Power conversion device and drive device

Abstract

To continue motor driving while suppressing torque fluctuation even after failure of a switching element.SOLUTION: In a power conversion circuit 30, a circuit breaker 70 is installed on an output line of each phase, to conduct or break alternating current. A power-semiconductor failure-location determination unit 18 determines a failure location of a switching element. A circuit breaker controller 17 sets a phase corresponding to the switching element determined to be the failure location by the power-semiconductor failure-location determination unit 18 as a failure phase, to control the circuit breaker 70 of the failure phase so as to conduct alternating current of the failure phase in a predetermined specified electric angle within one cycle of the electric angle, and break alternating current of the failure phase in the other electric angle except the specified electric angle. A failure-time current controller 15 controls driving of the other switching element different from the switching element determined to be the failure location.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power converter and a drive device. [Background technology]

[0002] When a switching element that constitutes an inverter experiences a short-circuit fault, the current in the failed phase cannot be controlled, which can result in excessive motor output torque or burnout of the motor windings. For this reason, a technique is known in which the current in the failed phase is interrupted using a circuit breaker or the like in the event of a short-circuit fault.

[0003] Patent Document 1 describes an invention for an electric power steering device that, when a switching element or motor fails, turns off the circuit breaker of the failed phase and drives the two normal phase switching elements to continue driving the motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-6963 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electric power steering device described in Patent Document 1, the output torque drops to 0 [Nm] at two electrical angles during one electrical angle cycle, resulting in a drop in average output torque compared to normal operation. In order to increase the average output torque, it is necessary to increase the normal two-phase torque, but doing so poses the problem of increased torque fluctuations. [Means for solving the problem]

[0006] The power conversion device according to the present invention includes a power conversion circuit in which upper and lower arm circuits, each having switching elements connected in series, are connected in parallel for at least three phases, and which outputs AC current generated by the switching elements of each phase to a motor via an output line; a circuit breaker provided on the output line of each phase and conducting or blocking the AC current; a first fault location determination unit that determines a fault location of the switching elements; a circuit breaker control unit that determines, as a fault phase, a phase corresponding to a switching element determined to be the fault location by the first fault location determination unit, and controls the circuit breaker of the fault phase so that the AC current of the fault phase is conducted at a predetermined specific electrical angle within one cycle of the electrical angle and is blocked at other electrical angles excluding the specific electrical angle; and a fault current control unit that controls driving of other switching elements different from the switching element determined to be the fault location. A drive device according to the present invention includes a power conversion device that outputs three-phase AC current, and a motor that is driven by the three-phase AC current. The power conversion device includes a power conversion circuit in which upper and lower arm circuits, each having switching elements connected in series, are connected in parallel for three phases, and the AC current generated by the switching elements of each phase is output to the motor via an output line. The power conversion device also includes a circuit breaker that is provided on the output line of each phase and conducts or cuts off the AC current. A first fault location determination unit that determines a fault location of the switching elements. A circuit breaker control unit that determines, as a fault phase, a phase corresponding to a switching element determined by the first fault location determination unit to be the fault location, and controls the circuit breaker of the faulty phase so that the AC current of the faulty phase is conducted at a predetermined specific electrical angle within one electrical angle cycle and the AC current of the faulty phase is cut off at other electrical angles excluding the specific electrical angle. A fault current control unit that controls drive of other switching elements different from the switching element determined to be the fault location. [Effects of the Invention]

[0007] Even after a switching element failure, the motor can continue to be driven while suppressing torque fluctuations. [Brief explanation of the drawings]

[0008] [Figure 1] Example of a vehicle equipped with a drivetrain [Figure 2] Configuration example of power conversion device and drive device according to first embodiment of the present invention [Figure 3] Power conversion circuit and motor configuration example [Figure 4] Example of circuit breaker configuration using semiconductor switches [Figure 5] Example of internal state determination by the state determination unit in the first embodiment of the present invention [Figure 6] Example of a specific electrical angle at which the circuit breaker of the faulted phase is in a conducting state [Figure 7] 1 is a control flowchart according to a first embodiment of the present invention; [Figure 8] Example of output torque when one phase fails in the first embodiment of the present invention [Figure 9] FIG. 10 is an explanatory diagram of the switching timing of a circuit breaker in a second embodiment of the present invention. [Figure 10] Configuration example of a power conversion device and a drive device according to a third embodiment of the present invention [Figure 11] FIG. 10 is an explanatory diagram of the switching timing of a circuit breaker in a third embodiment of the present invention. [Figure 12] 10 is a control flowchart according to a third embodiment of the present invention; [Figure 13] FIG. 10 is an explanatory diagram of the switching timing of a circuit breaker in the fourth embodiment of the present invention. [Figure 14] 10 is a control flowchart according to a fourth embodiment of the present invention; [Figure 15] Configuration example of a power conversion device and a drive device according to a fifth embodiment of the present invention [Figure 16] Example of internal state determination by the state determination unit in the fifth embodiment of the present invention [Figure 17] 10 is a flowchart illustrating a circuit breaker diagnosis according to a fifth embodiment of the present invention. [Figure 18] 10 is a control flowchart according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 is a diagram showing an example of a vehicle equipped with a drive unit of the present invention. The vehicle 1 shown in FIG. 1 is equipped with drive wheels 2 and non-drive wheels 3, and is also equipped with a drive unit 200. This drive unit 200 is connected to an axle 4 to which drive wheels 2 are attached at both ends, and has a power conversion device 100 and a motor 190 (see FIG. 2) inside. Then, in response to the driver's operation of the accelerator pedal, the power conversion device 100 and the motor 190 are controlled to generate drive force, which is transmitted to the axle 4. This drives the drive wheels 2 and causes the vehicle 1 to travel. Alternatively, a reducer may be provided in the drive unit, and the drive force of the motor 190 may be transmitted to the axle 4 via the reducer.

[0010] 1, the front wheels of the vehicle 1 are drive wheels 2 and the rear wheels are non-drive wheels 3, and the drive unit 200 is connected to the axle 4 on the front wheel side, but the rear wheels may be drive wheels and the drive unit 200 may be connected to the axle on the rear wheel side. Also, all the front and rear wheels may be drive wheels and the drive unit 200 may be connected to each axle, or independent drive units 200 may be installed and connected to the left and right drive wheels rather than to axles.

[0011] Next, each embodiment of the power conversion device 100 and the driving device 200 will be described below.

[0012] (First embodiment) 2 is a diagram showing an example of the configuration of a power conversion device 100 and a drive device 200 according to a first embodiment of the present invention. This example shows an example of a power conversion device and a drive device that improves the average output torque while maintaining torque fluctuations when a power semiconductor fails, making it easier for the vehicle to start.

[0013] The driving device 200 includes the power conversion device 100 and a motor 190. The motor 190 is a three-phase AC motor having three internal windings, and may be, for example, a synchronous motor using permanent magnets or an induction motor without permanent magnets. The motor 190 is also equipped with an angle sensor (not shown) for measuring the electrical angle of the motor, and this angle sensor outputs the measured electrical angle to the power conversion device 100 as an angle sensor value θ.

[0014] Around the drive device 200, there are an electronic control device 230, a DC power supply 210, and a fault notification device 220. The electronic control device 230 transmits information such as a target torque T* to the drive device 200. The DC power supply 210 is a power source for driving the motor 190, and corresponds to, for example, a battery. The fault notification device 220 receives a fault notification signal from the drive device 200 and notifies the passenger of the occurrence of a fault. Methods for notifying the passenger of a fault include, for example, turning on a lamp, emitting a warning sound, or notifying by voice.

[0015] The power conversion device 100 converts DC power obtained from a DC power supply 210 into AC power to drive the motor 190. The power conversion device 100 also has a function of converting the motive power of the motor 190 into DC power to charge the DC power supply 210. The power conversion device 100 internally includes a control circuit 10, a driver circuit 20, a power conversion circuit 30, a voltage sensor 40, an AC current sensor 50, a circuit breaker drive circuit 60, and a circuit breaker 70. The power conversion circuit 30 receives a drive signal 20a from the driver circuit 20 to drive internal power semiconductors and control the current flowing to the motor 190. The circuit breaker drive circuit 60 drives the circuit breaker 70 to cut off the connection between the power conversion circuit 30 and the motor 190. The internal configuration of the power conversion circuit 30 will be described first using FIG. 3, and the internal configuration of the control circuit 10 and other components will be described later.

[0016] 3 is a diagram showing an example of the configuration of the power conversion circuit 30 and the motor 190. The power conversion circuit 30 has a smoothing capacitor 31 and six power semiconductor elements 32 therein.

[0017] The smoothing capacitor 31 is a capacitor that smoothes the current generated by turning on / off the power semiconductor element 32 and suppresses ripples in the DC current supplied from the DC power supply 210 to the power conversion circuit 30. For example, an electrolytic capacitor or a film capacitor is used as this smoothing capacitor 31.

[0018] The power semiconductor element 32 is a switching element that switches on / off in response to a drive signal 20a input from the driver circuit 20, and converts DC power and AC power. Examples of the power semiconductor element 32 include a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). The power semiconductor element 32 also has a sense terminal 33. A certain percentage, for example, 1 / 100 or 1 / 1000 of the current flowing between the collector and emitter (between the drain and source) of the power semiconductor element 32 is output from the sense terminal 33 as a sense current. The sense current is output from the power conversion circuit 30 to the driver circuit 20. In the following embodiment, an IGBT is used as the power semiconductor element 32.

[0019] The six power semiconductor elements 32 are divided into two upper and two lower groups for each phase, and the outputs are connected to the windings of each phase of the motor 190. Hereinafter, the upper three power semiconductor elements 32 will be collectively referred to as the upper arm, and the lower three power semiconductor elements 32 will be collectively referred to as the lower arm. That is, the power conversion circuit 30 is provided with an upper arm circuit in which two upper and lower arm power semiconductor elements 32 are connected in series for each phase (U phase, V phase, W phase) of the motor 190. The power conversion circuit 30 has wiring connected to the positive and negative sides of the DC power supply 210, respectively, and is configured such that the upper and lower arm circuits for each phase are connected in parallel between these wirings.

