Power conversion device, switching failure detection method for power conversion device, and program

Abstract

A short-circuit fault and an open-circuit fault of a switch used in an inrush current suppression circuit are detected without using a voltage detector. A power conversion device (1) is provided with: a smoothing capacitor (21) connected to a DC bus line of a DC power supply unit (2); a resistor (22) for suppressing an inrush current flowing to the smoothing capacitor (21); and a switch (23) connected in parallel to the resistor (22). The power conversion device (1) is provided with a current sensor (26) which is connected in series with the switch (23) and detects the current flowing to the switch (23), a switch control unit which opens the switch (23) at the start of operation and closes the switch (23) when a predetermined condition is satisfied, and a fault detection unit which detects the fault of the switch on the basis of the detection value of the current sensor (26).

Description

Technical Field

[0001] The present invention relates to a power conversion device, a switch fault detection method and a program for the power conversion device. Background Art

[0002] Conventionally, in a power conversion device, a smoothing capacitor is provided to smooth the fluctuation component of DC power. In a power conversion device having such a smoothing capacitor, when the power is turned on, a current much higher than the steady state (hereinafter referred to as "rush current") is generated in a short time in order to charge the smoothing capacitor.

[0003] In order to suppress such an inrush current, an inrush current suppression circuit is provided in the power conversion device. The inrush current suppression circuit includes, for example, a resistor provided on the input side of the smoothing capacitor and a switch connected in parallel with the resistor. When the power conversion device is started, the switch is opened to charge the smoothing capacitor via the resistor. After the charging is completed, the switch is closed to enter normal operation (see Patent Documents 1 and 2).

[0004] Here, when a switch used in the inrush current suppression circuit fails, it is necessary to quickly detect the failure in order to prevent degradation and damage of the elements of the power conversion device.

[0005] For example, Patent Document 1 discloses detecting the resistance voltage across the two ends of a resistor constituting an inrush current suppression circuit or the resistance current flowing through the resistor, and determining that a switch has failed when the resistance voltage or the resistance current does not become less than a second threshold value even after a predetermined period of time has passed after the switch is closed.

[0006] In addition, Patent Document 2 discloses the following method: a self-arc extinguishing element such as a GTO (Gate Turn-Off thyristor) thyristor is used as a switch, and a voltage detector is provided for respectively detecting the voltage on the input side and the voltage on the output side of the inrush current suppression circuit, and a short-circuit fault of the switch is detected based on the voltage detected by the voltage sensor and the gate control signal of the switch. Specifically, Patent Document 2 discloses the following content: when the power conversion device stops, the power conversion device is stopped after the switch is turned off, thereby setting a period in which the switch is turned off, and during this period, when no voltage difference is generated between the input side voltage and the output side voltage detected by the voltage detector, the short-circuit fault of the switch is detected.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2020-145809

[0010] Patent Document 2: Japanese Patent Application Publication No. 2001-245401

[0011] Problem that the invention aims to solve

[0012] In the switch failure determination method disclosed in Patent Document 1, an open circuit failure of the switch can be easily detected, but a half-disconnection failure of the switch is difficult to determine.

[0013] In the switch failure determination method disclosed in Patent Document 2, a short-circuit failure of the switch can be detected quickly, but it is necessary to provide voltage detectors on the input side and the output side of the inrush current suppression circuit. Summary of the invention

[0014] The present invention is completed in view of such a situation, and its purpose is to provide a power conversion device, a switch failure detection method and a program for the power conversion device that can detect short-circuit failure and open-circuit failure of a switch used in an inrush current suppression circuit without using a voltage detector.

[0015] Means used to solve problems

[0016] A first aspect of the present invention is a power conversion device comprising: a smoothing capacitor connected to a DC bus of a DC power supply unit, a resistor for suppressing an inrush current flowing to the smoothing capacitor, and a switch connected in parallel with the resistor, wherein the power conversion device comprises: a current sensor connected in series with the switch to detect a current flowing to the switch; a switch control unit which sets the switch to an open state at the start of operation and then closes the switch when a prescribed condition is satisfied; and a fault detection unit which detects a fault in the switch based on a detection value of the current sensor.

[0017] A second aspect of the present invention is a program for causing a computer to function as the failure detection unit.

