Motor drive device

Abstract

If an upper branch of a U-phase (15) fails due to a short circuit, the lower branches of a V-phase (16) and a W-phase (17) are switched as opposite branches. When only the lower branch of the V-phase (16) is switched on, a path of motor current (Iu) is formed that passes through an IGBT element (Q6) from a V-phase coil, thus reducing the motor current (Iu) returning to the short-circuited phase. Furthermore, the switching operation of the branch opposite to the short-circuited branch generates an alternating current in a motor-generator (MG2). Consequently, it is possible to continuously drive the motor-generator (MG2) while preventing an increase in the current passing through the short-circuited phase, without adding a new device setup. This ensures the vehicle can be driven in emergency operating mode.

Description

Technical field

[0001] The present invention relates to a motor drive device and in particular a motor drive device which enables continuous operation of the motor when a drive or control circuit which controls a drive of the motor is disabled by a short circuit. Background of the invention

[0002] Recently, hybrid and electric vehicles have gained increasing attention as environmentally friendly options. A hybrid vehicle, in addition to a conventional engine, features a DC power source, an inverter, and a motor controlled by the inverter as power sources. Specifically, power is generated by driving the engine, with the DC voltage from the DC power source being converted into AC voltage by the inverter. This AC voltage then drives the motor, thus generating power.

[0003] An electric vehicle has a DC power source, an inverter, and a motor driven by the inverter as power sources.

[0004] In a motor drive device installed in a hybrid vehicle or an electric vehicle as such, typically when a malfunction, such as a short circuit of a switching element forming the inverter, is detected, the inverter operation is stopped to prevent excessive heating of the switching element caused by an overcurrent flowing to the short-circuited switching element.

[0005] At this point, a counter-electromotive force is generated in a motor coupled to the vehicle's drive shaft, corresponding to the rotational speed. Consequently, if the motor speed is high, the current passing through the inverter can increase undesirably when a high counter-electromotive force is received. Therefore, in some vehicle types, in response to the detection of an inverter malfunction, a clutch located between the drive shaft and the motor is disengaged to stop power transmission from the drive shaft to the motor, and the vehicle enters a so-called emergency running mode, in which the vehicle travels to a location with the clutch disengaged so as not to obstruct pedestrian or vehicle traffic.

[0006] At this point, emergency driving depends solely on the inertia acting on the drive wheels, as no power is being supplied to the drive shaft. Consequently, it is difficult to ensure a sufficient driving distance to reliably move the vehicle to a safe area.

[0007] In light of the aforementioned circumstances, a method for ensuring the torque required for emergency operation has recently been proposed. For example, Japanese patent publication number JP 2004-120 883 A discloses a converter for driving a three-phase AC motor, in which operation of a three-phase AC motor can continue even if a switching element forming the converter fails.

[0008] According to this patent application, the converter for driving a three-phase AC motor comprises a DC power supply circuit with a rectifier circuit that rectifies an output of an AC power supply, a converter circuit formed by first to third parallel-connected branch circuits, each comprising two series-connected semiconductor switching elements and converting a DC voltage from the DC power supply into a three-phase AC voltage, and a PWM control device for PWM control (PWM: Pulse Width Modulation) of the converter circuit, driving a three-phase AC motor with star-connected excitation windings of three phases.

[0009] In the inverter, the DC power supply circuit includes a voltage divider circuit that equally divides the output voltage of the rectifier circuit and outputs it to a neutral point. The first to third branch circuits have first to third starting points formed by a node of two semiconductor switching elements. A neutral point interconnect circuit is provided between the neutral point and the first to third starting points for selectively connecting the neutral point to any one of the first to third starting points.

[0010] In the setup described above, if one of the multiple semiconductor switching elements that make up the inverter circuit is found to be faulty, the neutral-point connection circuit connects the neutral point and the starting point of the branch circuit containing the failed semiconductor switching element. As a result, the excitation windings of the three-phase AC motor reach a state equivalent to that in which normal two-phase excitation windings are V-connected. In this state, the PWM control device performs PWM control of four semiconductor switching elements, which are contained in two branch circuits, regulating the current flowing through the V-connected two-phase excitation windings, thereby generating a three-phase balanced output current to drive the AC motor.

[0011] Furthermore, Japanese patent disclosure number JP H09-23501A discloses a control device for an electric vehicle in which a fault diagnosis circuit is used as an auxiliary motor control device to perform motor drive control instead of a motor control circuit when a defect is found in one of three current sensors that detect currents flowing through respective phases of a three-phase motor, or in a current control circuit that performs control based on the detected current from the current sensors.

[0012] According to this procedure, a backup microcomputer is provided as the fault diagnosis circuit and the replacement motor drive control device, separate from a microcomputer that acts as the original motor control circuit.

[0013] According to the inverter for driving a three-phase AC motor, disclosed in Japanese patent publication number JP 2004-120 883 A, a neutral-point connection circuit is required to continue operating the three-phase AC motor even after a fault in a semiconductor switching element has been detected. This circuit connects the starting point of the branch circuit containing the short-circuited semiconductor switching element to the neutral point of the DC power supply circuit. This inevitably leads to a larger inverter and increased device costs.

[0014] Furthermore, the control device for an electric vehicle according to Japanese patent publication number H09-23501A provides control circuits corresponding to the normal and abnormal states of the current sensor. Consequently, as in the method according to Japanese patent publication number JP2004-120883A, this presents difficulties regarding the size and cost of the device. Other patent publications do not disclose a method for controlling the drive of a short-circuited inverter solely by means of an existing device setup.

[0015] The article “Influence of the current control strategy on the PMSM drive performance during failures” by N. Bianchi et al, Proceedings of EPE Conference, 1997, pages 1330 to 1335, describes the control of a permanent magnet synchronous motor in the event of a failure of an electronic power converter or the motor connections.

[0016] The printed document JP H08-186 984 A describes a failsafe for an inverter.

[0017] The present invention has been made to solve the aforementioned difficulties, and an associated objective is to provide a motor drive device which, with a simple and inexpensive device design, can ensure the safety and output power of a motor when a fault in a converter is detected.

[0018] This problem is solved by a motor drive device according to claim 1. Advantageous embodiments are specified in the dependent claims.

[0019] According to one embodiment, a motor drive device is provided, comprising: a three-phase AC motor; a power source capable of supplying direct current to the first and second power supply lines; a power conversion device that performs power conversion between the first and second power lines and the three-phase AC motor; and a control device that controls the power conversion device such that the output of the three-phase AC motor reaches a setpoint. The power conversion device comprises first to third circuits, each connected to coils of the first to third phases of the three-phase AC motor.Each of the first to third circuits has first and second switching elements connected in series via a connection node (the midpoint between the first and second switching elements of each of the first to third circuits) to the coil of a respective phase of the three-phase AC motor. The control device comprises a short-circuit detection unit that detects a switching element failed due to a short circuit from the first to third circuits, and a motor drive control unit that, in response to the detection of a short-circuited switching element by the short-circuit detection unit, controls currents flowing through coils of respective phases of the three-phase AC motor by switching at least one switching element opposite the short-circuited switching element with the interposed connection node.

[0020] In the motor drive device described above, if a short circuit of a switching element occurs in one or two of the first to third circuits, a switching element belonging to a normal circuit that does not include the failed switching element and forms a branch different from the branch formed by the corresponding switching element is caused to perform a switching operation, thereby suppressing an increase in the current passing through the circuit that has failed due to the short circuit, and enabling the three-phase AC motor to be driven continuously.Consequently, both motor safety and output power can be easily achieved through the existing device setup without adding the neutral point linking circuit or auxiliary motor control device that has traditionally been provided to deal with a short circuit fault.

[0021] Preferably, in response to the detection of a short-circuit fault in the first switching element of the first circuit, the motor drive control unit controls currents flowing through coils of respective phases of the three-phase AC motor by means of a switching operation of the second switching element of the second and third circuits.

[0022] In the motor drive device described above, if a short circuit occurs in a switching element forming one of the first to third circuits, the switching elements forming the remaining two normal circuits are caused to perform the switching operation, thereby suppressing an increase in the current passing through the normal circuits, allowing the three-phase AC motor to be driven continuously.

[0023] Preferably, the short-circuit detection unit detects the short-circuited switching element based on the amplitude of currents flowing through coils of respective phases of the three-phase AC motor.

