WO2019240004A1 - Failure diagnosis method, power conversion device, motor module, and electric power steering device - Google Patents

Abstract

The failure diagnosis method according to the present disclosure is used in a power conversion device equipped with at least one H-bridge to diagnose a failure of the H-bridge. The failure diagnosis method includes: a step of generating a monitoring signal for monitoring a failure of an H-bridge on the basis of a first current sine wave of a phase current, a second current sine wave obtained by shifting the phase of the first current sine wave by 90 degrees, and the rotational speed of a motor; a step of generating a pre-failure signal on the basis of the results of comparison between the monitoring signal and a failure level threshold value; and a step of calculating the logical product of the pre-failure signal and an activation signal for enabling or disenabling the pre-failure signal, thereby generating a failure signal indicating whether the H-bridge is failed or not.

Description

Failure diagnosis method, power conversion device, 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. In particular, high quality assurance is required from the viewpoint of safety in the in-vehicle field. Therefore, a redundant design that can continue safe operation even if a part of the component fails is adopted. As an example of a redundant design, it is considered to provide two power conversion devices for one motor. As another example, it is considered to provide a backup microcontroller in the main microcontroller.

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 set of the motor and includes a first inverter unit, a power supply relay, a reverse connection protection relay, and the like. The second system is connected to the second winding set of the motor and includes a second inverter unit, a power supply relay, a reverse connection protection relay, and the like. When there is no failure in the motor drive device, it is possible to drive the motor using both the first system and the second system. On the other hand, when a failure occurs in one of the first system and the second system, or one of the first winding group and the second winding group, the power relay is connected to the failed system or from the power source. The power supply to the system connected to the winding set is cut off. It is possible to continue motor driving 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 set fails, motor drive can be continued by a system that does not fail.

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

It is desired to appropriately detect a failure of the H bridge, particularly an open failure of the switch element in the H bridge.

The embodiment of the present disclosure provides a failure diagnosis method capable of appropriately diagnosing an open failure of a switch element in an H bridge.

An exemplary fault diagnosis method of the present disclosure uses an H-bridge for use in a power converter that includes at least one H-bridge that converts power from a power source into power supplied to a motor having at least one phase winding. A failure diagnosis method for diagnosing a failure, comprising: a first current sine wave of a phase current measured by a current sensor; a second current sine wave obtained by shifting the phase of the first current sine wave by 90 °; and the motor Generating a monitoring signal for monitoring a failure of the H-bridge based on the rotation speed, and generating a pre-failure signal based on a comparison result between the monitoring signal and a threshold of the failure level; Whether or not the H-bridge has failed by calculating a logical product of the pre-failure signal and an activation signal that enables or disables the pre-failure signal Including the steps of: generating a fault signal indicating a.

An exemplary power converter of the present disclosure is a power converter that converts power from a power source into power supplied to a motor having at least one phase winding, the power converter including at least one H-bridge and the at least one A control circuit for controlling the switching operation of the switching elements of the two H-bridges, wherein the control circuit sets the phase of the first current sine wave of the phase current measured by the current sensor to 90 °. Based on the second current sine wave obtained by shifting and the rotational speed of the motor, a monitoring signal for monitoring the H-bridge failure is generated, and the comparison result between the monitoring signal and the failure level threshold value is obtained. By generating a pre-failure signal based on and calculating a logical product of the pre-failure signal and an activation signal that enables or disables the pre-failure signal H-bridge to generate a fault signal indicating whether or not a failure.

According to exemplary embodiments of the present disclosure, a failure diagnosis method, a power conversion device, a motor module including the power conversion device, and the motor module capable of appropriately diagnosing an open failure of a switch element in an H-bridge An electric power steering apparatus is provided.

