WO2020080170A1 - Failure diagnosis method, power conversion device, motor module, and electric power steering device - Google Patents

Abstract

The failure diagnosis method according to an embodiment of the present disclosure diagnoses a failure of a power conversion device 1000 for converting the power from a power supply 101 to a power supplied to a motor 200 having n-phase (n is an integer of 3 or more) windings. The failure diagnosis method includes steps of: determining the magnitude relationship between the sum of the voltage VA1 between both ends of an A-phase low-side switch element of a first inverter 120 and the voltage VA2 between both ends of an A-phase low-side switch element of a second inverter 130 and a saturation voltage Vsat1; determining the magnitude relationship between the inter-phase voltage VBC between B-phase and C-phase and a saturation voltage Vsat2; and determining the presence or absence of a failure of the A-phase on the basis of the determination result of the magnitude relationship between the sum of the voltages between both ends and the saturation voltage Vsat1 and the determination result of the magnitude relationship between the inter-phase voltage and the saturation voltage Vsat2.

Description

Failure diagnosis method, power converter, motor module and electric power steering device

The present disclosure relates to a failure diagnosis method, a power conversion device, a motor module, and an electric power steering device.

In recent years, an electromechanical integrated motor in which an electric motor (hereinafter, simply referred to as “motor”), an inverter and an ECU are integrated has been developed. Particularly in the field of vehicles, high quality assurance is required from the viewpoint of safety. Therefore, a redundant design has been introduced that allows safe operation to continue even if some of the parts fail. As an example of the redundant design, it is considered to provide two power conversion devices for one motor. As another example, providing a backup microcontroller in the main microcontroller is being considered. ‥

Patent Document 1 discloses a motor drive device having a first system and a second system. The first system is connected to the first winding group of the motor and has a first inverter section, a power supply relay, a reverse connection protection relay, and the like. The second system is connected to the second winding group of the motor and has a second inverter section, a power supply relay, a reverse connection protection relay, and the like. It is possible to drive the motor using both the first system and the second system when no failure occurs in the motor drive device. On the other hand, when a failure occurs in one of the first system and the second system, or in one of the first winding set and the second winding set, the power relay relays the power to the failed system or the failure. The power supply to the system connected to the winding set is cut off. It is possible to continue driving the motor using the other system that has not failed. ‥

Patent Documents 2 and 3 also disclose a motor drive device having a first system and a second system. Even if one system or one winding group fails, the motor drive can be continued by the system that has not failed.

Japanese Patent Publication: Japanese Patent Laid-Open No. 2016-34204 Japanese Patent Publication: Japanese Patent Laid-Open No. 2016-32977 Japanese Patent Publication: Japanese Patent Laid-Open No. 2008-132919

In the above-mentioned conventional technique, it is required to properly detect the failure of the power conversion device. ‥

Embodiments of the present disclosure provide a failure diagnosis method capable of appropriately diagnosing a phase failure in a power conversion device.

An exemplary failure diagnosis method of the present disclosure is a failure diagnosis for diagnosing a failure of a power conversion device that converts electric power from a power supply into electric power supplied to a motor having n-phase (n is an integer of 3 or more) windings. A method, wherein the power converter includes a first inverter connected to a first end of each phase winding of the motor, and a second inverter connected to a second end of each phase winding of the motor. , N number of H-bridges each having a first high-side switching element, a first low-side switching element, a second high-side switching element and a second low-side switching element, the n-phase being the first phase and the second phase. Phase and a third phase, the failure diagnosis method comprises: a voltage across the first-phase low-side switch element in the first inverter and a voltage across the first-phase low-side switch element in the second inverter. And a step of determining a magnitude relationship with the first saturation voltage; a step of determining a magnitude relationship between the interphase voltage between the second phase and the third phase and a second saturation voltage; Determining the presence or absence of the failure of the first phase based on the determination result of the magnitude relationship between the sum and the first saturation voltage and the determination result of the magnitude relationship between the interphase voltage and the second saturation voltage. . ‥

An exemplary power conversion device according to the present disclosure is a power conversion device that converts power from a power source into power to be supplied to a motor having n-phase (n is an integer of 3 or more) windings. The apparatus includes a first inverter connected to a first end of each phase winding of the motor, a second inverter connected to a second end of each phase winding, and a first high side switch. An n-phase H-bridge having an element, a first low-side switch element, a second high-side switch element, and a second low-side switch element, and a control circuit for controlling the operation of the first and second inverters. Includes a first phase, a second phase and a third phase, and the control circuit is configured such that the control circuit has a voltage across the low-side switching element of the first phase in the first inverter and a low-side voltage of the first phase in the second inverter. The sum of the voltage across the switch element and the first saturation voltage is determined, and the interphase voltage between the second phase and the third phase and the second saturation voltage are determined. , The presence or absence of the failure of the first phase is determined based on the determination result of the magnitude relationship between the sum of the voltage across both ends and the first saturation voltage and the determination result of the magnitude relationship between the interphase voltage and the second saturation voltage. To do.

According to an exemplary embodiment of the present disclosure, a failure diagnosis method capable of appropriately diagnosing a phase failure in a power conversion device, a power conversion device, a motor module including the power conversion device, and an electric motor including the motor module. A power steering device is provided.

FIG. 1 is a block diagram schematically showing a motor module according to an embodiment. FIG. 2 is a circuit diagram schematically showing the inverter unit according to the embodiment. FIG. 3A is a schematic diagram showing an A-phase H bridge. FIG. 3B is a schematic diagram showing a B-phase H bridge. FIG. 3C is a schematic diagram showing a C-phase H bridge. FIG. 4 is a functional block diagram showing a controller that performs overall motor control. FIG. 5 is a functional block diagram showing functional blocks for performing high-side failure diagnosis of each phase. FIG. 6 is a functional block diagram showing functional blocks for performing low-side failure diagnosis of each phase. FIG. 7 is a schematic diagram showing a lookup table for determining the constants Ksat1 and Ksat2 from the rotation speed ω and the current amplitude value. FIG. 8: is a graph which illustrates the current waveform (sine wave) obtained by plotting the current value which flows into each winding of A-phase, B-phase, and C-phase of a motor when controlling a power converter device according to three-phase electricity supply control. Is. FIG. 9 is a graph exemplifying a current waveform obtained by plotting current values flowing in the windings of the B-phase and C-phase of the motor when the power converter is controlled according to the two-phase energization control when the A-phase fails. Is. FIG. 10 is a graph exemplifying a current waveform obtained by plotting a current value flowing in each winding of the C phase and A phase of the motor when the power converter is controlled according to the two-phase energization control when the B phase fails. Is. FIG. 11 is a graph exemplifying current waveforms obtained by plotting current values flowing in windings of the A phase and B phase of the motor when the power converter is controlled according to the two-phase energization control when the C phase fails. Is. FIG. 12 is a graph showing the waveform of the simulation result of the sum of the actual voltages VA1 and VA2 when the high-side switch element SW_A1H has an open failure. FIG. 13 is a graph showing a waveform of a simulation result of the sum of the actual voltages VB1 and VB2 when the high side switch element SW_A1H has an open failure. FIG. 14 is a graph showing a waveform of a simulation result of the sum of the actual voltages VC1 and VC2 when the high side switch element SW_A1H has an open failure. FIG. 15 is a graph showing the waveform of the simulation result of the interphase voltage VBC when the high side switch element SW_A1H has an open failure. FIG. 16 is a graph showing a waveform of a simulation result of the interphase voltage VCA when the high side switch element SW_A1H has an open failure. FIG. 17 is a graph showing the waveform of the simulation result of the interphase voltage VAB when the high side switch element SW_A1H has an open failure. FIG. 18 is a functional block diagram showing functional blocks for performing failure diagnosis of the second inverter. FIG. 19 is a functional block diagram showing functional blocks for performing failure diagnosis of the first inverter. FIG. 20 is a schematic diagram showing a lookup table for determining the saturation voltage Vsat from the rotation speed ω and the current amplitude value. FIG. 21 is a graph showing waveforms of simulation results of the actual voltage VA1 (upper side) and the actual voltage VA2 (lower side) when the low side switch element SW_A1L has an open failure. FIG. 22 is a graph showing waveforms of simulation results of the actual voltage VB1 (upper side) and the actual voltage VB2 (lower side) when the low side switch element SW_A1L has an open failure. FIG. 23 is a graph showing waveforms of simulation results of the actual voltage VC1 (upper side) and the actual voltage VC2 (lower side) when the low-side switch element SW_A1L has an open failure. FIG. 24 is a schematic diagram showing an electric power steering device according to an exemplary embodiment.