[0020] In this embodiment, the motor neutral point 191 is in a floating state, but may be connected to the ground (not shown). Methods for connecting the motor neutral point 191 to the ground include a direct grounding method, a resistance grounding method, a compensation reactor grounding method, and an arc-suppression reactor grounding method.

[0021] The configuration of this embodiment will be described with reference back to Fig. 2. The voltage sensor 40 is a sensor that measures the output voltage of the DC power supply 210, and outputs the measured voltage value to the control circuit 10 as a voltage sensor value 40a.

[0022] The AC current sensor 50 measures the AC current flowing through each phase (U phase, V phase, W phase) of the motor 190 and outputs the measured AC current for each phase as an AC current sensor value 50a to the control circuit 10. In this embodiment, three AC current sensors 50 are provided, one for each phase, but AC current sensors may be provided for only two phases. In this case, since the relationship U phase current + V phase current + W phase current = 0 holds, the control circuit 10 calculates the AC current sensor value for the remaining phase. In this embodiment, the current flowing from the power conversion circuit 30 to the motor 190 is treated as a positive current, and the current flowing from the motor 190 to the power conversion circuit 30 is treated as a negative current.

[0023] The driver circuit 20 receives a PWM (Pulse Width Modulation) signal 16a output by a PWM signal generating unit 16 (described later) and outputs a drive signal 20a for switching on / off the power semiconductor element 32. The driver circuit 20 also uses a sense current 33a output from the power semiconductor element 32 to detect the occurrence of a short-circuit failure in the power semiconductor element 32 and outputs a short-circuit failure detection signal 20b to the control circuit 10.

[0024] Normally, the PWM signal 16a is generated so that the upper and lower power semiconductor elements 32 are not turned on at the same time, but if the power semiconductor elements 32 experience a short circuit, the upper and lower power semiconductor elements 32 may be turned on at the same time. If the upper and lower power semiconductor elements 32 are turned on at the same time, a large through current will flow through the power semiconductor elements 32. The driver circuit 20 monitors whether the sense current 33a of each power semiconductor element 32 is equal to or greater than a certain threshold, and if the sense current 33a is equal to or greater than the certain value, it determines that the power semiconductor element 32 in the corresponding phase has a short circuit. The driver circuit 20 then outputs a short circuit failure detection signal 20b for each phase.

[0025] In this embodiment, the sense current 33a of the power semiconductor element 32 is used to determine whether or not a short circuit has occurred in the power semiconductor element 32, but other methods may be used to detect whether or not a short circuit has occurred in the power semiconductor element 32. For example, a shunt resistor for measuring current may be disposed on the collector side or emitter side of the power semiconductor element 32, and the value of the current flowing through the shunt resistor may be measured to detect whether or not a short circuit has occurred in the power semiconductor element 32. In addition, because the collector-emitter voltage of the power semiconductor element 32 increases in accordance with the current flowing, another method is to measure the collector-emitter voltage to detect whether or not a short circuit has occurred in the power semiconductor element 32.

[0026] The circuit breaker drive circuit 60 receives a circuit breaker control signal 17a output by a circuit breaker control unit 17, which will be described later, and outputs a circuit breaker drive signal 60a for switching the circuit breaker 70 between the conductive and cut-off states.

[0027] The circuit breaker 70 is provided on the output line of each phase connecting the power conversion circuit 30 and the windings of the motor 190, and is switched between a conductive and cut-off state in response to the circuit breaker drive signal 60a to conduct or cut off the AC current flowing from the power conversion circuit 30 to the windings of the motor 190 via the output line of each phase. When the circuit breaker 70 is in a conductive state, AC current flows between the power conversion circuit 30 and the windings of the motor 190, and when the circuit breaker 70 is in a cut-off state, no current flows. In this embodiment, a circuit breaker 70 is provided for each phase of the motor 190.

[0028] In this embodiment, the circuit breaker 70 is disposed inside the power conversion device 100, but the circuit breaker 70 may be disposed inside the motor 190, or may be disposed independently of the power conversion device 100 and the motor 190. However, if the circuit breaker 70 is disposed inside the motor 190, the motor 190 must be disassembled when replacing the circuit breaker 70. Therefore, if the circuit breaker 70 is disposed inside the power conversion device 100, the work of replacing the circuit breaker 70 becomes easier.

[0029] The circuit breaker 70 can be, for example, a mechanical switch such as a relay, or a semiconductor switch such as an IGBT or MOSFET. A semiconductor switch has the advantage of switching between conductive and cut-off states faster than a mechanical switch. However, a semiconductor switch may allow current to flow through an internal freewheeling diode even when the switch is in the off state. For this reason, when a semiconductor switch is used as the circuit breaker 70, it is necessary to adopt a configuration that reliably cuts off current when the switch is switched off.

[0030] Fig. 4 is a diagram showing an example of the configuration of a circuit breaker 70 using a semiconductor switch. For example, as shown in Fig. 4, by connecting two semiconductor switches 71 in series in opposite directions, it is possible to realize a circuit breaker 70 that can interrupt current flowing in both directions.

[0031] On the other hand, although mechanical switches have a longer switching time than semiconductor switches, they can reliably interrupt current in both directions with a single switch, making them superior in terms of cost to semiconductor switches.

[0032] The configuration of the circuit breaker 70 is not limited to the semiconductor switch or mechanical switch of the circuit configuration shown in Fig. 4. The circuit breaker 70 can be realized with any circuit configuration as long as it can reliably conduct or cut off the AC current that is output from the power conversion circuit 30 and flows through the windings of the motor 190.

[0033] The control circuit 10 communicates with an external electronic control device 230 and receives a target torque T* of the motor 190 from the electronic control device 230. When the power conversion device 100 is normal, the control circuit 10 outputs a PWM signal 16a based on the target torque T* to control the current of each phase output from the power conversion device 100 to a predetermined value, and drives the power conversion circuit 30 via the driver circuit 20. Furthermore, when the control circuit 10 determines that a fault has occurred inside the power conversion device 100, it outputs a fault notification signal to an external fault notification device 220.

[0034] The control circuit 10 includes a CPU, RAM, ROM, and communication circuit (none of which are shown). The ROM may be an electrically erasable programmable ROM (EEPROM) or a flash ROM. The control circuit 10 may also include a logic circuit configured using hardware such as an FPGA (Field Programmable Gate Array).

[0035] The control circuit 10 also has functional blocks including a motor speed calculation unit 11, a target current calculation unit 12, a normal current control unit 13, a fault current control unit 15, a PWM signal generation unit 16, a circuit breaker control unit 17, a power semiconductor fault location determination unit 18, and a state determination unit 19. These functional blocks may be realized, for example, by a CPU in the control circuit 10 executing a predetermined program, or some or all of them may be realized by hardware such as an FPGA.

[0036] The motor speed calculation unit 11 calculates the motor rotation speed (rotational speed) from the change in the angle sensor value θ of the motor 190, and outputs the calculated motor speed value 11a to the target current calculation unit 12.

[0037] Using the target torque T*, the voltage sensor value 40a, and the motor speed value 11a output by the motor speed calculation unit 11, the target current calculation unit 12 outputs a target current value 12a to the normal current control unit 13. The target current value 12a is calculated as a current value that should be passed through the motor 190 so that the motor 190 outputs a torque equal to the target torque T*. The target current value 12a is expressed, for example, in the form of a d-axis target current value and a q-axis target current value.

[0038] The normal-state current control unit 13 calculates a duty value 13a for each phase using the target current value 12a output by the target current calculation unit 12, the motor angle sensor value θ, the AC current sensor value 50a for each phase, and the voltage sensor value 40a, and outputs the duty value 13a to the PWM signal generation unit 16. The method of calculating the duty value 13a by the normal-state current control unit 13 will be described in detail later.

[0039] The fault-time current control unit 15 calculates a duty value 15a for each phase and a circuit breaker switching signal 15b for controlling the state of the circuit breaker 70 in the event of a fault, using the target current value 12a output by the target current calculation unit 12, the motor angle sensor value θ, the AC current sensor value 50a and the voltage sensor value 40a for each phase, and the power semiconductor fault information 18a output by the power semiconductor fault location determination unit 18. The fault-time current control unit 15 then outputs the calculated duty value 15a and circuit breaker switching signal 15b to the PWM signal generation unit 16 and the circuit breaker control unit 17, respectively. The method by which the fault-time current control unit 15 calculates the duty value 15a and the circuit breaker switching signal 15b will be described in detail later.

[0040] The PWM signal generating unit 16 switches the signal to be output to the driver circuit 20 depending on the internal state 19a output from the state determining unit 19. The PWM signal generating unit 16 has an internal timer, and when the internal state 19a is a "normal state," the PWM signal generating unit 16 generates a PWM signal 16a using the timer value and a duty value 13a for each phase output from the normal-state current control unit 13, and outputs the PWM signal 16a to the driver circuit 20. When the internal state 19a is a "single-phase failure state" (described later), the PWM signal generating unit 16 generates a PWM signal 16a using the timer value and a duty value 15a for each phase output from the failure-state current control unit 15, and outputs the PWM signal 16a to the driver circuit 20. When the internal state 19a is a "two or more-phase failure state" (described later), the PWM signal generating unit 16 outputs a PWM signal 16a to the driver circuit 20 that does not drive the motor 190. The state in which the motor 190 is not driven may be, for example, a state in which all six power semiconductor elements 32 in the power conversion circuit 30 are turned off (called a freewheel state in this embodiment).

[0041] The circuit breaker control unit 17 generates and outputs a circuit breaker control signal 17a for switching the circuit breaker 70 of each phase between conduction and cut-off, using the internal state 19a output from the state determination unit 19, the power semiconductor failure information 18a output from the power semiconductor failure location determination unit 18, and the circuit breaker switching signal 15b output from the fault-time current control unit 15. A method for calculating the circuit breaker control signal 17a by the circuit breaker control unit 17 will be described in detail later.

[0042] The power semiconductor failure location determination unit 18 determines the failure location and failure mode of the power semiconductor element 32 based on the PWM signal 16a, the short-circuit failure detection signal 20b output by the driver circuit 20, and the AC current sensor values ​​50a of each phase. The failure modes of the power semiconductor element 32 are broadly divided into two types: short-circuit failure and open-circuit failure. In the case of a short-circuit failure, the power semiconductor element 32 is always in the ON state, and in the case of an open-circuit failure, the power semiconductor element 32 is always in the OFF state. The power semiconductor failure location determination unit 18 determines that a short-circuit failure has occurred if the short-circuit failure detection signal 20b is output from the driver circuit 20, and determines that an open-circuit failure has occurred if the AC current sensor values ​​50a of each phase do not change within a predetermined value.

