Power conversion device, motor drive device, and refrigeration cycle application equipment

Abstract

This power conversion device (2) comprises a detection section (22) that uses a common mode transformer (221) to detect a common mode current flowing through a power line and outputs the detected value, an adjustment circuit section (23) that adjusts the detected value, a compensation signal generation section (25) that uses the detected value after adjustment by the adjustment circuit section (23) to generate a compensation signal to compensate for the common mode current, a compensation signal injection section (26) having an injection capacitor (262) that injects the compensation signal into a ground line, and a control power supply section (24) that supplies control power to the compensation signal generation section (25), wherein a filter (30) that carries out a feedback control is formed by the detection section (22), the adjustment circuit section (23), the compensation signal generation section (25), the compensation signal injection section (26), and the control power supply section (24), and the adjustment circuit section (23) adjusts a control gain of the filter (30) by adjusting the detected value, and adjusts the gain and phase of the open-loop transfer characteristics of the filter (30) in a high-frequency band outside the compensation band.

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device that performs power conversion, a motor drive device, and a refrigeration cycle application device.

[0002] Conventionally, there are power conversion devices that convert AC power supplied from an AC power source into desired AC power using a rectifier, a smoothing capacitor, an inverter, etc., and output the converted AC power to a load. When a common-mode current occurs in such a power conversion device, the power conversion device's control becomes unstable due to the influence of noise caused by the common-mode current, and this can also cause instability in the control of other devices receiving power from the same AC power source. Power conversion devices can remove noise caused by common-mode current to some extent by using a reactor or a filter consisting of a combination of a reactor and a capacitor. However, to improve the noise removal effect, a large reactor is required, which increases the size and cost of the device. To address this problem, Patent Document 1 discloses technology for a noise reduction device for a power conversion device that achieves high performance while reducing size and cost.

[0003] Patent No. 3044650

[0004] However, the above-described conventional technology has a problem in that, in order to perform a stable compensation operation, it is necessary to provide a feedback characteristic that does not cause oscillation in the high frequency band.

[0005] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can prevent oscillation in high frequency bands and perform a stable compensation operation for common mode current.

[0006] To solve the above-mentioned problems and achieve the object, a power conversion apparatus according to the present disclosure includes a detection unit that detects a common-mode current flowing in a power line using a common-mode transformer and outputs the detected value, an adjustment circuit unit that adjusts the detected value, a compensation signal generation unit that generates a compensation signal that compensates for the common-mode current using the detected value adjusted by the adjustment circuit unit, a compensation signal injection unit having a capacitor that injects the compensation signal into a ground line, and a control power supply unit that supplies control power to the compensation signal generation unit. In the power conversion apparatus, the detection unit, adjustment circuit unit, compensation signal generation unit, compensation signal injection unit, and control power supply unit form a filter that performs feedback control. The adjustment circuit unit adjusts the detection value to adjust the control gain of the filter, thereby adjusting the gain and phase of the open-loop transfer characteristic in a high-frequency band outside the compensation band of the filter.

[0007] The power conversion device according to the present disclosure has an advantage that it is possible to prevent oscillation in the high frequency band and perform a stable compensation operation for the common mode current.

[0008] FIG. 1 is a diagram showing a simplified equivalent circuit of the input portion of the detection unit, adjustment circuit unit, and compensation signal generation unit of the power conversion device shown in FIG. 1; FIG. 2 is a diagram showing an example of a method for adjusting the detection gain in the power conversion device according to embodiment 1; FIG. 3 is a diagram showing an example of a configuration of a refrigeration cycle application device according to embodiment 2; FIG. 4 is a diagram showing an example of a phase lag compensation circuit provided in the adjustment circuit unit of the power conversion device according to embodiment 1; FIG. 5 is a diagram showing an example of a phase lead compensation circuit provided in the adjustment circuit unit of the power conversion device according to embodiment 1;

[0009] Hereinafter, a power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] First Embodiment. FIG. 1 is a first diagram illustrating a configuration example of a power conversion device 2 according to a first embodiment. The power conversion device 2 is connected to an AC power supply 1 and a motor 3. The power conversion device 2 converts first AC power supplied from the AC power supply 1 into second AC power having a desired amplitude and phase and supplies the second AC power to the motor 3. In the example of FIG. 1 , the AC power supply 1 is a single-phase AC power supply, but it may be a three-phase AC power supply. The power conversion device 2 includes a passive filter 21, a detector 22, an adjustment circuit 23, a control power supply 24, a compensation signal generator 25, a compensation signal injection unit 26, a rectifier 27, a smoothing capacitor 28, and an inverter 29. The detector 22, the adjustment circuit 23, the control power supply 24, the compensation signal generator 25, and the compensation signal injection unit 26 form a filter 30 that functions as a common-mode current canceller and performs feedback control. The power conversion device 2 and the motor 3 form a motor drive device 5.

