Power conversion device

Abstract

To solve the problem that there is the risk of occurrence of trouble in a switching element caused by occurrence of overshoot in an output current from an inverter circuit due to a change of a power supply voltage that occurs during control.SOLUTION: A power conversion device comprises: a power conversion circuit configured by including one or more circuits in which two or more switching elements are connected via an AC terminal between DC terminals; current detection means for detecting a current of the AC terminal; voltage detection means for detecting voltages of the DC terminals; and a control section for performing ON / OFF control on the switching elements on the basis of an output command value. The power conversion device further comprises: voltage change detection means which outputs a change of the voltage detected by the voltage detection means; and output command value compensation means for compensating the output command value so as to suppress overshoot of an AC current outputted from the AC terminal in accordance with the voltage change outputted from the voltage change detection means.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a power conversion device.

Background Art

[0002] AC motors are widely used as a driving power source for home appliances such as air conditioners and refrigerators, industrial robot arms, and electric vehicles. In addition, an AC motor is driven by AC power converted from a DC power source by an inverter circuit, which is a power conversion device, to achieve high-efficiency and high-response driving. The inverter circuit is composed of a circuit in which one or more legs, each having two or more switching elements such as IGBTs (Insulated Gate Transistors) or MOSFETs (Metal-Oxide-semiconductor field-effect transistors) connected in series, are connected in parallel. A DC power source such as a battery is connected to this inverter circuit, and by controlling the switching elements of the inverter circuit to be turned on and off by a control unit, AC power is transmitted from the wiring connected to the connection points of the switching elements of each leg to each phase of the AC motor.

[0003] In a circuit in which an AC motor and an inverter circuit are connected, when driving conditions or operational abnormalities occur, the voltage of the DC power source (power supply voltage) connected to the inverter circuit may change steeply. As a result, since the change in the power supply voltage becomes a disturbance, an event occurs in which the inverter circuit does not output appropriately. In particular, depending on the driving conditions, the control unit of the inverter circuit may operate to change the current flowing through the AC motor due to the change in the power supply voltage. In this case, the influence of the disturbance due to the change in the power supply voltage becomes even greater.

[0004] Patent Document 1 proposes a method of suppressing the influence of a disturbance due to a change in the power supply voltage by newly providing a waveform data setter and a reference wave generator in an inverter control device and controlling the switching elements of the inverter circuit according to the change in the power supply voltage.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In Patent Document 1, by newly providing a waveform data setter and a reference wave generator in the inverter control device, the influence of disturbances caused by changes in the power supply voltage is suppressed. However, what Patent Document 1 assumes as the change in the power supply voltage is only when the polarity of the output current of the inverter circuit is reversed, and there is a possibility that the influence of disturbances caused by changes in the power supply voltage due to driving conditions and operation abnormalities cannot be suppressed.

[0007] This disclosure is made to solve the above-mentioned problems. By newly adding an output command value compensator using the change in the power supply voltage as an information source and compensating the output command value using this, an object is to provide a power conversion device capable of reducing the overshoot of current.

Means for Solving the Problems

[0008] The power conversion device of this disclosure includes a power conversion circuit configured to have one or more circuits in which two or more switching elements are connected between DC terminals via AC terminals, current detection means for detecting the current of the AC terminals, voltage detection means for detecting the voltage of the DC terminals, and a control unit for controlling the switching elements to be turned on and off based on an output command value, and includes voltage change detection means for outputting the change in the voltage detected by the voltage detection means, and output command value compensation means for compensating the output command value so as to suppress the overshoot of the alternating current output from the AC terminals in response to the voltage change output from the voltage change detection means.

Effects of the Invention

[0009] According to the power conversion device of the present disclosure, even when a disturbance is superimposed on the current control system due to a change in the power supply voltage, based on the amount of voltage change detected by the voltage change detector or the amount of change in the current command value, the output command value compensation means limits the voltage command value to converge the voltage command value increased due to the disturbance within the range of the voltage command value without considering the disturbance and compensate for the influence of the disturbance, so that overshoot of the current can be reduced.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, a preferred embodiment of the power conversion device according to the present application will be described with reference to the drawings. For the same content and corresponding parts, the same reference numerals are assigned, and detailed descriptions thereof are omitted. Similarly, in the following embodiments, duplicate descriptions of the configurations with the same reference numerals are omitted.