[0043] Note that, because the short-circuit failure detection signal 20b output by the driver circuit 20 when a short-circuit failure occurs is separated for each phase, the power semiconductor failure location determination unit 18 can identify in which phase the failure has occurred from the short-circuit failure detection signal 20b, but cannot identify which of the upper and lower arms has the failure. Therefore, the power semiconductor failure location determination unit 18, for example, compares the timing at which the short-circuit failure detection signal 20b is output with the state of the PWM signal 16a, and determines that the short-circuit failure has occurred in the arm for which the short-circuit failure detection signal 20b is in the OFF state, of the PWM signals 16a of the upper and lower arms of the phase in which the failure has occurred. This is because the upper and lower power semiconductor elements 32 are not normally turned on at the same time, and therefore, when a short-circuit failure in a power semiconductor element 32 is detected, it is considered that a short-circuit failure has occurred in a power semiconductor element 32 that should have been turned off, causing the upper and lower power semiconductor elements 32 to be turned on simultaneously. When the power semiconductor failure location determination unit 18 determines that a short circuit failure has occurred in the power semiconductor element 32, it outputs power semiconductor failure information 18a indicating the failure location and failure mode to the fault current control unit 15, the circuit breaker control unit 17, the state determination unit 19, and the external failure notification device 220.

[0044] Furthermore, when an open circuit fault occurs, the power semiconductor fault location determination unit 18 can determine in which phase the fault has occurred from the AC current sensor values ​​50a for each phase output by the AC current sensor 50, but cannot determine which of the upper and lower arms has the fault. Therefore, the power semiconductor fault location determination unit 18 determines in which of the upper and lower arms the open circuit fault has occurred, for example, by dividing the AC current sensor values ​​50a for each phase into positive and negative current values, smoothing each value, and comparing them with a predetermined threshold. When the power semiconductor fault location determination unit 18 determines that an open circuit fault has occurred in the power semiconductor element 32, it outputs power semiconductor fault information 18a indicating the fault location and failure mode to the fault-time current control unit 15, the circuit breaker control unit 17, the state determination unit 19, and the external fault notification device 220.

[0045] The state determination unit 19 determines whether the state of the power conversion device 100 is a "normal state," a "single-phase fault state," or a "two or more phase fault state," based on the power semiconductor fault information 18a output by the power semiconductor fault location determination unit 18. Then, the state determination unit 19 outputs an internal state 19a representing the current state of the power conversion device 100 to the PWM signal generation unit 16 and the circuit breaker control unit 17.

[0046] FIG. 5 is a diagram illustrating an example of an internal state determination by the state determination unit 19 in the first embodiment of the present invention. The state determination unit 19 determines a next state from the current state and the occurrence at regular intervals and updates the next state to the current state. The initial state is a "normal state." First, when the current state is a "normal state," if the state determination unit 19 receives power semiconductor failure information 18a from the power semiconductor failure location determination unit 18 indicating that a power semiconductor element 32 of one of the phases has failed, the state determination unit 19 changes the next state to a "single-phase failure state." Otherwise, the next state remains the "normal state." Furthermore, when the current state is a "single-phase failure state," if the state determination unit 19 receives power semiconductor failure information 18a from the power semiconductor failure location determination unit 18 indicating that a power semiconductor element 32 of a phase different from the previously failed phase has failed, the state determination unit 19 changes the next state to a "two or more phase failure state." For example, when the current state is a "single-phase failure state" due to a failure of the U-phase power semiconductor element 32, if new power semiconductor failure information 18a is notified about the V-phase or W-phase power semiconductor element 32, the next state is changed to a "two or more phase failure state." In other cases, the next state remains the "single-phase failure state." If the current state is a "two or more phase failure state," the state determination unit 19 keeps the next state as the "two or more phase failure state."

[0047] Next, we will describe the current control during normal operation and the current control during one-phase failure, which are respectively performed by the normal operation current control unit 13 and the fault operation current control unit 15. Note that although this embodiment shows an example in which absolute conversion coefficients are used during axis conversion, relative conversion coefficients may also be used.

[0048] In normal current control, first, target current calculation unit 12 shown in Fig. 2 determines a d-axis target current value and a q-axis target current value corresponding to target torque T*. Next, normal current control unit 13 calculates duty value 13a for each phase so as to achieve the d-axis target current value and q-axis target current value determined by target current calculation unit 12. Then, PWM signal generation unit 16 generates PWM signal 16a for each phase in accordance with duty value 13a for each phase calculated by normal current control unit 13. At this time, circuit breaker control unit 17 controls all three-phase circuit breakers 70 to be in a conductive state.

[0049] The normal-state current control unit 13 converts the three-phase AC current sensor values ​​50a output from the AC current sensor 50 into d-axis and q-axis current values ​​using the formula [1]. In [Formula 1], Iu, Iv, and Iw are the AC current sensor values ​​of the U phase, V phase, and W phase, respectively, and θ is the angle sensor value. Furthermore, Id is the d-axis current value after conversion, and Iq is the q-axis current value after conversion.

[0050]

number

[0051] Next, normal-state current control unit 13 calculates the difference between this d-axis current and the d-axis target current value, and the difference between the q-axis current and the q-axis target current value. Normal-state current control unit 13 then performs feedback control on the d-axis current difference and the q-axis current difference to determine the d-axis target voltage value and the q-axis target voltage value. Normal-state current control unit 13 converts these d-axis target voltage value and q-axis target voltage value into the form of the α-axis target voltage value and the β-axis target voltage value using [Equation 2] so that they become the α-axis and β-axis values. In [Equation 2], Vd is the d-axis target voltage value, Vq is the q-axis target voltage value, θ is the angle sensor value, Vα is the α-axis target voltage value, and Vβ is the β-axis target voltage value.

[0052]

number

[0053] Then, the normal-state current control unit 13 converts the α-axis target voltage value and the β-axis target voltage value into target voltage values ​​for each of the U-phase, V-phase, and W-phase using [Equation 3]. In [Equation 3], Vα is the α-axis target voltage value, Vβ is the β-axis target voltage value, Vu is the U-phase target voltage value, Vv is the V-phase target voltage value, and Vw is the W-phase target voltage value.

[0054]

number

[0055] Finally, the normal-state current control unit 13 calculates the duty value 13a of each phase from the target voltage value of each phase and the voltage sensor value 40a.

[0056] In the current control during a single-phase fault, first, the target current calculation unit 12 determines the d-axis target current value and the q-axis target current value according to the target torque T*, as in the normal state. Next, the fault-time current control unit 15 calculates the duty value 13a of the faulty phase so that one of the power semiconductor elements 32 in the upper or lower arm of the faulty phase is always on and the other is always off. Specifically, in the case of a short-circuit fault, the fault-time current control unit 15 calculates the duty value 13a of the power semiconductor element 32 on the upper or lower opposite arm side to be 0 so that the power semiconductor element 32 in phase with the fault location indicated by the power semiconductor fault information 18a is always off. In the case of an open-circuit fault, the fault-time current control unit 15 calculates the duty value 13a of the power semiconductor element 32 on the upper or lower opposite arm side to be 1 so that the power semiconductor element 32 in phase with the fault location indicated by the power semiconductor fault information 18a is always on.

[0057] In addition, while the motor angle sensor value θ is within a certain range of electrical angles (hereinafter referred to as the "specific electrical angle"), the fault current control unit 15 corrects the target voltages in the conversion portion from the α-axis target voltage value (Vα) and the β-axis target voltage value (Vβ) to the U-phase target voltage value (Vu), the V-phase target voltage value (Vv), and the W-phase target voltage value (Vw). The specific electrical angle corresponds to the range of electrical angles within one electrical angle cycle that brings the circuit breaker 70 of the faulty phase into a conductive state, and differs for each faulty phase as described below.

[0058] For example, when a short-circuit fault occurs in power semiconductor element 32 of the U-phase upper arm and power semiconductor element 32 of the U-phase lower arm is controlled to the OFF state, or when an open-circuit fault occurs in power semiconductor element 32 of the U-phase lower arm and power semiconductor element 32 of the U-phase upper arm is controlled to the ON state, assuming that the voltage of DC power supply 210 is Vdc, the voltage output from the U-phase upper and lower arm circuits is fixed at ½ Vdc. Furthermore, when a short-circuit fault occurs in power semiconductor element 32 of the U-phase lower arm and power semiconductor element 32 of the U-phase upper arm is controlled to the OFF state, or when an open-circuit fault occurs in power semiconductor element 32 of the U-phase upper arm and power semiconductor element 32 of the U-phase lower arm is controlled to the ON state, the voltage output from the U-phase upper and lower arm circuits is fixed at −½ Vdc. Therefore, even if the target voltages of the U-phase, V-phase, and W-phase are converted as usual, power conversion circuit 30 cannot output voltages that match the target voltages. Therefore, in order to be able to output voltages equivalent to the α-axis target voltage value (Vα) and β-axis target voltage value (Vβ) that were the same as before the failure, even after the failure occurs, it is necessary to calculate the target voltages for the remaining two phases, taking into account the deviation in the output voltage of the faulty phase.

[0059] When a short-circuit fault occurs in U-phase power semiconductor element 32, the target voltage values ​​for the V and W phases are calculated using Equation 4. Here, when the voltage of DC power supply 210 is Vdc, if power semiconductor element 32 in the U-phase upper arm has a short-circuit fault and power semiconductor element 32 in the U-phase lower arm is controlled to the off state, or if an open-circuit fault occurs in power semiconductor element 32 in the U-phase lower arm and power semiconductor element 32 in the U-phase upper arm is controlled to the on state, the value of the U-phase target voltage value (Vu) is set to 1 / 2·Vdc. Also, if power semiconductor element 32 in the U-phase lower arm has a short-circuit fault and power semiconductor element 32 in the U-phase upper arm is controlled to the off state, or if an open-circuit fault occurs in power semiconductor element 32 in the U-phase upper arm and power semiconductor element 32 in the U-phase lower arm is controlled to the on state, the value of the U-phase target voltage value (Vu) is set to -1 / 2·Vdc.