[0011] The passive filter 21 is a power converter configured with a Y capacitor that bypasses the common mode current, etc. In the example of Fig. 1, the passive filter 21 is configured with a capacitor, a choke coil, a Y capacitor, an X capacitor, a reactor, etc., but the components used and their arrangement are not limited to the example of Fig. 1. Note that the grounding point at which the Y capacitor provided in the passive filter 21 shown in Fig. 1 is connected to ground is actually located outside the power conversion device 2.

[0012] The detector 22 detects the common mode current flowing through the power line at a stage subsequent to the passive filter 21. As shown in FIG. 1 , the detector 22 detects the common mode current using a common mode transformer 221. The detector 22 outputs the detected value of the common mode current to the adjustment circuit unit 23.

[0013] The adjustment circuit unit 23 adjusts the detection value detected by the detection unit 22 to adjust the control gain of the filter 30, i.e., the characteristics of the filter 30. In the example of FIG. 1 , the adjustment circuit unit 23 adjusts the detection value detected by the detection unit 22 using a base resistor 231 and an LPF (Low Pass Filter) capacitor 232. That is, the adjustment circuit unit 23 includes a low-pass filter. In the example of FIG. 1 , the low-pass filter is a capacitor connected in parallel to the auxiliary winding side of the common mode transformer 221 of the detection unit 22. The cutoff frequency of the low-pass filter is, for example, 10 MHz or less. Note that, as will be described later, the adjustment circuit unit 23 can also adjust the detection value detected by the detection unit 22 using a component other than the LPF capacitor 232.

[0014] The control power supply unit 24 is disposed between the smoothing capacitor 28 and the inverter 29, branches the DC power supplied from the smoothing capacitor 28 to the inverter 29, and supplies the branched DC power to the compensation signal generation unit 25 as a control power supply for operating the compensation signal generation unit 25.

[0015] The compensation signal generator 25 generates a compensation signal for reducing the common-mode current, i.e., for compensating for the common-mode current, using the detection value adjusted by the adjustment circuit 23. The compensation signal generator 25 includes bipolar transistors 251 and 252. The compensation signal generator 25 generates the compensation signal by driving the bipolar transistors 251 and 252 using the control power supplied from the control power supply 24 in accordance with the detection value. The compensation signal is a current having an opposite phase to the common-mode current. The power conversion device 2 can reduce the common-mode current leaking to the ground from the power conversion device 2 by injecting the compensation signal to ground. Ideally, the compensation signal should match a current waveform obtained by inverting the amplitude of the common-mode current. However, as long as it is possible to reduce the common-mode current, the compensation signal may have a slightly different amplitude from the current waveform obtained by inverting the amplitude of the common-mode current, and may not necessarily match perfectly. The compensation signal generator 25 outputs the generated compensation signal to the compensation signal injection unit 26.

[0016] The compensation signal injection unit 26 injects to the ground the compensation signal generated by the compensation signal generation unit 25. The compensation signal injection unit 26 injects to the ground the compensation signal acquired from the compensation signal generation unit 25 via the injection resistor 261 and the injection capacitor 262. Note that the grounding point at which the injection capacitor 262 provided in the compensation signal injection unit 26 shown in FIG. 1 is connected to the ground is actually located outside the power conversion device 2.

[0017] The rectifier 27 is a power converter that rectifies the AC power that has passed through the passive filter 21 and the detection unit 22. The rectifier 27 is, for example, a diode bridge configured with four diodes, but the configuration of the rectifier 27 is not limited to this.

[0018] The smoothing capacitor 28 smoothes the DC power rectified by the rectifier 27. The smoothing capacitor 28 supplies the smoothed DC power to the inverter 29, and also to the compensation signal generating unit 25 by being branched by the control power supply unit 24.

