CN112119580A

CN112119580A - Fault diagnosis method, power conversion device, motor module, and electric power steering device

Info

Publication number: CN112119580A
Application number: CN201980031754.4A
Authority: CN
Inventors: A·哈德利
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2018-05-15
Filing date: 2019-03-27
Publication date: 2020-12-22
Also published as: JPWO2019220780A1; WO2019220780A1

Abstract

A failure diagnosis method of an embodiment of the present disclosure diagnoses a failure of a power conversion device (1000) that converts power from a power source (101) into power to be supplied to a motor (200). The fault diagnosis method comprises the following steps: an acquisition step of acquiring A1 st actual voltage (VA1) indicating a voltage across both ends of A1 st low-side switching element (SW _ A1L), a saturation voltage (Vsat) of the 1 st low-side switching element, and a voltage peak value (Vpeak) determined from a d-axis voltage and a q-axis voltage in a dq coordinate system; and a diagnosis step of diagnosing whether or not the 2 nd inverter (130) has a failure based on the 1 st actual voltage, the saturation voltage, and the voltage peak.

Description

Fault diagnosis method, power conversion device, motor module, and electric power steering device

Technical Field

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

Background

In recent years, an electromechanical motor in which an electric motor (hereinafter, simply referred to as "motor"), an inverter, and an ECU are integrated has been developed. In the field of vehicle mounting in particular, high quality assurance is required from the viewpoint of safety. Therefore, a redundant design is adopted which can continue the safety operation even if a part of the components fails. As an example of the redundant design, a method of providing two power conversion devices to one motor has been studied. As another example, a method of providing a standby microcontroller to a main microcontroller is studied.

Patent document 1 discloses a motor drive device having a1 st system and a2 nd system. The 1 st system is connected to the 1 st coil group of the motor, and includes a1 st inverter unit, a power supply relay, a reverse connection protection relay, and the like. The 2 nd system is connected to the 2 nd coil group of the motor, and has a2 nd inverter unit, a power supply relay, a reverse connection protection relay, and the like. When no trouble occurs in the motor driving device, the motor can be driven by using both the 1 st system and the 2 nd system. On the other hand, when one of the 1 st and 2 nd systems or one of the 1 st and 2 nd coil groups fails, the power supply relay cuts off the supply of electric power from the power supply to the failed system or the system connected to the failed coil group. The motor drive can be continued using another system in which no failure has occurred.

Patent documents 2 and 3 also disclose motor driving apparatuses having the 1 st system and the 2 nd system. Even if one system or one coil group is failed, the motor driving can be continued by the system that is not failed.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open gazette: japanese patent laid-open publication No. 2016-34204

Patent document 2: japanese laid-open gazette: japanese patent laid-open publication No. 2016 & 32977

Patent document 3: japanese laid-open gazette: japanese patent laid-open No. 2008-132919

Disclosure of Invention

Problems to be solved by the invention

In the above-described prior art, it is required to appropriately detect a failure of the inverter.

Embodiments of the present disclosure provide a fault diagnosis method capable of appropriately diagnosing a fault of an inverter.

Means for solving the problems

An exemplary fault diagnosis method of the present disclosure diagnoses a fault of a power conversion device that converts power from a power supply into power supplied to a motor having at least one phase winding, wherein the power conversion device has: a1 st inverter connected to one end of the at least one phase winding and having a1 st high-side switching element and a1 st low-side switching element; a2 nd inverter connected to the other end of the at least one phase winding and having a2 nd high-side switching element and a2 nd low-side switching element; and an H-bridge including the 1 st high-side switching element, the 1 st low-side switching element, the 2 nd high-side switching element, and the 2 nd low-side switching element, the failure diagnosis method including the steps of: an acquisition step of acquiring a1 st actual voltage indicating a voltage across the 1 st low-side switching element, a saturation voltage of the 1 st low-side switching element, and a voltage peak determined from a d-axis voltage and a q-axis voltage in a dq coordinate system; and diagnosing whether or not the 2 nd inverter has a fault based on the 1 st actual voltage, the saturation voltage, and the voltage peak.

An exemplary power conversion device of the present disclosure converts power from a power source into power supplied to a motor having at least one phase winding, wherein the power conversion device has: a1 st inverter connected to one end of the at least one phase winding and having a1 st high-side switching element and a1 st low-side switching element; and a2 nd inverter connected to the other end of the at least one phase winding and having a2 nd high-side switching element and a2 nd low-side switching element; an H-bridge including the 1 st high-side switching element, the 1 st low-side switching element, the 2 nd high-side switching element, and the 2 nd low-side switching element; and a control circuit that controls operations of the 1 st inverter and the 2 nd inverter, wherein the control circuit acquires a1 st actual voltage indicating a voltage across the 1 st low-side switching element, a saturation voltage of the 1 st low-side switching element, and a voltage peak determined from a d-axis voltage and a q-axis voltage in a dq coordinate system, and diagnoses a fault in the 2 nd inverter based on the 1 st actual voltage, the saturation voltage, and the voltage peak.