[0060]

number

[0061] When a short-circuit fault occurs in the V-phase power semiconductor element 32, the target voltage values ​​for the U and W phases are calculated using Equation 5. Here, when the voltage of DC power supply 210 is Vdc, similarly to the case of a U-phase fault, if a short-circuit fault occurs in the power semiconductor element 32 of the V-phase upper arm and the power semiconductor element 32 of the V-phase lower arm is controlled to the off state, or if an open-circuit fault occurs in the power semiconductor element 32 of the V-phase lower arm and the power semiconductor element 32 of the V-phase upper arm is controlled to the on state, the value of the V-phase target voltage value (Vv) is set to ½·Vdc. Furthermore, if a short-circuit fault occurs in the power semiconductor element 32 of the V-phase lower arm and the power semiconductor element 32 of the V-phase upper arm is controlled to the off state, or if an open-circuit fault occurs in the power semiconductor element 32 of the V-phase upper arm and the power semiconductor element 32 of the V-phase lower arm is controlled to the on state, the value of the V-phase target voltage value (Vv) is set to −½·Vdc.

[0062]

number

[0063] When the W-phase power semiconductor element 32 has a short-circuit fault, the target voltage values ​​for the U and V phases are calculated using Equation 6. When the voltage of DC power supply 210 is Vdc, similarly to when a U-phase fault or a V-phase fault occurs, if the power semiconductor element 32 in the W-phase upper arm has a short-circuit fault and the power semiconductor element 32 in the W-phase lower arm is controlled to the off state, or if an open-circuit fault occurs in the power semiconductor element 32 in the W-phase lower arm and the power semiconductor element 32 in the W-phase upper arm is controlled to the on state, the W-phase target voltage value (Vw) is set to ½·Vdc. Also, if the power semiconductor element 32 in the W-phase lower arm has a short-circuit fault and the power semiconductor element 32 in the W-phase upper arm is controlled to the off state, or if an open-circuit fault occurs in the power semiconductor element 32 in the W-phase upper arm and the power semiconductor element 32 in the W-phase lower arm is controlled to the on state, the W-phase target voltage value (Vw) is set to −½·Vdc.

[0064]

number

[0065] As described above, after setting the corrected target voltage value of each phase at the specific electrical angle, the fault-time current control unit 15 calculates the duty value 15a of each phase from the set target voltage value of each phase and the voltage sensor value 40a, similar to the normal-time current control unit 13.

[0066] Furthermore, the fault current control unit 15 generates a circuit breaker switching signal 15b based on the angle sensor value θ, separately from calculating the duty value 15a, and outputs the signal to the circuit breaker control unit 17. At this time, the fault current control unit 15 generates the circuit breaker switching signal 15b such that the circuit breaker 70 of the faulted phase is in a conductive state only for a specific electrical angle, and the circuit breakers 70 of the two phases other than the faulted phase are always in a conductive state.

[0067] The circuit breaker control unit 17 generates a circuit breaker control signal 17a based on the circuit breaker switching signal 15b output by the fault current control unit 15. At this time, the circuit breaker control signal 17a is changed so that the circuit breaker 70 of the faulted phase is in a conductive state only during a specific electrical angle and in a cut-off state at other electrical angles, and so that the circuit breakers 70 of the two phases other than the faulted phase are always in a conductive state.

[0068] In this embodiment, the fault current control unit 15 generates the circuit breaker switching signal 15b based on the angle sensor value θ, and the circuit breaker control unit 17 changes the circuit breaker control signal 17a based on this circuit breaker switching signal 15b, thereby performing switching control of the circuit breaker 70. However, the circuit breaker control unit 17 may determine whether the current electrical angle is a specific electrical angle based on the angle sensor value θ, and control the conductive / blocked state of the circuit breaker 70 of the faulty phase in accordance with the determination result.

[0069] FIG. 6 is a diagram showing an example of a specific electrical angle at which the circuit breaker 70 of the faulted phase is brought into a conductive state. In current control during a single-phase fault, the fault-time current control unit 15 corrects the target voltage, and the specific electrical angle at which the circuit breaker 70 of the faulted phase is brought into a conductive state is determined, for example, as shown in FIG. 6, depending on the faulted phase. In each fault condition shown in FIG. 6, by carrying out the current control during a single-phase fault as described above within the range of each specific electrical angle, the power conversion circuit 30 can output the same d-axis target voltage value and q-axis target voltage value as those during normal operation. Note that α in FIG. 6 is a variable that changes depending on the values ​​of the d-axis target voltage and the q-axis target voltage.

[0070] In this embodiment, the specific electrical angle for current control in the event of a single-phase failure is set to a range of 120° for each failed phase, as shown in FIG. 6 . However, current control in the event of a single-phase failure may be performed within a narrower range of electrical angles than the specific electrical angle, or conversely, current control in the event of a single-phase failure may be performed within a wider range of electrical angles than the specific electrical angle. However, the narrower the range of electrical angles for current control in the event of a single-phase failure, the less effective the output torque will be. On the other hand, the wider the range of electrical angles for current control in the event of a single-phase failure, the more unstable the control will be. Therefore, it is preferable to determine the range of potential angles for current control in the event of a single-phase failure, taking these factors into consideration.

[0071] Fig. 7 is an example of a control flowchart in the first embodiment of the present invention. In this embodiment, the control circuit 10 shown in Fig. 2 periodically performs the control shown in the flowchart in Fig. 7 at regular intervals.

[0072] First, in the process of step S100, the control circuit 10 determines whether or not the internal state 19a output from the state determination unit 19 is a "normal state." If the internal state 19a is a "normal state," the process proceeds to step S101, and if it is not a "normal state," the process proceeds to step S104.

[0073] In the process of step S101, the control circuit 10 performs current control during normal operation in accordance with the torque command value. More specifically, as described above, the target current calculation unit 12 generates a target current value 12a corresponding to the target torque T*, and the normal-operation current control unit 13 generates a duty value 13a for each phase corresponding to this target current value 12a. The PWM signal generation unit 16 then generates a PWM signal 16a based on the duty value 13a for each phase and outputs the PWM signal 16a to the driver circuit 20. At this time, the circuit breaker control unit 17 outputs a circuit breaker control signal 17a so that the three-phase circuit breakers 70 are always in a conductive state.

[0074] Next, in the processing of step S102, the power semiconductor failure location determination unit 18 determines whether an open circuit failure or a short circuit failure has been detected in any of the power semiconductor elements 32, based on the AC current sensor values ​​50a of each phase output by the AC current sensor 50 and the short circuit failure detection signal 20b output by the driver circuit 20. If an open circuit failure or a short circuit failure is detected, the power semiconductor failure location determination unit 18 determines the failure location as described above using the AC current sensor values ​​50a and the PWM signal 16a, and outputs power semiconductor failure information 18a based on the determination result, after which the process proceeds to step S103.

[0075] In the process of step S103, the state determination unit 19 determines that the current state of the power conversion device 100 is a "single-phase fault state" and updates the internal state 19a. After executing the process of step S103, the control circuit 10 ends the control flowchart in FIG.

[0076] On the other hand, if no failure is detected in any of the power semiconductor elements 32 in step S102, the control circuit 10 does not execute the process of step S103 and ends the control flowchart in Fig. 7. In this case, the power semiconductor failure location determination unit 18 does not output the power semiconductor failure information 18a, and the state determination unit 19 maintains the internal state 19a as the "normal state."

[0077] If it is determined in step S100 that the internal state 19a output from the state determination unit 19 is not a "normal state," the control circuit 10 determines in the process of step S104 whether the internal state 19a is a "single-phase failure state." If the internal state 19a is a "single-phase failure state," the process proceeds to step S105; otherwise, the process proceeds to step S108.

[0078] In the process of step S105, the control circuit 10 performs current control during one-phase failure in accordance with the torque command value. More specifically, as described above, the target current calculation unit 12 generates the target current value 12a corresponding to the target torque T*, and the failure-time current control unit 15 generates the duty value 15a for each phase corresponding to this target current value 12a. Then, the PWM signal generation unit 16 generates a PWM signal 16a based on the duty value 15a for each phase and outputs the PWM signal 16a to the driver circuit 20. This controls the driving of the power semiconductor elements 32 other than the power semiconductor element 32 determined to be the failure location by the power semiconductor failure location determination unit 18.

[0079] Furthermore, the fault current control unit 15 generates a circuit breaker switching signal 15b and outputs it to the circuit breaker control unit 17 so that the circuit breakers 70 other than those of the faulty phase are always in a conductive state and the circuit breaker 70 of the faulty phase is in a conductive state only during a specific electrical angle. The circuit breaker control unit 17 outputs a circuit breaker control signal 17a based on the circuit breaker switching signal 15b output from the fault current control unit 15. As a result, the circuit breaker 70 of the phase corresponding to the power semiconductor element 32 determined to be the faulty part by the power semiconductor fault part determination unit 18 is controlled so that the AC current generated by the power semiconductor element 32 of the faulty phase is conducted during a predetermined conduction period corresponding to a specific electrical angle within one cycle of the electrical angle of the motor 190 and the AC current is interrupted during other periods.

[0080] Next, in the process of step S106, the power semiconductor failure location determination unit 18 determines whether an open circuit failure or a short circuit failure has been detected in any of the power semiconductor elements 32 in a phase other than the phase in which a failure has already been detected. If an open circuit failure or a short circuit failure has been detected, the power semiconductor failure information 18a is updated and output, and the process proceeds to step S107.

[0081] In the process of step S107, the state determination unit 19 determines that the current state of the power conversion device 100 is a "two or more phases fault state" and updates the internal state 19a. After executing the process of step S107, the control circuit 10 ends the control flowchart in FIG.

[0082] On the other hand, if no failure is detected in the power semiconductor element 32 of a phase other than the faulty phase in step S106, the control circuit 10 does not execute the process of step S107 and ends the control flowchart in Fig. 7. In this case, the state determination unit 19 maintains the internal state 19a as the "one-phase faulty state."

