Power conversion device and control method of power conversion device

Abstract

In the control method of the power conversion device of the present invention, in step (S301), the AC current sensor value (Ius, Ivs, Iws) is obtained, and in step (S303), the positive current values ​​of the U phase, V phase and W phase output from the first half-wave rectifier (451) and the negative current values ​​of the U phase, V phase and W phase output from the second half-wave rectifier (452) are filtered respectively and output to the determination unit (454). In step (S304), it is determined whether the positive current value of the U phase after filtering is within the threshold value (1). If it is within the threshold value (1), in step (S305), it is determined that the upper arm switch element (Tuu) of the U phase is open-circuited. If the negative current value of the U phase after filtering is within the threshold value (2), in step (S307), the determination unit (454) determines that the lower arm switch element (Tul) of the U phase is open-circuited.

Description

Technical Field

[0001] The invention relates to a power conversion device and a control method of the power conversion device. Background Art

[0002] Hybrid vehicles and electric vehicles are equipped with a power conversion device to drive the motor. The power conversion device switches the switching elements constituting the upper arm circuit and the lower arm circuit corresponding to each phase of the motor, thereby converting the direct current supplied by the battery into alternating current to drive the motor.

[0003] In recent years, the need to detect abnormalities and failures in power conversion devices has increased based on functional safety standards for automobiles. Therefore, it is necessary to perform diagnosis that can detect abnormalities and failures in power elements as well.

[0004] Patent document 1 discloses a device for detecting the amplitude peak of the first half cycle of the output current from a switching element, detecting the amplitude peak of the second half cycle following the first half cycle, and outputting a fault detection signal of the switching element when the amplitude peak of the first half cycle or the amplitude peak of the second half cycle is close to 0 and the deviation between the amplitude peak of the first half cycle and the amplitude peak of the second half cycle exceeds a threshold.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-246182 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] In the device described in Patent Document 1, it is impossible to identify which of the switching elements constituting the upper arm circuit and the lower arm circuit has failed.

[0010] Technical solutions adopted to solve technical problems

[0011] The power conversion device of the present invention includes: a three-phase inverter circuit, which is composed of an upper arm circuit and a lower arm circuit corresponding to each phase of a three-phase motor, and converts a direct current into a three-phase alternating current; a current detection unit, which is used to detect the output current of each phase of the inverter circuit; and a fault diagnosis unit, which diagnoses an open circuit fault of a switching element constituting the inverter circuit based on the output current of each phase, and the fault diagnosis unit has: a first half-wave rectifier, which outputs a positive current in the output current of each phase; and a second half-wave rectifier, which outputs a negative current in the output current of each phase, and the fault diagnosis unit determines the switching element in which an open circuit fault has occurred based on the outputs of the first half-wave rectifier and the second half-wave rectifier.

[0012] The control method of the power conversion device of the present invention, the power conversion device corresponds to each phase of the three-phase motor and is composed of an upper arm circuit and a lower arm circuit to form an inverter circuit, and converts a direct current into a multi-phase alternating current, detects the output current of each phase of the inverter circuit, and diagnoses the open circuit fault of the switching element constituting the inverter circuit based on the output current of each phase, that is, performs a fault diagnosis process, the fault diagnosis process performs a first half-wave rectification of the positive current in the output current of each phase, and a second half-wave rectification of the negative current in the output current of each phase, and the fault diagnosis process determines the switching element in which the open circuit fault has occurred based on the output of the first half-wave rectification and the second half-wave rectification.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to determine which switching element of the switching elements constituting the upper arm circuit and the lower arm circuit has failed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a circuit configuration diagram of the power conversion device according to the first embodiment.

[0016] Figure 2 It is the circuit structure diagram of the inverter circuit.

[0017] Figure 3 This is a flowchart showing the processing operation of the fault diagnosis unit according to the first embodiment.

[0018] Figure 4 This is a flowchart showing the processing operation of the PWM signal generating unit according to the first embodiment.

[0019] Figure 5 (A) Figure 5 (B) Figure 5 (C) Figure 5(D) Figure 5 (E) shows an example of a current waveform when an open-circuit failure occurs in the U-phase upper arm switching element according to the first embodiment.

[0020] Figure 6 This is a circuit configuration diagram of a power conversion device according to Embodiment 2.

[0021] Figure 7 This is a flowchart showing the processing operation of the fault diagnosis unit according to the second embodiment.

[0022] Figure 8 (A) Figure 8 (B) Figure 8 (C) Figure 8 (D) Figure 8 (E) shows an example of a current waveform when an open-circuit failure occurs in the U-phase upper arm switching element according to the second embodiment.

[0023] Fig. 9 This is a circuit configuration diagram of a power conversion device according to a third embodiment.

[0024] Fig.10 This is a flowchart showing the processing operation of the PWM signal generating unit according to the third embodiment.

[0025] Fig.11 This is a circuit configuration diagram of a power conversion device according to a fourth embodiment.

[0026] Fig.12 This is a flowchart showing the processing operation of the fault diagnosis unit according to the fourth embodiment.

[0027] Fig.13 (A) Fig.13 (B) Fig.13 (C) Fig.13 (D) Fig.13 (E) Fig.13 (F) Fig.13 (G) Fig.13 (H) shows an example of a current waveform when an open-circuit failure occurs in the U-phase upper arm switching element according to the fourth embodiment. DETAILED DESCRIPTION

[0028] [Implementation Method 1]

[0029] Figure 1 1 is a circuit configuration diagram of the power conversion device 100 according to the first embodiment.

[0030] The power conversion device 100 converts the DC power obtained from the DC power supply 10 into AC power to drive the motor 20 during power operation. The DC power supply 10 is a power source for driving the motor 20. In addition, the power conversion device 100 converts the power of the motor 20 into DC power during regeneration and charges the DC power supply 10.

[0031] The motor 20 is a three-phase motor having three windings inside. In addition, the motor 20 is equipped with an angle sensor (not shown) for measuring the rotation angle of the motor 20, and the angle sensor outputs the measured rotation angle as an angle sensor value to the power conversion device 100. The power conversion device 100 detects a fault described later and notifies the fault notification device 30 of the fault.

[0032] The power conversion device 100 includes a control circuit 40, a drive circuit 50, and an inverter circuit 60. The control circuit 40 includes a motor speed calculation unit 41, a target current calculation unit 42, a duty ratio calculation unit 43, a PWM signal generation unit 44, and a fault diagnosis unit 45. The fault diagnosis unit 45 includes a first half-wave rectification unit 451, a second half-wave rectification unit 452, a filter unit 453, and a determination unit 454.

[0033] The voltage sensor 70 is a sensor that measures the output voltage of the DC power supply 10 , and outputs the measured voltage value as a voltage sensor value to the target current calculation unit 42 in the control circuit 40 .