[0024] Further preferably, the short-circuit detection unit determines that the first switching element of the first circuit is short-circuited in response to a current flowing through the coil of the first phase of the three-phase AC motor that is offset, or has an offset, whereby an amplitude of a stable operation of the three-phase AC motor in one direction of a first polarity is exceeded.

[0025] In the motor drive device described above, it is possible to easily identify a single switching element out of a total of six that has failed due to a short circuit. As a result, it is possible to easily select a switching element to be switched and to continue driving the three-phase AC motor.

[0026] Preferably, in response to the detection of a short-circuit fault of the first switching element of each of the first and second circuits, the motor drive control unit controls currents flowing through coils of respective phases of the three-phase AC motor by means of a switching operation of the second switching element of the third circuit.

[0027] Preferably, in response to the detection of a short-circuit fault of the first switching element of the first circuit and the second switching element of the second circuit, the motor drive control unit controls currents flowing through coils of respective phases of the three-phase AC motor by switching the first and second switching elements of the third circuit.

[0028] In the motor drive device described above, if a short circuit occurs in switching elements forming two of the first to third circuits, the switching element forming the remaining normal circuit is switched, thereby suppressing an increase in the current flowing through the normal circuit, allowing the three-phase AC motor to be driven continuously. Consequently, the motor output characteristic, or motor output curve, can be further improved during a short-circuit fault.

[0029] Preferably, the short-circuit detection unit detects the short-circuited switching element based on the amplitude of an intermediate phase voltage of the three-phase AC motor.

[0030] Preferably, the short-circuit detection unit maintains prescribed upper and lower threshold values, which are set in advance based on the amplitude of the interphase voltage of the three-phase AC motor in the stable operating state, detecting the short-circuited switching element based on a magnitude relationship between the amplitude of the interphase voltage of the three-phase AC motor and the upper and lower threshold values.

[0031] In the motor drive device described above, it is possible to easily identify up to six switching elements that have failed due to a short circuit. As a result, it is possible to easily select the switching element to be switched and to continue driving the three-phase AC motor.

[0032] Preferably, the three-phase AC motor is coupled to a drive shaft of a vehicle.

[0033] In the motor drive device described above, even if a switching element forming the drive circuit fails due to a short circuit, it is possible to continuously drive the three-phase AC motor in a simple manner using the existing device design and to ensure the vehicle can be driven in emergency mode. As a result, a highly reliable vehicle can be realized in a simple and cost-effective way.

[0034] According to the present invention, motor safety and output power can be ensured with a simple and inexpensive device design when a malfunction of the inverter is detected. As a result, it is possible to maintain driving performance in emergency mode and achieve higher reliability in a simple and inexpensive manner in the vehicle that is equipped with the motor drive device according to the present invention. Brief description of the drawing Fig. Figure 1 shows a block diagram illustrating a configuration relating to a motor generator control of a vehicle according to an embodiment 1 of the present invention. Fig. Figure 2 shows a schematic circuit diagram of a motor drive device according to embodiment 1 of the present invention. Fig. Figure 3 shows a functional block diagram of the in Fig. 2 control device shown. Fig. Figure 4 shows a diagram illustrating how to identify a branch of the inverter that has failed due to a short circuit. Fig. Figure 5 shows an output signal waveform of a motor current flowing through a short-circuited U-phase. Fig. Figure 6 shows an output signal waveform of a motor current flowing through a multitude of short-circuited phases. Fig. Figure 7 shows a diagram relating to a motor generator drive control. Fig. Figure 8 shows a diagram relating to a motor generator drive control. Fig. Figure 9 shows a timing diagram of control signals for switching branches opposite the upper U-phase branch. Fig. Figure 10 shows output signal waveforms of motor currents flowing through V and W phases when the upper U phase branch is short-circuited. Fig. Figure 11 shows output signal waveforms of motor currents flowing through respective phases, according to the motor drive control of the present invention. Fig. Figure 12 shows a flowchart illustrating the motor drive control according to embodiment 1 of the present invention. Fig. Figure 13 shows a block diagram of a motor drive device according to an unclaimed example. Fig. Figure 14 shows a functional block diagram of the in Fig. Control device shown in 13. Fig. Figure 15 shows a representation for the definition of intermediate phase voltages of the motor generator. Fig. Figure 16 shows output signal waveforms of intermediate phase voltages when an upper W-phase branch is short-circuited. Fig. Figure 17 shows relationships between the signal patterns of intermediate phase voltages of the motor generator, the short-circuited phase and the short-circuited branch. Fig. Figure 18 shows output signal waveforms of intermediate phase voltages of the motor generator when a large number of phases are short-circuited. Fig. Figure 19 shows relationships between the signal patterns of intermediate phase voltages of the motor generator, the short-circuited phase and the short-circuited branch. Fig. Figure 20 shows relationships between the signal patterns of intermediate phase voltages of the motor generator, the short-circuited phase and the short-circuited branch. Fig. Figure 21 shows a representation illustrating the manner of identifying a short-circuited section according to an embodiment 2 of the present invention based on the unclaimed example. Fig. Figure 22 shows a diagram illustrating the drive control of the motor generator. Fig. Figure 23 shows a timing diagram of control signals for switching a lower W-phase branch as a branch opposite the upper U- and V-phase branches. Fig. Figure 24 shows a flowchart illustrating the motor drive control according to an embodiment 3 of the present invention. Preferred embodiments of the invention

[0035] Exemplary embodiments of the present invention are described in detail below with reference to the figures. In the figures, the same reference numerals denote the same or corresponding sections. [Example 1]

[0036] Fig. Figure 1 shows a block diagram illustrating a configuration that demonstrates a motor generator control of a vehicle according to an embodiment 1 of the present invention.

[0037] With reference to Fig. 1 The vehicle comprises a power engine ENG, a battery B, a transaxle assembly 50, a power control unit (PCU) 20 controlling motor generators MG1 and MG2, a drive shaft 52, wheels 54 and a control device 30.

[0038] The power unit ENG generates driving force using combustion energy from fuel, such as gasoline, as a source. Battery B supplies electrical power to the power control unit 20. Battery B consists of a rechargeable secondary battery, typically a nickel hydride battery, a lithium-ion battery, or a high-capacity capacitor.

[0039] The transaxle arrangement 50 comprises a gearbox and an axle as an integrated assembly and includes a power split device PSD, a reduction device RD, a differential gear (DG) 53, the motor generators MG1 and MG2 and a clutch 51.

[0040] The power control unit 20 converts the direct current supplied by battery B into alternating current and outputs it to the motor generator MG2. Alternatively, the power control unit 20 converts alternating current supplied by the motor generators MG1 and MG2 into direct current and outputs it to battery B.

[0041] The power splitting device PSD is able to split the driving force generated by the power machine ENG into one route that transmits the force through the reduction device RD and the DG 53 to the drive shaft 52 for driving the wheels 54, and a route that transmits the force to the motor generator MG1.

[0042] Each of the motor-generators MG1 and MG2 can function as both a generator and an electric motor. However, motor-generator MG1 primarily operates as a generator and is therefore often referred to simply as a "generator." Motor-generator MG2 mainly operates as an electric motor and is consequently sometimes called an "electric motor."

[0043] The motor-generator MG1 is set in rotation by the driving force from the power machine ENG, which is transmitted via the power-splitting device PSD, and generates electrical power. The electrical power generated by the motor-generator MG1 is supplied to the power control unit 20 and used either as electrical power to charge the battery B or as electrical power to drive the motor-generator MG2.

[0044] The motor-generator MG2 is driven to rotate by the alternating current supplied by the power control unit 20. The driving force generated by the motor-generator MG2 is transmitted to the drive shaft 52 via the coupling 51, the reduction device RD, and the DG 53. The coupling 51 is implemented as a hydraulic coupling, an electromagnetic coupling, or the like, transmitting the output torque of the motor-generator MG2 through the reduction device RD and the DG 53 to the wheels 54 with a torque transmission ratio corresponding to a control command from the control unit 30.

[0045] When the motor-generator MG2 is rotated while the wheels 54 are decelerating during regenerative braking, the electromotive force (alternating current) generated in the motor-generator MG2 is supplied to the power control unit 20. In this case, the power control unit 20 converts the supplied alternating current into direct current and outputs it to battery B, thereby charging battery B.

[0046] In Fig. Figure 2 shows a schematic circuit diagram of a motor drive device according to the present embodiment.