[0012] Embodiment 1. <Description of Comparative Example> Before describing this embodiment, the occurrence of overshoot in the current flowing through the motor will be described using the block configuration diagram of the power conversion device of the comparative example and the block diagram of the current control system. FIG. 1 is a block configuration diagram showing the configuration of the power conversion device 1, and FIG. 2 is a block diagram of the current control system of FIG. 1. An inverter circuit 50 is provided in which IGBTs connected in parallel, singly or in plurality, form one arm, and series circuits of the upper arms 5, 7, 9 and the lower arms 6, 8, 10 are connected in three parallel.

[0013] A smoothing capacitor 11 and a DC power supply 2 are connected in parallel with the series circuits of the upper and lower arms. Also, the connection points of the upper arms 5, 7, 9 and the lower arms 6, 8, 10 are connected to an AC motor 3 which is a load. A rotation angle sensor 4 such as a resolver is disposed on the AC motor 3. The control unit 12 executes motor control calculation with the DC voltage detection value v dc detected by the voltage sensor 24, the phase current detection values i u of the AC motor 3 detected by the current sensor 25, i v , i w , and the angle detection value θ of the rotation angle sensor 4 of the AC motor 3 as inputs, and calculates output command values (voltage command values v* d , v* q (in FIG. 2, v* dq ). The voltage command value is, for example, the duty ratio of the voltage. The calculated voltage command value v* dq is converted into v* u , v* v , v* w (in FIG. 2, v* uvw ), and the converted voltage command value v* uvwAccording to this, by outputting on and off signals to the gate drive circuit 14, the gate drive circuit 14 outputs drive signals 16 to 21 to each arm 5 to 10 to drive the IGBT. By controlling the on and off states of each arm 5 to 10, the line voltage and phase voltage of the AC motor 3 are generated to control the AC motor 3. In this way, the DC power of the DC power supply 2 is power-converted by the power conversion device 1, and AC power is supplied to the AC motor 3.

[0014] Figure 2 is a block diagram of a current control system for explaining motor control calculations in the control unit 12. Torque command value τ*, rotational speed ω of the AC motor 3, power supply voltage v of the inverter circuit 50 PN The current command value i* derived from the map I*Map d , i* q (i* in Figure 2 dq ) and the current i flowing through the AC motor 3 d , i q (in Figure 2, i dq ) are subjected to PI control so that the difference becomes 0, and the voltage command value v* uvw is output.

[0015] Figure 3 is a block diagram of the current control system when considering the change in the power supply voltage v PN in the current control system of Figure 2. In the current control system, the change in the power supply voltage v PN affects as an external disturbance (v noise ) of the voltage command value output by the PI control. Also, depending on the drive region, the current command value may change due to the power supply voltage v PN . As a result, since a voltage command value different from the voltage command value v* dq output by the PI control is commanded to the inverter circuit 50, the voltage applied to the AC motor 3 does not become an appropriate value, and as a result, the current flowing through the AC motor 3 deviates from the current command value i* dq . When this current deviation acts in the positive direction, the current i flowing through the AC motor 3 dqOvershoot may occur, and there is a risk of malfunction in the switching elements 5 to 10 of the inverter circuit 50. As a method of reducing the influence of disturbances from a control perspective, there is a method of measuring the disturbance term of the current control system and compensating for it. However, it is difficult to directly measure the disturbance term caused by changes in the power supply voltage.

