that generates a gate pulse signal GP for PWM control by comparing a carrier wave that is a triangular wave and a signal wave that is a sine wave. More specifically, as shown in FIG. 3, the inverter control unit 130 compares the carrier wave Vs with the signal waves Vu, Vv, and Vw to generate the gate pulse signal GP (gate pulse signals GPu to GPz), This is a device for outputting the generated signal to the switching elements 113U to 113Z.

  As shown in FIG. 4, the inverter control unit 130 includes a torque pattern calculation unit 131 that generates a torque command, a current command calculation unit 132 that generates a current command, a voltage command calculation unit 133 that generates a voltage command, a signal Modulation rate / voltage phase calculation unit 134 for calculating the modulation rate and voltage phase of the waves Vu, Vv, Vw, carrier frequency calculation unit 135 for calculating the frequency of the carrier wave Vs, and gate pulse generation unit for generating the gate pulse signal GP 136.

  The torque pattern calculation unit 131, the current command calculation unit 132, the voltage command calculation unit 133, and the modulation factor / voltage phase calculation unit 134 generate information for the gate pulse generation unit 136 to generate the signal waves Vu, Vv, and Vw. It is a calculating part. Torque pattern calculation unit 131 calculates a torque to be generated by AC motor 200 based on cab command MC and vehicle body weight VL, and outputs the torque to current command calculation unit 132 as a torque command. The current command calculation unit 132 calculates a current command based on the torque command and each detection value (voltage detection value ES, voltage detection value EFC, current detection value IS) input from the power conversion unit 110. The voltage command calculation unit 133 generates a voltage command based on the current command and each detected value input from the power conversion unit 110. The modulation factor / voltage phase calculation unit 134 calculates the modulation factors and voltage phases of the signal waves Vu, Vv, and Vw based on the current command, and outputs them to the gate pulse generation unit 136. The calculation method of the modulation factor and voltage phase of the signal waves Vu, Vv, Vw is not limited to the above method, and various known methods can be used.

  The carrier frequency calculation unit 135 is a calculation unit that calculates the frequency of the carrier wave Vs (hereinafter referred to as “carrier frequency”). As shown in FIG. 5, the carrier frequency calculation unit 135 includes a basic carrier frequency acquisition unit 135a that acquires a basic carrier frequency, a carrier frequency gain acquisition unit 135b that acquires a carrier frequency gain, a basic carrier frequency and a carrier frequency gain. And a multiplier 135c for multiplication.

  The basic carrier frequency acquisition unit 135a stores a carrier frequency table shown in FIG. The carrier frequency table is a table showing the relationship between the train speed FM and the basic carrier frequency Fb. As shown in FIG. 6, when the speed FM is a high value, the basic carrier frequency Fb changes according to the speed FM. On the other hand, when the train speed FM is a low value, the basic carrier frequency Fc is fixed at a high frequency (reference frequency Fa). This is because the AC waveform collapse has a greater effect on the motor efficiency as the AC motor 200 operates at a lower speed. In the following description, the state of the inverter control device 100 when the basic carrier frequency Fb is a fixed value is referred to as “asynchronous mode”, and the state of the inverter control device 100 when the basic carrier frequency Fb changes according to the speed FM. The state is called “synchronous mode”.

  Note that the reference frequency Fa is a value determined in consideration that the inverter circuit 113 does not exceed the upper limit temperature TH2 even if the AC motor 200 is used under the worst possible use conditions. At this time, the upper limit temperature TH2 may be a design upper limit temperature of the switching elements 113U to 113Z.

  The basic carrier frequency acquisition unit 135a receives the current train speed FM as shown in FIG. The basic carrier frequency acquisition unit 135a acquires the basic carrier frequency Fb corresponding to the current train speed FM from the carrier frequency table. Then, the basic carrier frequency acquisition unit 135a outputs the acquired basic carrier frequency Fb to the multiplier 135c.

  The carrier frequency gain acquisition unit 135b stores a carrier frequency gain table shown in FIG. The carrier frequency gain table is a table showing the relationship between the temperature measurement value TH of the inverter circuit 113 and the room for increasing the basic carrier frequency Fc. More specifically, it is a table showing the relationship between the temperature measurement value TH of the inverter circuit 113 and the carrier frequency gain G. The carrier frequency gain G is a value that is multiplied by the basic carrier frequency Fb. As shown in FIG. 7, the carrier frequency gain G is fixed at the gain G1 until the temperature measurement value TH reaches the temperature TH1. When the temperature exceeds TH1, the carrier frequency gain G gradually decreases. The carrier frequency gain G becomes 1 when the temperature measurement value TH reaches the upper limit temperature TH2.

