WO2020183542A1 - Power converter and air conditioner using same - Google Patents

Abstract

This power converter comprises: a rectifier that rectifies AC voltage supplied from an AC power supply; a smoothing capacitor that smooths the voltage rectified by the rectifier; an inverter section that has a plurality of switching elements and converts DC voltage smoothed by the smoothing capacitor to AC voltage; a load current detector that detects the load current supplied from the inverter section to a load; and a control unit that has a failure detection unit that extracts a feature quantity from the load current of a set period, the feature quantity being the physical quantity obtained from the load current, and the failure detection unit detecting failure of the switching element on the basis of the extracted feature quantity.

Description

Power converter and air conditioner using it

The present invention relates to a power converter that converts electric power from a commercial power source into electric power supplied to a load, and an air conditioner using the electric power converter.

In a conventional air conditioner, a motor that drives a compressor, a fan, or the like is used to improve energy consumption efficiency (COP: Coefficient of Performance) and year-round energy consumption efficiency (APF: Annual Performance Factor) during cooling operation and heating operation. Generally, an inverter device is used. The inverter is configured by using a plurality of semiconductor elements, and drives the motor by applying a voltage simulating a sine wave to a motor to be driven by a combination of switching of each semiconductor element.

At this time, if even one of the plurality of semiconductor elements constituting the inverter fails, the inverter cannot output a sine wave voltage, which is the original function. Therefore, various methods have been proposed for detecting a failure of a semiconductor element constituting an inverter and notifying the abnormality.

For example, Patent Document 1 describes an electric motor drive system that detects an abnormality in a semiconductor element of an inverter based on a waveform of a current flowing through the electric motor. In the system described in Patent Document 1, an on signal and an off signal are continuously transmitted to all switching elements of either the upper arm or the lower arm in an inverter composed of a plurality of semiconductor elements immediately before the start of operation. Given. Then, when the waveform of the current flowing through the motor becomes a pulsating waveform different from the normal state due to each on signal, the motor drive system determines that the motor or the cable between the motor and the inverter has a short-circuit failure. To do. That is, in the system described in Patent Document 1, when the semiconductor element is turned on or off before the start of operation, the failure of the semiconductor element is detected depending on whether or not a current flows as intended.

Japanese Patent No. 5339164

By the way, when one of a plurality of semiconductor elements fails, the motor may continue to be driven without causing an abnormality such as an overcurrent depending on the operating state. In this case, a distorted voltage is supplied from the sinusoidal voltage to the motor to be driven, unlike the sinusoidal voltage. Therefore, the motor cannot be driven stably and the rotation speed becomes uneven, and as a result, the vibration of the motor increases. Then, in some cases, the generated vibration causes an abnormality in the device on the side to which the voltage is supplied.

When the device to which the voltage is supplied is an air conditioner, a refrigerant such as R410A or R32, which is a flammable refrigerant, circulates inside the pipe. Therefore, if the pipe is damaged by vibration, the refrigerant leaks to the outside. There is a risk of Therefore, when supplying a voltage to such a device, it is necessary to be able to detect a failure of the semiconductor element of the inverter even when the device on the side of supplying the voltage is in operation.

However, the method described in Patent Document 1 is limited to just before the start of operation of the inverter, and when the semiconductor element fails during the operation of the inverter, that is, during the driving of the motor, the failure cannot be detected.

The present invention has been made in view of the above-mentioned problems in the prior art, and is a power conversion device capable of detecting a failure of a semiconductor element constituting an inverter even during operation, and air conditioning using the power conversion device. The purpose is to provide the device.

The power conversion device of the present invention has a rectifier that rectifies an AC voltage supplied from an AC power supply, a smoothing capacitor that smoothes the voltage rectified by the rectifier, and a plurality of switching elements, and is smoothed by the smoothing capacitor. An inverter unit that converts the converted DC voltage into an AC voltage, a load current detector that detects the load current supplied from the inverter unit to the load, and a feature amount that is a physical quantity obtained from the load current are set. It is provided with a control unit having a failure detection unit that extracts from the load current for a cycle and detects a failure of the switching element based on the extracted feature amount.