Hereinafter, embodiments of a failure diagnosis method for an inverter, a power conversion device, a motor module, and an electric power steering device according to the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid unnecessary redundancy in the following description and facilitate understanding by those skilled in the art, detailed description may be omitted more than necessary. For example, detailed description of well-known matters and repeated description of substantially the same configuration may be omitted. ‥

In the present specification, the present disclosure will be described with an example of a power converter that converts electric power from a power supply into electric power supplied to a three-phase motor having three-phase (A-phase, B-phase, and C-phase) windings. The form will be described. However, a power converter for converting power from a power source into power supplied to an n-phase motor having n-phase (n is an integer of 4 or more) winding such as four-phase or five-phase, and an inverter used in the device. The failure diagnosis method is also within the scope of the present disclosure. ‥

(Embodiment 1) [1. Structures of Motor Module 2000 and Power Converter 1000] FIG. 1 schematically shows a typical block configuration of the motor module 2000 according to the present embodiment. ‥

The motor module 2000 typically includes a power converter 1000 having an inverter unit 100 and a control circuit 300, and a motor 200. The motor module 2000 is modularized and may be manufactured and sold, for example, as an electromechanical integrated motor having a motor, a sensor, a driver and a controller. ‥

The power converter 1000 can convert the power from the power supply 101 (see FIG. 2) into the power to be supplied to the motor 200. The power converter 1000 is connected to the motor 200. For example, the power converter 1000 can convert DC power into three-phase AC power that is a pseudo sine wave of A phase, B phase, and C phase. In the present specification, “connection” between parts (components) mainly means electrical connection. ‥

The motor 200 is, for example, a three-phase AC motor. The motor 200 includes an A-phase winding M1, a B-phase winding M2, and a C-phase winding M3, and is connected to the first inverter 120 and the second inverter 130 of the inverter unit 100. More specifically, the first inverter 120 is connected to one end of each phase winding of the motor 200, and the second inverter 130 is connected to the other end of each phase winding. ‥

The control circuit 300 includes, for example, a power supply circuit 310, an angle sensor 320, an input circuit 330, a controller 340, a drive circuit 350, and a ROM 360. Each component of the control circuit 300 is mounted on, for example, one circuit board (typically a printed board). The control circuit 300 is connected to the inverter unit 100 and controls the inverter unit 100 based on the input signals from the current sensor 150 and the angle sensor 320. The control method includes vector control, pulse width modulation (PWM) or direct torque control (DTC), for example. However, depending on the motor control method (for example, sensorless control), the angle sensor 320 may be unnecessary.

The control circuit 300 can realize the closed loop control by controlling the target position, rotation speed, current, and the like of the rotor of the motor 200. The control circuit 300 may include a torque sensor instead of the angle sensor 320. In this case, the control circuit 300 can control the target motor torque. ‥

The power supply circuit 310 generates a power supply voltage (eg, 3V, 5V) required for each block in the circuit based on the voltage of the power supply 101, for example, 12V. ‥

The angle sensor 320 is, for example, a resolver or a Hall IC. Alternatively, the angle sensor 320 is also realized by a combination of an MR sensor having a magnetoresistive (MR) element and a sensor magnet. The angle sensor 320 detects a rotation angle of the rotor (hereinafter referred to as “rotation signal”) and outputs the rotation signal to the controller 340. ‥

The input circuit 330 receives the phase current detected by the current sensor 150 (hereinafter sometimes referred to as “actual current value”), and sets the level of the actual current value to the input level of the controller 340 as necessary. The actual current value is converted and output to the controller 340. The input circuit 330 is, for example, an analog-digital (AD) conversion circuit. ‥

The controller 340 is an integrated circuit that controls the entire power conversion apparatus 1000, and is, for example, a microcontroller or an FPGA (Field Programmable Gate Array). The controller 340 controls the switching operation (turn-on or turn-off) of each switch element (typically a semiconductor switch element) in the first and second inverters 120 and 130 of the inverter unit 100. The controller 340 sets a target current value according to the actual current value and the rotor rotation signal, generates a PWM signal, and outputs the PWM signal to the drive circuit 350. ‥

The drive circuit 350 is typically a pre-driver (sometimes called a “gate driver”). The drive circuit 350 generates a control signal (gate control signal) for controlling the switching operation of each switch element in the first and second inverters 120 and 130 of the inverter unit 100 according to the PWM signal, and outputs a control signal to the gate of each switch element. give. When the drive target is a motor that can be driven at a low voltage, the pre-driver may not be necessarily required. In that case, the function of the pre-driver may be implemented in the controller 340. ‥

The ROM 360 is, for example, a writable memory (for example, PROM), a rewritable memory (for example, flash memory), or a read-only memory. The ROM 360 stores a control program including a command group for causing the controller 340 to control the power conversion device 1000. For example, the control program is once expanded in the RAM (not shown) at the time of booting. ‥

A specific circuit configuration of the inverter unit 100 will be described with reference to FIG. ‥

FIG. 2 schematically shows the circuit configuration of the inverter unit 100 according to this embodiment. ‥

The power supply 101 generates a predetermined power supply voltage (for example, 12V). As the power supply 101, for example, a DC power supply is used. However, the power supply 101 may be an AC-DC converter or a DC-DC converter, or a battery (storage battery). The power supply 101 may be a single power supply common to the first and second inverters 120 and 130 as shown, or may be a first power supply (not shown) for the first inverter 120 and a second power supply for the second inverter 130. Second power source (not shown) may be provided. ‥

Although not shown, coils are provided between the power supply 101 and the first inverter 120 and between the power supply 101 and the second inverter 130. The coil functions as a noise filter and smoothes high frequency noise included in the voltage waveform supplied to each inverter or high frequency noise generated in each inverter so as not to flow out to the power supply 101 side. A capacitor is connected to the power supply terminal of each inverter. The capacitor is a so-called bypass capacitor and suppresses voltage ripple. The capacitor is, for example, an electrolytic capacitor, and the capacity and the number of capacitors used are appropriately determined according to design specifications and the like. ‥

The first inverter 120 has a bridge circuit composed of three legs. Each leg has a high side switch element, a low side switch element, and a shunt resistor. The A-phase leg has a high side switch element SW_A1H, a low side switch element SW_A1L, and a first shunt resistor S_A1. The B-phase leg has a high side switch element SW_B1H, a low side switch element SW_B1L, and a first shunt resistor S_B1. The C-phase leg has a high side switch element SW_C1H, a low side switch element SW_C1L, and a first shunt resistor S_C1. ‥

As the switch element, for example, a field effect transistor (typically MOSFET) having a parasitic diode formed therein, or a combination of an insulated gate bipolar transistor (IGBT) and a free wheeling diode connected in parallel thereto can be used. . ‥

The first shunt resistor S_A1 is used to detect the A-phase current IA1 flowing through the A-phase winding M1 and is connected, for example, between the low-side switch element SW_A1L and the GND line GL. The first shunt resistor S_B1 is used to detect the B-phase current IB1 flowing through the B-phase winding M2, and is connected, for example, between the low-side switch element SW_B1L and the GND line GL. The first shunt resistor S_C1 is used to detect the C-phase current IC1 flowing through the C-phase winding M3, and is connected, for example, between the low-side switch element SW_C1L and the GND line GL. The three shunt resistors S_A1, S_B1 and S_C1 are commonly connected to the GND line GL of the first inverter 120. ‥

The second inverter 130 has a bridge circuit composed of three legs. Each leg has a high side switch element, a low side switch element, and a shunt resistor. The A-phase leg has a high-side switch element SW_A2H, a low-side switch element SW_A2L, and a shunt resistor S_A2. The B-phase leg has a high-side switch element SW_B2H, a low-side switch element SW_B2L, and a shunt resistor S_B2. The C-phase leg has a high-side switch element SW_C2H, a low-side switch element SW_C2L, and a shunt resistor S_C2. ‥