[0034] The AC current sensor 90 is a sensor for measuring the AC current flowing in each phase (U phase, V phase, W phase) of the motor 20. Specifically, the AC current Iu flowing through the U phase is measured, and the AC current sensor value Ius is output to the duty cycle calculation unit 43, the first half-wave rectifier 451, and the second half-wave rectifier 452. Similarly, the AC current Iv flowing through the V phase is measured, and the AC current sensor value Ivs is output to the duty cycle calculation unit 43, the first half-wave rectifier 451, and the second half-wave rectifier 452. Similarly, the AC current Iw flowing through the W phase is measured, and the AC current sensor value Iws is output to the duty cycle calculation unit 43, the first half-wave rectifier 451, and the second half-wave rectifier 452. In addition, in the present embodiment, one AC current sensor is provided for each phase, and a total of three AC current sensors are provided, but it is also possible to provide AC current sensors only in two phases, and calculate the AC current sensor value of the remaining one phase according to the relationship of Ius+Ivs+Iws=0. In this manner, the AC current sensor 90 detects the output current of each phase of the inverter circuit 60 .

[0035] The motor speed calculation unit 41 calculates a motor speed value based on a change in an angle sensor value in the motor 20 , and outputs the calculated motor speed value to the target current calculation unit 42 .

[0036] The control circuit 40 communicates with an electronic control device (not shown) provided outside the power conversion device 100 , receives a target torque of the motor 20 from the external electronic control device, and inputs the target torque to the target current calculation unit 42 .

[0037] The target current calculation unit 42 calculates the current value to be flowed to the motor 20 using the target torque, the voltage sensor value, and the motor speed value output by the motor speed calculation unit 41, and outputs the current value as a target current value to the duty ratio calculation unit 43. The target current value is expressed in the form of a d-axis target current value and a q-axis target current value, for example.

[0038] The duty calculation unit 43 calculates U-phase duty value Du, V-phase duty value Dv, and W-phase duty value Dw based on the target current value outputted from the target current calculation unit 42 and the AC current sensor values ​​Ius, Ivs, and Iws, and outputs them to the PWM signal generation unit 44 .

[0039] In this embodiment, the U-phase duty cycle value Du represents the on-time ratio of the U-phase upper arm circuit switch element, and the on-time ratio of the U-phase lower arm circuit switch element is represented by 1-Du. Similarly, the V-phase duty cycle value Dv represents the on-time ratio of the V-phase upper arm circuit switch element, and the on-time ratio of the V-phase lower arm circuit switch element is represented by 1-Dv. The W-phase duty cycle value Dw represents the on-time ratio of the W-phase upper arm circuit switch element, and the on-time ratio of the W-phase lower arm circuit switch element is represented by 1-Dw.

[0040] The PWM signal generating unit 44 has a timer (not shown) inside, generates a PWM (Pulse Wide Modulation) signal based on the timer value, the U-phase duty value Du, the V-phase duty value Dv, and the W-phase duty value Dw, and outputs the PWM signal to the driving circuit 50 .

[0041] When the abnormal notification signal is output from the fault diagnosis unit 45, the PWM signal generation unit 44 controls the PWM signal so as not to drive the motor 20. The state of not driving the motor 20 is, for example, a state in which all six switching elements in the inverter circuit 60 are turned off (referred to as a freewheeling state in this embodiment). As other examples, a state in which three switching elements of the upper arm circuit among the six switching elements are set to be turned on and three switching elements of the lower arm circuit are set to be turned off (referred to as an upper arm active short-circuit state in this embodiment), and conversely, a state in which the three switching elements of the upper arm circuit are set to be turned off and the three switching elements of the lower arm circuit are set to be turned on (referred to as a lower arm active short-circuit state in this embodiment).

[0042] The drive circuit 50 receives the PWM signal output from the PWM signal generation unit 44 , and outputs a drive signal for switching the switching element on and off to the inverter circuit 60 .

[0043] The inverter circuit 60 has a filter capacitor and six switching elements therein, and converts DC power obtained from the DC power supply 10 into AC power during power operation to drive the motor 20. In addition, during regeneration, the power of the motor 20 is converted into DC power to charge the DC power supply 10.

[0044] The fault diagnosis unit 45 includes a first half-wave rectifier 451 , a second half-wave rectifier 452 , a filter unit 453 , and a determination unit 454 , and performs fault diagnosis of the switching element in the inverter circuit 60 .

[0045] The first half-wave rectifying section 451 extracts only positive current values ​​from the AC current sensor values ​​Ius, Ivs, and Iws, and outputs the positive current values ​​to the filtering section 453 .

[0046] The second half-wave rectifying section 452 extracts only negative current values ​​from the AC current sensor values ​​Ius, Ivs, and Iws, and outputs the negative current values ​​to the filtering section 453 .

[0047] The filter unit 453 filters the three-phase positive current values ​​output from the first half-wave rectifier unit 451 and the three-phase negative current values ​​output from the second half-wave rectifier unit 452 .

[0048] The determination unit 454 determines which part of the switching element in the inverter circuit 60 has failed using the six current values ​​output from the filter unit 453 , and outputs a failure notification signal corresponding to the failed part to the failure notification device 30 and the PWM signal generation unit 44 .

[0049] In the present embodiment, each component of the first half-wave rectifier 451, the second half-wave rectifier 452, the filter 453, and the determination unit 454 is respectively provided in the control circuit 40, but is not limited to this structure. For example, a part of each component may be provided in the control circuit 40, and the remaining component may be composed of hardware independent of the control circuit 40. In addition, the first half-wave rectifier 451, the second half-wave rectifier 452, the filter 453, and the determination unit 454 may all be composed of hardware independent of the control circuit 40.

[0050] In addition, each structure in the control circuit 40 may not adopt a hardware structure, but may realize the function of each structure by a CPU and a program. When each structure in the control circuit 40 is realized by a CPU and a program, the advantage is that the cost can be reduced due to the reduction in the amount of hardware. On the other hand, when each structure is composed of hardware independent of the control circuit 40, the advantage is that the processing load of the control circuit 40 is reduced, thereby further speeding up the diagnostic processing.

[0051] The fault notification device 30 notifies the user of the power conversion device 100 of the occurrence of a fault. As a method of notifying the occurrence of a fault, for example, methods such as lighting a lamp, emitting a warning sound, and notifying by voice can be cited. In addition, the fault notification device 30 uses the fault notification signal output from the determination unit 454 to generate information about the fault content and the fault location, and keeps it internally. The fault notification device 30 has a communication circuit (not shown) inside, and communicates with a device (not shown) outside the power conversion device 100. When a request to output the fault content and the fault location information is received from a device outside the power conversion device 100, the fault notification device 30 outputs this information to the device outside the power conversion device 100. As a result, the user of the power conversion device 100 can understand what kind of fault has occurred in which switching element of the power conversion device 100. In addition, a response strategy corresponding to the fault location can be adopted.

[0052] Figure 2 2 is a circuit diagram of the inverter circuit 60 .

