Power Conversion Equipment

Abstract

To provide a power conversion device suppressing heat evolution of a Y capacitor by current flowing when a ground fault has occurred in an inverter.SOLUTION: A power conversion device 100 performs a power conversion through a high potential side wiring 301 and a low potential side wiring 302 between a battery 200 and a motor 400, and has an inverter 500 connected to the high potential side wiring and the low potential side wiring and having a plurality of switches 521 and 522, Y capacitors 310 and 320 connected to the high potential side wiring and the low potential side wiring in parallel with the inverter, and also connected to ground, and a control device 600 for controlling the plurality of switches so as to further decrease the number of switches of the plurality of switches when the inverter is in ground fault than when the inverter is not in ground fault.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosure described herein relates to a power conversion device that converts power between a battery and a motor. [Background technology]

[0002] Patent Document 1 describes a smoothing circuit F connected to a battery B via a power line S, and a three-phase AC conversion circuit E connected in parallel therewith. The smoothing circuit F includes a Y capacitor that removes, via ground, high-frequency components leaking from the three-phase AC conversion circuit E to the smoothing circuit F. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4314513 Summary of the Invention [Problem to be solved by the invention]

[0004] If the three-phase AC conversion circuit E has a ground fault, an unintended current may flow through the Y capacitor, which may result in the Y capacitor overheating.

[0005] Therefore, an object of the present disclosure is to provide a power conversion device in which heat generation in the Y capacitor due to a current flowing when an inverter has a ground fault is suppressed. [Means for solving the problem]

[0006] A power conversion device according to one aspect of the present disclosure includes: A power conversion device (100) that performs power conversion between a battery (200) and a motor (400) via a high-potential side wiring (301) and a low-potential side wiring (302), An inverter (500) connected to a high potential side wiring and a low potential side wiring and having a plurality of switches (521, 522); Y capacitors (310, 320) connected to the high-potential side wiring and the low-potential side wiring in a manner parallel to the inverter and also connected to earth; A control device (600) that controls the multiple switches so that the number of times the multiple switches are switched is reduced when the inverter has a ground fault compared to when the inverter does not have a ground fault. 、 The control device has a motor adjustment unit (630) that reduces at least one of the torque and the rotation speed of the motor when a ground fault occurs in the inverter.

[0007] This makes it easier to suppress the current flowing through the Y capacitors (310, 320) when a ground fault occurs in the inverter (500). It is also possible to suppress heat generation in the Y capacitors (310, 320).

[0008] It should be noted that the reference numbers in parentheses above merely indicate the corresponding relationship with the configurations described in the embodiments described below, and do not in any way limit the technical scope. [Brief description of the drawings]

[0009] [Figure 1] 2 is an electric circuit diagram illustrating a power conversion device including a carrier control unit and an in-vehicle system. FIG. [Diagram 2] FIG. 11 is a schematic diagram illustrating the relationship between the carrier frequency and the number of switches. [Diagram 3] 4 is a flowchart illustrating a process of the control device. [Figure 4] FIG. 11 is a diagram illustrating an example of data illustrating the relationship between a carrier frequency and an effective value. [Diagram 5] 2 is an electric circuit diagram illustrating a power conversion device including a drive control unit and an in-vehicle system. FIG. [Figure 6] 4 is a flowchart illustrating a process of the control device. [Figure 7] FIG. 11 is a schematic diagram illustrating the relationship between the control method and the number of switches. [Figure 8] 2 is an electric circuit diagram illustrating a power conversion device including a carrier control unit and a drive control unit and an in-vehicle system. FIG. [Figure 9]4 is a flowchart illustrating a process of the control device. [Figure 10] 2 is an electric circuit diagram illustrating a power conversion device and an in-vehicle system including a carrier control unit, a drive control unit, and a motor control unit. FIG. [Figure 11] 4 is a flowchart illustrating a process of the control device. [Figure 12] 4 is a graph illustrating the relationship between the rotation speed and torque of a motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be used to designate parts corresponding to matters described in the preceding embodiment, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, the other embodiment described previously may be applied to the other parts of the configuration.

[0011] In addition to combinations of parts that are explicitly stated as possible in each embodiment, it is also possible to partially combine embodiments, embodiments and variations, and variations even if not explicitly stated, provided that there are no particular problems with the combination.