The shunt resistor S_A2 is used to detect the A-phase current IA2, and is connected, for example, between the low-side switch element SW_A2L and the GND line GL. The shunt resistor S_B2 is used to detect the B-phase current IB2, and is connected, for example, between the low side switch element SW_B2L and the GND line GL. The shunt resistor S_C2 is used to detect the C-phase current IC2, and is connected, for example, between the low-side switch element SW_C2L and the GND line GL. The three shunt resistors S_A2, S_B2, and S_C2 are commonly connected to the GND line GL of the second inverter 130. ‥

The current sensor 150 described above includes, for example, shunt resistors S_A1, S_B1, S_C1, S_A2, S_B2, S_C2 and a current detection circuit (not shown) that detects a current flowing through each shunt resistor. ‥

The A-phase leg of the first inverter 120 (specifically, the node between the high-side switch element SW_A1H and the low-side switch element SW_A1L) is connected to one end A1 of the A-phase winding M1 of the motor 200, and is connected to the second inverter. The A-phase leg of 130 is connected to the other end A2 of the A-phase winding M1. The B-phase leg of the first inverter 120 is connected to one end B1 of the B-phase winding M2 of the motor 200, and the B-phase leg of the second inverter 130 is connected to the other end B2 of the winding M2. The C-phase leg of the first inverter 120 is connected to one end C1 of the C-phase winding M3 of the motor 200, and the C-phase leg of the second inverter 130 is connected to the other end C2 of the winding M3. ‥

FIG. 3A schematically shows the configuration of the phase A H-bridge BA. FIG. 3B schematically shows the configuration of the B-phase H bridge BB. FIG. 3C schematically shows the configuration of the C-phase H bridge BC. ‥

The inverter unit 100 includes H bridges BA, BB and BC of A phase, B phase and C phase. The A-phase H bridge BA includes a high-side switch element SW_A1H and a low-side switch element SW_A1L in the leg on the first inverter 120 side, a high-side switch element SW_A2H, a low-side switch element SW_A2L in the leg on the second inverter 130 side, and a winding. With M1. ‥

The B-phase H bridge BB includes a high-side switch element SW_B1H, a low-side switch element SW_B1L in the leg on the first inverter 120 side, a high-side switch element SW_B2H, a low-side switch element SW_B2L in the leg on the second inverter 130 side, and a winding. With M2. ‥

The C-phase H bridge BC includes a high-side switch element SW_C1H and a low-side switch element SW_C1L in the leg on the first inverter 120 side, a high-side switch element SW_C2H, a low-side switch element SW_C2L in the leg on the second inverter 130 side, and a winding. With M3. ‥

The control circuit 300 (specifically, the controller 340) can identify the faulty inverter of the first inverter 120 and the second inverter 130 by executing the fault diagnosis of the inverter described below. The details of the failure diagnosis of the inverter will be described below. ‥

[2. Phase Failure Diagnosis Method] A specific example of a failure diagnosis method for diagnosing a phase failure in the power conversion apparatus 1000 shown in FIG. 1 will be described with reference to FIGS. 4 to 7. As a result of earnest research, the inventor of the present application has found that a phase failure in a power conversion device can be diagnosed by the following method. The failure diagnosis method of the present disclosure can be suitably used for a power conversion device including a plurality of H bridges, for example, a full bridge type power conversion device. The failure in this specification refers to an open failure of the switch element. The open failure is a failure in which the switch element always has a high impedance. In this specification, the occurrence of an open failure in the high-side switch element SW_A1H or SW_A2H of the first inverter 120 may be referred to as an A-phase high-side failure. ‥

In the failure diagnosis, for example, the current and voltage expressed in the dq coordinate system, the actual voltage indicating the voltage across the low-side switch element, and the motor rotation speed ω are acquired. The current and voltage expressed in the dq coordinate system include the d-axis voltage Vd, the q-axis voltage Vq, the d-axis current Id, and the q-axis current Iq. In the dq coordinate system, the axis corresponding to the zero phase is represented as the z axis. The rotation speed ω is represented by a rotation speed (rpm) at which the rotor of the motor rotates in a unit time (for example, 1 minute) or a rotation speed (rps) at which the rotor rotates in a unit time (for example, 1 second). ‥

The actual voltage of the switch element will be described with reference to FIGS. 3A to 3C. ‥

A first actual voltage and a second actual voltage are defined for each of the H bridges BA, BB, and BC of the A phase, the B phase, and the C phase. The first actual voltage indicates the voltage across the first low-side switch element in the leg on the first inverter 120 side in each phase H-bridge. In other words, the first actual voltage corresponds to the node potential between the first high side switch element and the first low side switch element in the leg on the first inverter 120 side. The second actual voltage indicates the voltage across the second low-side switch element in the leg on the second inverter 130 side. In other words, the second actual voltage corresponds to the node potential between the second high side switch element and the second low side switch element in the leg on the second inverter 130 side. The voltage across the switch element is equal to the source-drain voltage Vds of the FET that is the switch element.

For the A-phase H bridge BA, the first actual voltage refers to the voltage VA1 across the low-side switching element SW_A1L shown in FIG. 3A, and the second actual voltage refers to the voltage VA2 across the low-side switching element SW_A2L shown in FIG. 3A. . For the B-phase H bridge BB, the first actual voltage refers to the voltage VB1 across the low-side switching element SW_B1L shown in FIG. 3B, and the second actual voltage refers to the voltage VB2 across the low-side switching element SW_B2L shown in FIG. 3B. . For the C-phase H bridge BC, the first actual voltage refers to the voltage VC1 across the low-side switch element SW_C1L shown in FIG. 3C, and the second actual voltage refers to the voltage VC2 across the low-side switch element SW_C2L shown in FIG. 3C. . ‥

Next, based on the acquired current and voltage of the dq coordinate system, the first actual voltage, the second actual voltage, and the rotation speed, the phase failure is diagnosed. ‥

When it is determined that there is a failed phase, a failure signal indicating the failure of the phase is generated and output to the motor control unit described later. For example, a failure signal is a signal that is asserted when a failure occurs. ‥

The above-mentioned failure diagnosis is repeatedly executed, for example, in synchronization with the cycle of measuring each phase current by the current sensor 150, that is, the cycle of AD conversion. ‥

The algorithm for realizing the failure diagnosis method according to the present embodiment can be realized only by hardware such as an application specific integrated circuit (ASIC) or FPGA, or by a combination of a microcontroller and software. You can In the present embodiment, the operation subject of the failure diagnosis is the controller 340 of the control circuit 300. ‥

FIG. 4 exemplifies the functional blocks of the controller 340 for performing overall motor control. FIG. 5 exemplifies functional blocks for performing high-side failure diagnosis of each phase. FIG. 6 exemplifies functional blocks for performing low-side failure diagnosis of each phase. ‥

In this specification, each block in the functional block diagram is shown in a functional block unit rather than in a hardware unit. The software used for motor control and failure diagnosis may be, for example, a module forming a computer program for executing a specific process corresponding to each functional block. Such a computer program is stored in the ROM 360, for example. The controller 340 can read an instruction from the ROM 360 and sequentially execute each process. ‥

The controller 340 has, for example, a failure diagnosis unit 700 and a motor control unit 900. As described above, the failure diagnosis of the present disclosure can be suitably combined with motor control (for example, vector control), and can be incorporated in a series of processes of motor control. ‥

The failure diagnosis unit 700 acquires the d-axis current Id, the q-axis current Iq, the d-axis voltage Vd, the q-axis voltage Vq, and the rotation speed ω of the motor 200 in the dq coordinate system. Fault diagnosis unit 700 further obtains first actual voltages VA1, VB1, VC1 and second actual voltages VA2, VB2 and VC2. ‥