[0018] A third aspect of the present invention is a switch failure detection method for an electric power conversion device, the electric power conversion device comprising: a smoothing capacitor connected to a DC bus of a DC power supply unit, a resistor for suppressing an inrush current flowing to the smoothing capacitor, and a switch connected in parallel with the resistor, wherein a current sensor connected in series with the switch detects a current flowing to the switch, and a computer controls the opening and closing of the switch so that the switch is set to an open circuit state at the start of operation, and then the switch is closed when specified conditions are met, and a failure of the switch is detected based on the opening and closing control of the switch and the detection value of the current sensor.

[0019] Effects of the Invention

[0020] A short-circuit fault and an open-circuit fault of a switch used in an inrush current suppression circuit can be detected without using a voltage detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a circuit diagram showing a schematic configuration of a power conversion device according to a first embodiment of the present invention.

[0022] Figure 2 This is a flowchart for explaining an example of control at the time of startup of the power conversion device executed by the control device according to the first embodiment of the present invention.

[0023] Figure 3 This is a flowchart for explaining an example of control at the time of startup of the power conversion device executed by the control device according to the first embodiment of the present invention.

[0024] Figure 4 This is a diagram showing a path of current flow when the main contactor is closed in the open state of the switch, assuming that the power conversion device according to the first embodiment of the present invention is normal.

[0025] Figure 5 This is a diagram showing a path of current flow when the switch is closed with the main contactor turned on, assuming that the power conversion device according to the first embodiment of the present invention is normal.

[0026] Figure 6 This is a circuit diagram showing a schematic configuration of a power conversion device according to a second embodiment of the present invention.

[0027] Figure 7 This is a flowchart for explaining an example of control at the time of startup of the power conversion device executed by the control device according to the second embodiment of the present invention.

[0028] Figure 8 This is a flowchart for explaining an example of control at the time of startup of the power conversion device executed by the control device according to the second embodiment of the present invention.

[0029] Explanation of symbols

[0030] 1: Power conversion device;

[0031] 1a: Power conversion device;

[0032] 2: DC power supply unit;

[0033] 2a: DC power supply unit;

[0034] 3: Inverter;

[0035] 4: Electric motor;

[0036] 5: Control device;

[0037] 5a: Control device;

[0038] 21: Smoothing capacitor;

[0039] 22: resistance;

[0040] 23: switch;

[0041] 23a: switch;

[0042] 24: Coil;

[0043] 25: Main contactor;

[0044] 26: Current sensor;

[0045] 28: Gate driver;

[0046] 29: voltage divider resistor;

[0047] 30: Power supply;

[0048] Ith1: first current threshold;

[0049] Ith2: second current threshold;

[0050] Ith3: The third current threshold. DETAILED DESCRIPTION

[0051] [First embodiment]

[0052] Hereinafter, a power conversion device, a switch failure detection method for the power conversion device, and a program according to a first embodiment of the present invention will be described with reference to the drawings.

[0053] The power conversion device of this embodiment is used, for example, to drive a motor that drives an electric compressor. An example of the use of the electric compressor is a refrigeration unit for land transportation.

[0054] Hereinafter, a case where the power conversion device of the present embodiment is applied to a motor drive device for driving an electric compressor mounted on a refrigeration unit for land transportation will be described as an example.

[0055] In addition, the power conversion device of the present invention is not limited to the applications described below, but can be applied to various devices requiring power conversion.

[0056] Figure 1 1 is a circuit diagram showing a schematic configuration of a power conversion device 1 according to a first embodiment of the present invention. Figure 1As shown, the power conversion device 1 includes a DC power supply unit 2 and an inverter 3 that converts DC power from the DC power supply unit 2 into AC power. The AC power from the inverter 3 is applied to a motor 4, for example, to drive the motor 4. The power conversion device 1 also includes a control device 5 that controls each element constituting the power conversion device 1.