FIG. 1 is a block diagram schematically showing a typical block configuration of a motor module 2000 according to an exemplary embodiment 1. As shown in FIG. FIG. 2 is a circuit diagram schematically showing a circuit configuration of the inverter unit 100 according to the exemplary embodiment 1. As shown in FIG. FIG. 3 is a functional block diagram illustrating functional blocks of the controller 340 for performing overall motor control. FIG. 4A is a functional block diagram illustrating functional blocks of the monitoring signal unit 810A. FIG. 4B is a functional block diagram illustrating functional blocks of the monitoring signal unit 810B. FIG. 4C is a functional block diagram illustrating functional blocks of the monitoring signal unit 810C. FIG. 5 is a functional block diagram illustrating functional blocks of the cut-off frequency unit 820, the threshold unit 830, and the activation signal unit 840. FIG. 6 is a functional block diagram illustrating the pre-fault signal unit 850 and the fault signal unit 860. FIG. 7 is a functional block diagram illustrating another functional block of the monitoring signal unit 810A. FIG. 8 is a schematic diagram showing a change in the level of the A-phase monitoring signal ω2Ia_Peak2 when a failure occurs in the H-bridge. FIG. 9 exemplifies a current waveform (sine wave) obtained by plotting the current values flowing in the A-phase, B-phase, and C-phase windings of the motor 200 when the power conversion apparatus 1000 is controlled according to the three-phase energization control It is a graph to do. FIG. 10A shows a current waveform obtained by plotting the current values flowing in the B-phase and C-phase windings of the motor 200 when the power conversion apparatus 1000 is controlled according to the two-phase energization control when the A-phase H bridge fails. FIG. FIG. 10B shows a current waveform obtained by plotting 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 when the B-phase H-bridge fails. FIG. FIG. 10C shows a current waveform obtained by plotting the values of current flowing through 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 when the C-phase H-bridge fails. FIG. FIG. 11A is a graph showing a simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 250 rpm. FIG. 11B is a graph showing a simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 500 rpm. FIG. 11C is a graph showing a simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 750 rpm. FIG. 11D is a graph showing a simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 1000 rpm. FIG. 11E is a graph showing a simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 1500 rpm. FIG. 11F is a graph showing a simulation result of the detection time for the reference current Iq_ref when the motor is rotated at 1700 rpm. FIG. 12 is a schematic diagram illustrating a typical configuration of the electric power steering apparatus 3000 according to Exemplary Embodiment 2. As illustrated in FIG.

Hereinafter, embodiments of an H-bridge failure diagnosis method, 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 the following description from being unnecessarily redundant and to facilitate understanding by those skilled in the art, a more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted.

In the present specification, an embodiment of the present disclosure is described by taking, as an example, a power conversion device that converts power from a power source into power supplied to a three-phase motor having three-phase (A-phase, B-phase, and C-phase) windings. Will be explained. However, power from the power source is supplied to a motor having one-phase or two-phase windings, or an n-phase motor having n-phase windings such as four-phase or five-phase (n is an integer of 4 or more). A power conversion device that converts power and an H-bridge fault diagnosis method that is used in the power conversion device are also included in the scope of the present disclosure.

(Embodiment 1)
[1. Structure of motor module 2000 and power conversion apparatus 1000]
FIG. 1 schematically shows a typical block configuration of a motor module 2000 according to the present embodiment.

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

The power conversion apparatus 1000 can convert power from the power source 101 (see FIG. 2) into power supplied to the motor 200. The power conversion apparatus 1000 is connected to the motor 200. For example, the power conversion apparatus 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” between components (components) mainly means electrical connection.

The motor 200 is, for example, a three-phase AC motor such as a permanent magnet synchronous 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 input signals from the current sensor 150 and the angle sensor 320. Examples of the control method include vector control, pulse width modulation (PWM), and direct torque control (DTC). However, the angle sensor 320 may be unnecessary depending on the motor control method (for example, sensorless control).

The control circuit 300 can realize the closed loop control by controlling the target position, rotation speed, current, and the like of the motor 200. Note that 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 present disclosure is not limited to the block configuration of the motor module illustrated in FIG. 1, and has, for example, a block configuration including a first control circuit that controls the first inverter 120 and a second control circuit that controls the second inverter 130. Can do.

The power supply circuit 310 generates a power supply voltage (for example, 3V, 5V) necessary 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 the 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 changes the level of the actual current value to the input level of the controller 340 as necessary. The actual current value is 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 the target current value according to the actual current value and the rotation signal of the rotor, generates a PWM signal, and outputs it 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 supplies a control signal to the gate of each switch element. give. When the driving 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 can 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 apparatus 1000. For example, the control program is temporarily expanded in a 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 a circuit configuration of the inverter unit 100 according to 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, a DC-DC converter, or a battery (storage battery). The power source 101 may be a single power source common to the first and second inverters 120 and 130 as shown in the figure, or may be a first power source (not shown) for the first inverter 120 and for the second inverter 130. A second power source (not shown) may be provided.