For example, the fault diagnosis unit 700 may include a pre-calculation unit (not shown) that acquires Vpeak. The pre-computation unit uses the Clark transform to convert the three-phase currents Ia, Ib, and Ic acquired based on the measurement values of the current sensor 150 into the currents I _α and β on the α axis in the α β fixed coordinate system. Of the current I _β . The pre-calculation unit converts the currents I _α and I _β into the d-axis current Id and the q-axis current Iq in the dq coordinate system by using the Park transformation (dq coordinate transformation). The pre-calculation unit acquires the d-axis voltage Vd and the q-axis voltage Vq based on the currents Id and Iq, and calculates the voltage peak value Vpeak from the acquired Vd and Vq based on the following equation (1). Alternatively, the pre-calculation unit can also receive Vd and Vq necessary for calculating Vpeak from the motor control unit 900 that performs vector control. For example, the pre-computation unit acquires Vpeak in synchronization with the cycle in which the current sensor 150 measures each phase current. Vpeak = (2/3) ^1/2 (Vd ² + Vq ² ) ^1/2 Formula (1)

Fault diagnosis unit 700 refers to lookup table 740 (FIG. 7) to determine constants Ksat1 and Ksat2 based on currents Id and Iq and rotation speed ω. ‥

FIG. 7 schematically shows a look-up table (LUT) 740 that determines the constants Ksat1 and Ksat2 from the rotation speed ω and the current amplitude value. The LUT 740 associates the current amplitude value (Id ² + Iq ² ) ^1/2 determined based on the d-axis current and the q-axis current and the input of the rotation speed ω of the motor 200 with the constants Ksat1 and Ksat2.

The rotation speed ω is calculated based on the rotation signal from the angle sensor 320, for example. Alternatively, the rotation speed ω can be estimated by using, for example, a known sensorless control method. The actual voltage of each switch element is measured by, for example, a drive circuit (pre-driver) 350. ‥

In motor control, Id is generally treated as zero. Therefore, the current amplitude value becomes equal to Iq. For example, the constants Ksat1 and Ksat2 are determined from the obtained current amplitude value Iq and the rotation speed ω. Alternatively, as the constants Ksat1 and Ksat2, for example, preset values before driving may be used. For example, constant values depending on the system may be used as the constants Ksat1 and Ksat2. Further, Ksat1 and Ksat2 may have the same value. ‥

The failure diagnosis unit 700 calculates the saturation voltages Vsat1 and Vsat2 from the acquired constants Ksat1 and Ksat2 based on the following equations (2) and (3). Vsat1 = Vpeak / Ksat1 formula (2) Vsat2 = Vpeak / Ksat2 formula (3)

For example, the values of the saturation voltages Vsat1 and Vsat2 are 0.3-0.4 (V). This value is an example, and the present embodiment is not limited to this value. The failure diagnosis unit 700 diagnoses the presence or absence of a phase failure based on the above-described actual voltage, voltage peak value Vpeak, and saturation voltages Vsat1 and Vsat2. ‥

The failure diagnosis unit 700 generates a failure signal indicating a phase failure based on the diagnosis result and outputs it to the motor control unit 900. ‥

The motor control unit 900 uses, for example, vector control to generate a PWM signal that controls the overall switching operation of the switch elements of the first and second inverters 120 and 130. The motor control unit 900 outputs the PWM signal to the drive circuit 350. Further, the motor control unit 900 can switch the motor control from the three-phase energization control to the two-phase energization control when, for example, a failure signal is asserted. ‥

In this specification, each functional block may be referred to as a unit for convenience of description. Naturally, these notations are not used with the intention of limiting each functional block to hardware or software. ‥

When each functional block is implemented as software in the controller 340, the execution subject of the software may be the core of the controller 340, for example. As mentioned above, the controller 340 may be implemented by an FPGA. In that case, all or some of the functional blocks may be implemented in hardware. ‥

By distributing the processing using a plurality of FPGAs, it is possible to distribute the calculation load of a specific computer. In that case, all or a part of the functional blocks illustrated in FIGS. 4 to 6 may be distributed and implemented in a plurality of FPGAs. The plurality of FPGAs are communicably connected to each other by, for example, a vehicle-mounted control area network (CAN), and can send and receive data. ‥

The failure diagnosis unit 700 includes a failure diagnosis unit 701 for diagnosing the high-side failure of each phase shown in FIGS. 5 and 6, and a failure diagnosis unit 702 for diagnosing the low-side failure of each phase. Functional blocks of the failure diagnosis units 701 and 702 having substantially the same functions are designated by the same reference numerals, and detailed description thereof will not be repeated. ‥

The failure diagnosis unit 701 has absolute value calculators 711, 712, 713, comparators 721, 722, 723, 724, 725, 726, and logic circuits AND731, 732, 733. The failure diagnosis unit 702 includes absolute value calculators 711, 712, 713, comparators 721, 723, 725, 727, 728, 729, and logic circuits AND731, 732, 733. ‥

First, the diagnosis process for the presence or absence of a high-side failure in each phase will be described. ‥

The absolute value calculator 711 of the failure diagnosis unit 701 calculates the absolute value of the interphase voltage VBC between the B phase and the C phase. ‥

The interphase voltage VBC is represented by the following formula (4). VBC = (VB1 + VB2)-(VC1 + VC2) Formula (4)

The interphase voltage VBC is the difference between the sum of the voltage VB1 across the low-side switch element SW_B1L and the voltage VB2 across the low-side switch element SW_B2L, and the sum of the voltage VC1 across the low-side switch element SW_C1L and the voltage VC2 across the low-side switch element SW_C2L. Is. ‥

The comparator 721 compares the absolute value of the interphase voltage VBC with the saturation voltage Vsat2. When it is determined that the absolute value of VBC is Vsat2 or more (| VBC | ≧ Vsat2), the comparator 721 outputs “0” indicating that the phase A is normal to the logic circuit AND731. When the comparator 721 determines that the absolute value of VBC is less than Vsat2 (| VBC | <Vsat2), the comparator 721 outputs "1" indicating that the A phase is abnormal to the logic circuit AND731. ‥

The comparator 722 compares the sum “VA1 + VA2” of the voltage VA1 across the low-side switch element SW_A1L and the voltage VA2 across the low-side switch element SW_A2L with the negative value “−Vsat1” of the saturation voltage Vsat1. ‥

When the comparator 722 determines that “VA1 + VA2” is “−Vsat1” or more ((VA1 + VA2) ≧ −Vsat1), it outputs “0” indicating that the high side of the A phase is normal to the logic circuit AND731. When the comparator 722 determines that “VA1 + VA2” is less than “−Vsat1” ((VA1 + VA2) <− Vsat1), it outputs “1” indicating that the high side of the phase A is abnormal to the logic circuit AND731. ‥

The logic circuit AND731 takes the logical product of the output signals of the comparators 721 and 722. The logic circuit AND731 outputs a logical product to the motor control unit 900 as a failure signal AH_FD indicating the presence / absence of a failure on the high side of the A phase. ‥

When at least one of the output signals of the comparators 721 and 722 is "0", the logic circuit AND731 outputs "0" indicating that the high side of the A phase is normal as the failure signal AH_FD. When both of the output signals of the comparators 721 and 722 are "1", the logic circuit AND731 outputs "1" indicating that the high side of the A phase has a failure as the failure signal AH_FD. ‥

The absolute value calculator 712 calculates the absolute value of the interphase voltage VCA between the C phase and the A phase. ‥

The interphase voltage VCA is represented by the following equation (5). VCA = (VC1 + VC2)-(VA1 + VA2) Formula (5)

The interphase voltage VCA is the difference between the sum of the voltage VC1 across the low-side switch element SW_C1L and the voltage VC2 across the low-side switch element SW_C2L, and the sum of the voltage VA1 across the low-side switch element SW_A1L and the voltage VA2 across the low-side switch element SW_A2L. Is. ‥

The comparator 723 calculates the absolute value of the interphase voltage VCA and the saturation voltage Vs.
Compare the magnitude relationship with at2. When it is determined that the absolute value of VCA is Vsat2 or more (| VCA | ≧ Vsat2), the comparator 723 outputs “0” indicating that the B phase is normal to the logic circuit AND732. When it is determined that the absolute value of VCA is less than Vsat2 (| VCA | <Vsat2), the comparator 723 outputs “1” indicating that the B phase is abnormal to the logic circuit AND732.