Effects of the invention

According to exemplary embodiments of the present disclosure, a fault diagnosis method, a power conversion device, a motor module having the power conversion device, and an electric power steering device having the motor module, which can appropriately diagnose a fault of an inverter, are provided.

Drawings

Fig. 1 is a block diagram schematically illustrating a motor module of an embodiment.

Fig. 2 is a circuit diagram schematically illustrating an inverter unit of an embodiment.

Fig. 3A is a schematic diagram showing an a-phase H-bridge.

Fig. 3B is a schematic diagram showing an H bridge of the B phase.

Fig. 3C is a schematic diagram showing an H bridge of the C phase.

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 fault diagnosis of the 2 nd inverter.

Fig. 6 is a functional block diagram showing functional blocks for performing fault diagnosis of the 1 st inverter.

Fig. 7 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. 8 is a graph showing waveforms of simulation results of the actual voltage VA1 (upper side) and the actual voltage VA2 (lower side) in the case where the open failure has occurred in the low-side switching element SW _ A1L.

Fig. 9 is a graph showing waveforms of simulation results of the actual voltage VB1 (upper side) and the actual voltage VB2 (lower side) in the case where the open failure has occurred in the low-side switching element SW _ A1L.

Fig. 10 is a graph showing waveforms of simulation results of the actual voltage VC1 (upper side) and the actual voltage VC2 (lower side) in the case where the open failure has occurred in the low-side switching element SW _ A1L.

Fig. 11 is a schematic diagram showing an electric power steering apparatus according to an exemplary embodiment.

Detailed Description

Hereinafter, embodiments of the inverter fault diagnosis method, the power conversion device, the motor module, and the electric power steering device according to the present disclosure will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted in order to avoid unnecessarily obscuring the following description. For example, detailed descriptions of known matters and repetitive descriptions of substantially the same configuration may be omitted.

In the present specification, an embodiment of the present disclosure will be described by taking as an example a power conversion device that converts power from a power supply into power to be supplied to a three-phase motor having three-phase (a-phase, B-phase, and C-phase) windings. A power conversion device that converts power from a power supply into power to be supplied to an n-phase motor having four-phase or five-phase windings (n is an integer of 4 or more), and a method for diagnosing a fault of an inverter used in the device are also included in the present disclosure.

(embodiment mode 1)

[ 1] Structure of Motor Module 2000 and Power conversion device 1000 ]

Fig. 1 schematically shows a typical block structure of a motor module 2000 of the present embodiment.

Typically, the motor module 2000 has a power conversion apparatus 1000 and a motor 200, the power conversion apparatus 1000 having an inverter unit 100 and a control circuit 300. The motor module 2000 is modular and can be manufactured and sold as, for example, an electromechanical integrated motor having a motor, a sensor, a driver, and a controller.

The power conversion device 1000 can convert power from the power source 101 (see fig. 2) into power to be supplied to the motor 200. The power conversion device 1000 is connected to the motor 200. For example, the power conversion device 1000 can convert dc power into three-phase ac power that is pseudo sine waves of a phase, B phase, and C phase. In this specification, "connection" of components (constituent elements) mainly means electrical connection.

The motor 200 is, for example, a three-phase ac motor. The motor 200 has a winding M1 of a phase, a winding M2 of B phase, and a winding M3 of C phase, and is connected to the 1 st inverter 120 and the 2 nd inverter 130 of the inverter unit 100. Specifically, the 1 st inverter 120 is connected to one end of each phase winding of the motor 200, and the 2 nd 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. The components of the control circuit 300 are mounted on, for example, a 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 input signals from the current sensor 150 and the angle sensor 320. As a control method thereof, for example, there is vector control, Pulse Width Modulation (PWM), or Direct Torque Control (DTC). However, depending on the motor control method (e.g., sensorless control), the angle sensor 320 may not be necessary.

The control circuit 300 can control the position, the rotation speed, the current, and the like of the target rotor of the motor 200 to realize closed-loop control. In addition, the control circuit 300 may have 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 (e.g., 3V or 5V) necessary for each block in the circuit based on a voltage of, for example, 12V of the power supply 101.

The angle sensor 320 is, for example, a resolver or a hall IC. Alternatively, the angle sensor 320 may be implemented by a combination of a sensor magnet and a Magnetoresistive (MR) sensor having an MR element. The angle sensor 320 detects a rotation angle of the rotor (hereinafter referred to as a "rotation signal") and outputs the rotation signal to the controller 340.

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

The controller 340 is an integrated circuit that controls the entire power conversion device 1000, and is, for example, a microcontroller or an FPGA (Field Programmable Gate Array). The controller 340 controls the switching operation (on or off) of each switching element (typically, a semiconductor switching element) in the 1 st inverter 120 and the 2 nd inverter 130 of the inverter unit 100. The controller 340 sets a target current value based on the actual current value, the rotor rotation signal, and the like, generates a PWM signal, and outputs the PWM signal to the drive circuit 350.