[0057] The DC power supply unit 2 is provided with a smoothing capacitor 21 for smoothing the fluctuation component of the DC power. One end of the smoothing capacitor 21 is connected to the positive circuit of the DC power supply unit 2, and the other end is connected to the negative circuit of the DC power supply unit 2. In addition, the DC power supply unit 2 is provided with an inrush current suppression circuit for suppressing the inrush current flowing to the smoothing capacitor 21 when the power supply is turned on. The inrush current suppression circuit includes, for example, a resistor 22 provided at a position closer to the power supply side than the smoothing capacitor 21 and a switch 23 connected in parallel with the resistor 22. The resistor 22 is connected to the positive circuit of the DC power supply unit 2, for example. The switch 23 is, for example, a mechanical switch such as a relay switch.

[0058] The DC power supply unit 2 includes a coil 24 and a main contactor 25 connected in series with a resistor 22. The main contactor 25 is turned on and off (opened and closed) by, for example, a vehicle control device (e.g., a vehicle-side ECU (Electronic Control Unit)). The coil 24 and the smoothing capacitor 21 constitute a filter circuit. The filter circuit suppresses noise and harmonic current to the output side.

[0059] The current sensor 26 is connected in series with the switch 23. The current sensor 26 detects the current flowing to the switch 23 and outputs the current detection value to the control device 5. The current sensor 26 is, for example, an insulation current sensor. Examples of the insulation current sensor include a Hall element, an insulation amplifier, and the like.

[0060] The switches constituting the bridge circuit of the inverter 3 and the opening and closing of the switch 23 are controlled by the control device 5 .

[0061] The control device 5 is connected to the host ECU via a communication line, for example, and transmits and receives control signals to and from the host ECU. The control device 5 drives the inverter 3 according to the control signal from the host ECU, thereby controlling the AC power applied to the motor 4. The control device 5 controls the opening and closing of the switch 23 according to the control signal from the host ECU and the voltage across the smoothing capacitor 21.

[0062] Here, the “host ECU” may be an ECU mounted on a main substrate provided in the land transport refrigeration unit, may be a vehicle-side ECU, or may include both.

[0063] A voltage detection value corresponding to the positive voltage of the DC power supply unit 2 is output to the control device 5. The voltage detection value is, for example, a voltage detection value obtained by dividing the voltage across the smoothing capacitor 21 by a predetermined resistance ratio. In addition, a current detection value detected by the current sensor 26 is output to the control device 5.

[0064] The control device 5 has a fault detection function (fault detection unit) that detects a fault in the main contactor 25 and the switch 23 using the voltage detection value and the current detection value described above.

[0065] The control device 5 is, for example, a microcomputer. The control device 5 has, for example, a main storage device (Main Memory) composed of a writable memory such as a CPU (Central Processing Unit), a cache memory, and a RAM (Random Access Memory), and a secondary storage device (Secondary storage: memory). The secondary storage device is a non-transitory computer readable storage medium. An example of a non-transitory computer readable storage medium includes a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, and the like.

[0066] Next, refer to Figure 2 and Figure 3 , the control performed by the control device 5 at the time of starting the power conversion device 1 will be described. Figure 2 and Figure 3 This is a flowchart showing an example of processing steps when the power conversion device 1 is started. As an example, a series of processes described below are stored in the secondary storage device of the control device 5 in the form of a program, and the CPU (processor) reads the program into the main storage device and realizes various functions by executing information processing / calculation processing.

[0067] First, before the power supply of the power conversion device 1 is turned on, the main contactor 25 is disconnected (open state), and the switch 23 is turned on (SA1). In this state, the control device 5 determines whether the voltage detection value is greater than the first voltage threshold value Vth1 (SA2). As a result, when the voltage detection value is greater than the first voltage threshold value Vth1 (SA2: yes), it is determined to be a short-circuit fault of the main contactor 25 (SA3), and an error notification containing the fault content is sent to the ECU (SA4). As a result, the power supply to the power conversion device 1 is cut off by a contactor other than the main contactor 25. In addition, the switch 23 is turned off.

[0068] On the other hand, in step SA2, when the voltage detection value is less than the first voltage threshold value Vth1 (SA2: No), it is determined whether the current detection value is greater than the specified first current threshold value (first threshold value) Ith1 (SA5). As a result, when the current detection value is greater than the first current threshold value Ith1 (SA5: Yes), since the current is erroneously detected even though no current is flowing, it is determined that the current sensor 26 is faulty (SA6), and an error notification including the fault content is sent to the ECU (SA7). At this time, the main contactor 25 is open and the switch 23 is open.