The comparator 724 compares the sum “VB1 + VB2” of the voltage VB1 across the low-side switch element SW_B1L and the voltage VB2 across the low-side switch element SW_B2L with the negative value “−Vsat1” of the saturation voltage Vsat1. ‥

When the comparator 724 determines that “VB1 + VB2” is greater than or equal to “−Vsat1” ((VB1 + VB2) ≧ −Vsat1), the comparator 724 outputs “0” indicating that the high side of phase B is normal to the logic circuit AND732. When the comparator 724 determines that “VB1 + VB2” is less than “−Vsat1” ((VB1 + VB2) <− Vsat1), it outputs “1” indicating that the high side of phase B is abnormal to the logic circuit AND732. ‥

The logic circuit AND732 takes the logical product of the output signals of the comparators 723 and 724. The logic circuit AND732 outputs a logical product to the motor control unit 900 as a failure signal BH_FD indicating whether or not there is a failure on the high side of the B phase. ‥

When at least one of the output signals of the comparators 723 and 724 is “0”, the logic circuit AND732 outputs “0” indicating that the high side of the B phase is normal as the failure signal BH_FD. When both the output signals of the comparators 723 and 724 are "1", the logic circuit AND732 outputs "1" indicating that the high side of the B phase has a failure as the failure signal BH_FD. ‥

The absolute value calculator 713 calculates the absolute value of the interphase voltage VAB between the A phase and the B phase. ‥

The interphase voltage VAB is expressed by the following equation (6). VAB = (VA1 + VA2)-(VB1 + VB2) Formula (6)

The interphase voltage VAB is the difference between the sum of the voltage VA1 across the low-side switching element SW_A1L and the voltage VA2 across the low-side switching element SW_A2L, and the sum of the voltage VB1 across the low-side switching element SW_B1L and the voltage VB2 across the low-side switching element SW_B2L. Is. ‥

The comparator 725 compares the absolute value of the interphase voltage VAB with the saturation voltage Vsat2. When it is determined that the absolute value of VAB is Vsat2 or more (| VAB | ≧ Vsat2), the comparator 725 outputs “0” indicating that the C phase is normal to the logic circuit AND733. When the comparator 725 determines that the absolute value of VAB is less than Vsat2 (| VAB | <Vsat2), the comparator 725 outputs "1" indicating that the C phase is abnormal to the logic circuit AND733. ‥

The comparator 726 compares the sum “VC1 + VC2” of the voltage VC1 across the low-side switch element SW_C1L and the voltage VC2 across the low-side switch element SW_C2L with the negative value “−Vsat1” of the saturation voltage Vsat1. ‥

When the comparator 726 determines that “VC1 + VC2” is greater than or equal to “−Vsat1” ((VC1 + VC2) ≧ −Vsat1), the comparator 726 outputs “0” indicating that the high side of the C phase is normal to the logic circuit AND733. When it is determined that “VC1 + VC2” is less than “−Vsat1” ((VC1 + VC2) <− Vsat1), the comparator 726 outputs “1” indicating that the high side of the C phase is abnormal to the logic circuit AND733. ‥

The logic circuit AND733 takes the logical product of the output signals of the comparators 725 and 726. The logic circuit AND733 outputs a logical product to the motor control unit 900 as a failure signal CH_FD indicating whether or not there is a failure on the high side of the C phase. ‥

When at least one of the output signals of the comparators 725 and 726 is “0”, the logic circuit AND733 outputs “0” indicating that the high side of the C phase is normal as the failure signal CH_FD. When both the output signals of the comparators 725 and 726 are "1", the logic circuit AND733 outputs "1" indicating that the high side of the C phase has a failure as the failure signal CH_FD. ‥

Next, a diagnosis process for the presence or absence of a low side failure in each phase will be described. ‥

The failure diagnosis unit 702 executes the diagnosis of the presence or absence of the low side failure. In order to avoid repetition of description of the same processing, here, of the processing executed by the failure diagnosis unit 702, processing different from the failure diagnosis unit 701 will be described. ‥

The fault diagnosis unit 702 has comparators 727, 728, 729 instead of the comparators 722, 724, 726. ‥

The comparator 727 compares the sum “VA1 + VA2” of the voltage VA1 across the low-side switch element SW_A1L and the voltage VA2 across the low-side switch element SW_A2L with the saturation voltage Vsat1. ‥

When the comparator 727 determines that “VA1 + VA2” is equal to or smaller than “Vsat1” ((VA1 + VA2) ≦ Vsat1), it outputs “0” indicating that the low side of the A phase is normal to the logic circuit AND731. When the comparator 727 determines that “VA1 + VA2” is larger than “Vsat1” ((VA1 + VA2)> Vsat1), it outputs “1” indicating that the low side of the phase A is abnormal to the logic circuit AND731. ‥

The logic circuit AND731 takes the logical product of the output signals of the comparators 721 and 727. The logic circuit AND731 outputs a logical product to the motor control unit 900 as a failure signal AL_FD indicating the presence / absence of a failure on the low side of the phase A. ‥

When at least one of the output signals of the comparators 721 and 727 is "0", the logic circuit AND731 outputs "0" indicating that the low side of the A phase is normal as the failure signal AL_FD. When both the output signals of the comparators 721 and 727 are "1", the logic circuit AND731 outputs "1" indicating that the low side of the phase A has a failure as the failure signal AL_FD. ‥

The comparator 728 compares the sum “VB1 + VB2” of the voltage VB1 across the low-side switch element SW_B1L and the voltage VB2 across the low-side switch element SW_B2L with the saturation voltage Vsat1. ‥

When the comparator 728 determines that “VB1 + VB2” is “Vsat1” or less ((VB1 + VB2) ≦ Vsat1), it outputs “0” indicating that the low side of the B phase is normal to the logic circuit AND732. When it is determined that “VB1 + VB2” is larger than “Vsat1” ((VB1 + VB2)> Vsat1), the comparator 728 outputs “1” indicating that the low side of the B phase is abnormal to the logic circuit AND732. ‥

The logic circuit AND732 takes the logical product of the output signals of the comparators 723 and 728. The logic circuit AND732 outputs a logical product to the motor control unit 900 as a failure signal BL_FD indicating the presence or absence of a B-phase low-side failure. ‥

When at least one of the output signals of the comparators 723 and 728 is "0", the logic circuit AND732 outputs "0" indicating that the low side of the B phase is normal as the failure signal BL_FD. When both the output signals of the comparators 723 and 728 are “1”, the logic circuit AND732 outputs “1” indicating that the low side of the B phase has a failure as the failure signal BL_FD. ‥

The comparator 729 compares the sum “VC1 + VC2” of the voltage VC1 across the low-side switch element SW_C1L and the voltage VC2 across the low-side switch element SW_C2L with the saturation voltage Vsat1. ‥

When the comparator 729 determines that “VC1 + VC2” is less than or equal to “Vsat1” ((VC1 + VC2) ≦ Vsat1), it outputs “0” indicating that the low side of the C phase is normal to the logic circuit AND733. When it is determined that “VC1 + VC2” is larger than “Vsat1” ((VC1 + VC2)> Vsat1), the comparator 729 outputs “1” indicating that the low side of the C phase is abnormal to the logic circuit AND733. ‥

The logic circuit AND733 takes the logical product of the output signals of the comparators 725 and 729. The logic circuit AND733 outputs a logical product to the motor control unit 900 as a failure signal CL_FD indicating the presence or absence of a C-phase low-side failure. ‥

When at least one of the output signals of the comparators 725 and 729 is "0", the logic circuit AND733 outputs "0" indicating that the low side of the C phase is normal as the failure signal CL_FD. When both the output signals of the comparators 725 and 729 are "1", the logic circuit AND733 outputs "1" indicating that the low side of the C phase has a failure as the failure signal CL_FD. ‥

The motor control unit 900 changes the motor control according to the failure signal output from the failure diagnosis unit 700. For example, the motor control is switched from the three-phase energization control to the two-phase energization control. For example, when a failed phase is specified, two-phase energization control using the remaining two phases other than the phase including the failed switch element is performed. For example, when at least one of the failure signals AH_FD and AL_FD indicates “1” and it is determined that the phase A has failed, the motor control unit 900 turns off all the switch elements of the phase A H-bridge BA. . Then, the two-phase energization control using the remaining B-phase and C-phase H bridges BB and BC is performed. Thereby, even if one of the three phases fails, the power conversion apparatus 1000 can continue to drive the motor. ‥

FIG. 8 exemplifies a current waveform (sine wave) obtained by plotting current values flowing in the A-phase, B-phase, and C-phase windings of the motor 200 when the power converter 1000 is controlled according to the three-phase energization control. is doing. FIG. 9 is obtained by plotting current values flowing in the B-phase and C-phase windings of the motor 200 when the power converter 1000 is controlled according to the two-phase energization control when the A-phase H bridge BA fails. The current waveform is illustrated. The horizontal axis represents the motor electrical angle (deg), and the vertical axis represents the current value (A). In the current waveforms of FIGS. 8 and 9, current values are plotted for each 30 electrical degrees. I _pk represents the maximum current value (peak current value) of each phase.