[0053] The inverter circuit 60 has upper and lower arm series circuits of the UVW phases. The U-phase upper and lower arm series circuit 61 is composed of the U-phase upper arm switching element Tuu and the U-phase upper arm diode Duu, the U-phase lower arm switching element Tul and the U-phase lower arm diode Dul. The V-phase upper and lower arm series circuit 62 is composed of the V-phase upper arm switching element Tvu and the V-phase upper arm diode Dvu, the V-phase lower arm switching element Tvl and the V-phase lower arm diode Dvl. The W-phase upper and lower arm series circuit 63 is composed of the W-phase upper arm switching element Twu and the W-phase upper arm diode Dwu, the W-phase lower arm switching element Twl and the W-phase lower arm diode Dwl.

[0054] The upper arm circuit 64 includes a U-phase upper arm switching element Tuu and a U-phase upper arm diode Duu, a V-phase upper arm switching element Tvu and a V-phase upper arm diode Dvu, a W-phase upper arm switching element Twu and a W-phase upper arm diode Dwu. The lower arm circuit 65 includes a U-phase lower arm switching element Tul and a U-phase lower arm diode Dul, a V-phase lower arm switching element Tvl and a V-phase lower arm diode Dvl, a W-phase lower arm switching element Twl and a W-phase lower arm diode Dwl. The switching element is, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor).

[0055] The filter capacitor 66 filters the current generated by the on / off switching of the switching element, and suppresses the ripple of the DC current supplied from the DC power supply 10 to the inverter circuit 60. For example, an electrolytic capacitor or a film capacitor is used as the filter capacitor 66.

[0056] Figure 3 It is a flowchart showing the processing operation of the fault diagnosis unit 45 . Figure 3 The flowchart shown is repeatedly executed at regular intervals.

[0057] In step S301 , the fault diagnosis unit 45 acquires the AC current sensor values ​​Ius, Ivs, and Iws from the AC current sensor 90 .

[0058] In step S302, the first half-wave rectifier 451 extracts only the positive current values ​​of the U phase, V phase, and W phase from the AC current sensor values ​​Ius, Ivs, and Iws, and outputs them to the filter 453. In addition, the second half-wave rectifier 452 extracts only the negative current values ​​of the U phase, V phase, and W phase from the AC current sensor values ​​Ius, Ivs, and Iws, and outputs them to the filter 453.

[0059] In step S303 , the filter unit 453 filters the positive current values ​​of the U phase, V phase, and W phase output from the first half-wave rectifier unit 451 and the negative current values ​​of the U phase, V phase, and W phase output from the second half-wave rectifier unit 452 , and outputs them to the determination unit 454 .

[0060] In step S304, the determination unit 454 determines whether the filtered positive current value of the U phase is within threshold 1. If it is within threshold 1, it is determined in step S305 that the U phase upper arm switching element Tuu is in an open circuit fault. If it is not within threshold 1 in step S304, the process proceeds to step S306. In step S306, the determination unit 454 determines whether the filtered negative current value of the U phase is within threshold 2. If it is within threshold 2, it is determined in step S307 that the U phase lower arm switching element Tul is in an open circuit fault.

[0061] If it is not within the threshold 2 in step S306, the process proceeds to step S308. In step S308, the determination unit 454 determines whether the positive current value of the V phase after filtering is within the threshold 1. If it is within the threshold 1, the process determines in step S309 that the upper arm switching element Tvu of the V phase is in an open circuit fault. If it is not within the threshold 1 in step S308, the process proceeds to step S310. In step S310, the determination unit 454 determines whether the negative current value of the V phase after filtering is within the threshold 2. If it is within the threshold 2, the process determines in step S311 that the lower arm switching element Tvl of the V phase is in an open circuit fault.

[0062] If it is not within the threshold 2 in step S310, proceed to step S312. In step S312, the determination unit 454 determines whether the positive current value of the W phase after filtering is within the threshold 1. If it is within the threshold 1, it is determined in step S313 that the W phase upper arm switching element Twu is in an open circuit fault. If it is not within the threshold 1 in step S312, proceed to step S314. In step S314, the determination unit 454 determines whether the negative current value of the W phase after filtering is within the threshold 2. If it is within the threshold 2, it is determined in step S315 that the W phase lower arm switching element Twl is in an open circuit fault.

[0063] If any of the determination conditions in the above steps S304, S306, S308, S310, S312 and S314 is not satisfied, the process proceeds to step S316, and the determination unit 454 determines that no open-circuit failure occurs in each switching element.

[0064] In step S317 , the determination unit 454 outputs a fault notification signal corresponding to the fault location determined in each of the above steps S305 , S307 , S309 , S311 , S313 , and S315 to the fault notification device 30 and the PWM signal generation unit 44 .

[0065] Figure 4 2 is a flowchart showing the processing operation of the PWM signal generating unit 44 .

[0066] The PWM signal generating unit 44 receives the fault notification signal from the determining unit 454, and determines in step S401 whether an open circuit fault occurs in the upper arm switching element of any one of the U phase, the V phase, and the W phase. When an open circuit fault occurs, in step S402, a PWM signal for changing to a freewheeling state or a lower arm active short circuit state is generated and output to the driving circuit 50. At this time, the upper arm switching element cannot be turned on due to the open circuit fault, so it will not be changed to the upper arm active short circuit state.

[0067] The PWM signal generating unit 44 receives the fault notification signal from the determining unit 454, and determines in step S403 whether an open circuit fault occurs in the lower arm switching element of any phase of the U phase, the V phase, and the W phase. When an open circuit fault occurs, in step S404, a PWM signal for changing to a freewheeling state or an upper arm active short circuit state is generated and output to the driving circuit 50. At this time, the switching element of the lower arm cannot be turned on due to the open circuit fault, so it will not be changed to the lower arm active short circuit state.

[0068] When it is determined in steps S401 and S403 that an open circuit fault has not occurred, in step S405 , the PWM signal generating unit 44 continues the PWM operation, generates PWM signals corresponding to the duty values ​​Du, Dv, and Dw of each phase, and outputs the PWM signals to the driving circuit 50 .

[0069] In this way, when the fault diagnosis unit 45 detects an open circuit fault of the switching element, the PWM signal generation unit 44 generates a PWM signal according to the fault location to set the state of the switching element to any one of a freewheeling state, an upper arm active short circuit state, and a lower arm active short circuit state, so that the motor 20 is in a non-driven state, thereby safely stopping the operation of the motor 20 and the power conversion device 100.

[0070] The switching method of the freewheeling state, the upper arm active short-circuit state, and the lower arm active short-circuit state at the time of a fault may be changed according to the type and operation status of the motor 20 .

[0071] For example, if the type of the motor 20 is an induction motor, it is switched to the freewheeling state, and if it is a synchronous motor, it is switched to any one of the upper arm active short circuit state and the lower arm active short circuit state. In addition, for example, when the motor 20 rotates at a high speed, it is switched to any one of the upper arm active short circuit state and the lower arm active short circuit state, and when the motor 20 rotates at a low speed, it is switched to the freewheeling state.

[0072] Figure 5 2 is an example showing a current waveform when the U-phase upper arm switching element Tuu fails in an open circuit. Figure 5 An example is shown when the U-phase upper arm switching element Tuu fails in an open circuit at time t1.