[0019] The inverter 29 is a power converter that converts the DC power supplied from the smoothing capacitor 28 into AC power and outputs the AC power to the motor 3. The inverter 29 is configured with, for example, six switching elements, and converts the DC power into AC power by turning on and off the switching elements based on control signals from a control unit (not shown), but the configuration of the inverter 29 is not limited to this.

[0020] The motor 3 is a load connected to the power conversion device 2. In this embodiment, as shown in Fig. 1 , it is assumed that the motor 3 is connected to the ground point via a ground parasitic capacitance 4, and that a common mode current may flow from the motor 3 to the ground via the ground parasitic capacitance 4.

[0021] In the configuration of the power conversion device 2 shown in Fig. 1 , the ground point of the AC power supply 1, the ground point of the passive filter 21, the ground point of the compensation signal injection unit 26, and the ground point of the motor 3 via the ground parasitic capacitance 4 are electrically connected by a ground wire (not shown). That is, a common mode current flowing from one ground point to the ground may flow from another ground point into the power conversion device 2. Note that in the power conversion device 2, a common mode current may also flow to the ground from power converters such as the passive filter 21, the rectifier 27, and the inverter 29 via the ground parasitic capacitance (not shown). Note that the arrangement of the rectifier 27, the smoothing capacitor 28, the control power supply unit 24, and the like in the power conversion device 2 is merely an example and is not limited thereto, and arrangements other than those shown in Fig. 1 may also be used.

[0022] In the present embodiment, in the example of Fig. 1, the power conversion device 2 uses a low-pass filter as part of the adjustment circuit unit 23 to stably perform compensation for the common-mode current by setting the feedback characteristics of the filter 30 so that oscillation does not occur in the high-frequency band. By using a low-pass filter as part of the adjustment circuit unit 23, the power conversion device 2 can reduce the gain in the high-frequency band and prevent oscillation in the high-frequency band. Fig. 1 shows an example of a configuration in which an LPF capacitor 232 is connected in parallel to the auxiliary winding side of the common-mode transformer 221 of the detection unit 22, as an example of a low-pass filter.

[0023] FIG. 2 is a simplified equivalent circuit diagram of the detector 22, adjuster circuit 23, and input portion of compensation signal generator 25 of power converter 2 shown in FIG. 1 . In FIG. 2 , inductor L corresponds to common-mode transformer 221, capacitor C corresponds to LPF capacitor 232, and resistor R corresponds to base resistor 231. As shown in the equivalent circuit diagram of FIG. 2 , in power converter 2, main circuit common-mode current Icm is shunted according to the impedances of inductor L, capacitor C, and resistor R. As a result, base current Ib, which flows into the bases of bipolar transistors 251 and 252 of compensation signal generator 25, flows through resistor R, i.e., base resistor 231. A feature of the configuration of power converter 2 shown in FIG. 1 is that, since bipolar transistors 251 and 252 are used in compensation signal generator 25, base current Ib becomes the detection quantity, and therefore, main circuit common-mode current Icm is bypassed to LPF capacitor 232 rather than base resistor 231 in the high-frequency band, thereby reducing the detection gain. This allows the power conversion device 2 to reduce the gain of the feedback loop transfer characteristic in the high frequency band, thereby preventing oscillation in the high frequency band.

[0024] For reference, Fig. 3 shows an example of a method for adjusting the detection gain of the filter 30 of the power conversion device 2 shown in Fig. 1. Fig. 3 is a diagram showing an example of a method for adjusting the detection gain in the power conversion device 2 according to the first embodiment. In Fig. 3, the horizontal axis represents frequency, and the vertical axis represents detection gain. As shown in Fig. 3, the low cutoff frequency of the detection gain is determined by the impedance characteristic (hereinafter referred to as Z characteristic) of the inductor L and the Z characteristic of the resistor R, and the high cutoff frequency of the detection gain is determined by the Z characteristic of the resistor R and the Z characteristic of the capacitor C.

[0025] Fig. 4 is a diagram showing an example of the open-loop transfer characteristic of the filter 30 of the power conversion device 2 according to the first embodiment. In Fig. 4, the horizontal axis represents frequency, and the vertical axis represents the gain of the open-loop transfer characteristic. As described above, the filter 30 functions as a canceller for common-mode currents, and therefore the compensation band shown in Fig. 4 is the compensation band of the filter 30, i.e., the canceller. As shown in Fig. 4, the open-loop transfer characteristic of the filter 30 of the power conversion device 2 has a certain frequency band as the compensation band, and frequency bands lower than the compensation band and higher than the compensation band as being outside the compensation band.

