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

Abstract

A power conversion device (2) comprises: a detection unit (22) that detects a common mode current by means of a common mode transformer (221) and outputs a detected value; an adjustment circuit unit (23) that adjusts the detected value; a compensation signal generation unit (25) that generates a compensation signal that compensates for the common mode current by using the detected value after the adjustment by the adjustment circuit unit (23); a compensation signal injection unit (26) that has an injection capacitor (262) that injects the compensation signal into a ground line; and a control power supply unit (24) that supplies a control power supply to the compensation signal generation unit (25). The detection unit (22), the adjustment circuit unit (23), the compensation signal generation unit (25), the compensation signal injection unit (26), and the control power supply unit (24) constitute a filter (30) for performing a feedback control. A parallel impedance is configured on the auxiliary winding side of the common mode transformer (221). A series resonance due to the inductance of the common mode transformer (221) and a ground parasitic capacitance is damped by the parallel impedance.

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 the common mode current may worsen due to series resonance caused by the reactor for detecting the common mode current and the motor-to-ground parasitic capacitance between the motor, which is a load connected to the power conversion device, and the ground point.

[0005] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can suppress deterioration of common mode current caused by series resonance.

[0006] To solve the above-mentioned problems and achieve the object, the present disclosure provides a power conversion device that uses a power converter to convert AC power supplied from an AC power source or DC power supplied from a DC power source and supplies the converted power to a load. The power conversion device 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 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 supply to the compensation signal generation unit. In the power conversion device, 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. In the power conversion device, a parallel impedance is formed on the auxiliary winding side of the common-mode transformer using at least the impedance of the adjustment circuit unit, and the parallel impedance damps series resonance caused by the inductance of the common-mode transformer and at least one parasitic capacitance to ground of the power converter and the load.

[0007] The power conversion device according to the present disclosure has an advantage that it is possible to suppress deterioration of common mode current caused by series resonance.

[0008] FIG. 1 shows a configuration example of a power conversion device according to embodiment 1. FIG. 2 shows a configuration example of a power conversion device according to embodiment 1. FIG. 3 shows a configuration example of a power conversion device according to embodiment 1. FIG. 4 shows a configuration example of a power conversion device according to embodiment 1. FIG. 5 shows an example of a power conversion device according to embodiment 1. FIG. 6 shows an example of a power conversion device according to embodiment 1. FIG. 7 shows an example of a power conversion device according to embodiment 1. FIG. 8 shows an example of a 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, thereby adjusting 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. Note that the adjustment circuit unit 23 can also adjust the detection value detected by the detection unit 22 using a configuration other than the base resistor 231, and can also adjust the detection value detected by the detection unit 22 using another configuration together with the base resistor 231.

[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 this manner, the power conversion device 2 performs power conversion on the AC power supplied from the AC power source 1 using power converters such as the rectifier 27 and the inverter 29, and supplies the AC power obtained by the power conversion to the motor 3, which is a load. In this embodiment, the power conversion device 2 configures a parallel impedance on the auxiliary winding side of the common mode transformer 221 using at least the impedance of the adjustment circuit unit 23, and the parallel impedance damps series resonance caused by the inductance of the common mode transformer 221 and at least one parasitic capacitance to ground of the power converter and the motor 3, which is a load. Note that the series resonance is assumed to be LC series resonance. Although simply referred to as "series resonance" hereinafter, this also applies to LC series resonance. Furthermore, although the power supplied to the power conversion device 2 has been described as AC power supplied from the AC power source 1, this is not limiting. Although not shown, the power supplied to the power conversion device 2 can also be DC power supplied from a DC power source.

[0023] Here, we will explain why the power conversion device 2 can damp series resonance by using a parallel impedance configured on the auxiliary winding side of the common mode transformer 221. Fig. 2 shows an example of an equivalent circuit 40 of a power conversion device, as a comparative example, in which a parallel impedance is not configured on the auxiliary winding side of the common mode transformer for detecting common mode currents in the detection unit of the power conversion device. The equivalent circuit 40 shown in Fig. 2 is represented by a common choke 41 such as a choke coil of the passive filter 21, a Y capacitor 42 of the passive filter 21, a detection reactor 43 of the common mode transformer 221 of the detection unit 22, a common mode current source 44 that is a source of common mode current such as the inverter 29, and a ground parasitic capacitance 45 that is the ground parasitic capacitance 4 of the motor 3. In the equivalent circuit 40, when series resonance occurs due to the detection reactor 43 and the ground parasitic capacitance 45, the series impedance becomes extremely small at the resonance frequency. As a result, since the common mode voltage of the common mode current generated by the common mode current source 44 is constant, the common mode current deteriorates in the equivalent circuit 40 .

[0024] Fig. 3 is a diagram showing an example of an equivalent circuit 40a of the power conversion device 2 according to the first embodiment, in which a parallel impedance is configured on the auxiliary winding side of the common mode transformer 221 of the detection unit 22. The equivalent circuit 40a shown in Fig. 3 is obtained by adding a parallel impedance 46 to the equivalent circuit 40 shown in Fig. 2. By adding the parallel impedance 46 to the impedance of the detection reactor 43 corresponding to the common mode transformer 221, the equivalent circuit 40a can damp the series resonance caused by the detection reactor 43 and the ground parasitic capacitance 45, thereby suppressing deterioration of the common mode current.