For reference, in FIG. 10, when the B-phase H bridge BB fails, the current values flowing in the A-phase and C-phase windings of the motor 200 when the power converter 1000 is controlled according to the two-phase energization control are plotted. The current waveform obtained by the above is illustrated. In FIG. 11, when the C-phase H bridge BC fails, it is obtained by plotting the current values flowing in the A-phase and B-phase windings of the motor 200 when the power converter 1000 is controlled according to the two-phase energization control. A current waveform is illustrated. ‥

In the present embodiment, the order of the processes of the failure diagnosis units 701 and 702 described above is arbitrary. For example, the processing of the comparators 721, 723, 725 may be performed after the processing of the comparators 722, 724, 726, 727, 728, 729. ‥

Further, for example, the processing of the comparators 722, 724, 726, 727, 728, 729 may be performed, and the processing of the comparators 721, 723, 725 may be performed only when an abnormality is detected. In a use environment with little noise, the presence / absence of an abnormality can be determined only by the processing of the comparators 722, 724, 726, 727, 728, 729. If an abnormality is detected, the comparators 721, 723, and 725 can perform the processing to further improve the accuracy of determining the presence or absence of the abnormality. Moreover, the amount of calculation can be reduced by performing the processing of the comparators 721, 723, and 725 only when an abnormality is detected. By reducing the calculation amount, when a failure occurs, the failure can be dealt with in a shorter time. ‥

Further, the processing of the comparators 721, 723, 725 and the processing of the comparators 722, 724, 726, 727, 728, 729 may be performed at the same time. By performing these processes at the same time and determining the presence / absence of abnormality using the respective processing results, the presence / absence of abnormality can be accurately determined. For example, even in a use environment where noise is mixed in the voltage signal, it is possible to highly accurately determine whether or not there is an abnormality.

Below, the validity of the algorithm used for the fault diagnosis according to the present disclosure is verified by using the “Rapid Control Prototyping (RCP) System” of dSPACE and the Matlab / Simlink of MathWorks. A model of a surface magnet type (SPM) motor used in an electric power steering (EPS) device, which is controlled by vector control, was used for this verification. In the verification, the q-axis current command value Iq_ref was set to 3A, and the d-axis current command value Id_ref and the zero-phase current command value Iz_ref were set to 0A. The rotation speed ω of the motor was set to 1200 rpm. In the simulation, an open failure is generated in the high-side switch element SW_A1H of the first inverter 120 at time 1.54s. ‥

12 to 17 show simulation results of the waveform of each signal. The vertical axis of each graph represents voltage (V), and the horizontal axis represents time (s). ‥

FIG. 12 shows a waveform of the sum of the actual voltages VA1 and VA2 when the high side switch element SW_A1H has an open failure. FIG. 13 shows a waveform of the sum of the actual voltages VB1 and VB2 when the high-side switch element SW_A1H has an open failure. FIG. 14 shows a waveform of the sum of the actual voltages VC1 and VC2 when the high side switch element SW_A1H has an open failure. ‥

After the high-side switch element SW_A1H has an open failure at time 1.54s, it can be seen that “VA1 + VA2” is less than “−Vsat1” as shown in FIG. On the other hand, as shown in FIGS. 13 and 14, “VB1 + VB2” and “VC1 + VC2” are not less than “−Vsat1”. ‥

After the open failure of the high-side switch element SW_A1H at time 1.54s, it can be seen that the absolute value of the interphase voltage VBC is less than Vsat2, as shown in FIG. On the other hand, as shown in FIGS. 16 and 17, the absolute value of interphase voltage VCA and the absolute value of interphase voltage VAB are not less than Vsat2. ‥

As described above, the failure diagnosis of the present disclosure can be realized by a simple algorithm. Therefore, for example, in mounting the controller 340 on the controller, advantages such as reduction of the circuit size or the memory size can be obtained. Further, since the monitoring of the interphase voltage requires a small amount of calculation, it is possible to shorten the time until failure detection. ‥

In the present embodiment, the failure diagnosis described above may not be performed for all three phases, and the failure diagnosis may be performed for only one phase or two phases. For example, when the failure diagnosis is performed only for the A phase, only the process related to the A phase among the processes described above may be performed, and the process related to the B phase and the C phase may not be performed. ‥

Next, the failure diagnosis of the inverter will be described. ‥

FIG. 18 exemplifies a functional block for performing a failure diagnosis of the second inverter 130. FIG. 19 exemplifies a functional block for performing a failure diagnosis of the first inverter 120. ‥

The failure diagnosis unit 700 refers to the lookup table 840 (FIG. 20) and determines the saturation voltage Vsat based on the currents Id and Iq and the rotation speed ω. ‥

FIG. 20 schematically shows a lookup table (LUT) 840 that determines the saturation voltage Vsat from the rotation speed ω and the current amplitude value. The LUT 840 associates the relationship between the saturation voltage Vsat and the input of the current amplitude value (Id ² + Iq ² ) ^1/2 determined based on the d-axis current and the q-axis current and the rotation speed ω of the motor 200.

Table 1 illustrates the configuration of the LUT 840 that can be used for failure diagnosis. In motor control, Id is generally treated as zero. Therefore, the current amplitude value becomes equal to Iq. Table 1 shows Iq (A). The saturation voltage Vsat is determined from the obtained current amplitude value Iq and the rotation speed ω. Alternatively, as the saturation voltage Vsat, for example, a value set in advance before driving may be used. For example, as the saturation voltage Vsat, a constant value depending on the system (for example, about 0.1 V) may be used. ‥

The failure diagnosis unit 700 diagnoses whether or not there is a failure in the inverter based on the above-mentioned actual voltage, voltage peak value Vpeak, and saturation voltage Vsat. ‥

The failure diagnosis unit 700 generates a failure signal 1_FD indicating a failure of the first inverter 120 and a failure signal 2_FD indicating a failure of the second inverter 130 based on the diagnosis result, and outputs the failure signal 1_FD to the motor control unit 900. ‥

The failure diagnosis unit 700 has a failure diagnosis unit 801 for diagnosing the presence / absence of a failure in the second inverter 130 and a failure diagnosis unit 802 for diagnosing the presence / absence of a failure in the first inverter 120 shown in FIGS. 18 and 19. Fault diagnosis units 801 and 802 have substantially the same functional blocks, but the input actual voltages are different from each other. ‥

Each of the failure diagnosis units 801 and 802 includes an absolute value calculator 811, 814, 817, a multiplier 812, 813, 815, 816, 818, 819, an adder 831, 832, 833, and a comparator 851, 852. , 853 and a logic circuit OR871. ‥

First, the diagnosis processing for the presence / absence of a failure in the second inverter 130 will be described. ‥

The absolute value calculator 811 of the failure diagnosis unit 801 calculates the absolute value of the actual voltage VA1. The multiplier 812 multiplies the voltage peak value Vpeak by a constant “−½”. The multiplier 813 multiplies the saturation voltage Vsat by a constant “−1”. The adder 831 adds the output values of the absolute value calculator 811, the multipliers 812 and 813 to calculate the fault diagnosis voltage VA1_FD represented by the following equation (7). VA1_FD = | VA1 |-[(Vpeak / 2) + Vsat] Formula (7)

The comparator 851 compares “VA1_FD” with “zero”. When VA1_FD is less than or equal to zero (VA1_FD ≦ 0), the comparator 851 outputs “0” indicating that the actual voltage VA1 is normal to the logic circuit OR871. When VA1_FD is greater than zero (VA1_FD> 0), the comparator 851 outputs “1” indicating that the actual voltage VA1 is abnormal to the logic circuit OR871. ‥