[0016] <Description of Embodiment 1> In this embodiment, in order to reduce the overshoot described in the above comparative example, an output command value compensator 23 using the change in the power supply voltage v PN as an information source is provided to compensate the voltage command value v* dq . The configuration will be described below. FIG. 4 is a block configuration diagram of the power conversion device according to Embodiment 1. The configurations denoted by the same reference numerals as in FIG. 1 perform the same operations and functions as in FIG. 1, so the description thereof will be omitted. The main difference from FIG. 1 is that it includes a voltage change detector 22 and an output command value compensator 23.

[0017] The voltage change detector 22 detects the slope (change amount Δv dc ) due to the time change of the DC voltage detection value v dc detected by the voltage sensor 24 and outputs it to the output command value compensator 23. At this time, when noise is superimposed on the DC voltage detection value v dc , the voltage change detector 22 may detect a slope different from the actual one. Therefore, the slope due to the time change of the DC voltage detection value v dc may be detected via a high-frequency component removal filter.

[0018] The output command value compensator 23 compensates the voltage command value v* dq based on the voltage command value v* dq output by the control unit 12, the current command value i* dc , and the change amount Δv dc of the DC voltage detection value v dq which is the output from the voltage change detector 22. After that, the compensated voltage command value v* dq is converted into the voltage command value v* uvw . This voltage command value v* uvwBy outputting on and off signals to the gate drive circuit 14 according to this, the gate drive circuit 14 outputs drive signals 16 to 21 to each arm 5 to 10 to drive the IGBT.

[0019] An example of the hardware in the control unit 12 is shown in FIG. 5. It is composed of a processor 100 and a storage device 200. Although not shown, the storage device includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Also, an auxiliary storage device of a hard disk may be provided instead of the flash memory. The processor 100 controls, for example, until the above-described on and off signals are output to the gate drive circuit 14 by executing a program input from the storage device 200. In this case, the program is input from the auxiliary storage device to the processor 100 via the volatile storage device. Further, the processor 100 may output data such as calculation results to the volatile storage device of the storage device 200, or may store the data in the auxiliary storage device via the volatile storage device. Either or both of the voltage change detector 22 and the output command value compensator 23 may be stored in the control unit 12. In this case, the operations of the voltage change detector 22 and the output command value compensator 23 are executed by software.

[0020] FIG. 6 is a block diagram of the current control system in Embodiment 1. The control unit 12 and the output command value compensator 23 of the power conversion device 1 according to Embodiment 1 give a voltage command value v* uvw to the inverter circuit 50 through the gate drive circuit 14, and show the configuration until the inverter circuit 50 applies a voltage to the AC motor 3. PI control is performed so that the difference between the torque command value τ*, the rotational speed ω of the AC motor 3, the power supply voltage v PN of the inverter circuit 50, the current command value i* dq derived from the map I*Map, and the current i dq flowing through the AC motor 3 becomes 0, and the voltage command value v* dq is output.

[0021] In such control, the change amount Δv PN of the power supply voltage v dcand the current command value i* dq The change amount Δi* dq Based on this, the voltage command value v* output by the PI control dq For this, the output command value compensator 23 acts as a limiter 26 in FIG. 6 for the voltage command value v* dq The upper limit value is limited. The limit value of this limiter 26 is the voltage change amount Δv detected by the voltage change detector 22 dc and the current command value i* dq The change amount Δi* dq is determined based on. For example, when the power supply voltage v PN increases, the larger the voltage change amount Δv dc is, the smaller the value of the limiter 26 is set. Similarly, when the current command value i* dq increases, the larger the change amount Δi* dq is, the smaller the value of the limiter 26 is set. The limiter 26 starts the operation of limiting the upper limit value when the change amount Δv dc or the change amount Δi* dq of the current command value i* dq exceeds a predetermined threshold value, and ends the operation when it falls below.