The driver circuit 350 is typically a pre-driver (sometimes also referred to as a "gate driver"). The drive circuit 350 generates a control signal (gate control signal) for controlling the switching operation of each switching element in the 1 st inverter 120 and the 2 nd inverter 130 of the inverter unit 100 based on the PWM signal, and supplies the control signal to the gate of each switching element. When the driving target is a motor that can be driven at a low voltage, a pre-driver is not necessary. In this case, the function of the pre-driver can be installed in the controller 340.

ROM 360 is, for example, a writeable memory (e.g., PROM), rewriteable memory (e.g., flash memory), or read-only memory. The ROM 360 stores a control program including a group of instructions for causing the controller 340 to control the power conversion apparatus 1000. For example, the control program is loaded once in a RAM (not shown) at the time of startup.

A specific circuit configuration of the inverter unit 100 will be described with reference to fig. 2.

Fig. 2 schematically shows a circuit configuration of the inverter unit 100 of the present embodiment.

The power supply 101 generates a predetermined power supply voltage (for example, 12V). As the power source 101, for example, a dc power source is used. However, the power source 101 may be an AC-DC converter or a DC-DC converter, or may be a battery (secondary battery). The power source 101 may be a single power source shared by the 1 st inverter 120 and the 2 nd inverter 130 as shown in the figure, or may include a1 st power source (not shown) for the 1 st inverter 120 and a2 nd power source (not shown) for the 2 nd inverter 130.

Although not shown, coils are provided between the power source 101 and the 1 st inverter 120, and between the power source 101 and the 2 nd inverter 130. The coil functions as a noise filter, and smoothes high-frequency noise included in a 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. Further, a capacitor is connected to a power supply terminal of each inverter. The capacitor is a so-called bypass capacitor, and suppresses voltage fluctuation. The capacitor is, for example, an electrolytic capacitor, and the capacitance and the number of capacitors to be used are appropriately determined in accordance with design specifications and the like.

The 1 st inverter 120 has a bridge circuit composed of 3 legs. Each branch has a high-side switching element, a low-side switching element, and a shunt resistor. The phase a branch has a high-side switching element SW _ A1H, a low-side switching element SW _ A1L, and A1 st shunt resistor S _ A1. The phase-B branch has a high-side switching element SW _ B1H, a low-side switching element SW _ B1L and a1 st shunt resistor S _ B1. The C-phase branch has a high-side switching element SW _ C1H, a low-side switching element SW _ C1L and a1 st shunt resistor S _ C1.

As the switching element, for example, a field effect transistor (typically, MOSFET) in which a parasitic diode is formed, or a combination of an Insulated Gate Bipolar Transistor (IGBT) and a free wheel diode connected in parallel thereto can be used.

The 1 st shunt resistor S _ A1 is used to detect the a-phase current IA1 flowing through the a-phase winding M1, and is connected between the low-side switching element SW _ A1L and the GND line GL, for example. The 1 st shunt resistor S _ B1 is used to detect the B-phase current IB1 flowing through the B-phase winding M2, and is connected between the low-side switching element SW _ B1L and the GND line GL, for example. The 1 st shunt resistor S _ C1 is used to detect the C-phase current IC1 flowing through the C-phase winding M3, and is connected between the low-side switching element SW _ C1L and the GND line GL, for example. The 3 shunt resistors S _ a1, S _ B1, and S _ C1 are connected in common to the GND line GL of the 1 st inverter 120.

The 2 nd inverter 130 has a bridge circuit composed of 3 legs. Each branch has a high-side switching element, a low-side switching element, and a shunt resistor. The a-phase branch has a high-side switching element SW _ A2H, a low-side switching element SW _ A2L, and a shunt resistor S _ A2. The B-phase branch has a high-side switching element SW _ B2H, a low-side switching element SW _ B2L, and a shunt resistor S _ B2. The C-phase branch has a high-side switching element SW _ C2H, a low-side switching 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 between the low-side switching element SW _ A2L and the GND line GL, for example. The shunt resistor S _ B2 is used to detect the B-phase current IB2, and is connected between the low-side switching element SW _ B2L and the GND line GL, for example. The shunt resistor S _ C2 is used to detect the C-phase current IC2, and is connected between the low-side switching element SW _ C2L and the GND line GL, for example. The 3 shunt resistors S _ a2, S _ B2, and S _ C2 are connected in common to the GND line GL of the 2 nd inverter 130.

The current sensor 150 includes, for example, shunt resistors S _ a1, S _ B1, S _ C1, S _ a2, S _ B2, and S _ C2, and a current detection circuit (not shown) that detects a current flowing through each shunt resistor.

The a-phase arm of the 1 st inverter 120 (specifically, a node between the high-side switching element SW _ A1H and the low-side switching element SW _ A1L) is connected to one end A1 of the a-phase winding M1 of the motor 200, and the a-phase arm of the 2 nd inverter 130 is connected to the other end a2 of the a-phase winding M1. The B-phase branch of the 1 st inverter 120 is connected to one end B1 of the B-phase winding M2 of the motor 200, and the B-phase branch of the 2 nd inverter 130 is connected to the other end B2 of the winding M2. The C-phase branch of the 1 st inverter 120 is connected to one end C1 of the C-phase winding M3 of the motor 200, and the C-phase branch of the 2 nd inverter 130 is connected to the other end C2 of the winding M3.