Although not shown, coils are provided between the power source 101 and the first inverter 120 and between the power source 101 and the second inverter 130. The coil functions as a noise filter, and smoothes the high frequency noise included in the voltage waveform supplied to each inverter or the high frequency noise generated by 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 to be used are appropriately determined according to design specifications.

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 includes 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 IA flowing through the A-phase winding M1, and is connected between, for example, 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 IB flowing through the B-phase winding M2, and is connected between, for example, the low-side switch element SW_B1L and the GND line GL. The first shunt resistor S_C1 is used to detect a C-phase current IC flowing through the C-phase winding M3, and is connected between, for example, the low-side switch element SW_C1L and the GND line GL. The three shunt resistors S_A1, S_B1, and S_C1 are connected in common with 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 IA, 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 for detecting the B-phase current IB, 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 IC, 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 connected in common with the GND line GL of the second inverter 130.

The current sensor 150 described above includes, for example, a shunt resistor 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, a 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 the second inverter The 130 A-phase leg 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.

The inverter unit 100 includes A-phase, B-phase, and C-phase H bridges. Each phase H-bridge has two low-side switch elements, two high-side switch elements and a winding. For example, the A-phase H bridge 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. It has a line M1.

The control circuit 300 (specifically, the controller 340) can identify a faulty H bridge from among the three-phase H bridges by executing fault diagnosis of the H bridge described below. The failure of the switch element is broadly classified into “open failure” and “short-circuit failure”. “Open failure” refers to a failure in which the source-drain of the FET is opened (in other words, the resistance rds between the source and drain becomes high impedance), and “short-circuit failure” refers to a failure between the source and drain of the FET. Refers to a short circuit failure. In the present disclosure, an H-bridge failure refers to an open failure of a switch element in the H-bridge. For example, when an open failure occurs in the A-phase H-bridge high-side switch element SW_A1H, the failure is referred to as an A-phase H-bridge failure.

For example, if the faulty H-bridge is specified, the control circuit 300 can switch to motor control in which a two-phase winding is energized using a two-phase H-bridge other than the faulty H-bridge. In this specification, energizing the three-phase winding is referred to as “three-phase energization control”, and energizing the two-phase winding is referred to as “two-phase energization control”.

[2. Failure diagnosis method for H-bridge]
A specific example of a failure diagnosis method for diagnosing an H-bridge failure, which is used in, for example, the power conversion apparatus 1000 illustrated in FIG. 1, will be described with reference to FIGS. 3 to 8. However, the failure diagnosis method of the present disclosure can be suitably used for a power conversion device including at least one H bridge, for example, a full bridge type power conversion device.

A general-purpose pre-driver usually has a failure detection circuit that detects a short-circuit failure of a switch element in the inverter. For example, the short-circuit fault of the switch element is detected by comparing the measured source-drain voltage of the FET and the source-drain threshold voltage. Therefore, the diagnosis of the short circuit failure of the switch element can be performed using the drive circuit 350 in which the failure detection circuit is mounted. On the other hand, the function for detecting an open failure is not implemented in the pre-driver. Therefore, a technique for appropriately detecting an open failure of the switch element is desired.

In the present embodiment, a failure diagnosis for diagnosing, for each phase, whether or not an open failure has occurred in at least one of the four switching elements of the H-bridge, based on the product of the rotational speed ω and the peak value Ipeak of the phase current. Provide a method.

The outline of the failure diagnosis method for diagnosing H-bridge failure is as follows.

Step A: Based on the first current sine wave of the phase current measured by the current sensor 150, the second current sine wave obtained by shifting the phase of the first current sine wave by 90 °, and the rotational speed ω of the motor, H A monitoring signal for monitoring a bridge failure is generated for each phase. For example, the monitoring signal is represented by the square of the product of the measured peak value of the phase current and the rotational speed ω. The rotation speed ω is represented by a rotation speed (rpm) at which the rotor of the motor rotates per unit time (for example, 1 minute) or a rotation speed (rps) at which the rotor rotates at unit time (for example, 1 second).