[0022] FIG. 7 is a waveform diagram of the current or voltage controlled by the block diagram of FIG. 6. FIG. 7(a) is a waveform diagram in the case of the control shown in FIGS. 1 and 2 without using the output command value compensator 23, and FIG. 7(b) is a waveform diagram in the case where the output command value compensator 23 shown in FIG. 4 is used as the limiter 26 shown in FIG. 6. In FIG. 7(a), when the power supply voltage v PN rises, the current command values i* d , i* q increase, but the currents i d , i q do not increase following the current command values i* d , i* q , so the phase current is larger than in the steady state. In contrast, in the configuration of FIG. 6 using the limiter 26 which is the output command value compensator 23, as shown in FIG. 7(b), as the power supply voltage v PN rises, by limiting the voltage command values v* d , v* q , the current i d, i q and the current command value i* d , i* q The difference from can be reduced, and the overshoot of the current is reduced. As a result, the change in the phase current is minimized.

[0023] As described above, according to the power conversion device according to Embodiment 1, even when a disturbance (v PN ) is superimposed on the current control system due to a change in the power supply voltage v, the voltage change amount Δv noise detected by the voltage change detector 22 or the change amount Δi* dc of the current command value, based on which the limiter 26 limits the voltage command value v* dq dq to converge the voltage command value increased by the disturbance within the range of the voltage command value not considering the disturbance and compensate for the influence of the disturbance. Therefore, the overshoot of the current can be reduced.

[0024]

[0024] Embodiment 2. The block diagram of the current control system in FIG. 8 shows that a compensator 27 is arranged as the output command value compensator 23 in FIG. 4, and the compensation value by the compensator 27 is added to the power command value v* uvw after PI control. Since the configuration other than the compensator 27 in FIG. 8 is the same as that in FIG. 6, the description is omitted. The additional compensation value is based on the voltage change amount Δv dc detected by the voltage change detector 22 and the change amount Δi* dq of the current command value i*, for example, the larger the voltage change amount Δv dq when the power supply voltage v PN increases, the larger the compensation value is set, and similarly, the larger the change amount Δi* dc when the current command value i* dq increases, the larger the compensation value is set. dq dc The compensator 27 starts the operation of adding the compensation value when the voltage change amount Δv dc or the change amount Δi* dq of the current command value i* dq exceeds a predetermined threshold value, and ends the operation when it falls below the threshold value.

[0025] FIG. 9 is a waveform diagram of current or voltage controlled by the block diagram of FIG. 8. FIG. 9(a) is a waveform diagram in the case of the control shown in FIGS. 1 and 2 without using the output command value compensator 23, and FIG. 9(b) is a waveform diagram in the case where the output command value compensator 23 shown in FIG. 4 is used as the compensator 27 shown in FIG. 8. In FIG. 9(a), when the power supply voltage v PN rises, the current command values i* d , i* q increase, but the currents i d , i q do not increase following the current command values i* d , i* q , so the phase current is larger than in the steady state. On the other hand, in the configuration of FIG. 8 using the compensator 27 which is the output command value compensator 23, as shown in FIG. 9(b), as the power supply voltage v PN rises, the compensator 27 acts, and the compensation value is subtracted from the voltage command values v* d , v* q to change the voltage command values v* d , v* q . As a result, the difference between the currents i d , i q and the current command values i* d , i* q can be reduced, and the overshoot of the current is reduced. Thereby, the change in the phase current is minimized.

[0026] As described above, according to the power conversion device according to Embodiment 1, even when a disturbance (v PN ) is superimposed on the current control system due to a change in the power supply voltage v noise , the voltage command value v* dc detected by the voltage change detector 22 or the change amount Δi* dq of the current command value is used to subtract the compensation value from the voltage command value v* dq to correct the voltage command value increased by the disturbance and compensate for the influence of the disturbance, so that the overshoot of the current can be reduced.