[0073] Figure 5 (A) shows the output of the AC current sensor value Ius obtained by measuring the AC current Iu flowing through the U phase, the AC current sensor value Ivs obtained by measuring the AC current Iv flowing through the V phase, and the AC current sensor value Iws obtained by measuring the AC current Iw flowing through the W phase. Figure 5 (B) shows the output of the first half-wave rectifier 451 of the AC current sensor values ​​Ius, Ivs, and Iws. Figure 5 (C) shows the output of the second half-wave rectifier 452 of the AC current sensor values ​​Ius, Ivs, and Iws. Figure 5 (D) shows the output after the output of the first half-wave rectifier 451 is filtered by the filter 453 . Figure 5 (E) shows the output after the output of the second half-wave rectifier 452 is filtered by the filter 453 .

[0074] like Figure 5 As shown in (A), at time t1, when the U-phase upper arm switching element Tuu fails to open, the U-phase AC current does not flow in the positive direction (from the inverter circuit 60 to the motor 20), but flows in the negative direction (from the motor 20 to the inverter circuit 60). On the other hand, although the AC currents of the V-phase and W-phases after the U-phase upper arm switching element fails to open, the current flows in both the positive and negative directions.

[0075] Therefore, if Figure 5 As shown in (B), after the fault occurs, the positive current of the U-phase AC current output from the first half-wave rectifier 451 is always approximately 0 [A]. The positive currents of the V-phase and W-phase output from the first half-wave rectifier 451 have periods of approximately 0 [A] and periods of approximately not 0 [A].

[0076] In addition, if Figure 5 As shown in (C), the negative current of the U-phase AC current output from the second half-wave rectifier 452 still has a period of time that is not substantially 0 [A] even after the fault occurs. The negative current of the V-phase and W-phase also still has a period of time that is substantially 0 [A] and a period of time that is not substantially 0 [A].

[0077] like Figure 5 As shown in (D), after an open circuit fault occurs, the value obtained after filtering the positive current of the U-phase AC current is approximately 0 [A], which is within the threshold value 1, while the values ​​obtained after filtering the positive currents of the V-phase and W-phase AC currents are not within the threshold value 1. In addition, Figure 5 As shown in (E), the value obtained after filtering the negative current of the alternating current of the U phase, V phase, and W phase is not within the threshold value 2. Therefore, as shown in FIG. Figure 3As described in the flowchart of FIG. 1 , through the processing operation of the fault diagnosis unit 45, it is determined that the upper arm switching element Tuu of the U phase is open-circuited.

[0078] The positive current value of each phase output from the first half-wave rectifier 451 and the negative current value of each phase output from the second half-wave rectifier 452 also have a period of approximately 0 [A] and a period of approximately not being 0 [A] before the open circuit fault occurs. Therefore, if it is determined whether the positive current value output from the first half-wave rectifier 451 is within the threshold value 1, or if it is determined whether the negative current value output from the second half-wave rectifier 451 is within the threshold value 2, even if the switch element does not have an open circuit fault, it may be erroneously determined that an open circuit fault has occurred in a certain switch element. By using the filter unit 453 to filter the positive current value output from the first half-wave rectifier 451 and the negative current value output from the second half-wave rectifier 452, the current value after filtering is always a constant value under normal circumstances, thereby avoiding erroneous judgments.

[0079] [Implementation Method 2]

[0080] Figure 6 1 is a circuit configuration diagram of a power conversion device 101 according to Embodiment 2. The same reference numerals are given to the same components as those of the power conversion device 100 according to Embodiment 1, and description thereof will be omitted.

[0081] In the second embodiment, the configuration of the fault diagnosis unit 45 is different from that of the power conversion device 100 in the first embodiment. Figure 2 The circuit structure diagram shown is the same.

[0082] The fault diagnosis section 45 includes a first half-wave rectifying section 451 , a second half-wave rectifying section 452 , a maximum / minimum value acquiring section 455 , and a determining section 456 , and performs fault diagnosis of the switching element in the inverter circuit 60 .

[0083] In the present embodiment, each component of the first half-wave rectifier 451, the second half-wave rectifier 452, the maximum / minimum value acquisition unit 455, and the determination unit 456 is respectively arranged inside the control circuit 40, but is not limited to this structure. For example, a part of each component can be arranged inside the control circuit 40, and the remaining components can be composed of hardware independent of the control circuit 40. In addition, the first half-wave rectifier 451, the second half-wave rectifier 452, the maximum / minimum value acquisition unit 455, and the determination unit 456 can all be composed of hardware independent of the control circuit 40.

[0084] In addition, each structure in the control circuit 40 may not adopt a hardware structure, but may realize the function of each structure by a CPU and a program. When each structure in the control circuit 40 is realized by a CPU and a program, the number of hardware is reduced, so there is an advantage of being able to reduce costs. On the other hand, when each structure is composed of hardware independent of the control circuit 40, there is an advantage that the processing load of the control circuit 40 is reduced and the diagnostic process can be performed more quickly.

[0085] The maximum / minimum value acquisition unit 455 acquires the positive current of each phase output from the first half-wave rectifier 451, and holds the maximum value of the positive current of each phase internally. In addition, the maximum / minimum value acquisition unit 455 acquires the negative current of each phase output from the second half-wave rectifier 452, and holds the minimum value of the negative current of each phase internally. Then, the maximum / minimum value acquisition unit 455 outputs the maximum value of the positive current of each phase and the minimum value of the negative current of each phase to the determination unit 456 at regular intervals.

[0086] The determination unit 456 uses the maximum value of the positive current of each phase and the minimum value of the negative current of each phase output from the maximum / minimum value acquisition unit 455 to determine which switching element in the inverter circuit 60 has failed, and outputs a fault notification signal corresponding to the fault location to the fault notification device 30 and the PWM signal generation unit 44.

[0087] Figure 7 This is a flowchart showing the processing operation of the fault diagnosis unit 45 according to the second embodiment. Figure 7 The flowchart shown is repeatedly executed at regular intervals.

[0088] In step S701 , the fault diagnosis unit 45 acquires the AC current sensor values ​​Ius, Ivs, and Iws from the AC current sensor 90 .

[0089] In step S702, the first half-wave rectifier 451 extracts only the positive current values ​​of the U phase, V phase and W phase from the AC current sensor values ​​Ius, Ivs and Iws, and outputs them to the maximum / minimum value acquisition unit 455. In addition, the second half-wave rectifier 452 extracts only the negative current values ​​of the U phase, V phase and W phase from the AC current sensor values ​​Ius, Ivs and Iws, and outputs them to the maximum / minimum value acquisition unit 455.

[0090] In step S703, the maximum value / minimum value acquisition unit 455 updates the maximum values ​​of the positive currents of the U phase, V phase, and W phase output from the first half-wave rectifier 451 and holds them internally. The maximum value / minimum value acquisition unit 455 updates the minimum values ​​of the negative currents of the U phase, V phase, and W phase output from the second half-wave rectifier 452 and holds them internally.