[0012] (First embodiment) First, an on-vehicle system 10 will be described with reference to Fig. 1. This on-vehicle system 10 constitutes a system for an electric vehicle. The on-vehicle system 10 has a power conversion device 100, a battery 200, a motor 400, and a leakage detector 700. The power conversion device 100 has a first Y capacitor 310, a second Y capacitor 320, an inverter 500, and a control device 600.

[0013] The battery 200 has a plurality of secondary batteries. These secondary batteries are connected in series to form a battery stack. The SOC of this battery stack corresponds to the SOC of the battery 200. The secondary batteries may be lithium ion secondary batteries, nickel hydrogen secondary batteries, organic radical batteries, or the like. A high potential side wiring 301 is connected to a high potential side electrode of the battery 200. A low potential side wiring 302 is connected to a low potential side electrode of the battery 200. The battery 200 is connected to the motor 400 via the high potential side wiring 301 and the low potential side wiring 302.

[0014] The inverter 500 performs power conversion between the battery 200 and the motor 400. The inverter 500 converts DC power of the battery 200 into AC power. The power conversion converts AC power generated by power generation (regeneration) of the motor 400 into DC power.

[0015] The motor 400 is connected to an output shaft of an electric vehicle (not shown). The rotational energy of the motor 400 is transmitted to the running wheels of the electric vehicle via the output shaft. Conversely, the rotational energy of the running wheels is transmitted to the motor 400 via the output shaft.

[0016] The motor 400 is powered by AC power supplied from the inverter 500. This provides a propulsive force to the running wheels. The motor 400 also regenerates power using the rotational energy transmitted from the running wheels. The AC power generated by this regeneration is converted to DC power by the inverter 500. This DC power is supplied to the battery 200. The DC power is also supplied to various electrical loads mounted on the electric vehicle.

[0017] The first Y capacitor 310 and the second Y capacitor 320 are connected to the high potential side wiring 301 and the low potential side wiring 302 in a manner that they are parallel to the inverter 500. The first Y capacitor 310 and the second Y capacitor 320 are connected in series between the high potential side wiring 301 and the low potential side wiring 302.

[0018] Specifically, one of two electrodes of first Y capacitor 310 is connected to high potential side wiring 301 via first intermediate wiring 303. One of two electrodes of second Y capacitor 320 is connected to low potential side wiring 302 via third intermediate wiring 305. The other of the two electrodes of first Y capacitor 310 is connected to the other of the two electrodes of second Y capacitor 320 via second intermediate wiring 304. Furthermore, second intermediate wiring 304 is connected to ground wiring 306 which is connected to the vehicle earth.

[0019] The first Y capacitor 310 and the second Y capacitor 320 function to remove noise components leaking from the inverter 500 by discharging the noise components to the vehicle earth.

[0020] Of the noise components of the inverter 500, those flowing through the high potential side wiring 301 flow through the first intermediate wiring 303, the first Y capacitor 310, the second intermediate wiring 304, and the third intermediate wiring 305 to the vehicle earth.

[0021] Of the noise components of the inverter 500, the noise components flowing through the low potential side wiring 302 flow via the third intermediate wiring 305, the second Y capacitor 320, the second intermediate wiring 304, and the third intermediate wiring 305 to the vehicle earth.

[0022] The control device 600 is equipped with an ECU and a gate driver (not shown). The gate driver controls the inverter 500 based on a signal from the ECU. This controls the regeneration and power running of the motor 400 according to the SOC of the battery 200. SOC is an abbreviation for state of charge. ECU is an abbreviation for electronic control unit.

[0023] The ECU includes an information acquisition unit (not shown) that acquires information from the outside. The gate driver includes a switch control unit (not shown) that controls the on / off of the high-side switch 521 and the low-side switch 522.

[0024] The earth leakage detector 700 is connected between the low potential side electrode of the battery 200 and the vehicle earth. The earth leakage detector 700 has a function of detecting a current that unintentionally leaks from the inverter 500. The earth leakage information detected by the earth leakage detector 700 is transmitted to the control device 600.

[0025] <Inverter> The inverter 500 has a smoothing capacitor 540 and a three-phase switch module 510. The smoothing capacitor 540 and the three-phase switch module 510 are connected in parallel between the high potential side wiring 301 and the low potential side wiring 302. In addition, as described above, the first Y capacitor 310 and the second Y capacitor 320 are connected in series between the high potential side wiring 301 and the low potential side wiring 302.