[0083] If it is determined in step S104 that the internal state 19a output from the state determination unit 19 is not a "single-phase fault state," i.e., if the internal state 19a is a "two or more phase fault state," the control circuit 10 performs control in the processing of step S108 to stop driving the motor 190. For example, the PWM signal generation unit 16 outputs a PWM signal 16a to the driver circuit 20 so that the power conversion circuit 30 enters a freewheeling state, or the circuit breaker control unit 17 outputs a circuit breaker control signal 17a to the circuit breaker drive circuit 60 so that all circuit breakers 70 enter an interrupted state. Alternatively, both of these operations are performed. This stops driving the motor 190.

[0084] FIG. 8 is a diagram showing an example of output torque when one phase fails in the first embodiment of the present invention. In this example, it is assumed that the target torque T* is set to 100 [Nm] and a short-circuit fault occurs in the power semiconductor element 32 of the U-phase upper arm. In FIG. 8, the graph on the left shows example waveforms of the current and torque of each phase when the circuit breaker 70 of the U-phase, which is the failed phase, is shut off and motor drive continues using only the two normal phases (V phase and W phase) based on the same target voltage as in normal operation (conventional control). The graph on the right shows example waveforms of the current and torque of each phase when the current control in the event of one phase failure described in this embodiment is applied.

[0085] In the conventional control shown in the graph on the left, the U-phase circuit breaker 70 is in an off state, so no current flows through the U-phase, and torque is controlled using only the normal V-phase and W-phase currents. In this state, the output torque varies sinusoidally between the target torque and 0 [Nm], and the average torque is approximately 50% of the target torque. In order to improve the average torque in this state, the target torque must be made larger than normal, which further increases the amount of torque fluctuation.

[0086] On the other hand, in this embodiment, current control during one-phase failure is applied, and the U-phase circuit breaker 70 is turned on during the specific electrical angle as described above, allowing current to flow to the U-phase as well. As a result, as shown in the graph on the right, an output torque close to the target torque can be obtained during the specific electrical angle, thereby improving the average torque. When this control is applied, the output torque fluctuates between the target torque and 0 [Nm], so the torque fluctuation amount can be maintained at a value similar to that of conventional control.

[0087] As described above, the power conversion device 100 of this embodiment can improve the average torque while maintaining the same torque fluctuation amount as the conventional power conversion device 100 by applying current control during one-phase failure. Therefore, even after a failure, the acceleration capability of the vehicle 1 can be maintained to a certain extent, and deterioration of the ride comfort can be suppressed.

[0088] The current control in the event of one phase failure according to this embodiment is more effective in improving average torque than not only conventional control that uses the same target voltage during normal operation even during a failure, but also the control method described in the aforementioned Patent Document 1. In other words, with the control described in Patent Document 1, the output torque drops to 0 [Nm] at two electrical angles within one electrical angle cycle. However, when the current control in the event of one phase failure according to this embodiment is applied, the output torque can be improved to the same level as the target torque for one of the electrical angles, as shown in the graph on the right side of Figure 8. Therefore, the average torque can be improved compared to the control described in Patent Document 1.

[0089] According to the first embodiment of the present invention described above, the following advantageous effects are achieved.

[0090] (1) The power conversion device 100 includes a power conversion circuit 30, a circuit breaker 70, and a control circuit 10 that functions as a power semiconductor fault location determination unit 18, a circuit breaker control unit 17, and a fault-time current control unit 15. The power conversion circuit 30 has upper and lower arm circuits, each of which has power semiconductor elements 32, which are switching elements, connected in series, connected in parallel for at least three phases, and outputs AC current generated by the power semiconductor elements 32 of each phase to a motor 190 via an output line. The circuit breaker 70 is provided on the output line of each phase and conducts or cuts off the AC current. The power semiconductor fault location determination unit 18 determines the fault location of the power semiconductor element 32. The circuit breaker control unit 17 determines, as the faulty phase, the phase corresponding to the power semiconductor element 32 determined as the faulty location by the power semiconductor fault location determination unit 18, and controls the circuit breaker 70 of the faulty phase so that the AC current of the faulty phase is conducted at a predetermined specific electrical angle within one electrical angle cycle and the AC current of the faulty phase is cut off at electrical angles other than the specific electrical angle. The fault-time current control unit 15 controls the driving of the power semiconductor element 32 other than the power semiconductor element 32 determined to be the faulty part. In this way, even after a failure of the power semiconductor element 32, the driving of the motor 190 can be continued while suppressing torque fluctuations.

[0091] (2) The specific electrical angle has a range of 120° in electrical angle. This ensures that motor 190, which is a three-phase AC motor, can continue to be driven even if one of power semiconductor elements 32 fails.

[0092] (3) The circuit breaker control unit 17 changes the specific electrical angle for each faulty phase. This ensures that the motor 190 can continue to be driven even if a power semiconductor element 32 in any phase fails.

[0093] (Second embodiment) In this embodiment, an example of a power conversion device and a drive device is shown that improves the average output torque while maintaining torque fluctuations even after a power semiconductor failure when there is a delay in switching a circuit breaker, making it easier to start a vehicle.

[0094] The power conversion device 100 and the drive device 200 in this embodiment each have the same configuration as that described in the first embodiment in Fig. 2. Therefore, the power conversion device 100 and the drive device 200 of this embodiment will be described below using the configuration in Fig. 2.

[0095] FIG. 9 is an explanatory diagram of the switching timing of the circuit breaker 70 in the second embodiment of the present invention. In FIG. 9, (a) shows an example of a timing chart when there is no switching delay of the circuit breaker 70, and (b) shows an example of a timing chart when there is a switching delay of the circuit breaker 70. In both FIGS. 9(a) and 9(b), it is assumed that the power semiconductor element 32 in the U-phase upper arm has a short-circuit fault. It is also assumed that the specific electrical angle variable α in FIG. 6 described above is 0. Note that FIG. 9(a) corresponds to the switching timing of the circuit breaker 70 by current control when one phase has failed as described in the first embodiment, and FIG. 9(b) corresponds to the switching timing of the circuit breaker 70 by current control when one phase has failed in this embodiment.

[0096] 9(a) assumes an ideal state in which there is no switching delay of the circuit breaker 70. Therefore, at the start timing of the specific electrical angle (180 to 300 degrees), the circuit breaker control unit 17 switches the U-phase circuit breaker 70 from the interrupted state to the conductive state in response to a change in the circuit breaker switching signal 15b output from the fault current control unit 15. Also, at the end timing of the specific electrical angle, the circuit breaker control unit 17 switches the U-phase circuit breaker 70 from the conductive state to the interrupted state in response to a change in the circuit breaker switching signal 15b output from the fault current control unit 15.

[0097] However, because a typical circuit breaker 70 has a switching delay time, it is necessary to actually control the switching of the circuit breaker 70 taking this delay time into consideration. In this embodiment, as shown in FIG. 9( b), the switching timing of the circuit breaker 70 is set taking the delay time into consideration. Specifically, the timing at which the circuit breaker control unit 17 switches the circuit breaker 70 from the interrupted state to the conductive state is the same as in the case of FIG. 9( a), in which there is no switching delay. However, the timing at which the circuit breaker 70 switches from the conductive state to the interrupted state is advanced from the end timing of the specific electrical angle by the switching delay time of the circuit breaker 70. Note that such advancement of the switching timing of the circuit breaker 70 may be implemented by changing the timing of the circuit breaker switching signal 15b in the fault current control unit 15, or by changing the timing of the circuit breaker switching signal 15b in the circuit breaker control unit 17 without changing the timing of the circuit breaker switching signal 15b.

[0098] When the circuit breaker 70 is turned on, the output voltage of the faulted phase becomes ½ Vdc or −½ Vdc, as described above. In the current control during one-phase fault described in the first embodiment, the output voltages of the two normal phases are corrected within a specific electrical angle range, allowing the power conversion circuit 30 to output the same d-axis target voltage value and q-axis target voltage value as during normal operation. However, outside this range, the corrected voltages of the two normal phases become too large and cannot be fully corrected. This makes current control unstable. Therefore, it is desirable not to turn on the circuit breaker 70 of the faulted phase outside the specific electrical angle range. Therefore, in this embodiment, the timing at which the circuit breaker control unit 17 instructs the circuit breaker 70 to switch from the on state to the off state is advanced by the switching delay time of the circuit breaker 70, thereby preventing the circuit breaker 70 of the faulted phase from turning on outside the specific electrical angle range. This allows for stable current control even when there is a switching delay of the circuit breaker 70.

[0099] According to the second embodiment of the present invention described above, the circuit breaker control unit 17 instructs the circuit breaker 70 of the faulty phase to switch from a conductive state to a cut-off state earlier than the end timing of the specific electrical angle. This prevents the circuit breaker 70 of the faulty phase from entering a conductive state outside the range of the specific electrical angle, thereby stabilizing current control during a one-phase fault.

[0100] (Third embodiment) In this embodiment, an example of a power conversion device and a drive device is shown that, when there is a delay in switching the circuit breaker, reduces the processing load of the control circuit, improves the average output torque while maintaining torque fluctuations even after a power semiconductor failure, and makes it easier to start the vehicle.

[0101] Fig. 10 is a diagram showing an example of the configuration of a power conversion device 100 and a drive device 200 according to a third embodiment of the present invention. The power conversion device 100 in this embodiment has the same configuration as that shown in Fig. 2 described in the first embodiment, except that a motor speed value 11a calculated by a motor speed calculation unit 11 is output not only to a target current calculation unit 12 but also to a fault current control unit 15 and a circuit breaker control unit 17. In the following, a description of parts common to the first and second embodiments will be omitted.

[0102] FIG. 11 is an explanatory diagram of the switching timing of the circuit breaker 70 in the third embodiment of the present invention. In the second embodiment described above, switching control was performed when there is a switching delay in the circuit breaker 70. However, as shown in FIG. 11, when the delay time of the circuit breaker 70 is equivalent to 60 electrical degrees or more, this control method does not have enough time for the circuit breaker 70 of the faulty phase to be in a conductive state, and the current control effect in the event of a single-phase fault cannot be obtained. In other words, as the motor rotation speed increases, the proportion of the electrical angle occupied by the delay time of the circuit breaker 70 in one electrical angle cycle increases, and therefore, when the motor rotation speed is high, the current control effect in the event of a single-phase fault cannot be obtained.