[0047] With reference to Fig. 2 comprises a motor drive device 100, the battery B, voltage sensors 10 and 13, system relays SR1 and SR2, capacitors C1 and C2, a boost converter or amplifying converter 12, inverters 14 and 31, current sensors 24 and 28, and the control unit 30. Fig. 2 form the converters 14 and 31, which are provided according to the motor generators MG1 and MG2 respectively, and the boost converter 12, which is provided jointly for the converters 14 and 31, which are in Fig. 1 Power control unit shown 20.

[0048] Motor generators MG1 and MG2 consist of three-phase synchronous AC motors driven by electrical power stored in battery B and the motive power of the power machine ENG. Motor generator MG2 is a drive motor for generating torque to power the vehicle's drive wheels. Motor generator MG1 is a generator motor driven by the power machine ENG, functioning as an electric motor for the power machine ENG and capable of starting the power machine ENG.

[0049] The boost converter 12 includes a choke L1, IGBT elements (IGBT: Insulated Gate Bipolar Transistor or Bipolar transistor with insulated gate) Q1 and Q2, and diodes D1 and D2.

[0050] The choke L1 has one end that is connected to a power line of the battery B, and another end that is connected to a midpoint between the IGBT elements Q1 and Q2, i.e., that is connected between the emitter of the IGBT element Q1 and the collector of the IGBT element Q2.

[0051] The IGBT elements Q1 and Q2 are connected in series between a power supply line VL and a ground line SL. IGBT element Q1 has a collector connected to the power supply line VL, and IGBT element Q2 has an emitter connected to the ground line SL. Furthermore, diodes D1 and D2 are arranged between the collector and emitter of IGBT elements Q1 and Q2, respectively, causing current to flow from the emitter side to the collector side.

[0052] The inverter 14 converts a DC voltage output by the boost converter 12 into a three-phase AC current and supplies this to the motor-generator MG2 to drive the wheels 54. Furthermore, the inverter 14 feeds back power generated by the motor-generator MG2 during regenerative braking to the boost converter 12. At this time, the boost converter 12 is controlled by the control unit 30 to operate as a voltage-reducing circuit.

[0053] The converter 14 comprises a U-phase 15, a V-phase 16 and a W-phase 17. The U-phase 15, the V-phase 16 and the W-phase 17 are provided in parallel between the power supply line VL and the ground line SL.

[0054] The U-phase 15 comprises IGBT elements Q3 and Q4 connected in series. The V-phase 16 comprises IGBT elements Q5 and Q6 connected in series. The W-phase 17 comprises IGBT elements Q7 and Q8 connected in series. Furthermore, diodes D3 to D8 are connected between the collector and emitter of IGBT elements Q3 to Q8, causing current to flow from the emitter side to the collector side.

[0055] The midpoint of each phase is connected to one end of each phase's coils of the respective phases of the motor-generator MG2. Specifically, the motor-generator MG2 is a three-phase permanent magnet motor comprising three coils of the U, V, and W phases, all connected at one end to the midpoint. The U-phase coil has a corresponding other end connected to the midpoint between IGBT elements Q3 and Q4, the V-phase coil has a corresponding other end connected to the midpoint between IGBT elements Q5 and Q6, and the W-phase coil has a corresponding other end connected to the midpoint between IGBT elements Q7 and Q8. It should be noted that the switching elements included in the boost converter 12 and the inverter 14 are not limited to the IGBT elements Q1 to Q8, and may be formed from other power elements, such as MOSFETs.

[0056] The current sensor 24 detects a current MCRT2 (Iu, Iv, Iw) flowing through the motor generator MG2 and provides an output signal to the control device 30.

[0057] Inverter 31 is connected in parallel to inverter 14 and boost converter 12. Inverter 31 converts a DC voltage output by boost converter 12 into a three-phase AC current and outputs this to motor-generator MG1. When it receives the amplified voltage from boost converter 12, inverter 31 drives motor-generator MG1, for example, to start the operation of power machine ENG.

[0058] Furthermore, the inverter 31 feeds back the power generated by the motor-generator MG1 by a torque transmitted from a crankshaft of the engine ENG to the boost converter 12. At this time, the boost converter 12 is controlled by the control device 31 such that it operates as a voltage-reducing circuit.

[0059] Although not shown, the internal structure of inverter 31 is identical to that of inverter 14, and a detailed description thereof will not be repeated here. The current sensor 28 detects a current MCRT1 flowing through the motor generator MG1 and provides an output signal to the control unit 30.

[0060] As stated with reference to Fig. As described in Figure 1, the coupling 51 is arranged between the rotating shaft of the motor generator MG2 and the (not shown) reduction device RD. The coupling 51 connects / disconnects or engages / disengages the rotating shaft of the motor generator MG2 with / from the drive shaft 52 according to a control command from the control unit 30.

[0061] The battery is a rechargeable secondary battery, for example made of nickel hydride or lithium-ion. Instead of battery B, a rechargeable electrical storage device different from the secondary battery, such as a capacitor, can be used. The voltage sensor 10 detects a DC voltage Vb output by battery B and outputs the detected DC voltage Vb to the control unit 30.

[0062] The system relays SR1 and SR2 are switched on / off in response to a signal SE from the control unit 30.

[0063] The capacitor C1 smooths the DC voltage Vb applied by the battery B and outputs the smoothed DC voltage Vb to the boost converter 12.

[0064] The boost converter 12 amplifies the DC voltage Vb applied by battery B and applies the amplified voltage to capacitor C2. More precisely, upon receiving a signal PWMC from the control unit 30, the boost converter 12 amplifies the DC voltage for the duration that the IGBT element Q2 is kept switched on by the signal PWMC, applying the resulting voltage to capacitor C2.

[0065] Furthermore, when the PWMC signal is received from the control unit 30, the boost converter 12 reduces the DC voltage applied by the inverter 14 (or 31) through the capacitor C2, thereby charging the battery B.

[0066] Capacitor C2 smooths the DC voltage from boost converter 12 and applies the smoothed DC voltage to inverters 14 and 31. Voltage sensor 13 detects a voltage across opposite ends of capacitor C2, i.e., the output voltage Vm of boost converter 12 (which corresponds to the input voltage at inverters 14 and 31, the same applies below), and outputs the detected output voltage Vm to control device 30.

[0067] When the DC voltage from capacitor C2 is applied, the inverter 14 converts the DC voltage into an AC voltage based on a signal DRV2 from the control unit 30, thereby driving the motor-generator MG2. Accordingly, the motor-generator MG2 is driven to generate the required torque, indicated by a torque command value TR2. Furthermore, during regenerative braking of a hybrid or electric vehicle that uses the motor drive device 100, the inverter 14 converts the AC voltage generated by the motor-generator MG2 into a DC voltage based on the signal DRV2 from the control unit 30, applying the converted DC voltage to the boost converter 12 via capacitor C2.

[0068] When the DC voltage from capacitor C2 is applied, the inverter 31 converts the DC voltage into an AC voltage based on a signal DRV1 from the control unit 30, thereby driving the motor-generator MG1. Accordingly, the motor-generator MG1 is driven to generate the required torque, indicated by a torque command value TR1. Furthermore, during regenerative braking of a hybrid or electric vehicle that uses the motor drive device 100, the inverter 14 converts the AC voltage generated by the motor-generator MG1 into a DC voltage based on the signal DRV1 from the control unit 30, applying the converted DC voltage to the boost converter 12 via capacitor C2.

[0069] Regenerative braking includes braking with power recovery or power regeneration in response to foot braking by a driver operating the hybrid or electric vehicle, as well as deceleration (or stopping acceleration) during power recovery by releasing the accelerator pedal while driving without the foot brake being applied.

[0070] The control unit 30 receives the torque command values ​​TR1 and TR2 and motor speeds MRN1 and MRN2 from an external ECU (electronic control unit), the output voltage Vm from the voltage sensor 13, the DC voltage Vw from the voltage sensor 10, and motor currents MCRT1 and MCRT2 from a current sensor 24. Then, based on the output voltage Vm, the torque command value TR2, and the motor current MCRT2, the control unit 30 generates a signal DRV2 for switching control of the IGBT elements Q3 to Q8 of the inverter 14 when the inverter 14 drives the motor generator MG2, in a manner described below, outputting the generated signal DRV2 to the inverter 14.

[0071] Furthermore, the control device 30 generates a signal DRV1 for switching control of the IGBT elements Q3 to Q8 of the inverter 31 on the basis of the output voltage Vm, the torque command value TR1 and the motor current MCRT1 when the inverter 31 drives the motor generator MG1, outputting the generated signal DRV1 to the inverter 31.