[0026] In this embodiment, the adjustment circuit unit 23 of the power conversion device 2 adjusts the control gain of the filter 30 by adjusting the detection value, and adjusts the gain and phase of the open-loop transfer characteristic in the high frequency band outside the compensation band of the filter 30.

[0027] So far, the case where the compensation signal generating unit 25 of the power conversion device 2 includes bipolar transistors 251, 252, i.e., current-driven elements, as amplifying elements has been described, but the same effects as above can also be obtained when the compensation signal generating unit 25 of the power conversion device 2 includes voltage-driven elements such as MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) as amplifying elements. The following specifically describes the case where the compensation signal generating unit 25 includes MOSFETs as amplifying elements.

[0028] FIG. 5 is a second diagram illustrating a configuration example of the power conversion device 2 according to the first embodiment. The power conversion device 2 illustrated in FIG. 5 differs from the power conversion device 2 illustrated in FIG. 1 in that the common mode transformer 221 in the detection unit 22 is replaced with a common mode transformer 222, the base resistor 231 in the adjustment circuit unit 23 is replaced with gate resistors 233 and 234, the LPF capacitor 232 is replaced with LPF capacitors 235 and 236, and the bipolar transistors 251 and 252 in the compensation signal generation unit 25 are replaced with MOSFETs 253 and 254. That is, the adjustment circuit unit 23 includes a low-pass filter. Note that in FIG. 5, the LPF capacitors 235 and 236 may be disposed closer to the detection unit 22 than the gate resistors 233 and 234. By configuring the power conversion device 2 as shown in FIG. 5, it is possible to obtain the same effect as the power conversion device 2 shown in FIG. 1 even when the compensation signal generating unit 25 includes voltage-driven elements such as MOSFETs 253 and 254 as amplifying elements.

[0029] In the power conversion device 2, the adjustment circuit unit 23 is provided with a low-pass filter, i.e., a low-pass filter is applied as a configuration of the adjustment circuit unit 23 to reduce the gain in the high frequency band outside the compensation band and prevent oscillation in the high frequency band. However, the configuration for preventing oscillation in the high frequency band is not limited to a low-pass filter.

[0030] FIG. 6 is a diagram illustrating an example of a phase lag compensation circuit 237 included in the adjustment circuit unit 23 of the power conversion device 2 according to the first embodiment. The phase lag compensation circuit 237 is a phase compensation circuit configured with resistors 238 and 239 and a capacitor 240. The phase lag compensation circuit 237 illustrated in FIG. 6 is arranged, for example, in the power conversion device 2 illustrated in FIG. 5 in place of the LPF capacitors 235 and 236. In this way, even when the adjustment circuit unit 23 of the power conversion device 2 includes the phase lag compensation circuit 237 illustrated in FIG. 6, oscillation in the high frequency band can be prevented by controlling the phase of the gain of the open-loop transfer characteristic in the high frequency band outside the compensation band.

[0031] 7 is a diagram illustrating an example of a phase-lead compensation circuit 241 included in the adjustment circuit unit 23 of the power conversion device 2 according to the first embodiment. The phase-lead compensation circuit 241 is a phase compensation circuit configured with resistors 242 and 244 and a capacitor 243. The phase-lead compensation circuit 241 illustrated in FIG. 7 is arranged, for example, in the power conversion device 2 illustrated in FIG. 5 in place of the LPF capacitors 235 and 236. In this way, even when the adjustment circuit unit 23 of the power conversion device 2 includes the phase-lead compensation circuit 241 illustrated in FIG. 7, oscillation in the high-frequency band can be prevented by controlling the phase of the gain of the open-loop transfer characteristic in the high-frequency band outside the compensation band.

[0032] Fig. 8 is a diagram showing an example of a band elimination filter 245 included in the adjustment circuit unit 23 of the power conversion device 2 according to the first embodiment. The band elimination filter 245 is configured with a resistor 246, an inductor 247, and a capacitor 248. The band elimination filter 245 shown in Fig. 8 is arranged, for example, in the power conversion device 2 shown in Fig. 5 in place of the LPF capacitors 235, 236. In this way, even when the adjustment circuit unit 23 of the power conversion device 2 includes the band elimination filter 245 shown in Fig. 8, oscillation in the high frequency band can be prevented by reducing the gain of the open-loop transfer characteristic in the high frequency band outside the compensation band.