  As shown in FIG. 5, the current temperature measurement value TH of the inverter circuit 113 is input to the carrier frequency gain acquisition unit 135b. The carrier frequency gain acquisition unit 135b acquires the carrier frequency gain G corresponding to the current temperature measurement value TH of the inverter circuit 113 from the carrier frequency gain table. Then, the carrier frequency gain acquisition unit 135b outputs the acquired carrier frequency gain G to the multiplier 135c.

  Returning to FIG. 4, the multiplier 135c multiplies the basic carrier frequency Fb and the carrier frequency gain G to calculate the carrier frequency Fc. At this time, the multiplier 135c multiplies the basic carrier frequency Fb and the carrier frequency gain G only in the asynchronous mode. In the synchronous mode, the basic carrier frequency Fb is directly calculated as the carrier frequency Fc. Thereby, as shown in FIG. 8, the multiplier 135c can acquire the carrier frequency Fc whose value changes according to the temperature only during low-speed traveling. The multiplier 135c outputs the calculated carrier frequency Fc to the gate pulse generation unit 136.

  The gate pulse generation unit 136 is a pulse generation unit that generates a gate pulse signal GP. The gate pulse generator 136 generates signal waves Vu, Vv, Vw based on the modulation factor and voltage phase input from the modulation factor / voltage phase calculator 134. Further, the gate pulse generation unit 136 generates a carrier wave Vs based on the carrier frequency Fc input from the carrier frequency calculation unit 135. The gate pulse generator 136 compares the generated signal waves Vu, Vv, Vw and the carrier wave Vs to generate, for example, a gate pulse signal GP (gate pulse signals GPu to GPz) as shown in FIG. The gate pulse generation unit 136 outputs the generated gate pulse signals GPu to GPz to the gate terminals of the switching elements 113U to 113Z.

  The frequency of the switching pulse (gate pulse signal GP) output to the switching elements 113U to 113Z is the same as the carrier frequency Fc. According to the present embodiment, since the carrier frequency Fc, that is, the frequency of the switching pulse is changed based on the temperature of the inverter circuit 113 measured by the temperature measurement unit 120, it is determined in consideration of the worst use condition. The switching pulse can be raised beyond the reference frequency Fa. As a result, the inverter control device 100 can reduce the ripple current superimposed on the output current.

  Since the AC motor 200 used in vehicles such as trains and automobiles is in a moving environment, the worst use conditions such as temperature conditions and load fluctuations become very severe. For this reason, in the conventional apparatus, although there is considerable room for increasing the frequency of the switching pulse in a normal use state, the frequency of the switching pulse has to be set low. However, since the inverter control apparatus 100 according to the present embodiment uses the temperature information of the inverter circuit 113 to control the frequency of the switching pulse, the frequency of the switching pulse can be increased at least in a normal use state. When inverter control device 100 of the present embodiment is used for driving AC electric motor 200 that moves the vehicle, the effect of reducing ripple current is extremely large.

  The above-described embodiment is an example, and various changes and applications are possible.

  For example, in the above-described embodiment, the inverter control device 100 includes the power conversion unit 110. However, the inverter control device 100 may not include the power conversion unit 110. The inverter control unit 130 included in the inverter control device 100 may be configured to control the inverter circuit 113 outside the inverter control device 100.

  In the above-described embodiment, the inverter control device 100 is configured as a device that receives DC power and outputs AC power to the AC motor 200. However, the inverter control device 100 receives AC power and receives the AC power. 200 may be configured as an apparatus that outputs AC power. In this case, the power conversion unit 110 may include a converter circuit that converts AC power into DC power before the inverter circuit 113.

  In the above-described embodiment, the voltage-type three-phase two-level inverter circuit is used as the inverter circuit 113, but the inverter circuit 113 is not limited to the voltage-type three-phase two-level inverter circuit. For example, a single-phase inverter or a three-level inverter circuit may be used.