[0025] In the power conversion device 2 shown in FIG. 1 , the impedance of parallel impedance 46 of equivalent circuit 40a shown in FIG. 3 is the input impedance Zin of adjustment circuit unit 23 and compensation signal generator 25 as viewed from the auxiliary winding side of common mode transformer 221 of detection unit 22. Input impedance Zin of adjustment circuit unit 23 and compensation signal generator 25 is converted to impedance Zin' on the main circuit side by the square of the turns ratio of common mode transformer 221 of detection unit 22, i.e., "number of main circuit windings / number of auxiliary windings." In the power conversion device 2, it is assumed that input impedance Zin of adjustment circuit unit 23 and compensation signal generator 25 as viewed from the auxiliary winding side of common mode transformer 221 of detection unit 22 is designed so that impedance Zin' can suppress series resonance caused by detection reactor 43 and ground parasitic capacitance 45 on the main circuit side. In the power conversion device 2, the parallel impedance formed on the auxiliary winding side of the common mode transformer 221 of the detector 22 is set to be equal to or less than the impedance on the main circuit side of the common mode transformer 221 of the detector 22.

[0026] In the power conversion device 2, if the base resistor 231 is fixed and a sufficient amount of damping cannot be obtained, a damping resistor may be added in parallel to the auxiliary winding as shown in Fig. 4. Fig. 4 is a second diagram showing a configuration example of the power conversion device 2 according to the first embodiment. The power conversion device 2 shown in Fig. 4 is configured such that, compared to the power conversion device 2 shown in Fig. 1, a damping resistor 232 is added in parallel to the auxiliary winding of the common mode transformer 221 of the detection unit 22 in the adjustment circuit unit 23. This allows the power conversion device 2 to set the parallel impedance on the auxiliary winding side of the common mode transformer 221 to a value corresponding to the resonant frequency of the series resonance.

[0027] Furthermore, in the power conversion device 2, when the base resistor 231 is fixed and a sufficient amount of damping cannot be obtained, an inductor, a capacitor, or the like may be added instead of a resistor, as shown in FIG. 5 . FIG. 5 is a third diagram showing a configuration example of the power conversion device 2 according to the first embodiment. The power conversion device 2 shown in FIG. 5 is configured by adding a damping inductor 233 and a damping capacitor 234 to the auxiliary winding of the common mode transformer 221 of the detection unit 22 in the adjustment circuit unit 23, compared to the power conversion device 2 shown in FIG. 1 . This allows the power conversion device 2 to set the parallel impedance on the auxiliary winding side of the common mode transformer 221 to a value corresponding to the resonant frequency of the series resonance. In the example shown in FIG. 5 , the parallel impedance configured on the auxiliary winding side of the common mode transformer 221 of the detection unit 22 is a composite impedance of the damping inductor 233, the damping capacitor 234, and the base resistor 231 provided in the adjustment circuit unit 23, and the input impedance of the compensation signal generation unit 25.

[0028] In the power conversion device 2, it is also possible to add only the damping inductor 233 shown in Fig. 5 or the damping capacitor 234 shown in Fig. 5 to the example in Fig. 1. For example, in the power conversion device 2, if the damping capacitor 234 shown in Fig. 5 is added to the example in Fig. 1 and the input impedance of the compensation signal generation unit 25 is negligible, the parallel impedance configured on the auxiliary winding side of the common mode transformer 221 of the detection unit 22 is the combined impedance of the damping capacitor 234 and the base resistor 231 provided in the adjustment circuit unit 23. Note that in the example in Fig. 1, the parallel impedance configured on the auxiliary winding side of the common mode transformer 221 of the detection unit 22 in the power conversion device 2 is the combined impedance of the base resistor 231 provided in the adjustment circuit unit 23 and the input impedance of the compensation signal generation unit 25.

[0029] 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.

[0030] 6 is a first diagram showing a configuration example when power conversion device 2 according to Embodiment 1 includes a voltage-driven element as an amplifying element in compensation signal generation unit 25. Power conversion device 2 shown in FIG. 6 differs from power conversion device 2 shown in FIG. 1 in that common mode transformer 221 in detection unit 22 is replaced with common mode transformer 222, base resistor 231 is replaced with gate resistors 235 and 236 in adjustment circuit unit 23, and bipolar transistors 251 and 252 are replaced with MOSFETs 253 and 254 in compensation signal generation unit 25. In this case, the parallel impedance formed on the auxiliary winding side of common mode transformer 222 in detection unit 22 is the combined impedance of gate resistor 235 included in adjustment circuit unit 23 and the input impedance of MOSFET 253 in compensation signal generation unit 25, and the combined impedance of gate resistor 236 included in adjustment circuit unit 23 and the input impedance of MOSFET 254 in compensation signal generation unit 25. The input impedance of the compensation signal generating unit 25 is the impedance component of the gate-source capacitance Cgs of the MOSFETs 253 and 254. When the impedance component of the gate-source capacitance Cgs of the MOSFETs 253 and 254 is sufficiently small, the gate resistors 235 and 236 included in the adjustment circuit unit 23 serve as damping elements.