Step B: A pre-fault signal is generated for each phase based on the comparison result between the monitoring signal and the threshold of the fault level. The pre-failure signal is a high active signal, for example, and is a signal that is asserted when an open failure of the switch element occurs.

Step C: A fault signal indicating whether or not the H-bridge is faulty is generated for each phase by calculating the logical product of the pre-fault signal and an activation signal that enables or disables the pre-fault signal. The failure signal is, for example, a highly active signal, and is a signal that is asserted when an open failure of the switch element occurs.

Step D: A failure signal is output from the failure diagnosis unit 800 to the motor control unit 900 that controls the motor 200.

The above steps A to D are repeatedly executed in synchronization with, for example, a period in which each phase current is measured by the current sensor 150, that is, an AD conversion period.

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

FIG. 3 illustrates functional blocks of the controller 340 for performing overall motor control. FIG. 4A illustrates functional blocks of the monitoring signal unit 810A. FIG. 4B illustrates functional blocks of the monitoring signal unit 810B. FIG. 4C illustrates functional blocks of the monitoring signal unit 810C. FIG. 5 illustrates functional blocks of a cut-off frequency unit 820, a value unit 830, and an activation signal unit 840. FIG. 6 illustrates functional blocks of the pre-fault signal unit 850 and the fault signal unit 860.

In this specification, each block in the functional block diagram is shown not in hardware units but in functional block units. The software used for motor control and H-bridge failure diagnosis may be, for example, a module constituting 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 out commands from the ROM 360 and sequentially execute each process.

The controller 340 includes, for example, a failure diagnosis unit 800 and a motor control unit 900. As described above, the failure diagnosis of the present disclosure can be suitably combined with motor control such as vector control, and can be incorporated in a series of processes of motor control.

The fault diagnosis unit 800 obtains the motor rotation speed ω, the peak value Ipeak_ref of the reference current used for motor control, and the phase currents IA, IB and IC measured by the current sensor 150 as input signals. The reference current is sometimes called a current command value. The failure diagnosis unit 800 generates A, B, and C phase failure signals PhaseA_FD, PhaseB_FD, and PhaseC_FD based on these input signals, and outputs them to the motor control unit 900. The failure signal is a signal indicating whether or not the H bridge of each phase has failed.

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

In this specification, for convenience of explanation, each functional block may be expressed as a unit. Of course, these notations should not be interpreted 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 described above, the controller 340 can be realized by an FPGA. In that case, all or some of the functional blocks may be realized by hardware.

By distributing processing using a plurality of FPGAs, it is possible to distribute the computation load of a specific computer. In that case, all or some of the functional blocks shown in FIGS. 3 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, an in-vehicle control area network (CAN), and can transmit and receive data.

The failure diagnosis unit 800 includes monitoring signal units 810A, 810B, 810C, a cutoff frequency unit 820, a threshold unit 830, an activation signal unit 840, a pre-failure signal unit 850, and a failure signal unit 860. The supervisory signal units 810A, 810B and 810C are composed of substantially the same functional blocks. Hereinafter, the processing flow for generating the A-phase monitoring signal ω2Ia_Peak2 will be described using the A-phase monitoring signal unit 810A as an example.

As shown in FIG. 4A, the monitoring signal unit 810A generates a monitoring signal ω2Ia_Peak2 for monitoring a failure of the A-phase H bridge. The input signal is the rotation speed ω and the phase A current IA measured by the current sensor 150. In the present embodiment, the current waveform of the phase current is a sine wave expressed using Expression (1). Here, Ia_peak is a peak value of the phase current IA. The current sine wave represented by Expression (1) is referred to as a first current sine wave.
IA = Ia_peak · sin (ωt) Equation (1)

The monitor signal unit 810A is, for example, a programmable low-pass filter (hereinafter referred to as “PLPF”) 801, 806, 808, 810, 813, a square unit 802, 803, 807, 811, a square root unit 805, a multiplier 804, A differentiation unit 809 and an adder 812 are included. For example, the square unit 802 squares the first current sine wave filtered by the PLPF 801. The multiplier 804 multiplies the output ω ² of the square unit 803 by the output Ia ² of the square unit 802 to obtain ω ² Ia ² . The square root unit 805 calculates the square root ωIa of ω ² Ia ² , and the PLPF 806 filters ωIa. The square unit 807 obtains ω ² Ia ² after the filtering process by squaring again the filtered ωIa. Thus, the noise of the phase current can be effectively removed by performing some low-pass filter processes.