[0091] In step S704, the maximum / minimum value acquisition unit 455 determines whether a prescribed time has passed. If the prescribed time has not passed, the process ends. The prescribed time may be a fixed time or may be changed according to the operating conditions of the motor 20. In the case of a variable time, for example, it may be considered to be set to a time proportional to the rotation speed of the motor 20 or a time proportional to the cycle of the AC current.

[0092] Every time a predetermined time has passed, the process proceeds to step S705 , and the maximum values ​​of positive currents of the U-phase, V-phase, and W-phase and the minimum values ​​of negative currents of the U-phase, V-phase, and W-phase held internally are output to the determination unit 456 .

[0093] Thereafter, the process proceeds to step S706 , and the maximum / minimum value acquisition unit 455 resets the maximum values ​​of positive currents of the U-phase, V-phase, and W-phase, and the minimum values ​​of negative currents of the U-phase, V-phase, and W-phase, which are held internally.

[0094] In the next step S707, the determination unit 456 determines whether the maximum value of the positive current of the U phase is within the threshold value 3. If it is within the threshold value 3, it is determined in step S708 that the U phase upper arm switching element Tuu has an open circuit fault. If it is not within the threshold value 3 in step S707, the process proceeds to step S709. In step S709, the determination unit 456 determines whether the minimum value of the negative current of the U phase is within the threshold value 4. If it is within the threshold value 4, it is determined that the U phase lower arm switching element Tul has an open circuit fault.

[0095] If it is not within threshold 4 in step S709, the process proceeds to step S711. In step S711, the determination unit 456 determines whether the maximum value of the positive current of the V phase is within threshold 3. If it is within threshold 3, it determines in step S712 that the V phase upper arm switching element Tvu has an open circuit fault.

[0096] If it is not within the threshold value 3 in step S711, the process proceeds to step S713. In step S713, the determination unit 456 determines whether the minimum value of the negative current of the V phase is within the threshold value 4. If it is within the threshold value 4, it determines in step S714 that the V phase lower arm switching element Tv1 has an open circuit fault.

[0097] If it is not within the threshold value 4 in step S713, the process proceeds to step S715. In step S715, the determination unit 456 determines whether the maximum value of the positive current of the W phase is within the threshold value 3. If it is within the threshold value 3, the process determines in step S716 that an open circuit fault occurs in the upper arm switching element Twu of the W phase. If it is not within the threshold value 3 in step S715, the process proceeds to step S717. In step S717, the determination unit 456 determines whether the minimum value of the negative current of the W phase is within the threshold value 4. If it is within the threshold value 4, the process determines in step S718 that an open circuit fault occurs in the lower arm switching element Twl of the W phase.

[0098] When any of the determination conditions in the above steps S707 , S709 , S711 , S713 , S715 and S717 is not satisfied, the process proceeds to step S719 , and the determination unit 456 determines that an open-circuit failure has not occurred in each switching element.

[0099] In step S720 , the determination unit 456 outputs a fault notification signal corresponding to the fault location determined in each of the above steps S708 , S710 , S712 , S714 , S716 , and S718 to the fault notification device 30 and the PWM signal generation unit 44 .

[0100] Thus, when the fault diagnosis unit 45 detects an open circuit fault of the switching element, the PWM signal generation unit 44 executes Figure 4 The processing of the flowchart shown generates a PWM signal to set the state of the switching element to any one of the freewheeling state, the upper arm active short-circuit state, and the lower arm active short-circuit state according to the fault location.

[0101] Figure 8 2 is an example showing a current waveform when the U-phase upper arm switching element Tuu fails in an open circuit. Figure 8 An example is shown when the U-phase upper arm switching element Tuu fails in an open circuit at time t1.

[0102] Figure 8 (A) shows the output of the AC current sensor value Ius obtained by measuring the AC current Iu flowing through the U phase, the AC current sensor value Ivs obtained by measuring the AC current Iv flowing through the V phase, and the AC current sensor value Iws obtained by measuring the AC current Iw flowing through the W phase. Figure 8 (B) shows the output of the first half-wave rectifier 451 of the AC current sensor values ​​Ius, Ivs, and Iws. Figure 8 (C) shows the output of the second half-wave rectifier 452 of the AC current sensor values ​​Ius, Ivs, and Iws. Figure 8 (D) shows the maximum value of the output of the first half-wave rectifier 451 .

[0103] Figure 8(E) shows the minimum value of the output of the second half-wave rectifier 452 .

[0104] like Figure 8 As shown in (A), at time t1, when the U-phase upper arm switching element Tuu has an open circuit failure, the U-phase AC current does not flow in the positive direction (the direction from the inverter circuit 60 to the motor 20), but flows in the negative direction (the direction from the motor 20 to the inverter circuit 60). On the other hand, although the AC currents of the V-phase and W-phases after the U-phase upper arm switching element has an open circuit failure have distorted waveforms, currents flow in both the positive and negative directions.

[0105] Therefore, if Figure 8 As shown in (B), after the fault occurs, the positive current of the U-phase AC current output from the first half-wave rectifier 451 is always approximately 0 [A]. The positive currents of the V-phase and W-phase output from the first half-wave rectifier 451 have periods of approximately 0 [A] and periods of approximately not 0 [A].

[0106] In addition, if Figure 8 As shown in (C), even after a fault occurs, the negative current of the U-phase AC current output from the second half-wave rectifier 452 still has a period of time that is not substantially 0 [A]. The negative current of the V-phase and W-phase also still has a period of time that is substantially 0 [A] and a period of time that is not substantially 0 [A].

[0107] The maximum / minimum value acquisition unit 455 outputs the maximum value of the positive current of the U phase, V phase, and W phase and the minimum value of the negative current of the U phase, V phase, and W phase to the determination unit 456 every cycle of the AC current. Figure 8 As shown in (D), after the open circuit fault occurs, the maximum positive current of the U-phase AC current is approximately 0 [A], which is within the threshold value 3. On the other hand, the maximum positive currents of the V-phase and W-phase AC currents are not within the threshold value 3. In addition, Figure 8 As shown in (E), the minimum value of the negative current of the alternating current of the U phase, V phase, and W phase is not within the threshold value 4. Therefore, as shown in FIG. Figure 7 As described in the flowchart shown in FIG. 1 , through the processing operation of the fault diagnosis unit 45 , it is determined that an open-circuit fault occurs in the upper arm switching element Tuu of the U phase.

[0108] The positive current value of each phase output from the first half-wave rectifier 451 and the negative current value of each phase output from the second half-wave rectifier 452 also have a period of approximately 0 [A] and a period of approximately not being 0 [A] before an open circuit fault occurs. Therefore, when the maximum / minimum value acquisition unit 455 outputs the maximum value of the positive current and the minimum value of the negative current to the determination unit 456 for a prescribed time shorter than one cycle of the AC current, even if the switching element is normal, the maximum value of the positive current and the minimum value of the negative current are within the threshold value, and an open circuit fault may be erroneously detected in a certain switch.