[0026] As shown in FIG. 1, a first Y capacitor 310, a second Y capacitor 320, a smoothing capacitor 540, and a switch module 510 are connected in parallel in this order between a high potential side wiring 301 and a low potential side wiring 302 from a battery 200 toward a motor 400.

[0027] When the motor 400 is powered, the high-side switch 521 and the low-side switch 522 of each switch module 510 are PWM-controlled by a control signal from the ECU. As a result, the inverter 500 generates a three-phase AC current.

[0028] When the motor 400 generates power (regenerates power), the ECU, for example, stops outputting a control signal. As a result, AC power generated by the power generation of the motor 400 passes through the diodes provided in each of the switch modules 510. As a result, the AC power is converted into DC power.

[0029] In this embodiment, an n-channel IGBT is used as the switch included in each switch module 510. However, MOSFETs may also be used as these switches instead of IGBTs. When MOSFETs are used as the switches, the above-mentioned diodes may not be required.

[0030] These switches can be manufactured using semiconductors such as Si and wide-gap semiconductors such as SiC. There are no particular limitations on the materials used to construct the semiconductor elements.

[0031] <Switch module> The switch module 510 has, as switches, a high-side switch 521 and a low-side switch 522. The switch module 510 has, as diodes, a high-side diode 521a and a low-side diode 522a.

[0032] A cathode electrode of the high-side diode 521a is connected to a first collector electrode 531 which is a collector electrode of the high-side switch 521. An anode electrode of the high-side diode 521a is connected to a first emitter electrode 532 which is an emitter electrode of the high-side switch 521. A first gate electrode 535 of the high-side switch 521 is electrically connected to the control device 600.

[0033] A cathode electrode of the low-side diode 522a is connected to a second collector electrode 533 which is a collector electrode of the low-side switch 522. An anode electrode of the low-side diode 522a is connected to a second emitter electrode 534 which is an emitter electrode of the low-side switch 522. A second gate electrode 536 of the low-side switch 522 is electrically connected to the control device 600.

[0034] 1, the first collector electrode 531 is connected to the high potential side wiring 301. The second emitter electrode 534 is connected to the low potential side wiring 302. The first emitter electrode 532 and the second collector electrode 533 are connected to the motor 400 via the output bus bar 430.

[0035] More specifically, the switch module 510 includes a U-phase switch module 511 , a V-phase switch module 512 , and a W-phase switch module 513 .

[0036] A first emitter electrode 532 of the high-side switch 521 included in the U-phase switch module 511 and a second collector electrode 533 of the low-side switch 522 included in the U-phase switch module 511 are connected to the motor 400 via a U-phase output bus bar 431 .

[0037] A first emitter electrode 532 of the high-side switch 521 included in the V-phase switch module 512 and a second collector electrode 533 of the low-side switch 522 included in the V-phase switch module 512 are connected to the motor 400 via a V-phase output bus bar 432 .

[0038] A first emitter electrode 532 of the high-side switch 521 included in the W-phase switch module 513 and a second collector electrode 533 of the low-side switch 522 included in the W-phase switch module 513 are connected to the motor 400 via a W-phase output bus bar 433 .

[0039] <Control device> As described above, an ECU, a gate driver, etc. (not shown) are mounted on the control device 600. The gate driver performs PWM control of the high-side switch 521 and the low-side switch 522 provided in the inverter 500 based on a signal from the ECU.

[0040] However, in the on-vehicle system 10 shown in FIG. 1, when a ground fault occurs such that the inverter 500 has a ground fault to the vehicle earth, a leakage path 800 is formed between the inverter 500 and the vehicle earth.

[0041] In this case, the ground potential may fluctuate, causing unintended current leaking from inverter 500 to flow through first Y capacitor 310 and second Y capacitor 320 via ground wiring 306. If unintended current leaking from inverter 500 flows through first Y capacitor 310 and second Y capacitor 320, first Y capacitor 310 and second Y capacitor 320 may generate heat.

[0042] In this embodiment, therefore, the control device 600 is designed to suppress heat generation in the first Y capacitor 310 and the second Y capacitor 320 due to unintended current leaking from the inverter 500 when a ground fault occurs in the inverter 500. Specifically, the ECU included in the control device 600 is provided with a carrier control unit 610. As an example, the carrier control unit 610 is provided in a microcomputer (not shown) mounted on the control device 600.