Each of PLPF 801, 806, 808, 810 and 813 has a cut-off frequency fcut. The cut-off frequency unit 820 shown in FIG. 5 includes, for example, a gain unit 821 and an LPF 822. The cut-off frequency unit 820 determines the cut-off frequency fcut based on the multiplication value of the rotation speed ω and the gain.

In parallel with the calculation of ω ² Ia ² , the monitoring signal unit 810A performs a calculation for acquiring a second current sine wave obtained by shifting the phase of the first current sine wave by 90 °. To shift the phase by 90 ° means to advance or delay the initial phase by 90 °. That is, the phase of the second current sine wave is advanced or delayed by 90 ° with respect to that of the first current sine wave.

A specific example of advancing the phase by 90 ° is time differentiation. As shown in FIG. 4A, the monitoring signal unit 810A obtains the second current sine wave by time-differentiating the first current sine wave. The monitoring signal unit 810A preferably filters the phase current IA by the PLPF 808 before performing the differentiation operation by the differentiation unit 809. By this filtering process, it is possible to suppress amplification of noise superimposed on the phase current IA, which may be caused by subsequent differential calculation. The differentiating unit 809 time-differentiates the filtered first current sine wave to obtain a second current sine wave represented by Expression (2). That is, the second current sine wave is acquired by performing time differentiation after the first current sine wave is low pass filtered. Here, d / dt is a differential operator.
dIA / dt = ω · Ia_peak · cos (ωt) Equation (2)

The monitoring signal unit 810A preferably further filters the second current sine wave by the PLPF 810. By further filtering, it is possible to more appropriately suppress the amplification of noise superimposed on the phase current IA, which can be caused by differential operation. The square unit 811 obtains (dIA / dt) ² by squaring the filtered second current sine wave. The adder 812 generates the A-phase monitoring signal ω2Ia_Peak2 by adding (dIA / dt) ² to ω ² Ia ² based on Equation (3). The A phase monitoring signal ω2Ia_Peak2 is represented by the square of the product of the measured peak value Ia_peak of the phase current IA and the rotational speed ω.
ω ² Ia ² + (dIA / dt) ² = ω ² Ia_peak ² · sin ² (ωt) + ω ² · Ia_peak ² · cos ² (ωt) = ω ² Ia_peak ² formula (3)

When obtaining the monitoring signal ω2Ia_Peak2 based on the equation (3), it is preferable that the magnitudes of the two signal peaks input to the adder 812 be approximately the same. In the lower branch (arithmetic path) including the differential operation of the adder 812 shown in FIG. 4A, filter processing is performed twice. In accordance with this, the filtering process is performed twice also in the upper branch of the adder 812. As a result, two input signals having peaks corresponding to Ia_peak ^{2 can be} supplied to the adder 812.

The monitoring signal unit 810A preferably filters the generated monitoring signal ω2Ia_Peak2 with the PLPF 813. This final-stage filtering process can improve the response of failure diagnosis described later. The B and C phase monitoring signals ω2Ib_Peak2 and ω2Ic_Peak2 are generated in the same manner as the A phase monitoring signal ω2Ia_Peak2. See Figures 4B and 4C.

As described above, the phase of the second current sine wave may be delayed by 90 ° with respect to that of the first current sine wave. A specific example of delaying the phase by 90 ° is time integration. FIG. 7 illustrates functional blocks of the monitoring signal unit 810A using time integration.