[0109] Therefore, in the present embodiment, when determining an open-circuit failure of the switching element, it is desirable that the predetermined time be longer than one cycle of the alternating current.

[0110] [Implementation method 3]

[0111] Fig. 9 1 is a circuit configuration diagram of a power conversion device 102 according to Embodiment 3. The same reference numerals are given to the same components as those of the power conversion device 100 according to Embodiment 1, and description thereof will be omitted.

[0112] The third embodiment is different from the first embodiment in that the motor speed calculation unit 41 outputs the motor speed to the PWM signal generation unit 44. Figure 2 The circuit structure diagram shown is the same.

[0113] This embodiment 3 shows an example of a power conversion device 102 that can quickly identify the open-circuit fault location of a switching element and can continue the operation of the motor 20 when an open-circuit fault of a switching element occurs.

[0114] When the abnormality notification signal is output from the fault diagnosis unit 45 , the PWM signal generation unit 44 in the control circuit 40 determines whether to continue the PWM operation or control the PWM signal so as not to drive the motor 20 according to the motor speed.

[0115] Fig.10 4 is a flowchart showing the processing operation of the PWM signal generating unit 44. Figure 4 The same parts of the processing operation of the PWM signal generating unit 44 are denoted by the same reference numerals, and the description thereof is omitted.

[0116] exist Fig.10 In step S102, the PWM signal generating unit 44 determines whether the motor speed output from the motor speed calculating unit 41 is above the threshold value 5. If it is above the threshold value 5, then in steps S401 to S404, based on the Figure 4In step S102, if the motor speed is less than the threshold value 5, then in step S405, the PWM signal generating unit 44 continues the PWM operation, generates PWM signals corresponding to the duty cycle values ​​Du, Dv and Dw of each phase, and outputs the PWM signals to the driving circuit 50.

[0117] When an open-circuit failure occurs in one of the switching elements, the torque output by the motor 20 is inconsistent with the target torque. Therefore, in the first embodiment, the operation of the motor 20 is stopped for safety reasons. On the other hand, sometimes if the speed of the motor 20 is low, it is better to continue the operation of the motor 20 instead of stopping the drive of the motor 20 immediately. For example, consider the case where the power conversion device 102 of this embodiment is used in a hybrid vehicle or an electric vehicle.

[0118] At this time, the speed of the motor 20 is considered to be proportional to the vehicle speed. When the vehicle speed is high, the vehicle tends to be more difficult to control than when it is low.

[0119] Therefore, when the speed of the motor 20 is high, that is, the vehicle speed is high, if the output torque of the motor 20 does not match the target torque, the driver is more likely to have difficulty controlling the vehicle. On the other hand, if the speed of the motor 20 is low, that is, the vehicle speed is low, the driver may still be able to continue to control the vehicle even if the output torque of the motor 20 does not match the target value. If the driver can continue to control the vehicle, it is sometimes better to continue driving the vehicle to a place where repairs can be made, for example, rather than stopping the drive of the motor 20 to make the vehicle undriveable. The present embodiment takes this situation into consideration, and when the speed of the motor 20 is lower than a specified threshold, the driving action of the motor 20 is continued.

[0120] [Implementation Method 4]

[0121] Fig.11 1 is a circuit diagram of a power conversion device 103 according to Embodiment 4. The same reference numerals are given to the same parts as those of the power conversion device 100 according to Embodiment 1, and their descriptions are omitted. In Embodiment 4, the structure of the fault diagnosis unit 45 is different from that of the power conversion device 100 according to Embodiment 1. In addition, the inverter circuit 60 is different from the inverter circuit 60. Figure 2 The circuit structure diagram shown is the same.

[0122] The fault diagnosis unit 45 includes a first half-wave rectifier 451 , a second half-wave rectifier 452 , a full-wave rectifier 457 , a difference acquisition unit 458 , a filter unit 459 , and a determination unit 454 , and performs fault diagnosis of the switching elements in the inverter circuit 60 .

[0123] In the present embodiment, each component of the first half-wave rectifier 451, the second half-wave rectifier 452, the full-wave rectifier 457, the differential acquisition unit 458, the filter unit 459, and the determination unit 454 is respectively arranged inside the control circuit 40, but is not limited to this structure. For example, a part of each component can be arranged inside the control circuit 40, and the remaining components can be composed of hardware independent of the control circuit 40. In addition, the first half-wave rectifier 451, the second half-wave rectifier 452, the full-wave rectifier 457, the differential acquisition unit 458, the filter unit 459, and the determination unit 454 can all be composed of hardware independent of the control circuit 40.

[0124] In addition, each structure in the control circuit 40 may not adopt a hardware structure, but the function of each structure may be realized by a CPU and a program. When each structure in the control circuit 40 is realized by a CPU and a program, the number of hardware is reduced, thereby having the advantage of being able to reduce costs. On the other hand, when each structure is composed of hardware independent of the control circuit 40, there is an advantage that the processing load of the control circuit 40 is reduced, and the diagnostic processing can be performed more quickly.

[0125] The full-wave rectifier 457 obtains the absolute values ​​of the values ​​of the AC current sensor values ​​Ius, Ivs, and Iws. The differential acquisition unit 458 obtains the difference between the positive current value of each phase output from the first half-wave rectifier 451 and the absolute value of the current of each phase output from the full-wave rectifier 457, and outputs the difference to the filter unit 459. The differential acquisition unit 458 obtains the difference between the negative current value of each phase output from the second half-wave rectifier 452 and the absolute value of the current of each phase output from the full-wave rectifier 457, and outputs the difference to the filter unit 459.

[0126] The filter unit 459 filters each current difference output from the difference acquisition unit 458 .

[0127] The determination unit 454 determines which part of the switching element in the inverter circuit 60 has failed using the current difference value output from the filter unit 459 , and outputs a failure notification signal corresponding to the failed part to the failure notification device 30 and the PWM signal generation unit 44 .

[0128] Fig.12 This is a flowchart showing the processing operation of the fault diagnosis unit 45 according to the fourth embodiment. Fig.12 The flowchart shown is repeatedly executed at regular intervals.

[0129] In step S801 , the fault diagnosis unit 45 acquires the AC current sensor values ​​Ius, Ivs, and Iws from the AC current sensor 90 .

[0130] In step S802, the first half-wave rectifier 451 extracts only the positive current values ​​of the U phase, V phase and W phase from the AC current sensor values ​​Ius, Ivs and Iws, and outputs them to the differential acquisition unit 458. In addition, the second half-wave rectifier 452 extracts only the negative current values ​​of the U phase, V phase and W phase from the AC current sensor values ​​Ius, Ivs and Iws, and outputs them to the differential acquisition unit 458. In addition, the full-wave rectifier 457 obtains the absolute value of the current of the U phase, V phase and W phase from the AC current sensor values ​​Ius, Ivs and Iws, and outputs them to the differential acquisition unit 458.