The air conditioner of the present invention is a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger driven by electric power supplied from the above power conversion device are sequentially connected by a refrigerant pipe to circulate the refrigerant. It is equipped with.

As described above, according to the present invention, a feature amount is extracted from the load current supplied to the load, and a failure of the switching element is detected based on the extracted feature amount. As a result, it is possible to detect a failure of the semiconductor element constituting the inverter even during operation.

It is a circuit diagram which shows an example of the structure of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a hardware block diagram which shows an example of the structure of the control part of FIG. It is a hardware block diagram which shows another example of the structure of the control part of FIG. It is a graph which shows the load current of the phase corresponding to the failed element when at least one of the switching elements of FIG. 1 is open failure. It is a flowchart which shows an example of the flow of the failure detection processing by the power conversion apparatus which concerns on Embodiment 1. FIG. It is a hardware block diagram which shows an example of the structure of the air conditioner which concerns on Embodiment 4. FIG.

Embodiment 1.
Hereinafter, the power conversion device according to the first embodiment of the present invention will be described. The power conversion device according to the first embodiment generates an alternating current having a predetermined frequency from an alternating current power source such as a commercial power source, and supplies the alternating current to a load such as a motor of a compressor or a blower in an air conditioner, for example. It is a thing.

[Configuration of power converter 100]
FIG. 1 is a circuit diagram showing an example of the configuration of the power conversion device 100 according to the first embodiment. As shown in FIG. 1, an AC power supply 200 such as a three-phase AC power supply and a load 300 such as a motor are connected to the power conversion device 100. The power conversion device 100 includes a rectifier 1, a reactor 2, a smoothing capacitor 3, an inverter unit 4, a load current detector 5, and a control unit 10.

The rectifier 1 is an AC-DC converter to which an AC power supply 200 is connected and rectifies an AC voltage such as AC (Alternating Curent) 200V or AC400V supplied from the AC power supply 200 and converts it into a DC voltage. The rectifier 1 is composed of, for example, a three-phase full-wave rectifier in which six diodes 1a to 1f are bridge-connected.

Reactor 2 is connected to the output end of rectifier 1. The smoothing capacitor 3 smoothes and charges the voltage rectified by the rectifier 1 via the reactor 2.

The inverter unit 4 is composed of, for example, a plurality of switching elements, and converts a DC voltage smoothed and charged by a smoothing capacitor 3 into an AC voltage. A load 300 such as a compressor motor in the air conditioner is connected to the inverter unit 4, and the converted AC voltage is supplied to the load 300. In the first embodiment, the inverter unit 4 is composed of six switching elements 4a to 4f. The inverter unit 4 outputs an AC voltage, which is a PWM (Pulse Width Modulation) voltage, by controlling these switching elements 4a to 4f by the control unit 10. The switching elements 4a to 4f perform ON and OFF operations based on the switching signal supplied from the control unit 10.

As the switching elements 4a to 4f, for example, a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor), a silicon carbide (SiC) element having a large bandgap as compared with a silicon (Si) element, and gallium nitride (GaN). Wide bandgap semiconductors such as devices and diamond devices are used.

The load current detector 5 detects the load current output from the inverter unit 4 and supplied to the load 300. The load current detector 5 is composed of, for example, an ACCT (AC current transformer), a DCCT (DC (Direct Current) current transformer), a shunt resistor, or the like. The load current detector 5 may detect all of the three phases supplied to the load 300, or may detect any two phases and calculate the remaining one phase using Kirchhoff's law. Good.

The control unit 10 controls the inverter unit 4 based on the load current detected by the load current detector 5. The control unit 10 has an inverter control unit 11 and a failure detection unit 12.

The inverter control unit 11 generates a switching signal for operating each of the switching elements 4a to 4f of the inverter unit 4 based on the load current detected by the load current detector 5. Further, the inverter control unit 11 controls to stop the operation of the inverter unit 4 when the failure detection unit 12 detects a failure of the switching elements 4a to 4f.