[0072] Furthermore, the control device 30 generates a PWMC signal for switching control of the IGBT elements Q1 and Q2 of the boost converter 12 in a manner described above, based on the DC voltage Vw, the output voltage Vm, the torque command value TR2 (or TR1) and the motor speed MRN2 (or MRN1) when the inverter 14 (or 31) drives the motor generator MG2 (or MG1), outputting the signal to the boost converter 12.

[0073] Furthermore, the control device 30 generates a signal SE to switch the system relays SR1 and SR2 on / off, outputting the signal to the system relays SR1 and SR2.

[0074] Fig. Figure 3 shows a functional block diagram of the in Fig. 2 control device shown 30.

[0075] With reference to Fig. 3 comprises the control unit 30 as a control unit for the inverter 14, a motor control phase voltage calculation unit 32, an inverter drive signal conversion unit 34, an inverter fault detection unit 36, a short-circuit section detection unit 38, and a power transmission control unit 42. Although not shown, the control unit 30 further comprises devices for controlling the inverter 31 and the boost converter 12.

[0076] The motor control phase voltage calculation unit 32 receives an input voltage Vm from the inverter 14 via the voltage sensor 13, motor currents Iu, Iv, and Iw flowing through the respective phases of the motor generator MG2 from the current sensor 24, and receives the torque command value TR2 from the external ECU. Based on these input signals, the motor control phase voltage calculation unit 32 calculates voltage values ​​(hereinafter also referred to as voltage commands) Vu*, Vv*, and Vw* to be applied to the coils of the respective phases of the motor generator MG2, outputting the calculated results to the inverter drive signal conversion unit 34.

[0077] The inverter drive signal conversion unit 34 generates the signal DRV2, which actually switches each of the IGBT elements Q3 to Q8 of the inverter 14 on / off, based on the voltage commands Vu*, Vv* and Vw* of the coils of the respective phases from the motor control phase voltage calculation unit 32, outputting the generated signal DRV2 to each of the IGBT elements Q3 to Q8.

[0078] Accordingly, each of the IGBT elements Q3 to Q8 is switched-controlled and regulates the current flowing to each phase of the motor-generator MG2, such that the motor-generator MG2 outputs the specified torque. In this way, the motor drive current MCRT2 is controlled and the motor torque is output according to the torque command value TR2.

[0079] The inverter fault detection unit 36 ​​detects a malfunction of the inverter 14 while a drive of the motor-generator MG2 is being controlled. Fault detection of the inverter 14 is performed, for example, based on a reading from a current sensor integrated into each of the IGBT elements Q3 to Q8 of the inverter 14. In response to the detection of excessive current in any of the values ​​measured by the current sensors, the inverter fault detection unit 36 ​​determines a fault caused by a short circuit of an IGBT element Q3 to Q8, generating a FINV signal representing the determined result. The inverter fault detection unit 36 ​​outputs the generated FINV signal to the short-circuit detection unit 38 and the inverter drive signal conversion unit 34.

[0080] Fault detection of the inverter 14 can be performed based on the value detected by a temperature sensor located in each of the IGBT elements Q3 to Q8. In this case, in response to the detection of an IGBT element overheating, indicated by one of the values ​​detected by the temperature sensors reaching a high temperature, a fault caused by a short circuit of IGBT elements Q3 to Q8 is determined.

[0081] When the FINV signal is received from the inverter fault detection unit 36, the short-circuit section detection unit 38 identifies the IGBT in which the short circuit occurred, based on the motor currents Iu, Iv, and Iw from the current sensor 24. The short-circuit section detection unit 38 identifies the phase in which the short circuit occurred and the branch (upper branch or lower branch) in which the short circuit occurred in that phase, according to a procedure described below. The short-circuit section detection unit 38 then generates a signal DE indicating the identified short-circuited section and outputs the signal to the power transmission control unit 42 and the inverter drive signal conversion unit 34.

[0082] When the signal DE is received by the short-circuit detection unit 38, the power transmission control unit 42 disengages the clutch 51 to cut off power transmission between the motor-generator MG2 and the drive shaft 52. This prevents the motor-generator MG2 from receiving power transmitted by the wheels 54, because if the power were transmitted, it would rotate at high speed, generate a high back electromotive force, and increase the motor drive current. To this end, the power transmission control unit 42 intentionally disengages the clutch 51, thereby immediately reducing the motor speed.

[0083] As soon as the engine speed MRN2 decreases to a prescribed value or less, the power transmission control unit 42 re-engages the clutch 51, as described below. The vehicle thus enters an emergency operating mode in which the motor generator MG2 serves as a drive source.

[0084] Here, after the fault in the inverter 14 is detected, the inverter drive signal conversion unit 34 generates the signal DRV2 for switching control of the IGBT elements Q3 to Q8 of the inverter 14 based on the voltage commands Vu*, Vv* and Vw* of the coils of the respective phases from the motor control phase voltage calculation unit 32 and on the basis of the signal DE from the short-circuit section detection unit 38, outputting the generated signal DRV2 to the inverter 14. As a result, even after a fault caused by a short circuit, the inverter 14 can continuously control a drive of the motor generator MG2, thus enabling the vehicle to operate safely in emergency mode.

[0085] As described below, when inverter 14 fails due to a short circuit, the DRV2 signal is generated to initiate switching of a phase different from the phase to which the failed branch belongs. This prevents excessive current from flowing to the IGBT element of the branch that failed due to the short circuit. This allows the vehicle to be moved to a safe location while preventing inverter 14 from overheating.

[0086] As described above, the first feature of the motor drive device 100 according to the present invention is that, in response to a detection of a fault in the inverter 14, the branch that has failed due to the short circuit is identified from the three phases 15 to 17 that form the inverter 14.

[0087] The second feature of the motor drive device 100 is that, after the detection of the fault of the inverter 14, the motor generator MG2 is continuously driven by a switching control of a phase that is different from the phase to which the short-circuited branch belongs.

[0088] Due to these properties, the vehicle to which the motor drive device 100 is attached operates safely in emergency mode, while overheating of the inverter 14 is prevented. The first and second properties are described in more detail below.

[0089] First, the method for identifying the branch that has failed due to the short circuit of the inverter 14 is described, which is the first feature of the present invention.

[0090] Fig. Figure 4 shows a representation relating to the procedure for identifying the short-circuited branch of the converter 14.

[0091] With reference to Fig. 4 Let it be assumed that the upper branch of the U-phase 15 (i.e. the IGBT element Q3) among the three phases 15 to 17 that form the converter 14 has failed due to the short circuit.

[0092] At this time, in response to the detection of an excessive current by the current sensor provided in the IGBT element Q3, the inverter fault detection unit 36 ​​outputs the FINV signal to the inverter drive signal conversion unit 34 and stops the operation of the inverter 14. However, at this time the motor generator MG2 continues to rotate, as it receives rotations from the wheels 54. Consequently, a counter-electromotive force is generated in the motor generator MG2 according to the rotational speed. Thus, an excessive short-circuit current would be introduced to the short-circuited U-phase 15 in the inverter 14.

[0093] More precisely, when the power supply line VL of the inverter 14 is routed to the midpoint of the U-phase 15 due to the short circuit of the IGBT element Q3, the U-phase motor current Iu flows via a route from the power supply line VL through the midpoint of the U-phase 15 to the U-phase coil of the motor generator MG. At the midpoint of the motor generator MG2, the U-phase motor current Iu branches into a first route Rt1 from the V-phase coil through the midpoint of the V-phase 16 and the diode D5 to the power supply line VL, and a second route Rt2 from the W-phase coil through the midpoint of the W-phase coil 16 and the diode D17 to the power supply line VL.

[0094] Specifically, in the three phases 15 to 17, the short-circuited upper branch of the U-phase 15 and the diodes D5 and D7 of the V- and W-phases 16 and 17 form a closed circuit, with the motor-generator MG2 interposed. In the closed circuit, the relationship between the 3-phase motor currents Iu, Iv, and Iw shown in equation (1) below holds true: |Iu|=|Iv|+|Iw|

[0095] Accordingly, an excessive short-circuit current, approximately twice the current value in stable operation, may flow to the short-circuited U-phase 15, as shown in Fig. 5 is shown.

[0096] Fig. Figure 5 shows an output signal waveform of the motor current Iu flowing through the short-circuited U-phase 15.