[0031] When the impedance component of the gate-source capacitance Cgs of the MOSFETs 253 and 254 is sufficiently large, i.e., when a sufficient amount of damping cannot be obtained, the power conversion device 2 may add a damping resistor in parallel to the auxiliary winding as shown in FIG. 7 . FIG. 7 is a second diagram showing a configuration example in which the power conversion device 2 according to the first embodiment includes a voltage-driven element as the amplifying element of the compensation signal generating unit 25. The power conversion device 2 shown in FIG. 7 is configured such that, in the power conversion device 2 shown in FIG. 6 , damping resistors 237 and 238 are added in parallel to the auxiliary winding of the common mode transformer 222 of the detection unit 22 in the adjustment circuit unit 23. This allows the power conversion device 2 to set the parallel impedance on the auxiliary winding side of the common mode transformer 222 to a value corresponding to the resonant frequency of the series resonance. Furthermore, when the impedance component of the gate-source capacitance Cgs of the MOSFETs 253 and 254 is sufficiently large, that is, when a sufficient amount of damping cannot be obtained, the power conversion device 2 can also add, for two systems, components equivalent to the damping inductor 233 and damping capacitor 234 shown in FIG. 5 instead of the damping resistors 237 and 238, although not shown in the figure.

[0032] 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 the resistance value may be dynamically changeable. FIG. 8 is a fourth diagram illustrating a configuration example of the power conversion device 2 according to the first embodiment. The power conversion device 2 illustrated in FIG. 8 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. 9 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. 9 , 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 the high frequency band from 150 kHz to 10 MHz, for example.

[0033] 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 it as shown in FIGS. 8 and 9 . Although not shown, the power conversion device 2 can also appropriately change the resistance values ​​of the damping resistor 232, gate resistors 235 and 236, damping resistors 237 and 238, etc., by configuring them in the same manner as the base resistor 231 shown in FIG. 9 . Note that 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) provided in the inverter 29.

[0034] As described above, according to this embodiment, the power conversion device 2 damps the series resonance between the common mode transformer 221 or the common mode transformer 222 and the ground parasitic capacitance 4 of the motor 3, using the parallel impedance on the auxiliary winding side of the common mode transformer 221 or the common mode transformer 222 of the detection unit 22. This allows the power conversion device 2 to suppress deterioration of the common mode current caused by the series resonance.

[0035] Second Embodiment Fig. 10 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. 10, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0036] 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.

[0037] Inside the compressor 6, a compression mechanism 904 that compresses the refrigerant and a motor 3 that operates the compression mechanism 904 are provided.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] REFERENCE SIGNS LIST 1 AC power supply, 2 Power conversion device, 3 Motor, 4, 45 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, 40, 40a Equivalent circuit, 41 Common choke, 42 Y capacitor, 43 Detection reactor, 44 Common mode current source, 46 Parallel impedance, 221, 222 Common mode transformer, 231 Base resistor, 231a Switch, 231b, 231c Resistor, 232, 237, 238 Damping resistor, 233 Damping inductor, 234 Damping capacitor, 235, 236 Gate resistor, 251, 252 Bipolar transistor, 253, 254 MOSFET, 261 injection resistor, 262 injection capacitor, 900 refrigeration cycle application 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 that uses a power converter to convert AC power supplied from an AC power source or DC power supplied from a DC power source and supply the converted power to a load, 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, the adjustment circuit unit, the compensation signal generation unit, the compensation signal injection unit, and the control power supply unit form a filter that performs feedback control, and a parallel impedance is formed on the auxiliary winding side of the common mode transformer using at least the impedance of the adjustment circuit unit, and series resonance caused by the inductance of the common mode transformer and at least one parasitic capacitance to ground of the power converter and the load is damped by the parallel impedance.

2. The power conversion device according to claim 1, wherein the parallel impedance is equal to or less than an impedance on a main circuit side of the common mode transformer.

3. The power conversion device according to claim 1 or 2, wherein the parallel impedance is a composite impedance of an inductor, a capacitor, and a resistor included in the adjustment circuit section and an input impedance of a compensation signal generating section.

4. The power conversion device according to claim 1 or 2, wherein the parallel impedance is a composite impedance of a capacitor and a resistor included in the adjustment circuit section.

5. The power conversion device according to claim 1 or 2, wherein the parallel impedance is a composite impedance of a resistor included in the adjustment circuit section and an input impedance of the compensation signal generation section.

6. The power conversion device according to claim 3, further comprising: a control unit capable of changing the resistance value of the resistor.

7. A motor drive device comprising a power conversion device according to any one of claims 1 to 6.

8. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 6.

Images