The failure detection unit 12 detects a failure of the switching elements 4a to 4f of the inverter unit 4 based on the load current detected by the load current detector 5. The failure detection unit 12 acquires the feature amount from the load current for the set cycle such as one cycle, and compares the extracted feature amount with the threshold value set in advance for the feature amount, whereby the switching elements 4a to The failure of 4f is detected. The feature quantity is a physical quantity obtained from a load current that changes depending on the presence or absence of failure of the switching elements 4a to 4f. The threshold value is set with respect to the feature amount, and is set to a value larger than the feature amount generated during normal operation.

The control unit 10 is composed of hardware such as a circuit device that realizes various functions by executing software on an arithmetic unit such as a microcomputer. FIG. 2 is a hardware configuration diagram showing an example of the configuration of the control unit 10 of FIG. When various functions of the control unit 10 are executed by hardware, the control unit 10 of FIG. 1 is composed of a processing circuit 21 as shown in FIG. Each function of the inverter control unit 11 and the failure detection unit 12 of FIG. 1 is realized by the processing circuit 21.

When each function is executed by hardware, the processing circuit 21 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate). Array) or a combination of these is applicable. The functions of the inverter control unit 11 and the failure detection unit 12 may be realized by the processing circuit 21, or the functions of the respective parts may be realized by one processing circuit 21.

FIG. 3 is a hardware configuration diagram showing another example of the configuration of the control unit 10 of FIG. When various functions of the control unit 10 are executed by software, the control unit 10 of FIG. 1 is composed of a processor 31 and a memory 32 as shown in FIG. Each function of the inverter control unit 11 and the failure detection unit 12 is realized by the processor 31 and the memory 32.

When each function is executed by software, the functions of the inverter control unit 11 and the failure detection unit 12 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as a program and stored in the memory 32. The processor 31 realizes the functions of each part by reading and executing the program stored in the memory 32.

As the memory 32, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EEPROM (Erasable and Programmable ROM), EEPROM (Electrically Erasable Memory Volatile ROM, etc.) Is used. Further, as the memory 32, for example, a detachable recording medium such as a magnetic disk, a flexible disk, an optical disk, a CD (Compact Disc), an MD (Mini Disc), or a DVD (Digital Versaille Disc) may be used.

[Operation of power converter]
The operation of the power conversion device 100 according to the first embodiment will be described with reference to FIG. As shown in FIG. 1, when an AC voltage is supplied from the AC power supply 200, this AC voltage is supplied to the rectifier 1. The rectifier 1 rectifies and outputs the supplied AC voltage. The voltage output from the rectifier 1 is stored in the smoothing capacitor 3 via the reactor 2, whereby the smoothing capacitor 3 smoothes the voltage. The voltage smoothed by the smoothing capacitor 3 is converted into a three-phase AC voltage by the inverter unit 4. Then, the converted AC voltage is supplied to the load 300.

The operation of each of the switching elements 4a to 4f in the inverter unit 4 is controlled by the inverter control unit 11 of the control unit 10. The inverter control unit 11 generates a switching signal based on the detection result by the load current detector 5 and supplies it to the switching elements 4a to 4f.

On the other hand, the failure detection unit 12 determines whether or not the switching elements 4a to 4f of the inverter unit 4 have failed based on the current value of each phase detected by the load current detector 5. When it is determined that at least one of the switching elements 4a to 4f has failed, the failure detection unit 12 supplies information indicating that the failure has been detected to the inverter control unit 11. The inverter control unit 11 supplies the inverter unit 4 with a control signal for stopping the operation of the inverter unit 4 based on the information received from the failure detection unit 12.

[Failure of switching elements 4a to 4f]
Next, a case where the switching elements 4a to 4f of the inverter unit 4 fails will be described. If the switching elements 4a to 4f fail, the inverter unit 4 cannot supply a load current that becomes a sine wave to the load 300. In this case, among the load currents supplied to the load 300, the load current of the phase corresponding to the failed element has a waveform different from the waveform during normal operation.

FIG. 4 is a graph showing the load current of the phase corresponding to the failed element when at least one of the switching elements 4a to 4f of FIG. 1 has an open failure. The open failure is a failure in which the switching element cannot perform the switching operation and is in the open state. As shown in FIG. 4, for example, when at least one of the plurality of switching elements 4a to 4f has an open failure, the load current of the phase corresponding to the failed element becomes half wave. That is, the load current when one element fails to open has an asymmetric waveform on the positive side and the negative side.