[0131] In step S803, the difference acquisition unit 458 calculates the difference between the absolute value of the current of each phase and the positive current value (referred to as the positive side current difference) according to the following equations (1) to (3), and outputs the value to the filter unit 459. The difference acquisition unit 458 calculates the difference between the absolute value of the current of each phase and the negative current value (referred to as the negative side current difference) according to the following equations (4) to (6), and outputs the value to the filter unit 459.

[0132] The positive side current difference of phase U = the absolute value of the current of phase U - the positive current value of phase U...(1)

[0133] Positive side current difference of phase V = absolute value of current of phase V - positive current value of phase V...(2)

[0134] Positive side current difference of phase W = absolute value of current of phase W - positive current value of phase W...(3)

[0135] Negative side current difference of phase U = absolute value of current of phase U + negative current value of phase U...(4)

[0136] The negative side current difference of phase V = the absolute value of the current of phase V + the negative current value of phase V...(5)

[0137] Negative current difference of phase W = absolute value of current of phase W + negative current value of phase W...(6)

[0138] In step S804 , the filter unit 459 filters the positive side current difference values ​​of the U phase, V phase and W phase and the negative side current difference values ​​of the U phase, V phase and W phase output from the difference acquisition unit 458 , and outputs them to the determination unit 454 .

[0139] In the next step S805, the determination unit 454 determines whether the filtered U-phase positive side current differential value is within threshold 1 and within threshold 2. If the conditions are met, in step S806, it is determined that the U-phase lower arm switching element Tul has an open circuit fault.

[0140] Next, in step S807 , the determination unit 454 determines whether the filtered negative side current difference value of the U phase is within threshold 1 and within threshold 2 . If the conditions are met, in step S808 , it is determined that an open circuit fault occurs in the upper arm switching element Tuu of the U phase.

[0141] Next, in step S809, the determination unit 454 determines whether the filtered positive side current differential value of the V phase is within threshold 1 and within threshold 2. If the conditions are met, in step S810, it is determined that an open circuit fault occurs in the lower arm switching element Tv1 of the V phase.

[0142] Next, in step S811 , the determination unit 454 determines whether the filtered negative side current difference value of the V phase is within threshold 1 and within threshold 2 . If the conditions are met, in step S812 , it is determined that an open circuit fault occurs in the upper arm switching element Tvu of the V phase.

[0143] Next, in step S813, the determination unit 454 determines whether the filtered W-phase positive side current differential value is within threshold 1 and within threshold 2. If the conditions are met, in step S814, it is determined that an open-circuit fault occurs in the lower arm switching element Twl of the W-phase.

[0144] Next, in step S815, the determination unit 454 determines whether the filtered negative side current difference value of the W phase is within threshold 1 and within threshold 2. If the conditions are met, in step S816, it is determined that an open circuit fault occurs in the upper arm switching element Twu of the W phase.

[0145] When any of the determination conditions in steps S805 , S807 , S809 , S811 , S813 and S815 described above is not satisfied, the process proceeds to step S817 , and the determination unit 456 determines that an open-circuit failure has not occurred in each switching element.

[0146] In step S720 , the determination unit 456 outputs a fault notification signal corresponding to the fault location determined in each of the above steps S806 , S808 , S810 , S812 , S814 , and S816 to the fault notification device 30 and the PWM signal generation unit 44 .

[0147] Thus, when the fault diagnosis unit 45 detects an open circuit fault of the switching element, the PWM signal generation unit 44 executes Figure 4 The processing of the flow shown generates a PWM signal so as to set the state of the switching element to any one of the freewheeling state, the upper arm active short-circuit state, and the lower arm active short-circuit state according to the fault location.

[0148] Fig.13 2 is an example showing a current waveform when an open-circuit failure occurs in the U-phase upper arm switching element Tuu. Fig.13An example is shown in which an open-circuit failure occurs in the U-phase upper arm switching element Tuu at time t1.

[0149] Fig.13 (A) shows the output of the AC current sensor value Ius obtained by measuring the AC current Iu flowing through the U phase, the AC current sensor value Ivs obtained by measuring the AC current Iv flowing through the V phase, and the AC current sensor value Iws obtained by measuring the AC current Iw flowing through the W phase. Fig.13 (B) shows the output of the first half-wave rectifier 451 of the AC current sensor values ​​Ius, Ivs, and Iws. Fig.13 (C) shows the output of the second half-wave rectifier 452 of the AC current sensor values ​​Ius, Ivs, and Iws. Fig.13 (D) shows the output of the full-wave rectifier 457. Fig.13 (E) represents the positive side current difference of each phase. Fig.13 (F) represents the negative side current difference of each phase.

[0150] Fig.13 (G) represents the positive side current difference of each phase after filtering. Fig.13 (H) represents the negative side current difference of each phase after filtering.

[0151] like Fig.13 As shown in (A), at time t1, when the U-phase upper arm switching element Tuu has an open circuit failure, the U-phase AC current does not flow in the positive direction (the direction from the inverter circuit 60 to the motor 20), but flows in the negative direction (the direction from the motor 20 to the inverter circuit 60). On the other hand, although the AC currents of the V-phase and W-phases after the U-phase upper arm switching element has an open circuit failure have distorted waveforms, currents flow in both the positive and negative directions.

[0152] Therefore, if Fig.13 As shown in (B), after the fault occurs, the positive current of the U-phase AC current output from the first half-wave rectifier 451 is always approximately 0 [A]. In addition, the positive current of the V-phase and W-phase and the negative current of the U-phase, V-phase, and W-phase have periods of approximately 0 [A] and periods of approximately not 0 [A].

[0153] In addition, if Fig.13 As shown in (C), even after the fault occurs, the negative current of the U-phase AC current output from the second half-wave rectifier 452 still has a period of time that is not approximately 0 [A]. The negative current of the V-phase and W-phase also has a period of time that is approximately 0 [A] and a period of time that is not approximately 0 [A]. The output of the full-wave rectifier 457 is as follows: Fig.13 (D) as shown.

[0154] After the fault, the positive current of the U-phase AC current is approximately 0 [A], so the absolute value of the U-phase current is consistent with the absolute value of the negative current of the U-phase. Fig.13 As shown in (F), the negative side current difference of the U phase after the fault is also approximately 0 [A].

[0155] On the other hand, the positive side current differential of the U phase, V phase, and W phase and the negative side current differential of the V phase and W phase also have periods of approximately 0 [A] and periods of approximately non-0 [A] after the fault. After an open circuit fault occurs, the value obtained after filtering the negative side current differential of the U phase is approximately 0 [A], as shown in Fig.13 As shown in (H), it is within threshold 1 and within threshold 2.

[0156] like Fig.13 As shown in (G), the value obtained by filtering the current difference other than the negative side current difference of the U phase is not within the range of threshold 1 and threshold 2, so as shown in FIG. Fig.12 As described in the flow chart, it can be determined that an open-circuit fault occurs in the upper arm switching element Tuu of the U phase.

[0157] According to the above-described embodiment, the following effects can be obtained.