[0069] In step SA5, when the current detection value is less than the predetermined first current threshold value Ith1 (SA5: No), the control device 5 turns on the main contactor 25 while keeping the switch 23 in the open state (SA8). Figure 4 As shown, the power converter 1 is supplied with DC power from a power source (e.g., a high voltage battery mounted on a vehicle) 30. As a result, current flows from the power source 30 to the smoothing capacitor 21 via the main contactor 25, the coil 24, and the resistor 22. At this time, the resistor 22 suppresses the inrush current.

[0070] Next, the control device 5 determines whether the current detection value is greater than the second current threshold value Ith2 ( Figure 3 As a result, when the current detection value is greater than the second current threshold value Ith2 (SA9: Yes), a short circuit fault of the switch 23 is detected (SA10), and the process is transferred to Figure 2 Step SA7.

[0071] On the other hand, when the current detection value is less than the second current threshold value Ith2 (SA9: No), it is determined whether the charging of the smoothing capacitor 21 is completed (SA11). This can be determined, for example, by whether the voltage detection value is above a preset charging threshold value. In addition, it can also be determined by the time after the main contactor 25 is turned on. In this regard, since it is a well-known technology, a well-known technology can be appropriately adopted.

[0072] Next, when it is determined that the charging of the smoothing capacitor 21 is completed (SA11: Yes), the control device 5 closes the switch 23 while maintaining the main contactor 25 in the on state (SA12). Figure 5 As shown, current flows from the power source 30 to the inverter 3 via the main contactor 25 , the coil 24 , the current sensor 26 , and the switch 23 .

[0073] Next, the control device 5 determines whether the current detection value is below the third current threshold value Ith3 (SA13). As a result, if the current detection value is below the third current threshold value Ith3 (SA13: Yes), an open circuit fault of the switch 23 is detected (SA14), and the control device 5 returns to Figure 2 Step SA7.

[0074] On the other hand, when the current detection value is greater than the third current threshold value Ith3 (SA13: No), the control device 5 determines that the switch 23 is normal (SA15), and ends the start-up process. Thereafter, the control device 5 continues to perform the motor drive control based on the control signal from the vehicle ECU by performing normal operation control, that is, inverter control, etc.

[0075] As described above, according to the power conversion device 1 , the switch failure detection method, and the program of the present embodiment, the following effects are achieved.

[0076] The power conversion device 1 includes: a current sensor 26 connected in series with the switch 23 and detecting the current flowing to the switch 23, and a control device (fault detection unit) 5 that detects a fault of the switch 23 based on the detection value of the current sensor 26. The current sensor 26 is connected in series with the switch 23, so it can directly detect the current flowing to the switch 23. Thus, both an open circuit fault and a short circuit fault of the switch 23 can be quickly detected. In addition, the fault detection of the switch 23 can be performed without using a voltage sensor.

[0077] [Second embodiment]

[0078] A power conversion device 1a, a switch failure detection method and a program of the power conversion device 1a according to a second embodiment of the present invention are described with reference to the accompanying drawings. The power conversion device 1a of this embodiment is different from the first embodiment described above in that a semiconductor switch is used as the switch 23a. Hereinafter, the same reference numerals are given to the same structures as those in the first embodiment and the description thereof is omitted, and the differences are mainly described.

[0079] Figure 6 1 is a circuit diagram showing a schematic configuration of a power conversion device 1a according to a second embodiment of the present invention. Figure 6 As shown, the DC power supply unit 2a of the power conversion device 1a of the present embodiment includes a switch 23a. The switch 23a is a semiconductor switch, and examples thereof include SiC-MOSFET, IGBT (Insulated Gate Bipolar Transistor), and the like.

[0080] The power conversion device 1a further includes a gate driver (switch driver) 28 for driving the switch 23a. The gate driver 28 is, for example, an insulating gate driver. The gate driver 28 controls the on and off of the switch 23a according to a switch control signal from the control device 5a (for example, a microcomputer). Here, the on state of the switch 23a means that the current flows when the switch 23a is closed, and the off state of the switch 23a means that the current does not flow when the switch 23a is open.