Also, the waveform of the detected load current differs depending on the type of load current detector 5. For example, when the load current detector 5 is a DCCT or a shunt resistor, the detected load current is substantially the same as the actual current, and has a waveform indicated by reference numeral X in FIG. Further, when the load current detector 5 is ACCT, only the AC component is detected, so that the detected load current has a waveform indicated by reference numeral Y in FIG.

In this way, the load current whose waveform is asymmetrical due to an open failure of the element generates a characteristic physical quantity that is hardly included in normal operation. Therefore, in the first embodiment, the physical quantity generated by the opening failure of the element is acquired from the load current as a feature amount, and the opening failure of the switching elements 4a to 4f is detected based on the acquired feature amount.

[Failure detection processing]
FIG. 5 is a flowchart showing an example of a flow of failure detection processing by the power conversion device 100 according to the first embodiment. First, in step S1, the load current detector 5 detects the load current supplied to the load 300. In step S2, the failure detection unit 12 extracts the feature amount from the load current detected in step S1. In step S3, the failure detection unit 12 compares the detected feature amount with the threshold value set in advance for the feature amount.

As a result of the comparison, when the feature amount is larger than the threshold value (step S3; Yes), the failure detection unit 12 determines that at least one of the switching elements 4a to 4f has an open failure, and indicates an element failure. Information is supplied to the inverter control unit 11. In step S4, the inverter control unit 11 stops the operation of the inverter unit 4 based on the information received from the failure detection unit 12.

On the other hand, when the feature amount is equal to or less than the threshold value (step S3; No), the failure detection unit 12 determines that the element has not opened and failed, and a series of processes is completed.

As described above, the power conversion device 100 according to the first embodiment includes a failure detection unit 12 that extracts a feature amount from the load current detected by the load current detector 5. The failure detection unit 12 detects a failure of the switching elements 4a to 4f constituting the inverter unit 4 based on the load current flowing with respect to the load 300 when the power conversion device 100 is operating. Therefore, even when the power conversion device 100 is in operation, it is possible to detect a failure of the switching elements 4a to 4f.

Further, the power conversion device 100 according to the first embodiment can detect a failure of the switching elements 4a to 4f during the operation of the power conversion device 100. Therefore, it is possible to suppress a malfunction of the device due to the operation of the inverter unit 4 in a failed state.

In the first embodiment, the failure detection unit 12 compares the extracted feature amount with a preset threshold value, and detects a failure of the switching elements 4a to 4f when the feature amount is larger than the threshold value. Thereby, the failure of the switching elements 4a to 4f can be detected by a simple method of comparing the feature amount and the threshold value.

Further, as the load current detector 5, an ACCT that detects an AC component of the load current may be used. In the first embodiment, since the feature amount is extracted from the waveform of the load current, a simple current detector such as ACCT can be used if the feature amount can be extracted from the waveform.

In the first embodiment, wide bandgap semiconductors are used as the switching elements 4a to 4f. As a result, the carrier frequency can be set high, so that the response of the current control becomes higher, and even higher-order harmonics can be controlled and suppressed.

Embodiment 2.
Next, Embodiment 2 of the present invention will be described. In the second embodiment, a case where an even-order harmonic component with respect to the fundamental wave of the current waveform is used as a feature amount will be described. In the following description, detailed description of the parts common to the first embodiment will be omitted.

As described above, when the switching elements 4a to 4f are operating normally, the load current is a sine wave, so ideally it has only the frequency component of the fundamental wave. On the other hand, when at least one of the switching elements 4a to 4f fails and the waveform of the load current becomes asymmetric between the positive side and the negative side, the frequency component of the load current includes harmonics with respect to the fundamental wave. ..

Therefore, in the second embodiment, the failure detection unit 12 extracts the frequency component of the harmonic with respect to the fundamental wave as a feature amount, and detects an open failure of the switching elements 4a to 4f based on the extracted harmonic component. ..