[0103] Therefore, in this embodiment, at a motor rotation speed where the delay time of the circuit breaker 70 is equivalent to or greater than 60 electrical degrees, the control circuit 10 does not perform current control in the event of a one-phase fault, and controls the circuit breaker 70 to always be in the cut-off state. This eliminates unnecessary switching of the circuit breaker 70, reducing the processing load on the control circuit 10 in the power conversion device 100.

[0104] Fig. 12 is an example of a control flowchart in the third embodiment of the present invention. In this embodiment, the control circuit 10 shown in Fig. 10 periodically performs the control shown in the flowchart in Fig. 12 at regular intervals. In Fig. 12, the same processes as those in the control flowchart in Fig. 7 described in the first embodiment are denoted by the same symbols as in Fig. 7, and a description of those processes will be omitted.

[0105] In this embodiment, in the process of step S104, if the internal state 19a is the "one-phase failure state", the process proceeds to step S109, and if it is not the "one-phase failure state", the process proceeds to step S108.

[0106] In the process of step S109, the control circuit 10 determines whether the motor rotation number (rotation speed) is less than a predetermined threshold value based on the motor speed value 11a calculated by the motor speed calculation unit 11. If the motor rotation number is less than the threshold value, the process proceeds to step S105, and if it is equal to or greater than the threshold value, the process proceeds to step S110.

[0107] In the process of step S110, the control circuit 10 performs conventional fault control. Specifically, the circuit breaker 70 of the faulty phase is controlled to be always in the interrupted state, and the power semiconductor elements 32 of the two normal phases other than the faulty phase are controlled in the same manner as in normal operation. Then, the process proceeds to step S106.

[0108] As described above, according to the power conversion device 100 of this embodiment, when the motor rotation speed is below a predetermined threshold, the current control for one-phase failure is applied, but when the motor rotation speed is equal to or greater than the threshold, the current control for one-phase failure is not applied, and current control similar to the conventional method is performed in which the faulty phase is not energized. This eliminates unnecessary switching control of the circuit breaker 70, thereby reducing the processing load on the control circuit 10.

[0109] According to the third embodiment of the present invention described above, when the rotation speed of the motor 190 is equal to or greater than a predetermined threshold (step S109: No), the circuit breaker control unit 17 controls the circuit breaker 70 of the faulty phase so that the AC current is interrupted for the entire period of one electrical angle cycle (step S110). On the other hand, when the rotation speed of the motor 190 is less than the threshold (step S109: Yes), the circuit breaker control unit 17 controls the circuit breaker 70 of the faulty phase so that the AC current of the faulty phase is conducted at a specific electrical angle and is interrupted at electrical angles other than the specific electrical angle (step S105). This makes it possible to perform current control in the event of a one-phase fault while reducing the processing load on the control circuit 10.

[0110] (Fourth embodiment) In this embodiment, an example of a power conversion device and a drive device is shown that, when there is a delay in switching the circuit breaker, improves the average output torque while maintaining torque fluctuations even after a power semiconductor failure, making it easier to start the vehicle, using a method different from that of the second and third embodiments.

[0111] The power conversion device 100 and the drive device 200 in this embodiment each have the same configuration as that described in the first embodiment in Fig. 2. Therefore, the power conversion device 100 and the drive device 200 of this embodiment will be described below using the configuration in Fig. 2.

[0112] 13 is an explanatory diagram of the switching timing of the circuit breaker 70 in the fourth embodiment of the present invention. In FIG. 13, (a) shows an example of a timing chart when the circuit breaker switching and current control described in the second embodiment are performed, and (b) shows an example of a timing chart when the circuit breaker switching and current control according to this embodiment are performed. In both FIG. 13(a) and (b), it is assumed that an open circuit fault occurs in the power semiconductor element 32 of the U-phase upper arm.

[0113] In the first and second embodiments, regardless of whether the power semiconductor element 32 has an open circuit fault or a short circuit fault, in current control during a single-phase fault, one of the power semiconductor elements 32 in the upper or lower arm of the faulted phase is controlled to be always on and the other is always off, and the circuit breaker 70 of the faulted phase is controlled to be in a conductive state only for a specific electrical angle. Therefore, for example, in the second embodiment, when the power semiconductor element 32 in the U-phase lower arm has an open circuit fault, the power semiconductor element 32 in the U-phase upper arm is always kept in an on state, and the U-phase circuit breaker 70 is controlled to be in a conductive state for a period shorter than the specific electrical angle by the switching delay time of the circuit breaker 70, as shown in Figure 13(a).

[0114] However, when an open-circuit fault occurs in either the upper or lower arm power semiconductor element 32, output voltage control similar to the current control in the event of a single-phase fault described in the first and second embodiments can be achieved in the power conversion device 100 by controlling the on / off state of the power semiconductor element 32 on the opposite side and in the same phase as the fault location, rather than controlling the interruption / conduction of the circuit breaker 70. Therefore, in this embodiment, when an open-circuit fault occurs in a power semiconductor element 32, current control in the event of a single-phase fault is performed by controlling the circuit breaker 70 of the faulty phase to be always in a conductive state, and controlling the power semiconductor element 32 on the opposite side and in the same phase as the fault location to be in an on state only for a specific electrical angle.

[0115] 13(b), the circuit breaker 70 of the faulty phase (U-phase) is always kept in a conducting state, and the power semiconductor element 32 on the opposite side (U-phase upper arm) of the same phase as the faulty part is controlled to be in an on state only for the specific electrical angle described in the first embodiment. This makes it possible to realize current control in the event of a single-phase fault, similar to the first and second embodiments.

[0116] For example, when a mechanical switch is used for the circuit breaker 70, the delay time of the circuit breaker 70 in switching between conduction and interruption is long and the delay time of the power semiconductor element 32 in switching between on and off is short compared to this, by implementing the control of this embodiment, it is possible to reduce the influence of the switching delay time of the circuit breaker 70. As a result, even in a situation where the motor rotation speed is high, it becomes possible to apply control similar to the current control in the event of a single-phase failure to the power conversion device 100. Therefore, even when the vehicle 1 is traveling at high speed, it is possible to improve the average output torque while maintaining torque fluctuations similar to those of conventional control.

[0117] Fig. 14 is an example of a control flowchart in the fourth embodiment of the present invention. In this embodiment, the control shown in the flowchart of Fig. 14 is periodically performed at regular intervals by the control circuit 10 shown in Fig. 2. In Fig. 14, the same processes as those in the control flowchart of Fig. 7 described in the first embodiment are denoted by the same symbols as in Fig. 7, and a description of those processes will be omitted.

[0118] In this embodiment, in the process of step S104, if the internal state 19a is the "one-phase failure state", the process proceeds to step S111, and if it is not the "one-phase failure state", the process proceeds to step S108.

[0119] In the process of step S111, the control circuit 10 determines whether the fault state of the power semiconductor element 32 in which a fault has been detected is an open circuit fault. If an open circuit fault is detected, the process proceeds to step S112, and if a short circuit fault is detected instead of an open circuit fault, the process proceeds to step S105.

[0120] In the process of step S112, the control circuit 10 controls the circuit breaker 70 of the faulty phase so that it is always in a conductive state, and controls the power semiconductor element 32 on the opposite side of the faulty phase so that it is in the on state for only a specific electrical angle. In this way, current control in the event of a one-phase fault is performed. Then, the process proceeds to step S106.

[0121] As described above, according to the power conversion device 100 of this embodiment, when an open-circuit fault occurs in a power semiconductor element 32, the circuit breaker 70 of the faulty phase is controlled to be always in a conductive state, and the power semiconductor element 32 on the opposite side of the faulty phase but in the same phase as the faulty part is controlled to be in an on state only for a specific electrical angle. This eliminates the influence of the switching delay time of the circuit breaker 70, making it possible to perform current control in the event of a one-phase fault.

[0122] According to the fourth embodiment of the present invention described above, when an open-circuit fault occurs in a power semiconductor element 32 (step S111: Yes), the circuit breaker control unit 17 places the circuit breaker 70 of the faulty phase in a conductive state, and the fault-time current control unit 15 controls the drive of the power semiconductor element 32 of a phase other than the faulty phase and the power semiconductor element 32 of the upper and lower arm circuits in the faulty phase that is not the power semiconductor element 32 determined to be the faulty part (step S112). By doing so, the effect of the delay time in switching the conduction / cutoff of the circuit breaker 70 is reduced, and control similar to current control in the event of a single-phase fault can be achieved even when the motor rotation speed is high.

[0123] (Fifth embodiment) In this embodiment, an example of a power conversion device and a drive device that can improve the average output torque while maintaining torque fluctuation even after a failure of a power semiconductor, and can also cope with a failure of a circuit breaker, will be described.

[0124] Fig. 15 is a diagram showing an example of the configuration of a power conversion device 100 and a drive device 200 according to a fifth embodiment of the present invention. In addition to the same configuration as that shown in Fig. 2 described in the first embodiment, the power conversion device 100 in this embodiment further includes a circuit breaker fault location determination unit 14. In the following, descriptions of parts common to the first to fourth embodiments will be omitted.

[0125] When diagnosing the circuit breaker 70, the circuit breaker fault location determination unit 14 generates a predetermined duty value 14a for each phase and outputs it to the PWM signal generation unit 16. Also, during the diagnosis of the circuit breaker 70, it generates a predetermined circuit breaker switching signal 14b for each phase and outputs it to the circuit breaker control unit 17. The circuit breaker fault location determination unit 14 can determine whether or not the circuit breaker 70 of each phase has failed, using the AC current sensor value 50a for each phase output from the AC current sensor 50 when these signals are output. When the diagnosis of the circuit breaker 70 is completed, the circuit breaker fault location determination unit 14 outputs circuit breaker diagnosis information 14c to the state determination unit 19, indicating that the diagnosis of the circuit breaker 70 has been completed and, if there is a fault, the fault location.

[0126] 16 is a diagram showing an example of an internal state determination by the state determination unit 19 in the fifth embodiment of the present invention. In this embodiment, the initial state of the state determination unit 19 is a "circuit breaker diagnostic state." When the current state is the "circuit breaker diagnostic state," if the state determination unit 19 receives circuit breaker diagnostic information 14c from the circuit breaker fault location determination unit 14, the state determination unit 19 changes the next state to a "normal state."