[0027] Embodiment 3. The block diagram of the current control system in FIG. 10 arranges a compensator 28 as the output command value compensator 23 in FIG. 4, and adds the compensation value by the compensator 28 to the gain of the PI control. Since the configuration other than the compensator 28 in FIG. 10 is the same as that in FIG. 6, the description is omitted. The compensation value to be added is the voltage change amount Δv detected by the voltage change detector 22 dc and the change amount Δi* of the current command value i* dq . It is determined based on dq , for example, when the power supply voltage v PN increases, the larger the voltage change amount Δv dc , the larger the compensation value is set. Similarly, when the current command value i* dq increases, the larger the change amount Δi* dq , the larger the compensation value is set. The compensator 28 starts the operation of adding the compensation value when the change amount Δv of the voltage change amount dc or the change amount Δi* of the current command value i* dq exceeds a predetermined threshold value, and ends the operation when it falls below the threshold value. dq

[0028] FIG. 11 is a waveform diagram of the current or voltage controlled by the block diagram of FIG. 10. FIG. 11(a) is a waveform diagram in the case of the control shown in FIGS. 1 and 2 without using the output command value compensator 23, and FIG. 11(b) is a waveform diagram in the case where the output command value compensator 23 shown in FIG. 4 is used as the compensator 28 shown in FIG. 10. In FIG. 11(a), when the power supply voltage v PN rises, the current command values i* d , i* q increase, but the currents i d , i q do not increase following the current command values i* d , i* q , so the phase current is larger than in the steady state. On the other hand, in the configuration of FIG. 10 using the compensator 28, as shown in FIG. 11(b), as the power supply voltage v PN rises, the compensator 28 acts, and by subtracting the compensation value from the gain of the PI control shown in FIG. 10, the responsiveness of the current control system is adjusted, and the currents i d , i q and the current command value i*d , i* q The difference from i* is reduced. As a result, the overshoot of the current is reduced, and the change in the phase current is minimized.

[0029] As described above, according to the power conversion device according to Embodiment 1, even when a disturbance (v PN ) is superimposed on the current control system due to a change in the power supply voltage v noise , even if the voltage command value increases due to the disturbance by subtracting a compensation value from the gain of the PI control based on the voltage change amount Δv dc detected by the voltage change detector 22 or the change amount Δi* dq of the current command value, the overshoot of the current can be reduced in order to reduce the deviation from the voltage that is originally intended to be applied to the AC motor 3.

[0030] Although various exemplary embodiments and examples are described in the present application, the various features, aspects, and functions described in one or more of the embodiments are not limited to the application of a specific embodiment, but are applicable to the embodiments alone or in various combinations. Therefore, countless modifications that are not illustrated are assumed to be within the scope of the technology disclosed in the present specification. For example, it includes the case of modifying, adding, or omitting at least one component, and further, the case of extracting at least one component and combining it with the components of other embodiments.

[0031] Hereinafter, aspects of the present disclosure will be collectively described as appendices.

[0032] (Appendix 1) A power conversion circuit configured to include one or more circuits in which two or more switching elements are connected via AC terminals between DC terminals, current detection means for detecting the current of the AC terminals, voltage detection means for detecting the voltage of the DC terminals, a control unit for controlling the switching elements to be turned on and off based on an output command value, A power conversion device comprising Voltage change detection means for outputting the change in the voltage detected by the voltage detection means, Output command value compensation means for compensating the output command value so as to suppress the overshoot of the alternating current output from the AC terminal in response to the voltage change output from the voltage change detection means, a power conversion device provided with. (Appendix 2) The output command value compensation means is a limiter for limiting the upper limit value of the output command value, the power conversion device according to Appendix 1, characterized in that. (Appendix 3) The output command value compensation means limits the upper limit value of the output command value so that the larger the amount of change in the voltage change detected by the voltage change detection means, the smaller the upper limit value of the output command value, the power conversion device according to Appendix 1 or 2, characterized in that. (Appendix 4) The output command value compensation means limits the upper limit value of the output command value so that the larger the amount of change in the current command value output by the control unit, the smaller the upper limit value of the output command value, the power conversion device according to Appendix 1 or 2, characterized in that. (Appendix 5) The output command value compensation means is a compensator for adding a compensation value to the output command value, the power conversion device according to Appendix 1 or 2, characterized in that. (Appendix 6) The output command value compensation means is a compensator for adding a compensation value to the control gain of the control unit, the power conversion device according to Appendix 1 or 2, characterized in that. (Appendix 7) The control gain is the gain of proportional integral control of the current control system, the power conversion device according to Appendix 6, characterized in that. (Appendix 8) The output command value compensation means increases the compensation value so that the larger the amount of change in the voltage change detected by the voltage change detection means, the power conversion device according to Appendix 5 or 6, characterized in that. (Appendix 9) The output command value compensation means increases the compensation value so that the larger the amount of change in the current command value output by the control unit, the power conversion device according to Appendix 5 or 6, characterized in that. (Appendix 10) The output command value compensation means starts operating when it exceeds a predetermined threshold value and ends operating when it falls below the threshold value. The power conversion device according to any one of Appendices 1 to 8. (Appendix 11) The amount of change in the voltage change is the slope due to the time change of the voltage. The power conversion device according to Appendix 3 or 8. (Appendix 12) The voltage input to the voltage change detection means has the high-frequency components removed. The power conversion device according to any one of Appendices 1 to 11. (Appendix 13) The output command value is the duty ratio of the voltage, and the control unit controls the output command value so as to match the output of the power conversion circuit. The power conversion device according to any one of Appendices 1 to 12.