[0097] How it looks Fig. As can be seen in Figure 5, in stable operation the motor current Iu exhibits an AC signal waveform with constant amplitude (amplitude A). It should be noted that the motor currents Iv and Iw, which are not shown, also exhibit an AC signal waveform with an amplitude A, each with a phase difference of +120° or -120° in relation to the motor current Iu.

[0098] In contrast, after the short-circuit fault occurs, the motor current Iu becomes the sum of the motor currents Iv and Iw, exhibiting, as shown in the figure, a current waveform that is shifted or offset relative to the higher current. The absolute value of this shift or offset at this time exceeds the amplitude A during stable operation.

[0099] In light of the above description, the present embodiment is configured such that for each of the motor currents Iu, Iv, and Iw detected by the current sensor 24, the offset value is detected, and a determination is made as to whether the absolute value of the detected offset value exceeds the amplitude A in stable operation. In this configuration, a short-circuit fault of the phase corresponding to the motor current can be detected in response to a determination that the absolute value of the offset of one of the motor currents Iu, Iv, and Iw exceeds the amplitude A.

[0100] After the phase in which the short-circuit fault occurred has been determined based on the magnitude relationship between the offset value and the amplitude A, the short-circuited branch is identified based on the polarity of the offset value.

[0101] More precisely, the direction of the motor current flowing from each of phases 15 to 17 of the inverter 14 to the motor-generator MG2 is represented as a positive direction, and the direction of the current flowing from the motor-generator MG2 to each of phases 15 to 17 is represented as a negative direction. If the current values ​​of the motor currents Iu, Iv, and Iw increase in the positive direction, i.e., if the offset value has a positive polarity, it is determined that the upper branch has failed due to a short circuit. Conversely, if the current values ​​of the motor currents Iu, Iv, and Iw increase in the negative direction, i.e., if the offset value has a negative polarity, it is determined that the lower branch has failed due to a short circuit.

[0102] As described above, by detecting the motor currents Iu, Iv and Iw flowing through the coils of the respective phases by the current sensor 24 and by detecting the absolute value and polarity of the offset value with respect to the current signal waveform in the stable operation of the detected value, it is possible to identify the branch in which the short-circuit fault has occurred.

[0103] The short-circuit fault in the inverter 14 comprises a pattern according to Fig. 4, in which only one of the three phases has failed due to the short circuit, and additionally patterns in which two or three phases fail due to a short circuit. However, when two or three phases fail, the absolute value of the offset of the motor current detected by the current sensor 24 is different from that of a single-phase short-circuit fault, which is in Fig. Figure 5 shows that the amplitude A is relatively small and smaller than the amplitude A in stable operation. Consequently, this can be distinguished from the short-circuit fault of one phase.

[0104] Next, the drive control of the motor generator MG2 after the detection of the inverter fault is described as the second feature of the present invention.

[0105] The Fig. 7 and Fig. Figure 8 illustrates a drive control system for the motor generator MG2. Similar to Fig. 4 show the Fig. 7 and Fig. 8, that the upper branch of U-phase 15 (IGBT element Q3) has failed due to the short circuit.

[0106] With reference to the Fig. 7 and Fig. 8, if the upper branch of the U-phase 15 has failed due to the short circuit, the motor generator MG is driven by initiating switching operations of the lower branch of the V-phase 16 (IGBT element Q6) and the lower branch of the W-phase 17 (IGBT element Q8).

[0107] The lower branch of the V-phase 16 and the lower branch of the W-phase 17, which are switch-controlled, belong to normal phases that are different from the short-circuited U-phase 15, wherein these branches are opposite to the upper branch of the U-phase 15 with respect to a positional relationship, with the midpoints of the respective phases 15 to 17 being positioned between them. According to the present invention, a branch belonging to a phase that is different from the short-circuited phase and opposite to the short-circuited branch with respect to its positional relationship, wherein the midpoint of each of the phases 15 to 17 is positioned between them, is also simply referred to as an "opposite branch".

[0108] It becomes specific how it is in Fig. As shown in Figure 7, when only the lower branch of the V-phase 16 (IGBT element Q6) is switched on, the motor current Iu is routed from route Rt1, which extends from the V-phase coil of the motor generator MG through diode D5 to the power supply line VL, to route Rt10, which extends from the V-phase coil through the IGBT element Q6 to the ground line GL. Consequently, in the closed circuit formed by the upper branch of the U-phase 15 and the diodes D5 and D7 of the V- and W-phases 16 and 17, only the motor current Iw passing through diode D7 is returned. As a result, the motor current Iu is reduced.

[0109] Similarly, with reference to Fig. 8. When only the lower branch of the W-phase 17 (IGBT element Q8) is switched on, the motor current Iu is routed from route Rt2, which extends from the W-phase coil of the motor generator MG2 through diode D7 to the power supply line VL, to route Rt12, which extends from the W-phase coil through the IGBT element Q8 to the ground line GL. Consequently, in the closed circuit formed by the upper branch of the U-phase 15 and the diodes D5 and D7 of the V- and W-phases 16 and 17, only the motor current Iv passing through diode D5 is returned. As a result, the motor current Iu is reduced.

[0110] Fig. Figure 9 shows a timing diagram of a control signal to initiate a switching operation of the lower branch of the V-phase 16 and the lower branch of the W-phase 17 as branches opposite to the upper branch of the U-phase 15.

[0111] As it is in Fig. As shown in Figure 9, the lower branch of the V-phase 16 and the lower branch of the W-phase 17 are switched on and off with a prescribed duty cycle. By switching the lower branch of the V-phase 17 and the lower branch of the W-phase 16 on and off in this manner, a voltage waveform is generated at the midpoint of each of the phases 16 and 17. This waveform alternates between the power supply voltage and the ground voltage in a square wave with a prescribed duty cycle. As a result, a continuous alternating current flows through the motor generator MG2.

[0112] As described above, it becomes possible to continuously drive the motor-generator MG2 by switching branches opposite to the short-circuited branch, while preventing an increase in the current flowing through the short-circuited phase. As a result, the vehicle equipped with the motor drive device can safely travel to a safe location in emergency operating mode, using only the existing device setup, without the need for a new device to continuously drive the motor-generator MG2.

[0113] Once the vehicle has entered emergency driving mode, it is necessary to limit the power consumption of the motor-generator MG2 to ensure a sufficient driving distance. Specifically, the control unit 30 controls the inverter 14 such that the motor-generator MG2 is driven at a low torque and low speed. In doing so, the inverter drive signal conversion unit 34 of the control unit 30 sets a carrier frequency FC based on the torque and motor speed of the motor-generator MG2, which is necessary to ensure the vehicle can travel to the safe location.

[0114] Fig. Figure 10 shows output signal waveforms of the motor currents Iv and Iw, which flow through the V-phase 16 and the W-phase 17 respectively, when the upper branch of the U-phase 15 has failed due to the short circuit.

[0115] Fig. Figure 11 shows output signal waveforms of the motor currents Iu, Iv and Iw, which flow through respective phases 15 to 17, according to the motor drive control of the present invention. Fig. 11 results from a switching control of the lower branch of the V-phase 16 and the lower branch of the W-phase 17 as the opposite branches when the upper branch of the U-phase 16 has failed due to the short circuit, as is the case with reference to the Fig. 6 and Fig. 7 is described.

[0116] If the Fig. 10 and Fig. Comparing figures 11, it is evident that the offset caused by the short-circuit fault of the upper branch in the motor current Iu passing through the U-phase 15 has a reduced absolute value when the opposite branches are switched. Accordingly, it becomes possible to drive the motor-generator MG2 while preventing an increase in the current passing through the short-circuited phase.

[0117] Fig. Figure 12 shows a flowchart representing a motor drive control according to embodiment 1 of the present invention.

[0118] With reference to Fig. 12. The inverter fault detection unit 36 ​​detects a malfunction of the inverter 14 based on a value detected by the current sensor provided in each of the IGBT elements Q3 to Q8 while a drive of the motor generator MG2 is being controlled (step S01). At this time, in response to the detection of excessive current in one of the values ​​detected by the current sensors, the inverter fault detection unit 36 ​​determines a fault caused by a short circuit in one of the IGBT elements Q3 to Q8, generating a FINV signal representing the determination result. The generated FINV signal is output to the short-circuit section detection unit 38 and the inverter drive signal conversion unit 34.

[0119] When the FINV signal is received, the inverter drive signal conversion unit 34 stops once a generation of the DRV signal for a switching control of each of the IGBT elements Q3 to Q8 of the inverter 14 in order to protect the IGBT elements from excessive current, thereby placing the inverter 14 in a floating state (step S02).