[0081] The gate driver 28 has an internal abnormality diagnosis function. For example, when the output voltage relative to the input voltage is outside the specified voltage value (input and output logic are inconsistent), the gate driver 28 determines that the input and output are abnormal, and sets the RDY signal to "L" (LOW) and outputs it. In addition, when no internal abnormality is detected, that is, in a normal state, the RDY signal is set to "H" (HIGH).

[0082] In addition, the gate driver 28 has a function of detecting that the switch 23a is in an overcurrent state. When an overcurrent state is detected, the FLT signal is set to "L" (LOW). For example, if an overcurrent flows to the switch 23a, a voltage (potential difference) greater than a specified value is generated between the drain and source of the switch 23a (SiC-MOSFET). The specified value is set by the electrical characteristics of the switch 23a and the voltage-dividing resistor 29. When a drain-source voltage greater than a specified value is generated, the voltage output from the voltage-dividing resistor 29 to the gate driver 28 changes and becomes greater than a specified threshold. When the gate driver 28 detects that the voltage is greater than the threshold, it detects an overcurrent in the switch 23a, sets the FLT signal to "L" and outputs it. When an overcurrent in the switch 23a is not detected, that is, in a normal state, the FLT signal is set to "H" (HIGH).

[0083] Reference Figure 7 and Figure 8 Next, a control method at the time of startup of the power conversion device 1 executed by the control device 5a of this embodiment will be described. Figure 7 and Figure 8 This is a flowchart showing an example of processing steps when the power conversion device 1 is started. As an example, a series of processes described below are stored in the secondary storage device of the control device 5a in the form of a program, and the CPU (processor) reads the program into the main storage device and realizes various functions by executing information processing / calculation processing.

[0084] Since steps SB1 to SB7 correspond to steps SA1 to SA7 of the first embodiment, their description is omitted here.

[0085] In step SB8, the control device 5a determines whether the RDY signal from the gate driver 28 is "H", that is, whether it indicates a normal state (SB8). As a result, when the RDY signal is "L" (SB8: No), it is determined that there is an internal abnormality in the gate driver (SB9), and the process moves to step SB7. On the other hand, when the RDY signal is "H" (SB8: Yes), it is then determined whether the FLT signal is "H", that is, whether it indicates a normal state (SB10).

[0086] As a result, when the FLT signal is "L" (SB10: No), although the main contactor 25 is not turned on and no voltage is applied, the gate driver 28 determines that an overcurrent flows through the switch 23a, so it is determined that the gate driver 28 has a fault (SB11), and the process moves to step SB7. On the other hand, when the FLT signal is "H" (SB10: Yes), the switch 23a remains open and the main contactor 25 is turned on ( Figure 8 SB12). Therefore, if it is a normal state, the power conversion device 1 (refer to Figure 4 ) supplies DC power from a power source (e.g., a high-voltage battery on board a vehicle) 30.

[0087] In the next step SB13, the control device 5a determines whether the current detection value is greater than the second current threshold value Ith2, and determines whether the FLT signal is "L" (SB13). As a result, when both conditions are met, the control device 5a determines that the switch is short-circuited (SB14), and transfers to step SB7 (refer to Figure 7 ). As a result, the main contactor 25 is turned off, and the switch 23a is kept in the off state.

[0088] In fact, when a short-circuit fault occurs in the switch 23a, the current detection value should be greater than the second current threshold value Ith2, and the FLT signal should also be "L". That is, both conditions of step SB13 should be satisfied. Therefore, by obtaining the "AND" of the two conditions, the detection accuracy of the short-circuit fault of the switch 23a can be improved.

[0089] On the other hand, when only one of the above two conditions is satisfied, the detection results of the current sensor 26 and the gate driver 28 are inconsistent. In this case, it cannot be determined whether the switch 23a has a short-circuit failure, and further, it can be determined that the current sensor 26 or the gate driver 28 has a failure. Therefore, in step SB13, when both conditions are not satisfied by "AND", it is determined that at least one of the short-circuit failure of the switch 23a, the failure of the current sensor 26, and the failure of the gate driver 28 has occurred.

[0090] On the other hand, in step SB13, when any condition is not satisfied (SB13: No), it is determined whether the charging of the smoothing capacitor 21 is completed (SB15). The determination condition is the same as that of SA11 in the first embodiment.