Explanation of Signs

[0033] 1: Power conversion device, 2: DC power supply, 3: AC motor, 4: Rotation angle sensor, 5 to 10: Switching elements, 11: Smoothing capacitor, 12: Control unit, 14: Gate drive circuit, 16 to 21: Drive signals, 22: Voltage change detector, 23: Output command value compensator, 24: Voltage sensor, 25: Current sensor, 26: Limiter, 27, 28: Compensators, 50: Inverter circuit, 100: Processor, 200: Storage device.

Claims

1. A power conversion circuit configured to include one or more circuits in which two or more switching elements are connected via an AC terminal between DC terminals, current detection means for detecting the current of the AC terminal, voltage detection means for detecting the voltage between the DC terminals, a control unit for controlling the switching element to be turned on and off based on an output command value, A power conversion device comprising: voltage change detection means for outputting a change in the voltage detected by the voltage detection means, Output command value compensation means for compensating the output command value so as to suppress an overshoot of the AC current output from the AC terminal in response to the voltage change output from the voltage change detection means. A power conversion device provided with.

2. The power conversion device according to claim 1, wherein the output command value compensation means is a limiter that limits an upper limit value of the output command value.

3. The power conversion device according to claim 2, wherein the output command value compensation means limits the upper limit value of the output command value to be smaller as the amount of change in the voltage change detected by the voltage change detection means is larger.

4. The power conversion device according to claim 3, wherein the amount of change in the voltage change is a slope due to a change in voltage over time.

5. The power conversion device according to claim 2, wherein the output command value compensation means limits the upper limit value of the output command value to be smaller as the amount of change in the current command value output by the control unit is larger.

6. The power conversion device according to claim 1, wherein the output command value compensation means is a compensator that adds a compensation value to the output command value.

7. The power conversion device according to claim 1, wherein the output command value compensation means is a compensator that adds a compensation value to a control gain of the control unit.

8. The power conversion device according to claim 7, wherein the control gain is a gain of proportional integral control of a current control system.

9. The power conversion device according to claim 6 or 7, wherein the output command value compensation means increases the compensation value as the amount of change in the voltage change detected by the voltage change detection means increases.

10. The power conversion device according to claim 6 or 7, wherein the output command value compensation means increases the compensation value as the amount of change in the current command value output by the control unit increases.

11. The power conversion device according to any one of claims 1 to 8, wherein the output command value compensation means starts operating when the output command value exceeds a predetermined threshold value and ends operating when the output command value is below the predetermined threshold value.

12. The power conversion device according to claim 9, wherein the amount of change in the voltage change is the slope due to the time change of the voltage.

13. The power conversion device according to any one of claims 1 to 8, wherein the voltage input to the voltage change detection means has a high-frequency component removed.

14. The power conversion device according to any one of claims 1 to 8, wherein the output command value is the duty ratio of the voltage, and the control unit controls the output command value so as to match the output of the power conversion circuit.

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