The monitoring signal unit 810A may include an integration unit 820 instead of the differentiation unit 809. The monitoring signal unit 810A may acquire the second current sine wave by time-integrating the first current sine wave using the integration unit 820. The multiplier 804 multiplies the square of the second current sine wave by the square of the rotational speed ω. The adder 812 generates the monitoring signal ω2Ia_Peak2 by adding the output of the multiplier 804 filtered by the PLPF 806 to the square of the first current sine wave filtered by the PLPF 810 based on the equation (4). Can do.
ω2Ia_Peak2 = IA ² + (ω∫IAdt) ² = Ia_peak ² formula (4)

When performing a differentiation operation in the monitoring signal unit 810A, the monitoring signal ω2Ia_Peak2 includes the rotational speed ω in the coefficient, so that it is easy to diagnose a failure particularly at high speed rotation. When performing the integral operation, the monitoring signal ω2Ia_Peak2 does not depend on the rotational speed ω, and therefore, failure diagnosis can be easily performed.

The failure level threshold FD_Level can be determined based on the average values of the phase currents IA, IB and IC peak values Ia_Peak, Ib_Peak and Ic_Peak measured by the current sensor 150. The threshold unit 830 shown in FIG. 5 includes an average value unit 831 and a gain unit 832. The threshold unit 830 determines a failure level threshold FD_Level based on ω2Ia_Peak2 output from the monitoring signal unit 810A, ω2Ib_Peak2 output from the monitoring signal unit 810B, and ω2Ic_Peak2 output from the monitoring signal unit 810C. To do. For example, the average value unit 831 calculates the average value of ω2Ia_Peak2, ω2Ib_Peak2, and ω2Ic_Peak2. The gain unit 832 determines FD_Level by multiplying the average value by a variable gain. For example, the threshold unit 830 is implemented using a lookup table that applies a function of current and rotational speed. The value of the variable gain is set in the range of 0.01 to 0.95, for example. According to the threshold unit 830, since the peak value of each phase is used, it is not necessary to increase the variables for failure diagnosis processing.

The activation signal unit 840 shown in FIG. 5 has an absolute value unit 841 and a comparison unit 842. The comparison unit 842 generates an activation signal Zero_Level based on the comparison result between the peak value Ipeak_ref of the reference current used for controlling the motor and the minimum value I_min of the reference current. The activation signal Zero_Level is a signal indicating whether or not the reference current is zero. The peak value Ipeak_ref of the reference current is given by Equation (5). abs is an operator of an absolute value.
Ipeak_ref = [(2/3) ^1/2 (Id_ref ² + Iq_ref ² ) ^1/2 ] + [abs (Iz_ref) / (3) ^1/2 ] Equation (5)
Here, Id_ref is a d-axis reference current in the dq coordinate system, and Iq_req is a q-axis reference current in the dq coordinate system. Iz_ref is a z-phase reference current. The minimum value I_min of the reference current is set to about 10 mA, for example.

For example, the activation signal Zero_Level is a high active signal. The comparison unit 842 of the activation signal unit 840 asserts the activation signal Zero_Level when Ipeak_ref is greater than or equal to I_min. The comparison unit 842 negates the activation signal Zero_Level when Ipeak_ref is less than I_min.

FIG. 8 shows how the level of the A-phase monitoring signal ω2Ia_Peak2 changes when an open circuit failure occurs in the switching element of the H bridge. When the H-bridge is normal, the level of the monitoring signal ω2Ia_Peak2 indicates ω ² Ia_peak ² . When an open failure occurs in the switching element of the H bridge, the level of the monitoring signal ω2Ia_Peak2 drops to a level close to zero below the failure level threshold FD_Level. The signal level is much smaller than the normal signal level. In this specification, the time required for the change in the signal level is referred to as “detection time”. The earlier the detection time, the better the sensitivity or responsiveness for detecting a failure. As already described, it is possible to improve the responsiveness by filtering the generated monitoring signal ω2Ia_Peak2 with PLPF.

The pre-failure signal unit 850 shown in FIG. 6 includes three comparators 851. Three comparators 851 generate A, B, and C phase pre-fault signals A_Level_FD, B_Level_FD, and C_Level_FD, respectively. For example, when the A-phase monitoring signal ω2Ia_Peak2 is less than the failure level threshold FD_Level, the A-phase comparator 851 generates a pre-failure signal A_Level_FD indicating that the H-bridge is in a failure state. When the monitoring signal ω2Ia_Peak2 is equal to or greater than the failure level threshold FD_Level, the A-phase comparator 851 generates a pre-failure signal A_Level_FD indicating that the H-bridge is not in a failure state.