[0120] Next, when the FINV signal is received, the short-circuit section detection unit 38 identifies the IGBT element where the short-circuit fault occurred, based on the motor currents Iu, Iv, and Iw from the current sensor 24, according to the procedure described above (step S03). After identifying the phase where the short-circuit fault occurred and the branch (either the upper branch or the lower branch) that is short-circuited in that phase, the short-circuit section detection unit 38 generates a signal DE indicating the identified fault section and outputs the signal to the inverter drive signal conversion unit 34 and the power transmission control unit 42.

[0121] When the signal DE is received by the short-circuit detection unit 38, the power transmission control unit 42 disengages the clutch 51, thus cutting off the power transmission between the motor generator MG2 and the drive shaft 52 (step S04). Consequently, the motor speed decreases rapidly, thereby preventing the generation of a large back EMF in the motor generator MG2. It should be noted that if the motor speed is less than or equal to a specified speed, the clutch 51 may not disengage.

[0122] Furthermore, based on the signal DE from the short-circuit detection unit 38, the power transmission control unit 42 and the inverter drive signal conversion unit 34 determine whether only one phase has failed due to the short circuit (step S05). If it is determined that only one phase has failed due to the short circuit, the power transmission control unit 42 waits until the motor speed MRN2 reaches a prescribed value MRN_std or less (step S06), at which point it re-engages the clutch 51 (step S07). The vehicle then enters emergency operating mode, in which the motor generator MG2 serves as the power source.

[0123] Furthermore, if the short-circuit section detection unit 38 determines from the signal DE that the short-circuit fault has occurred in only one phase, the inverter drive signal conversion unit 34 changes the carrier frequency of a carrier signal from the carrier frequency for normal operation to a carrier frequency in the event of an inverter fault (step S08).

[0124] Furthermore, an alarm light is switched on in the driver's compartment to notify the user that the vehicle has entered emergency driving mode (step S09).

[0125] Based on the voltage commands Vu*, Vv* and Vw* of the respective phases received by the motor control phase voltage calculation unit 32 and the carrier signal with the modified carrier frequency fc, the inverter drive signal conversion unit 34 generates a signal DRV2 for switching control of the branches opposite to the short-circuited branch, outputting the generated signal DRV2 to the inverter 14 (step S10).

[0126] As a result, even after a short circuit fault occurs, the inverter continuously controls a drive of the motor generator MG2 and the vehicle can safely drive in emergency mode (step S11).

[0127] If in step S05 it is determined that a large number of phases have failed due to a short circuit, coupling of the clutch 51 by the power transmission control unit 42 does not take place, and the general vehicle stop control starts (step S12).

[0128] As described above, according to embodiment 1 of the present invention, in response to the detection of an inverter fault, the short-circuited branch is identified, and branches opposite to the identified failed branch are switched, thereby continuing to drive the motor-generator. Consequently, it becomes possible to ensure the vehicle can be driven in emergency mode while preventing excessive current flow to the failed branch. As a result, both motor safety and power output upon detection of an inverter fault can be achieved with a simple and inexpensive device design. [Example not covered by the invention]

[0129] With regard to the method for identifying the short-circuited branch of the converter 14 as the first feature of the present invention, unlike the method for identification based on the motor currents Iu, Iv and Iw of the converter 14, identification based on an intermediate phase voltage of the motor generator, as described below, is also possible.

[0130] Fig. Figure 13 shows a schematic block diagram of a motor drive device according to an example that is not encompassed by the invention and is not claimed in the patent claims (hereinafter referred to as the "unclaimed example"). The motor drive device 100A corresponds to the motor drive device 100 according to Fig. 1, wherein it additionally includes voltage sensors 18 to 20 for detecting the intermediate phase voltage of the motor generator 2 and has a control device 30A instead of the control device 30. Consequently, detailed descriptions of the sections corresponding to those according to Fig. 1 are identical, not repeated.

[0131] With reference to Fig. 13. Voltage sensor 18 detects an intermediate phase voltage Vvu between the U-phase and the V-phase of the motor generator MG2, outputting the detected intermediate phase voltage Vvu to the control unit 30A. Voltage sensor 19 detects an intermediate phase voltage Vwv between the V-phase and the W-phase of the motor generator MG2, outputting the detected intermediate phase voltage Vwv to the control unit 30A. Voltage sensor 20 detects an intermediate phase voltage Vuw between the U-phase and the W-phase of the motor generator MG2, outputting the detected intermediate phase voltage Vuw to the control unit 30A.

[0132] Fig. Figure 14 shows a functional block diagram of the in Fig. Control unit 30A shown in Figure 13. The control unit 30A according to Fig. 13 corresponds to the one in Fig. 2 Control device 30 shown, wherein the short-circuit section detection unit 38 is replaced by a short-circuit section detection unit 38A. Consequently, detailed descriptions of the sections corresponding to those according to Fig. 2 are identical, not repeated.

[0133] With reference to Fig. 4. When the signal FINV is received from the inverter fault detection unit 36, the short-circuit section detection unit 38A identifies, by the procedure described below, the phase in which the short-circuit fault occurred and the short-circuited branch in that phase (either the upper branch or the lower branch) based on the intermediate phase voltages Vvu, Vwv, and Vuw of the motor generator MG2, which are input from the voltage sensors 18 and 20 described above. The short-circuit section detection unit 38A then generates a signal DE indicating the identified short-circuit section and outputs this signal to the inverter drive signal conversion unit 34 and the power transmission control unit 42.

[0134] First, the intermediate phase voltage is defined, which is used in the procedure for identifying the short-circuit section according to the unstressed example.

[0135] Fig. Figure 15 shows a diagram relating to the definition of the intermediate phase voltages of the motor generator MG2.

[0136] With reference to Fig. 15. The interphase voltage Vvu between the U-phase and the V-phase of the motor-generator MG2 is considered positive if the V-phase has a higher potential than the U-phase, and negative if the U-phase has a higher potential than the V-phase. The interphase voltage Vwv between the V-phase and the W-phase of the motor-generator MG2 is considered positive if the W-phase has a higher potential than the V-phase, and negative if the V-phase has a higher potential than the W-phase. The interphase voltage Vuw between the W-phase and the U-phase of the motor-generator MG2 is considered positive if the W-phase has a higher potential than the U-phase, and negative if the U-phase has a higher potential than the W-phase.

[0137] Consequently, the voltage sensors output 18 to 20 positive or negative intermediate phase voltages Vvu, Vwv and Vuw corresponding to the potentials of the respective two phases.

[0138] Fig. Figure 16 shows output signal waveforms of the respective intermediate phase voltages Vvu, Vwv and Vuw when, as an example, the upper branch of the W-phase 17 has failed due to a short circuit.

[0139] With reference to Fig. Figure 16 shows the respective intermediate phase voltages Vvu, Vwv and Vuw alternating voltage signal waveforms with constant amplitude in stable operation.

[0140] After the point at which the upper branch of the W-phase 17 is short-circuited, the interphase voltage Vvu between the U-phase and the V-phase, excluding the short-circuited phases, exhibits the signal waveform shown in [1] in the figure. Specifically, the signal waveform amplitude increases in the positive and negative directions, exceeding preset upper and lower threshold values.

[0141] The interphase voltage Vwv between the V-phase and the W-phase, which corresponds to the short-circuited phase, exhibits the signal waveform shown in [2] in the figure. Specifically, the signal waveform amplitude increases only in the positive direction. This is because the potential of the W-phase 17 increases due to the increasing current flowing through the short-circuited W-phase 17.

[0142] The interphase voltage Vuw between the W-phase, corresponding to the short-circuited phase 17, and the U-phase exhibits the signal waveform shown in [3] in the figure. Specifically, the signal waveform amplitude increases only in the negative direction. This is because the potential of the W-phase 17 increases, as the current passing through the short-circuited W-phase increases, as in the case of the signal waveform shown above [2].

[0143] As described above, if one of the U, V, and W phases fails due to a short circuit, the intermediate phase voltage Vvu, Vwv, and Vuw of the motor generator MG2 will exhibit an amplitude between the two phases excluding the failed phase that is increased in both the positive and negative directions. Conversely, the intermediate phase voltage between two phases, one of which includes the failed phase 17, will have an amplitude that is increased either in the positive or negative direction, depending on the short-circuited phase. Fig. Figure 17 shows relationships between the signal patterns of the intermediate phase voltages Vvu, Vwv, and Vuw of the motor generator MG2, the short-circuited phase, and the short-circuited branch. As can be seen from Fig. As can be seen in Figure 17, the combination of voltage signal patterns [1] to [3] differs from branch to branch and from phase to phase that have failed due to the short circuit.