Fig. 3A schematically shows the structure of an a-phase H-bridge BA. Fig. 3B schematically shows the structure of the H-bridge BB of the B-phase. Fig. 3C schematically shows the structure of the C-phase H-bridge BC.

Inverter unit 100 has a phase a, a phase B, and a phase C H-bridges BA, BB, and BC. The a-phase H-bridge BA has a high-side switching element SW _ A1H and a low-side switching element SW _ A1L in the 1 st inverter 120-side branch, a high-side switching element SW _ A2H and a low-side switching element SW _ A2L in the 2 nd inverter 130-side branch, and a winding M1.

The B-phase H-bridge BB has a high-side switching element SW _ B1H and a low-side switching element SW _ B1L in the 1 st inverter 120-side branch, a high-side switching element SW _ B2H and a low-side switching element SW _ B2L in the 2 nd inverter 130-side branch, and a winding M2.

The C-phase H-bridge BC has a high-side switching element SW _ C1H and a low-side switching element SW _ C1L in the 1 st inverter 120-side branch, a high-side switching element SW _ C2H and a low-side switching element SW _ C2L in the 2 nd inverter 130-side branch, and a winding M3.

The control circuit 300 (specifically, the controller 340) can specify the inverter having the failure, out of the 1 st inverter 120 and the 2 nd inverter 130, by performing the inverter failure diagnosis described below. The following describes details of the failure diagnosis of the inverter.

[ 2 ] Fault diagnosis method for inverter ]

A specific example of a failure diagnosis method for diagnosing a failure of an inverter used in, for example, the power conversion apparatus 1000 shown in fig. 1 will be described with reference to fig. 4 to 7. The fault diagnosis method of the present disclosure is suitable for use in a power conversion apparatus having at least one H-bridge, for example, a full-bridge type power conversion apparatus. In this specification, the failure of the inverter refers to an open failure of the switching element. An open circuit fault is a fault in which the switching element is always high impedance. In this specification, for example, a case where an open fault occurs in the high-side switching element SW _ A1H or SW _ A1L of the 1 st inverter 120 is sometimes referred to as a fault of the 1 st inverter 120.

In the fault diagnosis, for example, the current and voltage indicated in the dq coordinate system, the actual voltage indicating the voltage across the low-side switching element, and the rotation speed ω of the motor are acquired. The current and voltage represented in the dq coordinate system include a d-axis voltage Vd, a q-axis voltage Vq, a d-axis current Id, and a q-axis current Iq. In the dq coordinate system, an axis corresponding to zero is represented as a z-axis. The rotation speed ω is expressed by the number of rotations (rpm) of the rotor of the motor per unit time (e.g., 1 minute) or the number of rotations (rps) of the rotor per unit time (e.g., 1 second).

The actual voltage of the switching element will be described with reference to fig. 3A to 3C.

The 1 st and 2 nd actual voltages are defined for the a, B and C phase H bridges BA, BB and BC, respectively. In the H-bridge of each phase, the 1 st actual voltage represents the voltage across the 1 st low-side switching element in the 1 st inverter 120-side branch. In other words, the 1 st actual voltage corresponds to a node potential between the 1 st high-side switching device and the 1 st low-side switching device in the 1 st inverter 120-side branch. The 2 nd actual voltage represents the both-end voltage of the 2 nd low-side switching element in the branch on the 2 nd inverter 130 side. In other words, the 2 nd actual voltage corresponds to a node potential between the 2 nd high-side switching device and the 2 nd low-side switching device in the branch on the 2 nd inverter 130 side. The voltage across the switching element is equal to the voltage Vds between the source and the drain of the FET as the switching element.

For the a-phase H-bridge BA, the 1 st actual voltage refers to the voltage VA1 across the low-side switching element SW _ A1L shown in fig. 3A, and the 2 nd 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 1 st actual voltage refers to the voltage VB1 across the low-side switching element SW _ B1L shown in fig. 3B, and the 2 nd 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 1 st actual voltage refers to the voltage VC1 across the low-side switching element SW _ C1L shown in fig. 3C, and the 2 nd actual voltage refers to the voltage VC2 across the low-side switching element SW _ C2L shown in fig. 3C.

Then, the inverter is diagnosed for a fault based on the obtained current and voltage of the dq coordinate system, the 1 st actual voltage, the 2 nd actual voltage, and the rotation speed.

When it is determined that the inverter has failed, a failure signal indicating that the inverter has failed is generated and output to a motor control unit described later. For example, a fault signal is a signal that is asserted when a fault occurs.

The above-described failure diagnosis is repeatedly performed in synchronization with, for example, the period of the current sensor 150 measuring the phase current of each phase, that is, the period of the AD conversion.

The algorithm for implementing the fault diagnosis method according to the present embodiment may be implemented by hardware such as an Application Specific Integrated Circuit (ASIC) or an FPGA, or may be implemented by a combination of a microcontroller and software. In the present embodiment, the controller 340 of the control circuit 300 is the main body of the failure diagnosis operation.