[0043] <Carrier control section> First, PWM control will be described with reference to Fig. 2. As shown in Fig. 2(a), a driving wave 410 for driving a motor 400 may be, for example, a sine wave. A carrier wave 420 for controlling the on / off switching of the high-side switch 521 and the low-side switch 522 described above may be, for example, a triangular wave.

[0044] 2(a) shows a comparison between drive wave 410 and carrier wave 420. FIG. 2(b) shows the relationship between the voltage applied to high-side switch 521 included in a specific phase and time as a result of the comparison between drive wave 410 and carrier wave 420.

[0045] As a result of comparing the drive wave 410 and the carrier wave 420, when the drive wave 410 is greater than the carrier wave 420, a voltage is applied to the first gate electrode 535 of the high-side switch 521. In other words, when the drive wave 410 is greater than the carrier wave 420, a specific high-side switch 521 is turned on.

[0046] Conversely, when the drive wave 410 is smaller than the carrier wave 420, no voltage is applied to the first gate electrode 535 of the high-side switch 521. When the drive wave 410 is smaller than the carrier wave 420, a certain high-side switch 521 is in the off state.

[0047] Although not shown, the relationship between the voltage applied to the low-side switch 522 included in a given phase and time is the inverse of the relationship between the voltage applied to the high-side switch 521 and time.

[0048] This method of changing the average voltage value during a certain period by changing the duration of voltage application to the high-side switch 521 and the low-side switch 522 is called PWM control. The motor control method of the inverter 500 in the first embodiment is a three-phase modulation method. The waveform of the voltage output from the inverter 500 is a sine wave.

[0049] As described above, the control device 600 has the carrier control unit 610. When the inverter 500 has a ground fault to the vehicle earth, an unintended current flows through the leakage path 800 to the leakage detector 700 via the ground wiring 306, the second intermediate wiring 304, the second Y capacitor 320, the third intermediate wiring 305, and the low potential side wiring 302, as shown in FIG.

[0050] As shown in FIG. 3, when leakage detector 700 detects the occurrence of a ground fault in inverter 500 in step S1000, the ground fault information is sent to the information acquiring unit.

[0051] When the information acquiring unit acquires the ground fault information sent from earth leakage detector 700 in step S1100, in step S1200, carrier control unit 610 reduces the carrier frequency of carrier wave 420. More specifically, carrier control unit 610 reduces the carrier frequency of carrier wave 420 below the carrier frequency of carrier wave 420 when inverter 500 does not have a ground fault.

[0052] 2(a), carrier wave 420 when inverter 500 is not grounded is shown by a solid line. Carrier wave 420 after the carrier frequency has been reduced is shown by a dashed line and a dot-dash line. For ease of explanation below, carrier wave 420 shown by a solid line is shown as a first carrier wave 421. Carrier wave 420 shown by a dashed line is shown as a second carrier wave 422. Carrier wave 420 shown by a dot-dash line is shown as a third carrier wave 423.

[0053] Of the three carrier waves 420, the first carrier wave 421 has the highest carrier frequency, and the third carrier wave 423 has the lowest carrier frequency.

[0054] Then, in step S1300, the switch control section applies a voltage to first gate electrode 535 and second gate electrode 536 based on driving wave 410 and carrier wave 420 having the carrier frequency reduced in step S1200.

[0055] 2(b), the upper part shows a first voltage signal 421a based on the drive wave 410 and the first carrier wave 421. The middle part shows a second voltage signal 422a based on the drive wave 410 and the second carrier wave 422. The lower part shows a third voltage signal 423a based on the drive wave 410 and the third carrier wave 423.

[0056] 2B, the number of times that high-side switch 521 switches decreases. Although not shown, the number of times that low-side switch 522 switches decreases similarly. The lower the carrier frequency, the fewer the number of times that high-side switch 521 and low-side switch 522 switch.

[0057] As shown in Fig. 4, as the number of switches decreases, the effective value of the current flowing through motor 400 decreases. In Fig. 4, the upper part shows a first current 421b based on first voltage signal 421a and its first effective value 421c. The middle part shows a second current 422b based on second voltage signal 422a and its second effective value 422c. The lower part shows a third current 423b based on third voltage signal 423a and its third effective value 423c. The lower the carrier frequency, the more the number of switches decreases, and the smaller the effective value of the current flowing through motor 400 becomes.

[0058] <Action and effect> Therefore, even if inverter 500 has a ground fault and a current flows to Y capacitors 310, 320 via ground wiring 306, the current flowing to Y capacitors 310, 320 is likely to be small. Heat generation of Y capacitors 310, 320 is likely to be suppressed. Note that Y capacitors 310, 320 refer to the first Y capacitor 310 and the second Y capacitor 320.