[0144] Consequently, the unclaimed example is set up to determine whether the amplitude of the intermediate phase voltages Vvu, Vwv, and Vuw, detected by voltage sensors 18 to 20, exceeds the upper and lower thresholds. With this configuration, if the amplitude of any one of the intermediate phase voltages Vvu, Vwv, or Vuw exceeds the upper and lower thresholds, and the amplitude of the remaining two intermediate phase voltages also exceeds either the upper or lower threshold, it is possible to identify the short-circuited phase and the short-circuited branch of that phase.

[0145] In fact, the short-circuit section detection unit 38 of the control device 30A stores in advance the relationships between the signal waveform patterns of the intermediate phase voltages Vvu, Vwv and Vuw of the motor generator MG2 and the short-circuited phase and the short-circuited branch as described in Fig. As shown in 17, in a memory area, by comparing the amplitude of the intermediate phase voltages Vvu, Vwv and Vuw from the voltage sensors 18 to 20 with the upper and lower threshold values ​​and by looking up the values ​​in Fig. The relationship shown in Figure 17 allows the short-circuited phase and the short-circuited branch to be identified.

[0146] Furthermore, according to the unclaimed example, the short-circuited phases and branches can be identified on the basis of the amplitude of the intermediate phase voltages Vvu, Vwv and Vuw of the motor generator MG2 not only when one phase fails, as described above, but also when two or three phases fail due to a short circuit.

[0147] Specifically, when a large number of phases are short-circuited, the interphase voltages Vvu, Vwv and Vuw of the motor generator MG2 exhibit one of a set of six patterns, i.e., the voltage signal waveform patterns [1] to [3], which are described in Fig. 16 are shown, and the voltage signal waveform patterns [4] to [6], which are shown in Fig. 18 are shown.

[0148] Fig. Figure 18 shows output signal waveforms of the intermediate phase voltages Vvu, Vwv and Vuw when a large number of phases are short-circuited.

[0149] With reference to Fig. Figure 18 shows the voltage signal waveform pattern [4] in a stable operating state, an alternating voltage signal waveform with constant amplitude, where the signal waveform amplitude gradually decreases after the point at which a plurality of phases are short-circuited.

[0150] In the stable operating state, the voltage signal waveform [5] shows an AC signal waveform with constant amplitude, whereby the signal amplitude increases only in the positive direction after the point at which a multitude of phases are short-circuited. The increased amplitude is smaller than the upper threshold value.

[0151] In the stable operating state, the voltage signal waveform [6] shows an AC signal waveform with constant amplitude, whereby the signal amplitude only increases in the negative direction after the point at which a large number of phases are short-circuited. The increased amplitude is smaller than the lower threshold value.

[0152] If two of the three phases are short-circuited, the intermediate phase voltages Vvu, Vwv and Vuw of the motor generator MG2 each exhibit one of the voltage signal waveform patterns [1] to [6] according to the Fig. Figures 16 to 18 show that the combination of voltage signal waveforms differs depending on the short-circuited phase. Fig. 19 is shown.

[0153] For example, with reference to Fig. 19, when the upper branch of the W-phase 17 and the upper branch of the V-phase 16 are short-circuited, the interphase voltage Vvu between the V-phase (the short-circuited phase) and the U-phase (which is not short-circuited) exhibits the voltage waveform pattern [2], with the amplitude exceeding the upper threshold. Furthermore, the interphase voltage Vwu between the W-phase (the short-circuited phase) and the U-phase (which is not short-circuited) exhibits the voltage waveform pattern [3], with the amplitude exceeding the lower threshold. In contrast, the interphase voltage Vwv between the V-phase and the W-phase (the short-circuited phases) exhibits the voltage waveform pattern [4], with the amplitude gradually decreasing.

[0154] If all three phases fail due to a short circuit, the intermediate phase voltages Vvu, Vwv, and Vuw will reach a point where they are in Fig. The 20 combinations of voltage signal waveforms shown are determined depending on the short-circuited branch in each phase.

[0155] With reference to Fig. 20 Assume that the upper branches of the U, V, and W phases are all short-circuited. This results in the U, V, and W phases of the motor generator MG2 having essentially the same potential, and consequently, the intermediate phase voltages Vvu, Vwv, and Vuw exhibit the voltage signal pattern [4], with the amplitude gradually decreasing.

[0156] From the above described, it is possible by a provision which of the in the Fig. 18 and Fig. Since the 20 combinations shown correspond to the signal pattern of the intermediate phase voltages Vvu, Vwv and Vuw of the motor generator MG2, it is possible to identify a large number of short-circuited phases and the short-circuited branch of each phase.

[0157] In fact, the short-circuit section detection unit 38A compares the amplitude of the intermediate-phase voltages Vvu, Vwv, and Vuw, input by the voltage sensors 18 to 20, with the upper and lower threshold values, thereby deriving the combination of voltage signal waveform patterns corresponding to the result of the comparison from the Fig. 18 and Fig. 20 is selected so that the short-circuited phase and branch can be identified. [Example 2]

[0158] Fig. Figure 21 illustrates the procedure for identifying the short-circuit section according to an embodiment 2 based on the unclaimed example.

[0159] With reference to Fig. Voltage sensors 21 to 26 are provided for each of the IGBT elements Q3 to Q8, which form the U-phase 15, the V-phase 16 and the W-phase 17, for detecting collector-emitter voltages VCE3 to VCE8. The voltage sensors 21 to 26 each detect the collector-emitter voltages VCE3 to VCE8 of the corresponding IGBT elements Q3 to Q8 and output the voltages to the short-circuit section identification unit 38A in the control device 30, which is not shown.

[0160] When the collector-emitter voltages VCE3 to VCE8 are received by the voltage sensors 21 to 26, the short-circuit section identification unit 38A determines whether each of the collector-emitter voltages VCE3 to VCE8 is equal to or higher than a prescribed threshold. In response to a determination that one of the collector-emitter voltages VCE3 to VCE8 (for example, VCE3) remains continuously below the threshold voltage for a prescribed period, the short-circuit section identification unit 38A determines that the IGBT element (i.e., IGBT element Q3) corresponding to the collector-emitter voltage is short-circuited. Consequently, even if a multitude of phases are short-circuited, it is possible to identify the short-circuited phases and branches using the short-circuit section identification procedure as modified.

[0161] The method for identifying the short-circuit section, described in the unclaimed example and in embodiment 2, is actually implemented as a replacement for a “detection of a short-circuit section by a motor current” in step S30 in the motor drive control sequence described in Fig. Figure 12 shows that if a short circuit of only one phase is determined by the identification method according to embodiment 2 of the present invention, the motor drive control according to step S06 and subsequent steps takes place, so that the vehicle can safely drive in emergency mode.

[0162] As described above, according to the unclaimed example and embodiment 2 of the present invention, when a converter fault is detected, the short-circuited branch can be identified more precisely. [Example 3]

[0163] The method for identifying the short-circuited section according to the unclaimed example described above and embodiment 2 makes it possible to identify the short-circuited branch, which is present not only in a single phase but also in each of the plurality of phases. Consequently, even if two of the three phases are short-circuited, it is possible to continuously drive the motor-generator MG2 while protecting the inverter 14 from overheating by initiating switching operation of the remaining normal phase in a manner described below.

[0164] The following describes the drive control of the motor generator MG2 after the detection of a short circuit between two phases.

[0165] Fig. Figure 22 illustrates the drive control of the motor generator MG2.

[0166] In Fig. 22 Assume that the upper branch of the U-phase 15 (the IGBT element Q3) and the upper branch of the V-phase 16 (the IGBT element Q5) are short-circuited.

[0167] With reference to Fig. 22, when the upper branches of the U-phase 15 and the V-phase 16 are both short-circuited, the lower branch of the W-phase 17 (the IGBT element Q8), which is the opposite branch to the short-circuited branches, is switched to drive the motor generator MG2.