Fig. 4 illustrates functional blocks of the controller 340 for performing overall motor control. Fig. 5 illustrates functional blocks for performing fault diagnosis of the 2 nd inverter 130. Fig. 6 illustrates functional blocks for performing fault diagnosis of the 1 st inverter 120.

In this specification, each block in the functional block diagram is not expressed in a unit of hardware but in a unit of functional block. The software used for motor control and fault diagnosis may be, for example, a module constituting a computer program for executing specific processing corresponding to each functional block. Such a computer program is stored in the ROM 360, for example. The controller 340 can read out instructions from the ROM 360 and sequentially execute each process.

The controller 340 has, for example, a failure diagnosis unit 800 and a motor control unit 900. Thus, the failure diagnosis of the present disclosure can be appropriately combined with motor control (e.g., vector control), and can be incorporated into a series of processes of the motor control.

The failure diagnosis unit 800 acquires the rotation speed ω of the motor 200 and the d-axis current Id, the q-axis current Iq, the d-axis voltage Vd, and the q-axis voltage Vq in the dq coordinate system. The fault diagnosis unit 800 also acquires 1 st actual voltages VA1, VB1, and VC1, and 2 nd actual voltages VA2, VB2, and VC 2.

For example, the failure diagnosis unit 800 may have a pre-operation unit (not shown) that acquires Vpeak. The pre-arithmetic unit converts the three-phase currents Ia, Ib, and Ic obtained from the measurement values of the current sensor 150 into the current I α on the α axis and the current I β on the β axis in the α β fixed coordinate system using clark conversion. The pre-operation unit transforms the currents I α, I β into a d-axis current Id and a q-axis current Iq in a dq coordinate system using park transformation (dq coordinate transformation). The pre-operation means acquires d-axis voltage Vd and q-axis voltage Vq from currents Id and Iq, and calculates voltage peak value Vpeak from the acquired Vd and Vq based on the following equation (1). Alternatively, the pre-arithmetic unit may receive Vd and Vq necessary for calculating Vpeak from the motor control unit 900 that performs vector control. For example, the pre-arithmetic unit acquires Vpeak in synchronization with the period of each phase current measured by the current sensor 150.

Vpeak＝(2/3)^1/2(Vd²+Vq²)^1/2Equation (1)

Fault diagnosis section 800 refers to lookup table 840 (fig. 7) and determines saturation voltage Vsat from currents Id and Iq and rotation speed ω.

Fig. 7 schematically shows a look-up table (LUT)840 that determines the saturation voltage Vsat from the rotation speed ω and the current amplitude value. The LUT 840 calculates the rotation speed ω of the motor 200 and a current amplitude value (Id) determined based on the d-axis current and the q-axis current²+Iq²)^1/2Is correlated with the relation between the saturation voltage Vsat.

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

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

[ Table 1]

Rotational speed (rpm)	1000	1500	1800
				Iq(A)	0.14	0.53	1.43
Vsat(V)	0.28～0.36	0.35～0.51	0.20～0.36

The failure diagnosis unit 800 diagnoses the presence or absence of a failure of the inverter based on the actual voltage, the voltage peak value Vpeak, and the saturation voltage Vsat.

The failure diagnosis unit 800 generates a failure signal 1_ FD indicating a failure of the 1 st inverter 120 and a failure signal 2_ FD indicating a failure of the 2 nd inverter 130 based on the diagnosis result, and outputs the signals to the motor control unit 900.

The motor control unit 900 generates a PWM signal for controlling the entire switching operation of the switching elements of the 1 st inverter 120 and the 2 nd inverter 130, for example, by using vector control. The motor control unit 900 outputs the PWM signal to the driving circuit 350.

When the failure signal is asserted and it is difficult to continue the torque assist of the motor 200, the motor control unit 900 stops the torque assist of the motor 200, for example. In this case, the power conversion apparatus 1000 may output a notification signal for attracting attention of a person to a notification apparatus (not shown). The notification means, for example, uses at least one of light, sound, and display to call attention of a person. Thus, it can be recognized that the torque assist of the motor 200 is stopped. When the motor 200 is mounted on the electric power steering apparatus, the driver of the automobile can recognize that the torque assist of the motor for assisting the steering operation is stopped. The driver can follow the attention call of the notification device to stop the vehicle at, for example, a shoulder of a road.

In this specification, for convenience of description, each functional block may be referred to as a unit. Of course, these labels are not used to limit the interpretation of the functional blocks as hardware or software.

In the case where each functional block is installed in the controller 340 as software, the main body of execution of the software may be, for example, the core of the controller 340. As described above, the controller 340 can be implemented by an FPGA. In this case, all or a part of the functional blocks can be realized by hardware.

By performing distributed processing using a plurality of FPGAs, the computational load of a specific computer can be distributed. In this case, all or a part of the functional blocks shown in fig. 4 to 6 can be distributed and mounted on a plurality of FPGAs. The FPGAs are communicably connected to each other, for example, through a Controller Area Network (CAN) mounted on the vehicle, and CAN transmit and receive data.