[0059] Also, unlike this embodiment, in a configuration in which the power conversion device 100 includes a boost circuit, when the inverter 500 has a ground fault, the voltage applied to the inverter 500 is lowered, thereby making it possible to suppress the current flowing through the Y capacitors 310, 320 when a ground fault occurs.

[0060] However, in this embodiment, even if the power conversion device 100 does not include a boost circuit, the above-described configuration makes it possible to suppress the current flowing through the Y capacitors 310 and 320 when a ground fault occurs in the inverter 500.

[0061] Even in power conversion device 100 that does not include a boost circuit, heat generation in Y capacitors 310, 320 can be suppressed when a ground fault occurs in inverter 500. Naturally, even if power conversion device 100 includes both a boost circuit and the above-mentioned configuration, heat generation in Y capacitors 310, 320 can be suppressed when a ground fault occurs in inverter 500. Regardless of the presence or absence of a boost circuit, heat generation in Y capacitors 310, 320 can be suppressed when a ground fault occurs in inverter 500. Even if a ground fault occurs in inverter 500, the vehicle can continue running.

[0062] Second embodiment Next, a second embodiment will be described with reference to Fig. 5 to Fig. 7. In the first embodiment, the control device 600 is provided with the carrier control unit 610, but the control device 600 does not necessarily have to include the carrier control unit 610. As shown in Fig. 5, the control device 600 may include a drive control unit 620.

[0063] As shown in FIG. 6, when leakage detector 700 detects the occurrence of a ground fault in inverter 500 in step S2000, the ground fault information is sent to the information acquisition unit.

[0064] When the information acquiring unit acquires the ground fault information sent from the earth leakage detector 700 in step S2100, the drive control unit 620 controls the drive wave 410 that drives the motor 400 in step S2200.

[0065] In step S2200, drive control unit 620 changes the drive method of inverter 500. As an example, the modulation method is changed from three-phase modulation to two-phase modulation as shown in Fig. 7. In Fig. 7, drive wave 410 in the case where three-phase modulation is adopted is shown as first drive wave 411. Drive wave 410 in the case where two-phase modulation is adopted is shown as second drive wave 412.

[0066] As another example, the drive wave 410 is changed from a sine wave to a square wave. In Fig. 7, the drive wave 410 when a sine wave is adopted is shown as a first drive wave 411. The drive wave 410 when a square wave is adopted is shown as a third drive wave 413.

[0067] In step S2300, based on carrier wave 420 and drive wave 410 whose drive method has been changed, the switch control unit applies a voltage to first gate electrode 535 and second gate electrode 536. As a result, the number of times high-side switch 521 and low-side switch 522 are switched decreases. Accordingly, the effective value of the current flowing through motor 400 decreases.

[0068] According to this, even if a ground fault occurs in the inverter 500, the current flowing through the Y capacitors 310, 320 is likely to be small. Heat generation in the Y capacitors 310, 320 is likely to be suppressed.

[0069] Third embodiment Next, a third embodiment will be described with reference to Fig. 8 and Fig. 9. In the first and second embodiments, the control device 600 is provided with either the carrier control unit 610 or the drive control unit 620, but as shown in Fig. 8, the control device 600 may include both the carrier control unit 610 and the drive control unit 620.

[0070] In this case, as shown in FIG. 9, when leakage detector 700 detects in step S3000 that a ground fault has occurred in inverter 500, the ground fault information is sent to the information acquisition unit.

[0071] When the information acquiring unit acquires the ground fault information sent from earth leakage detector 700 in step S3100, carrier control unit 610 reduces the carrier frequency of carrier wave 420 in step S3200.

[0072] Furthermore, when the information acquiring unit acquires ground fault information sent from earth leakage detector 700 in step S3100, drive control unit 620 controls drive wave 410 that drives motor 400 in step S3300. Note that steps S3200 and S3300 may be performed simultaneously or in any order. Furthermore, the order is not limited.

[0073] Then, based on carrier wave 420 having the reduced carrier frequency in step S3400 and drive wave 410 whose drive method has been changed, switch control section applies voltage to first gate electrode 535 and second gate electrode 536. As a result, the number of times high-side switch 521 and low-side switch 522 switch is reduced.