[0158] (1) The power conversion device 100, 101, 102, 103 of the present invention includes: a three-phase inverter circuit 60, which is composed of an upper arm circuit and a lower arm circuit corresponding to each phase of the three-phase motor 20, and converts a direct current into a three-phase alternating current; an alternating current sensor 90, which detects the output current of each phase of the inverter circuit 60; and a fault diagnosis unit 45, which diagnoses an open circuit fault of a switching element constituting the inverter circuit 60 based on the output current of each phase, and the fault diagnosis unit 45 has a first half-wave rectifier 451 that outputs a positive current in the output current of each phase, and a second half-wave rectifier 452 that outputs a negative current in the output current of each phase, and the fault diagnosis unit 45 determines the switching element that has an open circuit fault based on the outputs of the first half-wave rectifier 451 and the second half-wave rectifier 452. In this way, it is possible to determine which switching element of the switching elements constituting the upper arm circuit and the lower arm circuit has a fault.

[0159] (2) In the control method of the power conversion device 100, 101, 102, 103 of the present invention, the power conversion device 100, 101, 102, 103 corresponds to each phase of the three-phase motor 20 and is composed of an upper arm circuit and a lower arm circuit to form an inverter circuit 60, converts a DC current into a multi-phase AC current, detects the output current of each phase of the inverter circuit 60, and diagnoses the open circuit fault of the switching element constituting the inverter circuit 60 based on the output current of each phase, that is, performs a fault diagnosis process, and the fault diagnosis process includes: outputting the first half-wave rectification ( Figure 3 Step S302), outputting the second half-wave rectification of the negative current in the output current of each phase ( Figure 3 In step S302), the fault diagnosis process determines the switch element (s) having an open circuit fault in the switch element based on the outputs of the first half-wave rectification and the second half-wave rectification. Figure 3 Thus, it is possible to determine which switching element of the switching elements constituting the upper arm circuit and the lower arm circuit has failed.

[0160] The present invention is not limited to the above-described embodiments, and other embodiments that can be considered within the technical concept of the present invention are also included in the scope of the present invention as long as the features of the present invention are not impaired. In addition, a configuration combining the above-described embodiments is also possible.

[0161] Description of symbols

[0162] 10…DC power supply, 20…motor, 30…fault notification device, 40…control circuit, 41…motor speed calculation unit, 42…target current calculation unit, 43…duty ratio calculation unit, 44…PWM signal generation unit, 45…fault diagnosis unit, 50…drive circuit, 60…inverter circuit, 70…voltage sensor, 90…AC current sensor, 451…first half-wave rectification unit, 452…second half-wave rectification unit, 453…filter unit, 454…determination unit, 100, 101, 102, 103…power conversion device.

Claims

1. A power conversion device, characterized in that: include: A three-phase inverter circuit, which is composed of an upper arm circuit and a lower arm circuit corresponding to each phase of the three-phase motor and converts a direct current into a three-phase alternating current; a current detection unit, the current detection unit being used to detect an output current of each phase of the inverter circuit; as well as a fault diagnosis unit that diagnoses an open-circuit fault of a switching element constituting the inverter circuit based on the output current of each phase, The fault diagnosis unit comprises: a first half-wave rectifier, which outputs a positive current among the output currents of the respective phases; a second half-wave rectifier, which outputs a negative current among the output currents of the respective phases; and a full-wave rectifier, which outputs an absolute value of the output currents of the respective phases. The fault diagnosis unit diagnoses that the switching element of the lower arm circuit of the phase has an open circuit fault when the absolute value of the output of the first half-wave rectifier unit and the difference between the output of the full-wave rectifier unit in the output current of each phase is within a prescribed threshold value, and diagnoses that the switching element of the upper arm circuit of the phase has an open circuit fault when the absolute value of the output of the second half-wave rectifier unit and the difference between the output of the full-wave rectifier unit is within a prescribed threshold value.

2. The power conversion device according to claim 1, characterized in that: comprising a control circuit that outputs a PWM signal to the upper arm circuit and the lower arm circuit, When the fault diagnosis unit determines that an open circuit fault occurs in the upper arm circuit, the control circuit outputs a fault processing PWM signal, which turns off all switching elements of the upper arm circuit and the lower arm circuit constituting the inverter circuit, or turns on all switching elements of the lower arm circuit constituting the inverter circuit.

3. The power conversion device according to claim 1, characterized in that: comprising a control circuit that outputs a PWM signal to the upper arm circuit and the lower arm circuit, When the fault diagnosis unit determines that an open circuit fault occurs in the lower arm circuit, the control circuit outputs a fault processing PWM signal, which turns off all switching elements of the upper arm circuit and the lower arm circuit constituting the inverter circuit, or turns on all switching elements of the upper arm circuit constituting the inverter circuit.

4. The power conversion device according to claim 2 or 3, characterized in that: When the speed of the motor is equal to or higher than a predetermined threshold value and when the fault diagnosis unit determines that an open-circuit fault occurs in the upper arm circuit or the lower arm circuit, the control circuit outputs the fault processing PWM signal.

5. A control method for a power conversion device, The inverter circuit is composed of an upper arm circuit and a lower arm circuit corresponding to each phase of the three-phase motor, and converts the DC current into a multi-phase AC current. detecting the output current of each phase of the inverter circuit, diagnosing an open circuit fault of a switching element constituting the inverter circuit based on the output current of each phase, that is, performing a fault diagnosis process, The control method of the power conversion device is characterized in that: The fault diagnosis process performs first half-wave rectification for outputting a positive current in the output current of each phase, second half-wave rectification for outputting a negative current in the output current of each phase, and full-wave rectification for outputting an absolute value of the output current of each phase. The fault diagnosis processing diagnoses that the switching element of the lower arm circuit of the phase has an open circuit fault when the absolute value of the output of the first half-wave rectifier and the difference of the output of the full-wave rectifier in the output current of each phase is within a prescribed threshold value, and diagnoses that the switching element of the upper arm circuit of the phase has an open circuit fault when the absolute value of the output of the second half-wave rectifier and the difference of the output of the full-wave rectifier are within a prescribed threshold value.

6. The control method of the power conversion device according to claim 5, characterized in that: outputting a PWM signal to the upper arm circuit and the lower arm circuit, When it is determined that an open-circuit fault occurs in the upper arm circuit, a fault processing PWM signal is outputted to turn off all switching elements of the upper arm circuit and the lower arm circuit constituting the inverter circuit, or to turn on all switching elements of the lower arm circuit constituting the inverter circuit.

7. The control method of the power conversion device according to claim 5, characterized in that: outputting a PWM signal to the upper arm circuit and the lower arm circuit, When it is determined that an open-circuit fault occurs in the lower arm circuit, a fault processing PWM signal is outputted, which turns off all switching elements of the upper arm circuit and the lower arm circuit constituting the inverter circuit, or turns on all switching elements of the upper arm circuit constituting the inverter circuit.

8. The control method of the power conversion device according to claim 6 or 7, characterized in that: When the speed of the motor is equal to or higher than a predetermined threshold value and when it is determined that an open-circuit failure occurs in the upper arm circuit or the lower arm circuit, the failure processing PWM signal is output.

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