[0033] Fig. 9 is a diagram illustrating an example of a bandpass filter 249 included in the adjustment circuit unit 23 of the power conversion device 2 according to the first embodiment. The bandpass filter 249 is configured with an inductor 270, a capacitor 271, and a resistor 272. The bandpass filter 249 illustrated in Fig. 9 is arranged, for example, in the power conversion device 2 illustrated in Fig. 5 in place of the LPF capacitors 235 and 236. In this way, even when the adjustment circuit unit 23 of the power conversion device 2 includes the bandpass filter 249 illustrated in Fig. 9, it is possible to prevent oscillation in the high-frequency band by reducing the gain of the open-loop transfer characteristic in the high-frequency band outside the compensation band.

[0034] Fig. 10 is a diagram illustrating an example of a notch filter 273 included in the adjustment circuit unit 23 of the power conversion device 2 according to the first embodiment. The notch filter 273 is configured with resistors 274, 275, and 278 and capacitors 276, 277, and 279. The notch filter 273 illustrated in Fig. 10 is arranged, for example, in place of the LPF capacitors 235 and 236 in the power conversion device 2 illustrated in Fig. 5. In this way, even when the adjustment circuit unit 23 of the power conversion device 2 includes the notch filter 273 illustrated in Fig. 10, oscillation in the high frequency band can be prevented by reducing the gain at a specific frequency in the high frequency band outside the compensation band.

[0035] In this way, the adjustment circuit section 23 of the power conversion device 2 is not limited to the above example, and in addition to resistors, capacitors, inductors, etc., amplifiers, transistors, etc. may be used, and oscillation in the high frequency band can be prevented in various patterns, such as an Nth-order filter or a cascade connection of multiple filters.

[0036] The variations of the adjustment circuit unit 23 described in Figures 6 to 10 have been described in connection with the case where they are applied to the adjustment circuit unit 23 of the power conversion device 2 shown in Figure 5, but the present invention is not limited to this. The variations of the adjustment circuit unit 23 described in Figures 6 to 10 can be applied to the adjustment circuit unit 23 of the power conversion device 2 shown in Figure 1. In the power conversion device 2 shown in Figure 1, by adding a termination resistor to the auxiliary winding side of the common mode transformer 221 of the detection unit 22, it is possible to arrange any of the circuit configurations described in Figures 6 to 10 in place of the LPF capacitor 232.

[0037] In the example of FIG. 1 , the power conversion device 2 may have a configuration in which the resistance value of the base resistor 231 of the adjustment circuit unit 23 is set to a fixed value in advance to compensate for common-mode current in a desired frequency band, or may be configured to be dynamically changeable. FIG. 11 is a third diagram illustrating a configuration example of the power conversion device 2 according to the first embodiment. The power conversion device 2 illustrated in FIG. 11 is configured by adding a control unit 31 to the power conversion device 2 illustrated in FIG. 1 . The control unit 31 can change the resistance value of the adjustment circuit unit 23, i.e., the resistance value of the base resistor 231. FIG. 12 is a diagram illustrating an operation of switching the resistance value of the base resistor 231 included in the power conversion device 2 according to the first embodiment. In the example of FIG. 12 , the base resistor 231 includes a switch 231a and resistors 231b and 231c. The connection destination of the switch 231a can be changed under the control of the control unit 31. The resistor 231b is a resistor that can compensate for common-mode current in a low-frequency band from 1 kHz to 30 kHz, for example. The resistor 231c is a resistor that corresponds to compensation for common mode current in a high frequency band from 150 kHz to 10 MHz, for example.

[0038] For example, when the power conversion device 2 is applied to an air conditioner, the control unit 31 controls the switch 231a in accordance with the operating state of the air conditioner (not shown), such as the set temperature and the operating mode (cooling, heating, etc.), to appropriately change the resistance value of the base resistor 231. The power conversion device 2 can dynamically change the resistance value of the base resistor 231 of the adjustment circuit unit 23 by configuring the power conversion device 2 as shown in FIGS. 11 and 12. Although not shown, the power conversion device 2 can also appropriately change the resistance values ​​of gate resistors 233 and 234, resistors 238, 239, 242, 244, 246, 272, 274, 275, and 278 by configuring them in the same manner as the base resistor 231 shown in FIG. 12. The control unit 31 may be the same as or different from the aforementioned control unit for controlling the on / off of a switching element (not shown) included in the inverter 29.