[0074] According to this, even if a ground fault occurs in the inverter 500, the current flowing through the Y capacitors 310, 320 is likely to be small. Heat generation in the Y capacitors 310, 320 is likely to be suppressed.

[0075] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Fig. 10 to Fig. 12. In the first to third embodiments, the control device 600 includes at least one of the carrier control unit 610 and the drive control unit 620. However, the control device 600 may include a motor adjustment unit 630 that controls at least one of the rotation speed and torque of the motor 400, in addition to at least one of the carrier control unit 610 and the drive control unit 620.

[0076] In addition, in Figure 10, an example is shown in which the control device 600 includes both the carrier control unit 610 and the drive control unit 620, but the fourth embodiment also includes a form in which the control device 600 includes one of the drive control units 620 of the carrier control unit 610.

[0077] As shown in FIG. 11, when leakage detector 700 detects the occurrence of a ground fault in inverter 500 in step S4000, the ground fault information is sent to the information acquiring unit.

[0078] When the information acquiring unit acquires ground fault information in step S4100, in step S4200, the switch control unit applies voltage to the high-side switch 521 and the low-side switch 522 based on at least one of the carrier control unit 610 and the drive control unit 620. As a result, the number of times that the high-side switch 521 and the low-side switch 522 switch is reduced.

[0079] Then, in step S4300, motor adjustment unit 630 reduces at least one of the torque and the rotation speed applied to motor 400 as shown in the graph in FIG.

[0080] The reason for this is that there is a concern that the controllability of the motor 400 may decrease due to the reduced number of switching times in the power conversion device 100. Therefore, in step S4300, the torque applied to the motor 400 is reduced. This makes it easier to reduce the discomfort felt by the user when the number of switching times is reduced.

[0081] The torque applied to the motor 400 is reduced, thereby suppressing the current flowing through the motor 400. As a result, even if the inverter 500 has a ground fault, the current flowing through the Y capacitors 310, 320 is likely to be reduced. Heat generation in the Y capacitors 310, 320 is likely to be suppressed.

[0082] Furthermore, there is a concern that the reduced number of switches may cause the resonance range of the circuit constituting power conversion device 100 to overlap with the frequency of drive wave 410. In step S4300, the rotation speed of motor 400 is reduced to change the frequency of drive wave 410 so that the resonance range of the circuit does not overlap with the frequency of drive wave 410. This makes it possible to suppress the resonant current.

[0083] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, although various combinations and forms are shown in the present disclosure, other combinations and forms including only one element, more than one element, or less than one element are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0084] 100...power conversion device, 200...battery, 301...high potential side wiring, 302...low potential side wiring, 310...first Y capacitor, 320...second Y capacitor, 400...motor, 410...driving wave, 420...carrier wave, 500...inverter, 521...high side switch, 522...low side switch, 600...control device, 610...carrier control unit, 620...driving control unit, 630...motor adjustment unit

Claims

1. A power conversion device (100) that performs power conversion between a battery (200) and a motor (400) via a high-potential side wiring (301) and a low-potential side wiring (302), An inverter (500) connected to the high potential side wiring and the low potential side wiring and having a plurality of switches (521, 522); a Y capacitor (310, 320) connected to the high potential side wiring and the low potential side wiring in a manner parallel to the inverter and also connected to earth; A control device (600) that controls the plurality of switches so as to reduce the number of times the plurality of switches are switched when the inverter has a ground fault compared to when the inverter does not have a ground fault, The control device is a power conversion device having a motor adjustment unit (630) that reduces at least one of the torque and the rotation speed of the motor when a ground fault occurs in the inverter.

2. The control device has a carrier control unit (610) that reduces a carrier frequency of a carrier wave (420) that controls the on / off switching of each of the multiple switches, and when the inverter has a ground fault, the carrier control unit reduces the carrier frequency to reduce the number of times the switches are switched.

3. 3. The power conversion device according to claim 1 or 2, wherein the control device has a drive control unit (620) that changes a drive method of a drive wave (410) that drives the motor, and when the inverter has a ground fault, the drive control unit changes the drive method to reduce the number of times the switching occurs.

4. The power conversion device according to claim 3 , wherein the control device reduces the number of times of switching by causing the drive control unit to change the drive wave from a three-phase modulation method to a two-phase modulation method.

5. The power conversion device according to claim 3 , wherein the control device reduces the number of times the switching is performed by changing the drive wave from a sine wave to a rectangular wave by the drive control unit.

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