Similarly, the absolute value calculator 814 of the failure diagnosis unit 801 calculates the absolute value of the actual voltage VB1. The multiplier 815 multiplies the voltage peak value Vpeak by a constant “−½”. The multiplier 816 multiplies the saturation voltage Vsat by a constant “−1”. The adder 832 adds the output values of the absolute value calculator 814 and the multipliers 815 and 816 to calculate the fault diagnosis voltage VB1_FD represented by the following equation (8). VB1_FD = | VB1 |-[(Vpeak / 2) + Vsat] Formula (8)

The comparator 852 compares “VB1_FD” with “zero”. When VB1_FD is less than or equal to zero, the comparator 852 outputs “0” indicating that the actual voltage VB1 is normal to the logic circuit OR871. When VB1_FD is greater than zero, the comparator 852 outputs "1" indicating that the actual voltage VB1 is abnormal to the logic circuit OR871. ‥

The absolute value calculator 817 of the failure diagnosis unit 801 calculates the absolute value of the actual voltage VC1. The multiplier 818 multiplies the voltage peak value Vpeak by a constant “−½”. The multiplier 819 multiplies the saturation voltage Vsat by a constant “−1”. The adder 833 adds the output values of the absolute value calculator 817 and the multipliers 818 and 819 to calculate the fault diagnosis voltage VC1_FD represented by the following equation (9). VC1_FD = | VC1 |-[(Vpeak / 2) + Vsat] Formula (9)

The comparator 853 compares “VC1_FD” with “zero”. When VC1_FD is less than or equal to zero, the comparator 853 outputs “0” indicating that the actual voltage VC1 is normal to the logic circuit OR871. When VC1_FD is greater than zero, the comparator 853 outputs “1” indicating that the actual voltage VC1 is abnormal to the logic circuit OR871. ‥

The logic circuit OR871 takes the logical sum of the output signals of the comparators 851, 852 and 853. The logic circuit OR871 outputs a logical sum to the motor control unit 900 as a failure signal 2_FD indicating the presence / absence of a failure of the second inverter 130. ‥

When the output signals of the comparators 851, 852, 853 are all "0", the logic circuit OR871 outputs "0" indicating that the second inverter 130 is normal as the failure signal 2_FD. When at least one of the output signals of the comparators 851, 852, 853 is “1”, the logic circuit OR871 outputs “1” indicating that the second inverter 130 has a failure as the failure signal 2_FD. ‥

For example, when the low-side switch element SW_A2L has an open failure, no current flows through the switch element. As a result, the lower peak value (negative value) of the actual voltage VA2 increases and its absolute value decreases due to the influence of the counter electromotive force of the motor 200. When no open failure has occurred in the low-side switch element SW_A2L, VA1≈ [(Vpeak / 2) + Vsat], and the magnitude of the actual voltage VA1 becomes equal to | (Vpeak / 2) + Vsat |. On the other hand, when an open failure occurs in the low side switch element SW_A2L, this balance is lost. For example, since no current flows through the switch element SW_A2L, an extra voltage is applied to the switch element SW_A1L. The actual voltage VA1 increases and VA1_FD> 0. ‥

The failure diagnosis unit 802 shown in FIG. 19 executes the same processing as the failure diagnosis unit 801, and diagnoses the presence or absence of a failure in the first inverter 120. Instead of the actual voltages VA1, VB1 and VC1, the actual voltages VA2, VB2 and VC2 are input to the failure diagnosis unit 802. Since the other processes of the failure diagnosis unit 802 are the same as those of the failure diagnosis unit 801, detailed description thereof will be omitted here. ‥

Further, the fault diagnosis voltage may be obtained by a method other than the above calculation. For example, the fault diagnosis voltage VA1_FD may be obtained by the calculation of the following formula (10). VA1_FD = VA1 ² − [(Vpeak / 2) + Vsat] ² Formula (10)

Further, for example, the failure diagnosis voltage VA1_FD may be calculated by the following equation (11). A1_FD = [VA1 + (Vpeak / 2) + Vsat] [VA1- (Vpeak / 2) -Vsat] Formula (11): ‘A1_FD’

By using these calculations, it is possible to diagnose whether or not there is a failure in the inverter as in the above. ‥

Below, the validity of the algorithm used for the fault diagnosis according to the present disclosure is verified by using the “Rapid Control Prototyping (RCP) System” of dSPACE and the Matlab / Simlink of MathWorks. A model of a surface magnet type (SPM) motor used in an electric power steering (EPS) device, which is controlled by vector control, was used for this verification. In the verification, the q-axis current command value Iq_ref was set to 3A, and the d-axis current command value Id_ref and the zero-phase current command value Iz_ref were set to 0A. The rotation speed ω of the motor was set to 1200 rpm. In the simulation, an open failure is caused in the low side switch element SW_A1L of the first inverter 120 at time 1.641s. ‥

21 to 23 show simulation results of the waveform of each signal. The vertical axis of each graph represents voltage (V), and the horizontal axis represents time (s). ‥

FIG. 21 shows waveforms of the actual voltage VA1 (upper side) and the actual voltage VA2 (lower side) when the low-side switch element SW_A1L has an open failure. FIG. 22 shows waveforms of the actual voltage VB1 (upper side) and the actual voltage VB2 (lower side) when the low-side switch element SW_A1L has an open failure. FIG. 23 shows waveforms of the actual voltage VC1 (upper side) and the actual voltage VC2 (lower side) when the low-side switch element SW_A1L has an open failure.

It can be seen that after the open failure of the low-side switch element SW_A1L at time 1.641s, the lower peak value of the actual voltage VA1 rises as shown in FIG. Further, it can be seen that the upper peak value of the actual voltage VA2 is increasing. That is, the absolute value of the upper peak value of the actual voltage VA2 becomes large. As shown in FIGS. 22 and 23, the actual voltages VB1, VB2, VC1 and VC2 have a small degree of change. ‥

Even in the normal operation, it is possible that the actual voltage becomes slightly higher than Vpeak / 2. However, in the present embodiment, the value obtained by adding the saturation voltage Vsat to Vpeak / 2 is compared with the actual voltage. Therefore, it is possible to determine that a failure occurs only when a greatly changed actual voltage such as the actual voltage VA2 shown in FIG. 21 is generated. When the actual voltage is higher than Vpeak / 2 in the normal operation, the failure determination is not performed and the accuracy of the failure determination can be improved. ‥

By the above-described processing described with reference to FIGS. 5 and 6, it is possible to identify which phase has failed and which of the high side and the low side has failed. In addition, it is possible to identify which of the first and second inverters has failed by the processing described with reference to FIGS. 18 and 19. That is, based on the determination results of the processes shown in FIGS. 5, 6, 18, and 19, the motor control unit 900 determines which of the twelve switch elements included in the first and second inverters. It is possible to identify whether the car has failed. By being able to specify which switch element has failed, it is possible to change the control according to the position of the failed switch element. ‥

For example, when it is determined that the low side of the first phase is out of order and the first inverter is out of order, a neutral point may be formed on the high side of the first inverter. When it is determined that the high side of the first phase is out of order and the first inverter is out of order, a neutral point may be formed on the low side of the first inverter. For example, when the low side switch element SW_A1L fails, the low side switch elements SW_B1L and SW_C1L are turned off. Then, the high side switch elements SW_A1H, SW_B1H and SW_C1H are turned on. Accordingly, a neutral point is formed on the high side of the first inverter 120. By operating the second inverter 130 using this neutral point, the driving of the motor 200 can be continued. ‥

Further, for example, when the high-side switch element SW_A1H fails, the high-side switch elements SW_B1H and SW_C1H are turned off. Then, the low side switch elements SW_A1L, SW_B1L and SW_C1L are turned on. Accordingly, a neutral point is formed on the low side of the first inverter 120. By operating the second inverter 130 using this neutral point, the driving of the motor 200 can be continued. ‥

(Second Embodiment) FIG. 24 schematically shows a typical configuration of an electric power steering apparatus 3000 according to the present embodiment. ‥