[0091] When it is determined that the charging of the smoothing capacitor 21 is completed (SB15: Yes), the control device 5a turns the switch 23a to the on state while the main contactor 25 is maintained in the on state (SB16). Specifically, the control device 5a outputs a switch control signal to the gate driver 28 to turn on the switch 23a. The gate driver 28 applies a gate voltage to the gate of the switch 23a, and the switch 23a is turned on. If it is a normal state, the current flows from the power supply 30 through the main contactor 25, the coil 24, the current sensor 26, and the switch 23a (refer to Figure 5 ).

[0092] The control device 5a determines whether the RDY signal from the gate driver 28 is "H", that is, whether it indicates a normal state (SB17). If the RDY signal is "L" (SB17: No), it determines that there is an internal abnormality in the gate driver (SB18), and transfers to Figure 7 On the other hand, when the RDY signal is "H" (SB17: Yes), then, it is determined whether the current detection value is below the third current threshold value Ith3 (SB19). When the current detection value is below the third current threshold value Ith3 (SB19: Yes), an open circuit fault of the switch 23 is detected (SB20), and the process is transferred to step SB7. Figure 7 Step SB7.

[0093] On the other hand, when the current detection value is greater than the third current threshold value Ith3 (SB19: No), the control device 5 determines that the switch 23a is normal (SB21), and ends the start-up process. The control device 5a continues to perform the motor drive control based on the control signal from the vehicle ECU by performing normal operation control, that is, inverter control, etc.

[0094] As described above, according to the power conversion device 1a, the switch failure detection method, and the program of this embodiment, the following effects are achieved.

[0095] In the power conversion device 1a, the switch 23a is a semiconductor switch, and the power conversion device 1a has a gate driver 28 for driving the semiconductor switch. The gate driver 28 has a function of determining whether an overcurrent flows through the switch 23a (an overcurrent detection unit of the switch 23a) and an abnormality diagnosis function of diagnosing its own abnormality (an abnormality diagnosis unit). Therefore, the control device 5a can perform fault determination of the switch 23a, the current sensor 26, and the gate driver 28 based on the FLT signal for notifying the detection of the overcurrent and the RDY signal for notifying the gate driver 28 of the abnormality.

[0096] The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements may be applied to the above embodiments without departing from the gist of the invention, and the methods to which the changes or improvements are applied are also included in the technical scope of the present invention. In addition, the above embodiments may be appropriately combined.

[0097] The process flow at the time of startup described in the above embodiment is also an example, and unnecessary steps may be deleted, new steps may be added, or the process order may be changed without departing from the scope of the present invention.

[0098] For example, in the above embodiment, the case where DC power is supplied from the power supply 30 is described as an example, but the present invention is not limited to this example. For example, the power supply 30 may be an AC power supply. In this case, for example, as disclosed in Patent Document 1, the power conversion device 1, 1a may further include a rectifier for converting AC power into DC power.

[0099] In addition, the first current threshold Ith1, the second current threshold Ith2, and the third current threshold Ith3 in the above embodiments may all be set to the same value, may partly be set to the same value, or may all be set to different values. The method of determining these thresholds is a design matter.

[0100] In addition, in the above-mentioned embodiments, the case where the current value is output from the current sensor 26 is described as an example, but the present invention is not limited thereto. For example, the current sensor 26 may also have a current-voltage conversion characteristic for converting the current value into a voltage value, and the current value is converted into a voltage value according to the conversion characteristic and output to the control device 5, 5a. In this case, for the first current threshold value Ith1, the second current threshold value Ith2, and the third current threshold value Ith3, the value obtained by converting the current into a voltage using the common current-voltage conversion characteristic may also be used.

[0101] The power conversion device 1 , the switch failure detection method and the program of the power conversion device described in the above-described embodiment can be understood, for example, as follows.

[0102] The first embodiment of the power conversion device 1, 1a of the present invention comprises: a smoothing capacitor 21 connected to the DC bus of the DC power supply unit 2, 2a, a resistor 22 for suppressing the inrush current flowing to the smoothing capacitor, and a switch 23, 23a connected in parallel with the resistor, and the power conversion device comprises: a current sensor 26, which is connected in series with the switch to detect the current flowing to the switch; a switch control unit 5, 5a, which sets the switch to an open state at the start of operation and then closes the switch when a specified condition is met; and a fault detection unit 5, 5a, which detects a fault of the switch based on the detection value of the current sensor.