  In the above-described embodiment, the basic carrier frequency Fb is multiplied by the carrier frequency gain G only in the asynchronous mode. However, the basic carrier frequency Fb may be multiplied by the carrier frequency gain G also in the synchronous mode. It is also possible to set only the asynchronous mode without providing the synchronous mode.

  In the above-described embodiment, the carrier frequency Fc is changed based on the temperature of the inverter circuit 113. However, the inverter control unit 130 determines the frequency of the switching pulse (gate pulse signal GP) based on the temperature of the inverter circuit 113. May be changed directly.

  In the above-described embodiment, the temperature measurement unit 120 is installed on the surface of the semiconductor chip constituting the power conversion unit 110. However, if a cooler is attached to the power conversion unit 110, the temperature measurement unit 120 is installed. May be attached to the cooler. The inverter circuit 113 may be directly attached.

  In the above-described embodiment, the inverter control device 100 is a device that drives the AC motor 200 that moves the train. However, even if the inverter control device 100 is a device that drives the AC motor 200 that moves a vehicle such as a hybrid car or an electric vehicle. Good.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 100 Inverter control apparatus, 110 Power conversion part, 111 Reactor, 112 Capacitor, 113 Inverter circuit, 113U-113Z Switching element, 114 Current detector, 115 Voltage detector, 116 Voltage detector, 120 Temperature measuring part, 130 Inverter control part 131, torque pattern calculation unit, 132 current command calculation unit, 133 voltage command calculation unit, 134 modulation factor / voltage phase calculation unit, 135 carrier frequency calculation unit, 135a basic carrier frequency acquisition unit, 135b carrier frequency gain acquisition unit, 135c multiplication , 136 gate pulse generator, 200 AC motor, 300 cab, 400 current collector, 500 overhead wire, 600 wheels, 700 rails, P, N power input terminal, U, V, W AC output terminal, I1, I2, I3 information input Power terminal.

Claims (4)

An inverter control unit that outputs a switching pulse for PWM control to a switching element provided in an inverter circuit that is a circuit that drives an AC motor that moves the vehicle ;
A temperature measuring unit for measuring the temperature of the inverter circuit,
The inverter control unit
A carrier frequency calculation unit that calculates a frequency of a carrier wave used for generation of the switching pulse based on information on the temperature of the inverter circuit acquired from the temperature measurement unit;
A pulse generation unit that generates a switching pulse that is output to the switching element by comparing a carrier wave having a frequency calculated by the carrier frequency calculation unit and a signal wave that is a fundamental wave;
The carrier frequency calculator is
Even if the AC motor is used under the worst possible usage conditions that can be assumed, the frequency of the carrier wave that does not exceed a predetermined upper limit temperature is obtained as a reference frequency,
Calculate the frequency of the carrier wave based on the acquired reference frequency and the temperature of the inverter circuit measured by the temperature measurement unit,
The inverter control unit changes the frequency of the switching pulse based on the temperature of the inverter circuit measured by the temperature measurement unit,
Inverter control device. The carrier frequency calculator is
When the temperature of the inverter circuit is higher than a preset temperature, the reference frequency is acquired as the frequency of the carrier wave,
When the temperature of the inverter circuit is lower than a preset temperature, a frequency higher than the reference frequency is calculated as the frequency of the carrier wave.
The inverter control device according to claim 1 . A power conversion unit including the inverter circuit;
The inverter control device according to claim 1. An inverter control step for outputting a switching pulse for PWM control to a switching element provided in an inverter circuit which is a circuit for driving an AC motor that moves the vehicle ;
Measuring a temperature of the inverter circuit; and
A carrier frequency calculating step for calculating a frequency of a carrier wave used for generating the switching pulse based on the temperature information of the inverter circuit acquired in the temperature measuring step;
A pulse generation step of generating a switching pulse to be output to the switching element by comparing a carrier wave having a frequency calculated in the carrier frequency calculation step and a signal wave serving as a fundamental wave;
In the carrier frequency calculation step,
Even if the AC motor is used under the worst possible usage conditions that can be assumed, the frequency of the carrier wave that does not exceed a predetermined upper limit temperature is obtained as a reference frequency,
Calculating the frequency of the carrier wave based on the acquired reference frequency and the temperature of the inverter circuit measured in the temperature measurement step;
In the inverter control step, the frequency of the switching pulse is changed based on the temperature of the inverter circuit measured in the temperature measurement step.
Inverter control method.

Images