For example, the pre-failure signal A_Level_FD is a high active signal. When a failure occurs, the pre-failure signal A_Level_FD is asserted. The activation signal Zero_Level is used to enable or disable the pre-failure signal A_Level_FD. The pre-failure signal unit 850 generates B and C-phase pre-failure signals B_Level_FD and C_Level_FD in the same manner as the A phase.

6 has three AND units 861. The failure signal unit 860 shown in FIG. The AND unit 861 calculates a logical product of the pre-failure signal and the activation signal Zero_Level to generate a failure signal for each phase indicating whether or not the H-bridge has failed. For example, the A-phase AND unit 861 calculates the logical product of the A-phase pre-fault signal A_Level_FD and the activation signal Zero_Level, thereby indicating whether or not the A-phase H-bridge is faulty. Is generated. The failure signal unit 860 generates B and C phase failure signals PhaseB_FD and PhaseC_FD in the same manner as the A phase, and outputs them to the motor control unit 900.

When the absolute value of the peak value Ipeak_ref of the reference current is less than the minimum value I_min of the reference current, an activation signal Zero_Level that invalidates the pre-fault signal A_Level_FD is generated. In that case, even if the pre-failure signal A_Level_FD is in an asserted state, it is masked by the activation signal Zero_Level. For example, for normal motor driving, the reference current, which is a sine wave, periodically becomes a value close to zero. As a result, the level of the monitoring signal ω2Ia_Peak2 may be less than the failure level threshold FD_Level. Even if the H-bridge has not failed, the pre-failure signal A_Level_FD is asserted. In order to avoid this, the failure signal PhaseA_FD can be maintained in a negated state by masking the pre-failure signal A_Level_FD with the activation signal Zero_Level.

FIG. 9 exemplifies a current waveform (sine wave) obtained by plotting the current values flowing in the A-phase, B-phase, and C-phase windings of the motor 200 when the power conversion apparatus 1000 is controlled according to the three-phase energization control. are doing. FIG. 10A shows the current obtained by plotting the values of current flowing through 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 fails. The 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. 9 and 10A, current values are plotted every 30 electrical angles. I _pk represents the peak value of the phase current.

For reference, in FIG. 10B, when the B-phase H bridge 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 is illustrated. FIG. 10C shows the current obtained by plotting the values of the currents flowing through the A-phase and B-phase windings of the motor 200 when the power conversion apparatus 1000 is controlled according to the two-phase energization control when the C-phase H bridge fails. The waveform is illustrated.

For example, the motor control unit 900 performs three-phase energization control when it is normal, that is, when all of the failure signals PhaseA_FD, PhaseB_FD, and PhaseC_FD are negated. On the other hand, for example, when the failure signal PhaseA_FD is asserted, the motor control unit 900 uses the B and C phase H bridges other than the failed A phase H bridge to energize the windings M2 and M3. Energization control can be performed. Thereby, even if one-phase H-bridge of the three phases breaks down, power conversion apparatus 1000 can continue motor driving.

The results of verifying the validity of the algorithm used for H-bridge failure diagnosis according to the present disclosure using “Rapid Control Prototyping (RCP) System” of dSPACE and Matlab / Simulink of MathWorks are shown below. For this verification, a model of a surface magnet type (SPM) motor used in an electric power steering (EPS) apparatus, which is controlled by vector control, was used. The detection time in fault diagnosis of A-phase H-bridge under different conditions of current and rotational speed was verified. The d-axis reference current Id_ref and the z-phase reference current Iz_ref were set to 0 A, and the q-axis reference current Iq_ref was changed.

When the motor was rotated at 250, 500, 750, 1000, 1500 and 1700 rpm, the detection time for the reference current Iq_ref in the range from 0 A to 20 A was verified.

FIGS. 11A to 11F show simulation results of detection times with respect to the reference current Iq_ref when the motor is rotated at 250, 500, 750, 1000, 1500, and 1700 rpm, respectively. The vertical axis of the graph represents the detection time (ms), and the horizontal axis represents the reference current Iq_ref (A).