The failure diagnosis unit 800 includes a failure diagnosis unit 801 for diagnosing the presence or absence of a failure in the 2 nd inverter 130 and a failure diagnosis unit 802 for diagnosing the presence or absence of a failure in the 1 st inverter 120 shown in fig. 5 and 6. The

failure diagnosis units

801 and 802 have substantially the same functional blocks, but the actual voltages inputted are different from each other.

The

failure diagnosis units

801 and 802 have

absolute value operators

811, 814, 817,

multipliers

812, 813, 815, 816, 818, 819,

adders

831, 832, 833,

comparators

851, 852, 853, and a logic circuit OR 871, respectively.

First, a process of diagnosing the presence or absence of a failure in the 2 nd inverter 130 will be described.

Absolute value calculator 811 of failure diagnosis unit 801 calculates the absolute value of actual voltage VA 1. Multiplier 812 multiplies the voltage peak Vpeak by a constant "-1/2". Multiplier 813 multiplies saturation voltage Vsat by a constant "-1". Adder 831 adds the output values of absolute value calculator 811 and

multipliers

812 and 813 to calculate failure diagnosis voltage VA1_ FD represented by the following equation (2).

VA1_ FD ═ VA1| - [ (Vpeak/2) + Vsat ] equation (2)

The comparator 851 compares "VA 1_ FD" with "zero". In the case where VA1_ FD is zero OR less (VA1_ FD ≦ 0), the comparator 851 outputs "0" indicating that the actual voltage VA1 is normal to the logic circuit OR 871. In the case where VA1_ FD is larger than zero (VA1_ FD > 0), the comparator 851 outputs "1" indicating that the actual voltage VA1 is abnormal to the logic circuit OR 871.

Likewise, the absolute value operator 814 of the fault diagnosis unit 801 calculates the absolute value of the actual voltage VB 1. Multiplier 815 multiplies the voltage peak Vpeak by the constant "-1/2". The multiplier 816 multiplies the saturation voltage Vsat by a constant "-1". Adder 832 adds the output values of absolute value calculator 814 and

multipliers

815 and 816 to calculate fault diagnosis voltage VB1_ FD shown in equation (3) below.

VB1_ FD ═ VB1| - [ (Vpeak/2) + Vsat ] equation (3)

Comparator 852 compares "VB 1_ FD" with "zero". In the case where VB1_ FD is zero OR less, the comparator 852 outputs "0" indicating that the actual voltage VB1 is normal to the logic circuit OR 871. In the case where VB1_ FD is larger than zero, the comparator 852 outputs "1" indicating that the actual voltage VB1 is abnormal to the logic circuit OR 871.

Absolute value calculator 817 of fault diagnosis unit 801 calculates the absolute value of actual voltage VC 1. Multiplier 818 multiplies the voltage peak Vpeak by the constant "-1/2". The multiplier 819 multiplies the saturation voltage Vsat by a constant "-1". Adder 833 adds the output values of absolute value calculator 817 and

multipliers

818 and 819 to calculate failure diagnosis voltage VC1_ FD shown by equation (4) below.

VC1_ FD ═ VC1| - [ (Vpeak/2) + Vsat ] equation (4)

Comparator 853 compares "VC 1_ FD" with "zero". When VC1_ FD is zero OR less, comparator 853 outputs "0" indicating that actual voltage VC1 is normal to logic circuit OR 871. In the case where VC1_ FD is larger than zero, the comparator 853 outputs "1" indicating that the actual voltage VC1 is abnormal to the logic circuit OR 871.

The logic circuit OR 871 logically sums the output signals of the

comparators

851, 852 and 853. The logic circuit OR 871 outputs the logical sum to the motor control unit 900 as a failure signal 2_ FD indicating the presence OR absence of a failure of the 2 nd inverter 130.

When all the output signals of the

comparators

851, 852, and 853 are "0", the logic circuit OR 871 outputs "0" indicating that the 2 nd 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 OR 871 outputs "1" indicating that the 2 nd inverter 130 has failed as the failure signal 2_ FD.

For example, when the low-side switching element SW _ A2L has an open fault, no current flows in the switching element. As a result, the lower peak (negative value) of the actual voltage VA2 rises due to the influence of the back electromotive force of the motor 200, and the absolute value thereof becomes small. When the low-side switching element SW _ A2L does not have an open circuit fault, VA1 ≈ (Vpeak/2) + Vsat), and the magnitude of the actual voltage VA1 is equal to | (Vpeak/2) + Vsat |. In contrast, when the low-side switching element SW _ A2L has an open failure, the balance is broken. For example, since no current flows in the switching element SW _ A2L, an excessive voltage is applied to the switching element SW _ A1L. The actual voltage VA1 becomes large, VA1_ FD > 0.

The failure diagnosis unit 802 shown in fig. 6 executes the same processing as the failure diagnosis unit 801 to diagnose the 1 st inverter 120 for a failure. The actual voltages VA2, VB2, VC2 are input to the fault diagnosis unit 802 instead of the actual voltages VA1, VB1, VC 1. The other processing of the failure diagnosis unit 802 is the same as that of the failure diagnosis unit 801, and thus detailed description is omitted here.