[0127] Furthermore, when the state determination unit 19 receives power semiconductor failure information 18a from the power semiconductor failure location determination unit 18 indicating that a power semiconductor element 32 of one of the phases has failed, the state determination unit 19 changes the current state in accordance with the content of the circuit breaker diagnostic information 14c received up to that point from the circuit breaker failure location determination unit 14. Specifically, if the state determination unit 19 has received circuit breaker diagnostic information 14c indicating that a circuit breaker 70 of the same phase as the failed power semiconductor element 32 has failed, the state determination unit 19 changes the next state to a "two or more phases failed state." On the other hand, if the state determination unit 19 has received circuit breaker diagnostic information 14c indicating that a circuit breaker 70 of a phase different from the failed power semiconductor element 32 has failed or circuit breaker diagnostic information 14c indicating that the circuit breaker 70 is not failed, the state determination unit 19 changes the next state to a "single-phase failed state." If the current state is the "normal state" and the above conditions are not met, the next state remains the "normal state."

[0128] If the current state is a "single phase failure state" or a "two or more phase failure state", the process is the same as in the first embodiment.

[0129] Next, a method for diagnosing the circuit breaker 70 in this embodiment will be described. When the internal state output from the state determination unit 19 is the "circuit breaker diagnostic state," the PWM signal generation unit 16 generates the PWM signal 16a for each phase in accordance with the duty value 14a for each phase output from the circuit breaker fault location determination unit 14. Furthermore, when the internal state output from the state determination unit 19 is the "circuit breaker diagnostic state," the circuit breaker control unit 17 controls the conductive / interrupted state of the circuit breaker 70 for each phase in accordance with the circuit breaker switching signal 14b output from the circuit breaker fault location determination unit 14. The circuit breaker fault location determination unit 14 can determine whether the circuit breaker 70 for each phase has failed based on the AC current sensor value 50a for each phase output from the AC current sensor 50 when these signals are output.

[0130] Faults in the circuit breaker 70 can be broadly divided into two types: a stuck-on fault, in which the circuit breaker 70 does not change from an off state, and a stuck-on fault, in which the circuit breaker 70 does not change from a conductive state. If a stuck-on fault occurs in the circuit breaker 70 and a power semiconductor element 32 in the same phase as the failed circuit breaker 70 experiences a short-circuit fault, the power conversion device 100 will be unable to interrupt the AC current flowing through the faulty phase using either the circuit breaker 70 or the power semiconductor element 32. Therefore, in this case, it will be impossible to continue current control in the event of a single-phase fault. Therefore, in this embodiment, in order to determine such a situation, the circuit breaker fault location determination unit 14 diagnoses the presence or absence of a stuck-on fault in the circuit breakers 70 of each phase.

[0131] When determining whether or not a fixed continuity fault exists in a circuit breaker 70 for a certain phase as a diagnosis target phase, the circuit breaker fault location determination unit 14 selects one phase (hereinafter referred to as the "selected phase") other than the diagnosis target phase, generates a circuit breaker switching signal 14b, and outputs it to the circuit breaker control unit 17 so as to turn on the circuit breaker 70 of the selected phase and turn off the circuit breakers 70 of the other two phases. The circuit breaker fault location determination unit 14 also generates a duty value 14a and outputs it to the PWM signal generation unit 16 so as to turn on the power semiconductor elements 32 of the upper arm of the diagnosis target phase and the power semiconductor elements 32 of the lower arm of the selected phase for only a predetermined short time. Note that the upper arm and the lower arm may be interchanged in the combination of the power semiconductor elements 32 to be turned on at this time. That is, the power semiconductor elements 32 of the lower arm of the diagnosis target phase and the power semiconductor elements 32 of the upper arm of the selected phase may be turned on for only a predetermined short time.

[0132] When the circuit breaker switching signal 14b and duty value 14a are output as described above, if the circuit breaker 70 of the phase to be diagnosed is normally interrupted, no current flows through the phase to be diagnosed. However, if the circuit breaker 70 of the phase to be diagnosed has a fixed-conduction fault, a current path is formed that passes through the power semiconductor elements 32, circuit breaker 70, and motor winding of the phase to be diagnosed, and the motor winding, circuit breaker 70, and power semiconductor elements 32 of the selected phase, and current flows through this current path. Therefore, when performing the circuit breaker diagnosis operation described above, the circuit breaker fault location determination unit 14 determines whether a current greater than a certain value flows through the phase to be diagnosed based on the AC current sensor value 50a. If it is determined that a current flows, it determines that the circuit breaker 70 of the phase to be diagnosed has a fixed-conduction fault.

[0133] 17 is an example of a flowchart of circuit breaker diagnosis in the fifth embodiment of the present invention. In this embodiment, the circuit breaker fault location determination unit 14 performs control shown in the flowchart of FIG. 17 before the driver circuit 20 and the power conversion circuit 30 operate.

[0134] In the process of step S200, the circuit breaker fault location determination unit 14 performs a diagnosis operation for a stuck-on fault of the circuit breaker 70 of the U phase. Specifically, as described above, the circuit breaker fault location determination unit 14 sets the U phase as the phase to be diagnosed and either the V phase or the W phase as the selected phase, and outputs to the circuit breaker control unit 17 a circuit breaker switching signal 14b such that the circuit breaker 70 of the selected phase is in a conducting state and the circuit breaker 70 of the U phase and the circuit breakers 70 of the phases other than the selected phase are in a cut-off state. In addition, the circuit breaker fault location determination unit 14 outputs to the PWM signal generation unit 16 a duty value 14a such that the power semiconductor element 32 of the upper arm (or lower arm) of the U phase and the power semiconductor element 32 of the lower arm (or upper arm) of the selected phase are each in an on state for a short period of time.

[0135] When the circuit breaker fault location determination unit 14 outputs the duty value 14a and the circuit breaker switching signal 14b, the PWM signal generation unit 16 generates a PWM signal 16a based on the duty value 14a and outputs it to the driver circuit 20. In addition, the circuit breaker control unit 17 controls the conductive / blocked state of the circuit breaker 70 of each phase based on the circuit breaker switching signal 14b.

[0136] In the process of step S201, the circuit breaker fault location determination unit 14 determines whether or not a current equal to or greater than a certain value has flowed in the U phase, based on the U phase AC current sensor value 50a output from the AC current sensor 50. If a current equal to or greater than the certain value has flowed in the U phase, the circuit breaker fault location determination unit 14 then performs the process of step S202, and if not, the circuit breaker fault location determination unit 14 then performs the process of step S203.

[0137] In the process of step S202, the circuit breaker fault location determination unit 14 determines that the U-phase circuit breaker 70 has a fixed continuity fault. In the process of step S203, the circuit breaker fault location determination unit 14 determines that the U-phase circuit breaker 70 is normal. After the process of step S202 or S203 is performed, the process proceeds to step S204.

[0138] In the process of step S204, the circuit breaker fault location determination unit 14 performs a diagnosis operation for a stuck-on fault in the circuit breaker 70 of the V phase. Specifically, as described above, with the V phase as the phase to be diagnosed and either the U phase or the W phase as the selected phase, the circuit breaker switching signal 14b is output to the circuit breaker control unit 17 so that the circuit breaker 70 of the selected phase is in a conducting state and the circuit breaker 70 of the V phase and the circuit breakers 70 of the phases other than the selected phase are in a cut-off state. The circuit breaker switching signal 14b is also output to the PWM signal generation unit 16 so that the power semiconductor element 32 of the upper arm (or lower arm) of the V phase and the power semiconductor element 32 of the lower arm (or upper arm) of the selected phase are each in an on state for a short period of time.

[0139] When the circuit breaker fault location determination unit 14 outputs the duty value 14a and the circuit breaker switching signal 14b, the PWM signal generation unit 16 generates a PWM signal 16a based on the duty value 14a and outputs it to the driver circuit 20. In addition, the circuit breaker control unit 17 controls the conductive / blocked state of the circuit breaker 70 of each phase based on the circuit breaker switching signal 14b.

[0140] In the process of step S205, the circuit breaker fault location determination unit 14 determines whether or not a current equal to or greater than a certain value has flowed in the V phase, based on the V phase AC current sensor value 50a output from the AC current sensor 50. If a current equal to or greater than the certain value has flowed in the V phase, the circuit breaker fault location determination unit 14 then performs the process of step S206, and if not, the circuit breaker fault location determination unit 14 then performs the process of step S207.

[0141] In the process of step S206, the circuit breaker fault location determination unit 14 determines that the V-phase circuit breaker 70 has a fixed continuity fault. In the process of step S207, the circuit breaker fault location determination unit 14 determines that the V-phase circuit breaker 70 is normal. After the process of step S206 or S207 is performed, the process proceeds to step S208.

[0142] In the process of step S208, the circuit breaker fault location determination unit 14 performs a diagnosis operation for a stuck-on fault of the W-phase circuit breaker 70. Specifically, as described above, with the W-phase as the phase to be diagnosed and either the U-phase or the V-phase as the selected phase, the circuit breaker switching signal 14b is output to the circuit breaker control unit 17 so that the circuit breaker 70 of the selected phase is in a conducting state and the circuit breaker 70 of the W-phase and the circuit breakers 70 of the phases other than the selected phase are in a cut-off state. The circuit breaker switching signal 14b is also output to the PWM signal generation unit 16 so that the power semiconductor element 32 of the upper arm (or lower arm) of the W-phase and the power semiconductor element 32 of the lower arm (or upper arm) of the selected phase are each in an on state for a short period of time.

[0143] When the circuit breaker fault location determination unit 14 outputs the duty value 14a and the circuit breaker switching signal 14b, the PWM signal generation unit 16 generates a PWM signal 16a based on the duty value 14a and outputs it to the driver circuit 20. In addition, the circuit breaker control unit 17 controls the conductive / blocked state of the circuit breaker 70 of each phase based on the circuit breaker switching signal 14b.

[0144] In the process of step S209, the circuit breaker fault location determination unit 14 determines whether or not a current equal to or greater than a certain value has flowed in the W phase, based on the W-phase AC current sensor value 50a output from the AC current sensor 50. If a current equal to or greater than the certain value has flowed in the W phase, the circuit breaker fault location determination unit 14 then performs the process of step S210, and if not, the circuit breaker fault location determination unit 14 then performs the process of step S211.