[0168] More precisely, this occurs when only the lower branch of W-phase 17 (the IGBT element Q8) is switched on, as described in Fig. As shown in Figure 22, the motor current Iu is routed from route Rt3, which extends from the W-phase coil of the motor generator MG2 through diode D7 to the power supply line VL, to route Rt13, which extends from the W-phase coil through the IGBT element Q8 to the ground line GL. Similarly, the motor current Iv is routed from route Rt4, which extends from the W-phase coil of the motor generator MG2 through diode D7 to the power supply line VL, to route Rt13, which extends from the W-phase coil through the IGBT element Q8 to the ground line GL.

[0169] Consequently, in the closed circuit formed between the upper branches of the U-phase 15 and the V-phase 16 and the diode D7 of the W-phase 17, the motor current Iw passing through the diode D7 is reduced.

[0170] Fig. Figure 23 shows a timing diagram of a control signal for realizing the switching operation of the lower branch of the W-phase 17 as the branch opposite the upper branches of the U-phase 15 and the V-phase 16.

[0171] As it is in Fig. As shown in Figure 23, the lower branch of W-phase 17 is switched on and off with a prescribed duty cycle. When the lower branch of W-phase 17 is switched on and off in this manner, a voltage signal with square waves, switching between the power supply voltage and the ground voltage with a prescribed duty cycle, is generated at the midpoint of W-phase 17. As a result, a continuous alternating current flows through the motor generator MG2.

[0172] As described above, when the motor-generator MG2 is driven by the switching operation of the branch opposite the short-circuited branch(es), it becomes possible to drive the motor-generator MG2 continuously while preventing an increase in the current flowing through the normal phase. Consequently, the vehicle to which the drive device is attached can operate safely in emergency mode, while the inverter 14 is protected against overheating.

[0173] After the vehicle has entered emergency running mode, the control unit 30 controls the inverter 14 to ensure a sufficient driving distance by driving the motor generator MG2 with a low torque and a low speed.

[0174] At this time, when the signal DE is received by the short-circuit detection unit 38A, the inverter drive signal conversion unit 34 of the control device 30 changes the carrier frequency from a carrier frequency f1 for normal operation to a carrier frequency f2 in the event of inverter fault detection. The inverter drive signal conversion unit 34 then generates the signal DRV2 for switching control of the opposite branch, as shown in Fig. Figure 23 shows the use of the carrier signal whose carrier frequency has been changed to f2, outputting the generated signal DRV2 to the IGBT element of the opposite branch.

[0175] In the Fig. 22 and Fig. In section 23, an example is described in which the upper branch of U-phase 15 (the IGBT element Q3) and the upper branch of V-phase 16 (the IGBT element Q5) are short-circuited. As another example, when the upper branch of U-phase 15 (the IGBT element Q3) and the lower branch of V-phase 16 (the IGBT element Q6) are short-circuited, the lower branch of W-phase 17 (the IGBT element Q8) is connected as the branch opposite to the upper branch of U-phase 15, and the upper branch of W-phase 17 (the IGBT element Q7) is connected as the branch opposite to the lower branch of V-phase 16 (the IGBT element Q6) to drive the motor-generator MG2.

[0176] Fig. Figure 24 shows a flowchart illustrating the motor drive control according to embodiment 3 of the present invention. The diagram in Fig. The flowchart shown in section 24 corresponds to the flowchart according to Fig. 12, wherein the vehicle stop control (step S12), which is executed in response to a determination in step S05 that more than one phase is short-circuited, is replaced by steps S051 to S12 for the execution of the motor drive control.

[0177] Specifically determine with reference to Fig.24. If the short-circuit detection unit 38A determines by signal DE that more than one phase is short-circuited (No in step S05), the power transmission control unit 42 and the inverter drive signal conversion unit 34 determine whether the number of short-circuited phases is two (step S051). If it is determined that two phases are short-circuited, the power transmission control unit 42 waits for the motor speed MRN2 to reach a prescribed value MRN_std or less (step S06), at which point it re-couples the clutch 51 (step S07). Thus, the vehicle enters emergency running mode, using the motor generator MG2 as a drive power source.

[0178] In response to the determination that only two phases are short-circuited, the inverter signal conversion unit 34 changes the carrier frequency of the carrier signal from the carrier frequency for normal operation to the carrier frequency for the time of inverter fault detection (step S08).

[0179] Furthermore, an alarm light is switched on in the driver's compartment to notify the user that the vehicle has entered emergency running mode (step S09).

[0180] Based on the voltage commands Vu*, Vv* and Vw* of the coils of the respective phases from the motor control phase voltage calculation unit 32 and the carrier signal with the carrier frequency changed to fc, the inverter drive signal conversion unit 34 generates a signal DRV2 for a switching control of the branch of the normal phase that is opposite to the short-circuited branches, outputting the generated signal DRV2 to the inverter 14 (step S10).

[0181] As a result, even after two phases of the inverter 14 are short-circuited, the drive control of the motor generator MG2 continues, and the vehicle drives safely in emergency mode (step S11).

[0182] If in step S051 it is determined that all three phases are short-circuited, coupling of the clutch 51 by the power transmission control unit 42 is not performed, and the general vehicle stop control starts (step S12).

[0183] As described above, according to embodiment 3 of the present invention, even if a short-circuit fault of a plurality of phases is identified, the branch opposite the identified short-circuited branches is switched on, as long as at least one phase is normal, in order to continue driving the motor-generator. Thus, the vehicle can operate safely in emergency mode while preventing excessive current flow to the normal phase. As a result, motor safety and output power can be ensured upon detection of a converter malfunction with a simple and inexpensive device design.

[0184] Although the present invention has been described and illustrated in detail, it is evident that this serves only for illustration and as an example and is not to be understood as a limitation, the scope of the present invention being interpreted by the terms of the attached claims. Commercial applicability

[0185] The present invention can be applied to a motor drive device for driving a motor that is coupled to a drive shaft of a vehicle.

Claims

[1] Motor drive device with a three-phase AC motor (MG2); a power source (B) capable of supplying a direct current to the first and second power supply lines; a power conversion device (14) that performs a power conversion between the first and second power lines and the three-phase AC motor (MG2); and a control device (30) which controls the power conversion device (14) such that an output of the three-phase AC motor (MG2) reaches a target output; wherein The three-phase AC motor (MG2) has coils from the first to the third phases that are electrically connected, the power conversion device (14) comprises first to third circuits (15-17) which are each connected to the coils of the first to third phases of the three-phase AC motor (MG2); Each of the first to third circuits (15-17) has first and second switching elements (Q3-Q8) which are connected in series via a midpoint between the first and second switching element (Q3-Q8) of each of the first to third circuits (15-17) to the coil of the respective phase of the three-phase AC motor (MG2); and the control device (30) comprises: a short-circuit detection unit (38) that detects a switching element that has failed due to a short circuit from the first to third circuits (15-17), and a motor drive control unit (34) which, in response to the detection of a short-circuited switching element by the short-circuit detection unit (38), merely initiates a switching operation of at least one switching element belonging to a circuit that is different from the circuit to which the short-circuited switching element belongs and is arranged in a positional relationship opposite to the short-circuited switching element, wherein the midpoint of each of the first to third circuits is interposed, thereby controlling currents flowing through coils of respective phases of the three-phase AC motor (MG2), wherein the motor drive control unit (34), in response to a detection of a short-circuit fault of the first switching element of the first circuit, controls currents flowing through the coils of respective phases of the three-phase AC motor (MG2) by means of a switching operation of the second switching element of the second and the third circuit, taking into account a dead time in a control signal for the switching operation, wherein the second switching element of the second circuit and the second switching element of the third circuit are switched on and off with a prescribed duty cycle ratio, which generates a voltage signal waveform with square waves at the midpoints of the second and third circuits, causing a continuous alternating current to flow through the three-phase AC motor (MG2). [2] Motor drive device according to claim 1, wherein the short-circuit detection unit (38) detects the short-circuited switching element on the basis of an amplitude of currents flowing through coils of respective phases of the three-phase AC motor (MG2). [3] Motor drive device according to claim 2, wherein the short-circuit detection unit (38) determines that the first switching element of the first circuit is short-circuited in response to a current flowing through the coil of the first phase of the three-phase AC motor (MG2) being displaced, wherein an amplitude of a stable operation of the three-phase AC motor (MG2) is exceeded in one direction of a first polarity. [4] Motor drive device according to claim 1, wherein the short-circuit detection unit (38) detects the short-circuited switching element on the basis of a voltage between terminals of the first and second switching elements that form each of the first to third circuits. [5] Motor drive device according to claim 1, wherein the three-phase AC motor (MG2) is coupled to a drive shaft of a vehicle.

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