[0103] According to the power conversion device of the present invention, the current sensor is connected in series with the switch, so that the current flowing to the switch can be directly detected. As a result, both open circuit fault and short circuit fault of the switch can be detected quickly. In addition, the fault detection of the switch can be performed without using a voltage sensor.

[0104] The power conversion device according to the second aspect of the present invention may be such that, in the first aspect, the switch 23a is a semiconductor switch, and the power conversion device includes a switch driving unit 28 that drives the semiconductor switch according to a command from the switch control unit.

[0105] By using semiconductor switches, the response speed can be increased compared to the case of using mechanical switches. In addition, mechanical switches with excellent current resistance characteristics are large and expensive. In contrast, by using semiconductor switches, the components can be miniaturized and the cost can be reduced.

[0106] In a third aspect of the power conversion device of the present invention, in the first aspect or the second aspect, the current sensor is, for example, an insulating current sensor.

[0107] By using an insulation current sensor, the current resistance characteristics can be improved. In particular, when used in a power conversion device such as a car air conditioner, the power supply is supplied from a high-voltage battery on the car, so it becomes a high-voltage power supply. Even in such a case, by using an insulation current sensor, the current flowing to the switch can be reliably detected.

[0108] The fourth aspect of the power conversion device of the present invention, in any one of the first aspect to the third aspect, may be such that, in a state where no voltage is applied to the DC power supply unit, when the detection value of the current sensor is greater than a prescribed first threshold value, the fault detection unit detects a fault in the current sensor.

[0109] The state in which no voltage is applied to the DC power supply unit is a state in which no current flows to the switch. In this case, when the detection value of the current sensor is greater than the first threshold value, it is determined that the current sensor itself has a fault.

[0110] The fifth mode of the power conversion device of the present invention, in any one of the first mode to the fourth mode, may be that when a voltage is applied to the DC power supply unit and the switch is controlled to an open circuit state by the switch control unit, when the detection value of the current sensor is greater than a prescribed second threshold value, the fault detection unit detects a short circuit fault of the switch.

[0111] The situation where a voltage is applied to the DC power supply unit and the switch is controlled to an open state means a state where current does not flow to the switch. In this case, when the current sensor detects a detection value greater than the second threshold, it is determined that a short-circuit failure has occurred in the switch.

[0112] The sixth aspect of the power conversion device of the present invention, in any one of the first aspect to the fourth aspect, may be that when a voltage is applied to the DC power supply unit and the switch is controlled to a closed state by the switch control unit, when the detection value of the current sensor is below a prescribed third threshold value, the fault detection unit detects an open circuit fault of the switch.

[0113] The state where a voltage is applied to the DC power supply unit and the switch is controlled to be closed means a state where current flows to the switch. In this case, when the current sensor detects a detection value below the third threshold, it is determined that an open circuit failure has occurred in the switch.

[0114] The seventh aspect of the power conversion device of the present invention may be such that, in the second aspect, the switch drive unit has an abnormality diagnosis unit, and the fault detection unit detects the abnormality of the switch drive unit based on an abnormality notification signal (RDY signal "L") output from the switch drive unit.

[0115] Since the switch driving unit includes the abnormality diagnosing unit, abnormality of the switch driving unit can be easily detected.

[0116] The power conversion device of the eighth embodiment of the present invention, in the above-mentioned second embodiment or the above-mentioned seventh embodiment, may also be that the above-mentioned switch driving unit has an overcurrent detection unit for detecting whether an overcurrent flows to the above-mentioned switch 23a, and the above-mentioned fault detection unit detects the fault of the above-mentioned switch by evaluating the consistency between the overcurrent notification signal (FLT signal "L") output from the above-mentioned switch driving unit and the fault detection based on the detection value of the above-mentioned current sensor.

[0117] When a short circuit occurs in the switch, the detection value of the current sensor is greater than the second threshold value, and the overcurrent notification signal from the switch drive unit also becomes a signal indicating overcurrent. Therefore, when these two results are "AND", it is determined that the switch is faulty, which can improve the detection accuracy of the short circuit fault of the switch.