In the power conversion device 100 shown in FIG. 1, the failure detection unit 12 according to the second embodiment performs Fourier transform on the load current for a set cycle such as one cycle detected by the load current detector 5. Derivation of the frequency component of the load current. Then, the failure detection unit 12 acquires the current level of the even-numbered harmonic component such as the second harmonic of the fundamental wave as a feature amount from the derived frequency component. Further, the failure detection unit 12 detects an open failure of the switching elements 4a to 4f by comparing the acquired current level of the even-order harmonic component with a preset threshold value.

The failure detection process in the power conversion device 100 according to the second embodiment is the same as the process shown in FIG. Here, the failure detection unit 12 of the second embodiment performs Fourier transform on the load current at the time of extracting the feature amount in step S2, and extracts the even-order harmonic component from the frequency component of the load current.

Then, in step S3, the failure detection unit 12 compares the current level of the extracted even-order harmonic component with the preset threshold value, so that at least one of the switching elements 4a to 4f fails. Determine if you are doing it. The threshold value in this case is set to a value larger than the current level of the even-order harmonic component included in the load current during normal operation.

As described above, in the power conversion device 100 according to the second embodiment, the current level of the even-order harmonic component of the fundamental wave of the load current is extracted as a feature amount. Harmonic components of the fundamental wave are rarely contained in a normal sine wave. Therefore, when a high harmonic component is extracted from the load current, it can be determined that the load current is not normal. Therefore, the failure detection unit 12 uses the harmonic component as a feature amount to set the switching elements 4a to 4f. Failure can be easily detected.

Embodiment 3.
Next, Embodiment 3 of the present invention will be described. In the third embodiment, a case where the integrated amount of the load current is used as the feature amount will be described. In the following description, detailed description of the parts common to the first and second embodiments will be omitted.

When the switching elements 4a to 4f are operating normally, the load current is a sine wave, and the waveform is symmetrical between the positive side and the negative side. Therefore, since the current integrated amount on the positive side and the current integrated amount on the negative side in the preset period almost match, the total current integrated amount is ideally "0". On the other hand, when at least one of the switching elements 4a to 4f fails and the waveform of the load current becomes asymmetric between the positive side and the negative side, the current integrated amount on the positive side and the current integrated amount on the negative side Then there is a difference. That is, the total amount of integrated current in this case is not "0".

Therefore, in the third embodiment, the failure detection unit 12 extracts the integrated amount of the load current in the set cycle as a feature amount, and detects an open failure of the switching elements 4a to 4f based on the extracted current integrated amount. ..

In the power conversion device 100 shown in FIG. 1, the failure detection unit 12 according to the third embodiment integrates the load current detected by the load current detector 5 for the set cycle. Then, the failure detection unit 12 acquires the calculated current integrated amount as a feature amount. Further, the failure detection unit 12 detects an open failure of the switching elements 4a to 4f by comparing the acquired current integrated amount as the feature amount with a preset threshold value.

The failure detection process in the power conversion device 100 according to the third embodiment is the same as the process shown in FIG. Here, the failure detection unit 12 of the third embodiment calculates the load current integration amount for the set cycle at the time of extracting the feature amount in step S2. Then, in step S3, the failure detection unit 12 compares the calculated current integration amount as the feature amount with the preset threshold value, so that at least one of the switching elements 4a to 4f fails. Judge whether or not. The threshold value in this case is set to a value larger than the current integration amount for a set cycle such as one cycle during normal operation.

As described above, in the power conversion device 100 according to the third embodiment, the integrated amount of the load current for the set cycle is extracted as the feature amount. When the load current is normal, the load current has a symmetrical waveform on the positive side and the negative side, so that the integrated load current amount is “0”. Therefore, when the load current integration amount for the set cycle is not "0", the load current has an asymmetric waveform on the positive side and the negative side, and it can be determined that it is not normal. Therefore, the failure detection unit 12 can easily detect the failure of the switching elements 4a to 4f by using the current integration amount for the set cycle as the feature amount. Further, by using the load current integrated amount as the feature amount, it is possible to detect the failure of the switching elements 4a to 4f by a simple calculation.