Vehicles such as automobiles generally have an electric power steering device. The electric power steering device 3000 according to the present embodiment has a steering system 520 and an auxiliary torque mechanism 540 that generates an auxiliary torque. The electric power steering device 3000 generates an auxiliary torque that assists the steering torque of the steering system generated by the driver operating the steering wheel. The auxiliary torque reduces the driver's operational burden. ‥

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522, universal joints 523A and 523B, a rotary shaft 524, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B, tie rods 527A and 527B, and knuckles. 528A, 528B, and left and right steered wheels 529A, 529B. ‥

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, a vehicle electronic control unit (ECU) 542, a motor 543, a speed reduction mechanism 544, and the like. The steering torque sensor 541 detects the steering torque in the steering system 520. The ECU 542 generates a drive signal based on the detection signal of the steering torque sensor 541. The motor 543 generates an auxiliary torque according to the steering torque based on the drive signal. The motor 543 transmits the generated auxiliary torque to the steering system 520 via the speed reduction mechanism 544. ‥

The ECU 542 includes, for example, the controller 340 and the drive circuit 350 according to the first embodiment. In automobiles, an electronic control system centered on the ECU is built. In the electric power steering device 3000, for example, a motor drive unit is constructed by the ECU 542, the motor 543, and the inverter 545. The motor module 2000 according to the first embodiment can be preferably used in the system. ‥

The embodiments of the present disclosure are also suitably used for X-by-wire such as shift-by-wire, steering-by-wire, and brake-by-wire, and motor control systems such as traction motors. For example, an EPS that implements the failure diagnosis method according to the embodiment of the present disclosure is an autonomous vehicle that corresponds to levels 0 to 5 (automation standard) defined by the Government of Japan and the US Department of Transportation Highway Traffic Safety Administration (NHTSA). Can be installed.

The embodiments of the present disclosure can be widely used for various devices including various motors such as a vacuum cleaner, a dryer, a ceiling fan, a washing machine, a refrigerator, and an electric power steering device.

100: Inverter unit, 101: Power supply, 120: First inverter, 130: Second inverter, 140: Inverter, 150: Current sensor, 200: Motor, 300: Control circuit, 310: Power supply circuit, 320: Angle sensor, 330 : Input circuit, 340: micro controller, 350: drive circuit, 360: ROM, 1000: power converter, 2000: motor module, 3000: electric power steering device

Claims (16)

1. A failure diagnosis method for diagnosing a failure of a power conversion device that converts power from a power supply into power supplied to a motor having n-phase (n is an integer of 3 or more) windings, wherein the power conversion device comprises: A first inverter connected to the first end of each phase winding of the motor, a second inverter connected to the second end of each phase winding, and a first high-side switching element, It is provided with n H bridges having one low-side switch element, a second high-side switch element and a second low-side switch element, and the n-phase includes a first phase, a second phase and a third phase, and the failure The diagnostic method is the sum of the voltage across the low-side switching element of the first phase in the first inverter and the voltage across the low-side switching element of the first phase in the second inverter, and the first saturation. Determining the magnitude relationship with the pressure, determining the magnitude relationship between the interphase voltage between the second phase and the third phase, and the second saturation voltage, the sum of the voltage across both ends, and the first A failure diagnosis method comprising: a step of judging whether or not there is a failure of the first phase based on a result of judgment of a magnitude relationship with a saturation voltage and a result of judgment of a magnitude relationship between the interphase voltage and the second saturation voltage. .
2. The interphase voltage is the sum of the voltage across the second-phase low-side switch element in the first inverter and the voltage across the second-phase low-side switch element in the second inverter, and the first voltage in the first inverter. The fault diagnosis method according to claim 1, wherein the difference is the difference between the voltage across the three-phase low-side switch element and the voltage across the third-phase low-side switch element in the second inverter.
3. The step of determining the magnitude relationship between the interphase voltage and the second saturation voltage includes the step of determining the magnitude relationship by using the interphase voltage VBC represented by the following equation, and VBC = (VB1 + VB2)-( VC1 + VC2) where VB1 indicates the voltage across the second phase low-side switch element in the first inverter, VB2 indicates the voltage across the second phase low-side switch element in the second inverter, and VC1 indicates the voltage The fault diagnosis method according to claim 1 or 2, wherein a voltage across the third-phase low-side switch element in the first inverter is shown, and VC2 is a voltage across the third-phase low-side switch element in the second inverter. .
4. The step of determining the presence or absence of the failure is that the sum of the voltage across the first-phase low-side switch element in the first inverter and the voltage across the first-phase low-side switch element in the second inverter is the 4. The method according to claim 1, further comprising a step of determining that the low side of the first phase is out of order if the absolute value of the interphase voltage is larger than one saturation voltage and the absolute value of the interphase voltage is smaller than the second saturation voltage. The failure diagnosis method described in.
5. The step of determining the presence or absence of the failure is that the sum of the voltage across the first-phase low-side switching element in the first inverter and the voltage across the first-phase low-side switching element in the second inverter is negative. If the value is smaller than the first saturation voltage and the absolute value of the inter-phase voltage is smaller than the second saturation voltage, it is determined that the high side of the first phase has a failure. 5. The failure diagnosis method according to any one of 1 to 3.
6. Determining a magnitude relationship between a sum of a voltage across the first-phase low-side switch element in the first inverter and a voltage across the first-phase low-side switch element in the second inverter and the first saturation voltage. The fault diagnosis method according to claim 1, further comprising: performing a step of determining a magnitude relationship between the interphase voltage and the second saturation voltage after performing the above step.
7. Determining a magnitude relationship between a sum of a voltage across the first-phase low-side switch element in the first inverter and a voltage across the first-phase low-side switch element in the second inverter and the first saturation voltage. 6. The failure diagnosis method according to claim 1, wherein the step of determining the magnitude relationship between the interphase voltage and the second saturation voltage is performed simultaneously.
8. When it is determined that the first phase is out of order, the control of the first and second inverters is changed from the n-phase energization control to another m phase (m is different from the first phase of the n phases). The fault diagnosis method according to claim 1, further comprising a step of changing to m-phase energization control using an integer of 2 or more and less than n).
9. The fault diagnosis method according to claim 4, further comprising a step of determining whether or not there is a fault in at least one of the first and second inverters.
10. 10. The method according to claim 9, further comprising configuring a neutral point on a high side of the first inverter when it is determined that the low side of the first phase has a failure and the first inverter has a failure. Fault diagnosis method described.
11. The failure diagnosis method according to claim 5, further comprising a step of determining whether or not there is a failure in at least one of the first and second inverters.
12. 12. The method according to claim 11, further comprising configuring a neutral point on a low side of the first inverter when it is determined that the high side of the first phase has a failure and the first inverter has a failure. Fault diagnosis method described.
13. The first saturation voltage and the second saturation voltage are determined by using a look-up table having a current value determined based on the d-axis current and the q-axis current in the dq coordinate system and the rotation speed of the motor as inputs. The fault diagnosis method according to claim 1, further comprising a step of performing.
14. A power conversion device for converting power from a power source into power supplied to a motor having n-phase (n is an integer of 3 or more) winding, wherein the power conversion device is a winding for each phase of the motor. A first inverter connected to the first end of the, and a second inverter connected to the second end of the winding of each phase, a first high-side switch element, a first low-side switch element, a second high It is provided with n H bridges having a side switch element and a second low side switch element, and a control circuit for controlling the operation of the first and second inverters, wherein the n phase is a first phase, a second phase and The control circuit includes a third phase, and the control circuit includes a voltage across the low-side switching element of the first phase in the first inverter and the low-side switching element of the first phase in the second inverter. The magnitude relationship between the sum of the both-end voltage and the first saturation voltage is determined, and the magnitude relationship between the interphase voltage between the second phase and the third phase and the second saturation voltage is determined, and the both-end voltage is determined. Of the first phase based on the determination result of the magnitude relationship between the sum of the above and the first saturation voltage and the determination result of the magnitude relationship between the interphase voltage and the second saturation voltage, power conversion apparatus.
15. A motor module comprising a motor and the power conversion device according to claim 14.
16. An electric power steering apparatus comprising the motor module according to claim 15.
    

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