[0118] On the other hand, when these conditions do not match, it is determined that at least one of a short-circuit failure of the switch, a failure of the current sensor, and a failure of the gate driver has occurred.

[0119] The power conversion device of the ninth aspect of the present invention may be such that, in the eighth aspect, when no voltage is applied to the DC power supply unit and when an overcurrent notification signal is notified from the switch driving unit, the fault detection unit detects a fault in the switch driving unit.

[0120] The state in which the voltage is not applied to the DC power supply unit is the state in which the current does not flow to the switch. In such a case, when an overcurrent notification signal notifying an overcurrent is notified from the switch drive unit, it is determined that the switch drive unit itself has a fault.

[0121] The program of the present invention is a program for causing a computer to function as the failure detection unit of any one of the first to ninth aspects.

[0122] The present invention provides a switch failure detection method for a power conversion device, wherein the power conversion device comprises: a smoothing capacitor connected to a DC bus of a DC power supply unit, a resistor for suppressing an inrush current flowing to the smoothing capacitor, and a switch connected in parallel with the resistor, wherein a current sensor connected in series with the switch detects a current flowing to the switch, and a computer controls the opening and closing of the switch so that the switch is set to an open circuit state at the start of operation, and then the switch is closed when specified conditions are met, and a failure of the switch is detected based on the opening and closing control of the switch and the detection value of the current sensor.

Claims

1. A power conversion device comprising: a smoothing capacitor connected to a DC bus of a DC power supply unit, a resistor for suppressing an inrush current flowing to the smoothing capacitor, and a switch connected in parallel with the resistor, wherein: have: a current sensor connected in series with the switch to detect a current flowing to the switch; a switch control unit that sets the switch to an open state at the start of operation and then closes the switch when a predetermined condition is satisfied; as well as A fault detection unit detects a fault of the switch based on a detection value of the current sensor.

2. The power conversion device according to claim 1, characterized in that: The switch is a semiconductor switch, The power conversion device includes a switch driving unit that drives the semiconductor switch according to an instruction from the switch control unit.

3. The power conversion device according to claim 1, characterized in that , The current sensor is an isolated current sensor.

4. The power conversion device according to claim 1, characterized in that , The fault detection unit detects a fault in the current sensor when a detection value of the current sensor is greater than a predetermined first threshold value in a state where no voltage is applied to the DC power supply unit.

5. The power conversion device according to claim 1, characterized in that , When a voltage is applied to the DC power supply unit and the switch is controlled to an open state by the switch control unit, the fault detection unit detects a short-circuit fault of the switch when a detection value of the current sensor is greater than a predetermined second threshold value.

6. The power conversion device according to claim 1, characterized in that , When a voltage is applied to the DC power supply unit and the switch is controlled to a closed state by the switch control unit, the fault detection unit detects an open circuit fault of the switch when a detection value of the current sensor is less than a predetermined third threshold value.

7. The power conversion device according to claim 2, characterized in that: The switch driving unit includes an abnormality diagnosis unit. The fault detection unit detects an abnormality of the switch drive unit based on an abnormality notification signal output from the switch drive unit.

8. The power conversion device according to claim 2, characterized in that: The switch driving unit includes an overcurrent detection unit for detecting whether an overcurrent flows to the switch. The failure detection unit detects a failure of the switch by evaluating consistency between an overcurrent notification signal output from the switch driving unit and a failure detection based on a detection value of the current sensor.

9. The power conversion device according to claim 8, characterized in that , The failure detection unit detects a failure of the switch drive unit when an overcurrent notification signal is notified from the switch drive unit in a state where no voltage is applied to the DC power supply unit.

10. A program, characterized in that It is used to make a computer function as the failure detection unit according to claim 1.

11. A switch fault detection method for a power conversion device, characterized in that: The power conversion device comprises: a smoothing capacitor connected to a DC bus of a DC power supply unit, a resistor for suppressing an inrush current flowing to the smoothing capacitor, and a switch connected in parallel with the resistor, wherein: detecting a current flowing to the switch by a current sensor connected in series with the switch, The computer controls the opening and closing of the switch so that the switch is set to an open state at the beginning of the operation, and then the switch is closed when the specified conditions are met. The computer detects a failure of the switch based on the on / off control of the switch and the detection value of the current sensor.

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