Embodiment 4.
Next, Embodiment 4 of the present invention will be described. In the fourth embodiment, an example in which the power conversion device 100 described in the first to third embodiments is applied to the air conditioner will be described.

[Configuration of air conditioner 50]
FIG. 6 is a hardware configuration diagram showing an example of the configuration of the air conditioner 50 according to the fourth embodiment. The air conditioner 50 of FIG. 6 performs a cooling operation and a heating operation by a heat pump system.

As shown in FIG. 6, the air conditioner 50 includes an outdoor unit 50A including a compressor 51, a refrigerant flow path switching device 52, an outdoor heat exchanger 53 and an expansion device 54, and an indoor unit 50B including an indoor heat exchanger 55. It is composed of and. In the air conditioner 50, the compressor 51, the refrigerant flow path switching device 52, the outdoor heat exchanger 53, the expansion device 54, and the indoor heat exchanger 55 are sequentially connected by the refrigerant pipes, so that the refrigerant circulates in the refrigerant pipes. A refrigerant circuit is formed.

Of these, the compressor 51 has a compression element 51a that compresses the refrigerant, and a motor M as a load 300 that is connected to the compression element 51a and to which power is supplied by the power conversion device 100. The power conversion device 100 is the device according to the first embodiment described above, receives power from the AC power supply 200, supplies the converted power to the motor M, and drives the motor M to rotate.

The refrigerant flow path switching device 52 is, for example, a four-way valve, and switches between cooling operation and heating operation by switching the flow direction of the refrigerant. The outdoor heat exchanger 53 exchanges heat between the refrigerant and the outside air. The outdoor heat exchanger 53 functions as a condenser during the cooling operation and as an evaporator during the heating operation. The expansion device 54 expands the refrigerant. The indoor heat exchanger 55 exchanges heat between the refrigerant and the indoor air in the air-conditioned space. The indoor heat exchanger 55 functions as an evaporator during the cooling operation and as a condenser during the heating operation.

[Operation of air conditioner 50]
Next, the operation of the air conditioner 50 according to the fourth embodiment will be described with reference to FIG. Here, the cooling operation will be described as an example. When performing the cooling operation, the refrigerant flow path switching device 52 flows the refrigerant discharged from the compressor 51 toward the outdoor heat exchanger 53 and the refrigerant flowing out from the indoor heat exchanger 55 toward the compressor 51. It is assumed that the road has been switched in advance. At this time, the outdoor heat exchanger 53 functions as a condenser, and the indoor heat exchanger 55 functions as an evaporator.

When the motor M of the compressor 51 is rotationally driven by the power converter 100, the compression element 51a of the compressor 51 connected to the motor M compresses the low-temperature low-pressure refrigerant, and the compressor 51 discharges the high-temperature and high-pressure gas refrigerant. To do. The high-temperature and high-pressure gas refrigerant discharged from the compressor 51 flows into the outdoor heat exchanger 53 that functions as a condenser via the refrigerant flow path switching device 52.

The high-temperature and high-pressure gas refrigerant that has flowed into the outdoor heat exchanger 53 exchanges heat with the outside air and condenses while radiating heat, becomes a high-pressure liquid refrigerant, and flows out of the outdoor heat exchanger 53. The high-pressure liquid refrigerant flowing out of the outdoor heat exchanger 53 is expanded and depressurized by the expansion device 54 to become a low-temperature low-pressure gas-liquid two-phase refrigerant, which flows into the indoor heat exchanger 55 functioning as an evaporator.

The low-temperature, low-pressure gas-liquid two-phase refrigerant that has flowed into the indoor heat exchanger 55 exchanges heat with the air in the air-conditioned space to absorb and evaporate to cool the indoor air and become a low-temperature, low-pressure gas refrigerant that becomes indoor heat. Outflow from the exchanger 55. The low-temperature low-pressure gas refrigerant flowing out of the indoor heat exchanger 55 is sucked into the compressor 51 via the refrigerant flow path switching device 52 and compressed again. Hereinafter, the above-mentioned operation is repeated.