The failure diagnosis voltage may be obtained by a method other than the above calculation. For example, the failure diagnosis voltage VA1_ FD may be obtained by the following equation (5).

VA1_FD＝VA1²-〔(Vpeak/2)+Vsat〕²Formula (5)

For example, the failure diagnosis voltage VA1_ FD may be obtained by the following equation (6).

VA1_ FD ═ VA1+ (Vpeak/2) + Vsat [ VA1- (Vpeak/2) -Vsat ] equation (6)

The presence or absence of a failure in the inverter can be diagnosed using these calculations in the same manner as described above.

In the following, results of verifying the appropriateness of the algorithm used in the fault diagnosis of the present disclosure using the "Rapid Control Prototype (RCP) system" of dSPACE corporation and Matlab/Simulink of MathWorks corporation are shown. In this verification, a model for a surface magnet type (SPM) motor in an Electric Power Steering (EPS) device, which is controlled by vector control, is used. In the verification, the current reference value Iq _ ref for the q-axis is set to 3A, and the current reference value Id _ ref for the d-axis and the current reference value Iz _ ref for the zero phase are set to 0A. The rotation speed ω of the motor was set to 1200 rpm. In the simulation, the low-side switching element SW _ A1L of the 1 st inverter 120 was caused to have an open fault at time 1.64 s.

Simulation results of the waveforms of the respective signals are shown in fig. 8 to 10. The vertical axis of each graph represents voltage (V) and the horizontal axis represents time(s).

Fig. 8 shows waveforms of an actual voltage VA1 (upper side) and an actual voltage VA2 (lower side) in the case where an open failure has occurred in the low-side switching element SW _ A1L. Fig. 9 shows waveforms of the actual voltage VB1 (upper side) and the actual voltage VB2 (lower side) in the case where the open failure has occurred in the low-side switching element SW _ A1L. Fig. 10 shows waveforms of an actual voltage VC1 (upper side) and an actual voltage VC2 (lower side) in the case where an open failure has occurred in the low-side switching element SW _ A1L.

Therefore, the following steps are carried out: after the open-circuit failure of the low-side switching element SW _ A1L occurs at time 1.64s, the lower peak of the actual voltage VA1 rises as shown in fig. 8. In addition, it is known that: the upper peak of the actual voltage VA2 rises. That is, the absolute value of the upper peak of actual voltage VA2 becomes large. As shown in fig. 9 and 10, the actual voltages VB1, VB2, VC1, and VC2 have small variations.

Even in the normal operation, the actual voltage may become slightly larger 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 can be determined that a failure has occurred only when an actual voltage that changes greatly as in the case of the actual voltage VA2 shown in fig. 8 is generated. In the normal operation, the determination of a failure is not made when the actual voltage becomes greater than Vpeak/2, and thus the accuracy of the failure determination can be improved.

As described above, the fault diagnosis of the present disclosure can be realized by a simple algorithm. Therefore, for example, when the controller 340 is mounted, the circuit scale or the memory size can be reduced.

The fault diagnosis method of the present disclosure can also be applied to a full-bridge type power conversion apparatus. The full bridge has a single-phase H-bridge configuration, for example, a circuit configuration shown in fig. 3A. By applying the above-described failure diagnosis method to failure diagnosis of the full bridge, it is possible to detect a failure of the full bridge.

In the present embodiment, the above-described failure diagnosis 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 only the a-phase is subjected to the failure diagnosis, only the processing related to the a-phase, out of the processing described with reference to fig. 5 and 6, may be performed without performing the processing related to the B-phase and the C-phase.

(embodiment mode 2)

Fig. 11 schematically shows a typical configuration of an electric power steering apparatus 3000 of the present embodiment.

Vehicles such as automobiles generally have an electric power steering apparatus. The electric power steering apparatus 3000 of the present embodiment includes a steering system 520 and an assist torque mechanism 540 that generates an assist torque. The electric power steering apparatus 3000 generates an assist torque that assists a steering torque of a steering system generated by a driver operating a steering wheel. The operation load of the driver is reduced by the assist torque.

The steering system 520 may include, for example, a steering wheel 521, a steering shaft 522,

universal joints

523A, 523B, a rotating shaft 524, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A, 552B,

tie rods

527A, 527B, steering joints 528A, 528B, and left and right steered

wheels

529A, 529B.

The assist torque mechanism 540 is configured by, for example, a steering torque sensor 541, an automotive Electronic Control Unit (ECU)542, a motor 543, a speed reduction mechanism 544, and the like. The steering torque sensor 541 detects a steering torque in the steering system 520. ECU 542 generates a drive signal based on the detection signal of steering torque sensor 541. The motor 543 generates an assist torque corresponding to the steering torque based on the drive signal. The motor 543 transmits the generated assist 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 of embodiment 1. An electronic control system having an ECU as a core is built in an automobile. In the electric power steering apparatus 3000, for example, a motor drive unit is configured by the ECU 542, the motor 543, and the inverter 545. The motor module 2000 of embodiment 1 can be suitably used for this system.