[0145] In the process of step S210, the circuit breaker fault location determination unit 14 determines that the W-phase circuit breaker 70 has a fixed continuity fault. In the process of step S211, the circuit breaker fault location determination unit 14 determines that the W-phase circuit breaker 70 is normal. After the process of step S210 or S211 is performed, the process proceeds to step S212.

[0146] In the process of step S212, the circuit breaker fault location determination unit 14 generates circuit breaker diagnostic information 14c based on the diagnosis results of the circuit breakers 70 of each phase obtained in steps S202 to S203, S206 to S207, and S210 to S211, and outputs it to the state determination unit 19.

[0147] When the circuit breaker diagnostic information 14c is output from the circuit breaker fault location determination unit 14, the state determination unit 19 changes the internal state from the "circuit breaker diagnostic state" to the "normal state" and starts operation of the driver circuit 20 and the power conversion circuit 30.

[0148] After executing the process of step S212, the circuit breaker fault location determination unit 14 ends the control flowchart of Fig. 17. This completes the diagnostic operation of the circuit breaker 70.

[0149] Fig. 18 is an example of a control flowchart in the fifth embodiment of the present invention. In this embodiment, the control circuit 10 shown in Fig. 15 periodically performs the control shown in the flowchart in Fig. 18 at regular intervals. In Fig. 18, the same processes as those in the control flowchart in Fig. 7 described in the first embodiment are denoted by the same symbols as in Fig. 7, and a description of those processes will be omitted.

[0150] In this embodiment, if an open circuit fault or a short circuit fault is detected in any of the power semiconductor elements 32 in the process of step S102, the process proceeds to step S113.

[0151] In the processing of step S113, the state determination unit 19 determines whether or not the circuit breaker 70 of the same phase as the failed power semiconductor element 32 has failed, based on the circuit breaker diagnostic information 14c output from the circuit breaker failure location determination unit 14 in step S212 of Fig. 17 and the power semiconductor failure information 18a output from the power semiconductor failure location determination unit 18. As a result, if it is determined that the circuit breaker 70 of the same phase as the power semiconductor element 32 in which an open fault or short fault was detected in step S102 has failed, the process proceeds to step S114, and if it is determined that the circuit breaker 70 of a different phase has failed, the process proceeds to step S103.

[0152] In the process of step S114, the state determination unit 19 determines that the current state of the power conversion device 100 is a "two or more phases fault state" and updates the internal state 19a. After executing the process of step S114, the control circuit 10 ends the control flowchart in FIG. 18.

[0153] As described above, the power conversion device 100 of this embodiment determines whether or not there is a fixed-conduction fault in the circuit breaker 70 before starting operation of the driver circuit 20 and the power conversion circuit 30. When a fault occurs in a power semiconductor element 32, if the circuit breaker 70 in the same phase as the power semiconductor element 32 is in a fixed-conduction fault state, the current of the faulty phase cannot be interrupted and transition to single-phase fault current control cannot be performed. Therefore, the drive of the motor 190 is stopped in the same way as when two or more phases fail. Therefore, it is possible to take action to deal with a fault in the circuit breaker 70.

[0154] According to the fifth embodiment of the present invention described above, the power conversion device 100 includes the circuit breaker fault location determination unit 14 that determines the fault location of the circuit breaker 70. If the power semiconductor element 32 determined to be the fault location by the power semiconductor fault location determination unit 18 and the circuit breaker 70 determined to be the fault location by the circuit breaker fault location determination unit 14 are in the same phase (step S113: Yes), the current state of the power conversion device 100 is determined to be a "two or more phase fault state" (step S114), and driving of the motor 190 is stopped (step S108). As a result, when the circuit breaker 70 has failed and current control during one-phase failure cannot be performed, driving of the motor 190 can be safely stopped.

[0155] The present invention is not limited to the above-described embodiments and includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, or the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, part of the configuration of each embodiment can be added, deleted, or replaced with other configurations. Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, in part or in whole, by, for example, designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software, by a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in memory, a recording device such as a hard disk or solid-state drive (SSD), or a recording medium such as an IC card, SD card, or DVD. [Explanation of symbols]

[0156] 1: Vehicle 2: Drive wheels 3: Non-driving wheels 4: Axle 10: Control circuit 11: Motor speed calculation unit 11a: Motor speed value 12: Target current calculation section 12a: Target current value 13: Normal current control section 13a: Duty value 14: Circuit breaker fault location determination section 14a: Duty value 14b: Circuit breaker switching signal 14c: Circuit breaker diagnostic information 15: Fault current control section 15a: Duty value 15b: Circuit breaker switching signal 16:PWM signal generation section 16a:PWM signal 17: Circuit breaker control unit 17a: Circuit breaker control signal 18: Power semiconductor fault location determination unit 18a: Power semiconductor failure information 19: Status determination unit 19a: Internal state 20: Driver circuit 20a: drive signal 20b: Short circuit fault detection signal 30: Power conversion circuit 31: Smoothing capacitor 32: Power semiconductor element 33: Sense terminal 33a: Sense current 40: Voltage sensor 40a: Voltage sensor value 50: AC current sensor 50a: AC current sensor value 60: Circuit breaker drive circuit 60a: Circuit breaker drive signal 70: Circuit breaker 100: Power conversion device 190: Motor 191: Motor neutral point 200: Drive unit 210: DC power supply 220: Failure notification device 230: Electronic control device

Claims

1. a power conversion circuit in which upper and lower arm circuits, each having switching elements connected in series, are connected in parallel for at least three phases, and which outputs AC current generated by the switching elements of each phase to a motor via an output line; a circuit breaker provided on the output line of each phase to conduct or cut off the AC current; a first failure location determination unit that determines a failure location of the switching element; a circuit breaker control unit that controls the circuit breaker of the faulty phase, with the phase corresponding to the switching element determined as the faulty location by the first fault location determination unit as the faulty phase, so that the AC current of the faulty phase is conducted at a predetermined specific electrical angle within one cycle of the electrical angle and the AC current of the faulty phase is interrupted at other electrical angles excluding the specific electrical angle; a fault current control unit that controls driving of a switching element other than the switching element determined to be the faulty part.

2. The power conversion device according to claim 1, The specific electrical angle has a range of 120° in electrical angle.

3. The power conversion device according to claim 1, The circuit breaker control unit is a power conversion device that changes the specific electrical angle for each faulted phase.

4. The power conversion device according to claim 1, The power conversion device wherein the circuit breaker control unit instructs the circuit breaker of the faulty phase to switch from a conductive state to a cut-off state earlier than the end timing of the specific electrical angle.

5. The power conversion device according to claim 1, The circuit breaker control unit When the rotation speed of the motor is equal to or greater than a predetermined threshold value, the circuit breaker of the faulted phase is controlled so that the AC current is interrupted for an entire period of one cycle of the electrical angle; When the rotational speed of the motor is less than the threshold value, the power conversion device controls the circuit breaker of the faulty phase so that the AC current of the faulty phase is conducted at the specific electrical angle and is cut off at other electrical angles excluding the specific electrical angle.

6. The power conversion device according to claim 1, When the switching element has an open circuit fault, The circuit breaker control unit places the circuit breaker of the faulted phase in a conductive state, The fault current control unit is a power conversion device that controls the drive of the switching element of a phase other than the faulty phase and the switching element of the upper and lower arm circuits in the faulty phase that is not the switching element determined to be the faulty part.

7. The power conversion device according to claim 1, a second fault location determination unit that determines a fault location of the circuit breaker; A power conversion device that stops driving the motor when the switching element determined to be the faulty location by the first fault location determination unit and the circuit breaker determined to be the faulty location by the second fault location determination unit are in the same phase.

8. A drive device including a power conversion device that outputs a three-phase AC current and a motor that is driven by the three-phase AC current, The power conversion device is a power conversion circuit in which upper and lower arm circuits, each having a switching element connected in series, are connected in parallel for three phases, and which outputs AC current generated by the switching element of each phase to the motor via an output line; a circuit breaker provided on the output line of each phase to conduct or cut off the AC current; a first failure location determination unit that determines a failure location of the switching element; a circuit breaker control unit that controls the circuit breaker of the faulty phase, with the phase corresponding to the switching element determined as the faulty location by the first fault location determination unit as the faulty phase, so that the AC current of the faulty phase is conducted at a predetermined specific electrical angle within one cycle of the electrical angle and the AC current of the faulty phase is interrupted at other electrical angles excluding the specific electrical angle; a fault current control unit that controls driving of a switching element other than the switching element determined to be the faulty part.

9. 9. The drive device according to claim 8, The specific electrical angle has a range of 120° in electrical angle.

10. 9. The drive device according to claim 8, The circuit breaker control unit is a driving device that changes the specific electrical angle for each faulted phase.

11. 9. The drive device according to claim 8, The circuit breaker control unit instructs the circuit breaker of the faulty phase to switch from a conductive state to a cut-off state ahead of the end timing of the specific electrical angle.

12. 9. The drive device according to claim 8, The circuit breaker control unit When the rotation speed of the motor is equal to or greater than a predetermined threshold value, the circuit breaker of the faulted phase is controlled so that the AC current is interrupted for an entire period of one cycle of the electrical angle; a drive device that controls the circuit breaker of the faulty phase so that, when the rotational speed of the motor is less than the threshold value, the AC current of the faulty phase is conducted at the specific electrical angle and the AC current of the faulty phase is interrupted at other electrical angles excluding the specific electrical angle.

13. 9. The drive device according to claim 8, When the switching element has an open circuit fault, The circuit breaker control unit places the circuit breaker of the faulted phase in a conductive state, The fault current control unit is a drive device that controls the drive of the switching element of a phase other than the faulty phase and the switching element of the upper and lower arm circuits in the faulty phase that is not the switching element determined to be the faulty part.

14. 9. The drive device according to claim 8, a second fault location determination unit that determines a fault location of the circuit breaker; A drive device that stops driving the motor when the switching element determined to be the faulty location by the first fault location determination unit and the circuit breaker determined to be the faulty location by the second fault location determination unit are in the same phase.

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