Note that FIG. 6 shows an example in which the power conversion device 100 according to the first embodiment is applied to the compressor 51 of the air conditioner 50, but the present invention is not limited to this, and for example, the outdoor heat exchanger 53 is used. It may be applied to a power source for driving a fan (not shown) that blows air. Further, the power conversion device 100 may be generally applied to, for example, a heat pump device, a refrigeration device, and other refrigeration cycle devices.

As described above, in the air conditioner 50 according to the fourth embodiment, the compressor 51 provided in the refrigerant circuit is driven by the electric power supplied from the power conversion device 100. Since the power conversion device 100 can detect a failure of the switching elements 4a to 4f even while the inverter unit 4 is operating, it is possible to suppress a failure of the compressor 51 due to a failure of the switching elements 4a to 4f.

Although the embodiments 1 to 4 of the present invention have been described above, the present invention is not limited to the above-described embodiments 1 to 4 of the present invention, and varies within the range not deviating from the gist of the present invention. Can be transformed and applied. For example, in the second or third embodiment, when extracting an even-numbered harmonic component or a load current integrated amount as a feature amount, a case where one cycle is set as an example has been described, but the present invention is not limited to this. A plurality of cycles may be set as a set cycle. By extracting the feature amount with a plurality of set cycles, the proof stress against disturbances such as noise is improved, so that erroneous detection of open failure of the switching elements 4a to 4f can be suppressed.

Further, in the first to third embodiments, the feature amount and the threshold value are compared when the open failure of the switching elements 4a to 4f is detected, but this is not limited to this example. For example, the difference between the feature amounts of each phase may be calculated, and the calculated difference value may be compared with the threshold value set in advance for this difference value. This also makes it possible to detect an open failure of the switching elements 4a to 4f.

1 Rectifier, 1a, 1b, 1c, 1d, 1e, 1f diode, 2 reactor, 3 smoothing capacitor, 4 inverter part, 4a, 4b, 4c, 4d, 4e, 4f switching element, 5 load current detector, 10 control unit , 11 Inverter control unit, 12 Failure detection unit, 21 Processing circuit, 31 Processor, 32 Memory, 50 Air conditioner, 50A outdoor unit, 50B indoor unit, 51 compressor, 51a compression element, 52 refrigerant flow path switching device, 53 Outdoor heat exchanger, 54 expansion device, 55 indoor heat exchanger, 100 power converter, 200 AC power supply, 300 load.

Claims (9)

A rectifier that rectifies the AC voltage supplied from the AC power supply,
A smoothing capacitor that smoothes the voltage rectified by the rectifier,
An inverter unit that has a plurality of switching elements and converts a DC voltage smoothed by the smoothing capacitor into an AC voltage.
A load current detector that detects the load current supplied to the load from the inverter unit, and
A power conversion including a control unit having a failure detection unit that extracts a feature amount that is a physical quantity obtained from the load current from the load current for a set cycle and detects a failure of the switching element based on the extracted feature amount. apparatus. The failure detection unit
The extracted feature amount is compared with a preset threshold value, and
The power conversion device according to claim 1, wherein a failure of the switching element is detected when the feature amount is larger than the threshold value. The AC power supply is a three-phase AC power supply.
The failure detection unit
The difference value of the feature amount extracted for each phase is calculated, and
Comparing the calculated difference value with the preset threshold value,
The power conversion device according to claim 1, wherein a failure of the switching element is detected when the difference value is larger than the threshold value. The feature amount is
The power conversion device according to any one of claims 1 to 3, which is an even-order harmonic included in the frequency component of the load current. The feature amount is
The power conversion device according to any one of claims 1 to 3, which is a load current integrated amount obtained by integrating the load current for each set cycle. The set cycle is a plurality of cycles.
The failure detection unit
The power conversion device according to any one of claims 1 to 5, wherein the feature amount is extracted in the plurality of cycles. The load current detector is
The power conversion device according to any one of claims 1 to 6, which detects an AC component of the load current. The power conversion device according to any one of claims 1 to 7, wherein at least one of the switching elements is formed of a wide bandgap semiconductor. The power conversion device according to any one of claims 1 to 8.
An air conditioner including a compressor, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger that are driven by electric power supplied from the power converter and are sequentially connected by a refrigerant pipe to circulate the refrigerant.

Images