Embodiments of the present disclosure are also applicable to X-ray control systems such as shift-by-wire systems, steer-by-wire systems, and brake-by-wire systems, and motor control systems such as traction motors. For example, the EPS to which the failure diagnosis method of the embodiment of the present disclosure is mounted can be mounted on an autonomous vehicle corresponding to a level 0 to 5 (automated reference) stipulated by the japan government and the u.s.department of transportation road traffic safety agency (NHTSA).

Industrial applicability

Embodiments of the present disclosure can be widely applied to various apparatuses having various motors, such as a dust collector, a dryer, a ceiling fan, a washing machine, a refrigerator, and an electric power steering apparatus.

Description of the reference symbols

100: an inverter unit; 101: a power source; 120: 1 st inverter; 130: a2 nd inverter; 140: an inverter; 150: a current sensor; 200: a motor; 300: a control circuit; 310: a power supply circuit; 320: an angle sensor; 330: an input circuit; 340: a microcontroller; 350: a drive circuit; 360: a ROM; 1000: a power conversion device; 2000: a motor module; 3000: an electric power steering apparatus.

Claims

1. A failure diagnosis method of diagnosing a failure of a power conversion apparatus that converts electric power from a power source into electric power to be supplied to a motor having at least one phase winding, wherein,

the power conversion device includes:

a1 st inverter connected to one end of the at least one phase winding and having a1 st high-side switching element and a1 st low-side switching element;

a2 nd inverter connected to the other end of the at least one phase winding and having a2 nd high-side switching element and a2 nd low-side switching element; and

an H-bridge including the 1 st high-side switching element, the 1 st low-side switching element, the 2 nd high-side switching element, and the 2 nd low-side switching element,

the fault diagnosis method comprises the following steps:

an acquisition step of acquiring a1 st actual voltage indicating a voltage across the 1 st low-side switching element, a saturation voltage of the 1 st low-side switching element, and a voltage peak determined from a d-axis voltage and a q-axis voltage in a dq coordinate system; and

and a diagnosing step of diagnosing whether or not the 2 nd inverter has a fault based on the 1 st actual voltage, the saturation voltage, and the voltage peak.

2. The failure diagnosis method according to claim 1,

the diagnosing step comprises the steps of: the presence or absence of a fault of the 2 nd inverter is diagnosed according to the 1 st fault diagnosis voltage VA1_ FD shown in the following equation,

VA1_FD＝|VA1|-〔(Vpeak/2)+Vsat〕

where VA1 represents the 1 st actual voltage, Vpeak represents the voltage peak, and Vsat represents the saturation voltage.

3. The failure diagnosis method according to claim 1,

VA1_FD＝VA1²-〔(Vpeak/2)+Vsat〕²

4. The failure diagnosis method according to claim 1,

VA1_FD＝〔VA1+(Vpeak/2)+Vsat〕〔VA1-(Vpeak/2)-Vsat〕

5. The fault diagnosis method according to any one of claims 2 to 4,

in the case where the 1 st failure diagnosis voltage VA1_ FD is zero or less, it is diagnosed that the 2 nd inverter is normal,

if the 1 st failure diagnosis voltage VA1_ FD is greater than zero, it is diagnosed that the 2 nd inverter has failed.

6. The fault diagnosis method according to any one of claims 1 to 5,

the fault diagnosis method further includes the steps of: when it is diagnosed that the 2 nd inverter has a failure, a failure signal indicating that the 2 nd inverter has a failure is output.

7. The fault diagnosis method according to any one of claims 1 to 6,

the saturation voltage is determined based on the rotation speed of the motor and the d-axis current and the q-axis current in the dq coordinate system.

8. The fault diagnosis method according to any one of claims 1 to 7,

in the acquiring, the saturation voltage is determined using a lookup table that relates an input of a rotation speed of the motor and a current value determined according to the d-axis current and the q-axis current to the saturation voltage.

9. The fault diagnosis method according to any one of claims 1 to 8,

the motor has n-phase windings, n is an integer of 3 or more,

the power conversion device has n H-bridges,

performing the acquiring step and the diagnosing step in each of the n H-bridges.

10. A power conversion apparatus that converts power from a power source into power to be supplied to a motor having at least one phase winding, wherein,

the power conversion device includes:

a1 st inverter connected to one end of the at least one phase winding and having a1 st high-side switching element and a1 st low-side switching element; and

a2 nd inverter connected to the other end of the at least one phase winding and having a2 nd high-side switching element and a2 nd low-side switching element;

an H-bridge including the 1 st high-side switching element, the 1 st low-side switching element, the 2 nd high-side switching element, and the 2 nd low-side switching element; and

a control circuit for controlling the operation of the 1 st inverter and the 2 nd inverter,

the control circuit acquires a1 st actual voltage indicating a voltage across the 1 st low-side switching element, a saturation voltage of the 1 st low-side switching element, and a voltage peak determined from a d-axis voltage and a q-axis voltage in a dq coordinate system, and diagnoses the presence or absence of a failure in the 2 nd inverter based on the 1 st actual voltage, the saturation voltage, and the voltage peak.

11. A motor module having:

a motor; and

the power conversion device of claim 10.

12. An electric power steering apparatus having the motor module of claim 11.