[0039] As described above, according to this embodiment, in the power conversion device 2, the adjustment circuit unit 23 adjusts the control gain of the filter 30 by adjusting the detection value acquired from the detection unit 22, and adjusts the gain and phase of the open-loop transfer characteristic in a high frequency band outside the compensation band of the filter 30. This enables the power conversion device 2 to prevent oscillation in the high frequency band and to stably perform compensation operation for the common mode current.

[0040] Second Embodiment Fig. 13 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to a second embodiment. The refrigeration cycle-applied device 900 according to the second embodiment includes the power conversion device 2 described in the first embodiment. The refrigeration cycle-applied device 900 according to the second embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 13, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0041] The refrigeration cycle application equipment 900 includes a compressor 6 incorporating the motor 3 in embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910 attached via refrigerant piping 912.

[0042] Inside the compressor 6, a compression mechanism 904 that compresses the refrigerant and a motor 3 that operates the compression mechanism 904 are provided.

[0043] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 3 that is variably controlled in speed.

[0044] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 904.

[0045] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0046] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0047] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0048] REFERENCE SIGNS LIST 1 AC power supply, 2 Power conversion device, 3 Motor, 4 Ground parasitic capacitance, 5 Motor drive device, 6 Compressor, 21 Passive filter, 22 Detection unit, 23 Adjustment circuit unit, 24 Control power supply unit, 25 Compensation signal generation unit, 26 Compensation signal injection unit, 27 Rectifier, 28 Smoothing capacitor, 29 Inverter, 30 Filter, 31 Control unit, 221, 222 Common mode transformer, 231 Base resistor, 231a Switch, 231b, 231c, 238, 239, 242, 244, 246, 272, 274, 275, 278 Resistor, 232, 235, 236 LPF capacitor, 233, 234 Gate resistor, 237 Phase lag compensation circuit, 240, 243, 248, 271, 276, 277, 279 Capacitor, 241 phase lead compensation circuit, 245 band elimination filter, 247, 270 inductor, 249 band pass filter, 251, 252 bipolar transistor, 253, 254 MOSFET, 261 injection resistor, 262 injection capacitor, 273 notch filter, 900 refrigeration cycle applicable equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A power conversion device comprising: a detection unit that detects a common mode current flowing in a power line using a common mode transformer and outputs a detection value; an adjustment circuit unit that adjusts the detection value; a compensation signal generation unit that generates a compensation signal that compensates for the common mode current using the detection value adjusted by the adjustment circuit unit; a compensation signal injection unit having a capacitor that injects the compensation signal into a ground line; and a control power supply unit that supplies a control power source to the compensation signal generation unit, wherein the detection unit, adjustment circuit unit, compensation signal generation unit, compensation signal injection unit, and control power supply unit form a filter that performs feedback control, and the adjustment circuit unit adjusts the detection value to adjust the control gain of the filter and adjust the gain and phase of the open-loop transfer characteristic in a high-frequency band outside the compensation band of the filter.

2. The power conversion device according to claim 1, wherein the compensation signal generating section includes a bipolar transistor.

3. The power conversion device according to claim 1, wherein the compensation signal generating section includes a Metal-Oxide-Semiconductor Field Effect Transistor.

4. The power conversion device according to claim 2, wherein the adjustment circuit section includes a low-pass filter.

5. The power conversion device according to claim 4, wherein the low-pass filter is a capacitor connected in parallel to an auxiliary winding side of the common mode transformer.

6. The power conversion device according to claim 4 or 5, wherein the cutoff frequency of the low-pass filter is 10 MHz or less.

7. The power conversion device according to claim 3, wherein the adjustment circuit section includes a low-pass filter.

8. The power conversion device according to claim 2 or 3, wherein the adjustment circuit section includes a phase compensation circuit.

9. The power conversion device according to claim 2 or 3, wherein the adjustment circuit section includes a band elimination filter.

10. The power conversion device according to claim 2 or 3, wherein the adjustment circuit section includes a bandpass filter.

11. A motor drive device comprising a power conversion device according to any one of claims 1 to 10.

12. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 10.

Images