For example, according to the standard of an EPS system mounted on a vehicle, a detection time of 20 ms or less is required. From the simulation results, it can be seen that the detection time sufficiently satisfying the market requirement can be obtained in the motor drive range from low speed rotation to high speed rotation and in the motor drive range from low torque to high torque.

Conventionally, when a switching element of an H-bridge has an open failure, it has been difficult to accurately detect the open failure due to the influence of noise superimposed on the phase current. Even if the H-bridge is functioning normally, the phase current is a sine wave, and the current value periodically becomes zero. This made it more difficult to accurately detect open faults.

According to the present embodiment, the monitoring signal based on the square of the product of the peak value of the phase current and the rotation speed or the square of the peak value of the phase current is monitored. As a result, it is possible to easily diagnose the failure of the H-bridge without taking into consideration the variation of the phase current due to time dependence. Furthermore, by performing low-pass filter processing on the generated monitoring signal, it is possible to improve the responsiveness or sensitivity of failure detection.

(Embodiment 2)
FIG. 12 schematically shows a typical configuration of the electric power steering apparatus 3000 according to the present embodiment.

A vehicle such as an automobile generally has an electric power steering device. The electric power steering apparatus 3000 according to the present embodiment includes a steering system 520 and an auxiliary torque mechanism 540 that generates auxiliary torque. The electric power steering device 3000 generates auxiliary torque that assists the steering torque of the steering system that is generated when the driver operates the steering wheel. The burden on the driver's operation is reduced by the auxiliary torque.

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522, universal shaft joints 523A and 523B, a rotation 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, a knuckle 528A, 528B and left and right steering wheels 529A, 529B.

The auxiliary torque mechanism 540 includes, 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 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 corresponding 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 an automobile, an electronic control system with an ECU as a core is constructed. In the electric power steering apparatus 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 suitably used for the system.

The embodiment of the present disclosure is also suitably used for motor control systems such as X-by-wire such as shift-by-wire, steering-by-wire, and brake-by-wire, and a traction motor. For example, an EPS that implements a fault diagnosis method according to an embodiment of the present disclosure is an autonomous driving vehicle that corresponds to levels 0 to 5 (standards for automation) defined by the Japanese government and the US Department of Transportation's Road Traffic Safety Administration (NHTSA). Can be mounted.

The embodiment of the present disclosure can be widely used in 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.

Claims (16)

1. Converting power from the power source into power supplied to a motor having at least one phase winding;
   A failure diagnosis method for diagnosing a failure of an H bridge, which is used for a power conversion device including at least one H bridge,
   Based on the first current sine wave of the phase current measured by the current sensor, the second current sine wave obtained by shifting the phase of the first current sine wave by 90 °, and the rotational speed of the motor, the H-bridge failure Generating a monitoring signal for monitoring
   Generating a pre-failure signal based on a comparison result between the monitoring signal and a failure level threshold;
   Generating a fault signal indicating whether the H-bridge is faulty by calculating a logical product of the pre-fault signal and an activation signal that enables or disables the pre-fault signal;
   A fault diagnosis method including:
2. The fault diagnosis method according to claim 1, wherein, in the step of generating the monitoring signal, the second current sine wave is obtained by time differentiation of the first current sine wave.
3. 3. The failure diagnosis method according to claim 2, wherein the second current sine wave is acquired by performing time differentiation after the first current sine wave is subjected to low-pass filter processing.
4. The step of generating the monitoring signal includes generating the monitoring signal by adding the square of the second current sine wave to a multiplication value obtained by multiplying the square of the first current sine wave by the rotation speed. 4. The failure diagnosis method according to 2 or 3.
5. The fault diagnosis method according to claim 1, wherein, in the step of generating the monitoring signal, the second current sine wave is acquired by time-integrating the first current sine wave.
6. The step of generating the monitoring signal generates the monitoring signal by adding a square of a multiplication value obtained by multiplying the second current sine wave by the rotation speed to a square of the first current sine wave. 5. The failure diagnosis method according to 5.
7. The fault diagnosis method according to claim 6, further comprising a step of low-pass filtering the generated monitoring signal.
8. 8. The failure diagnosis method according to claim 1, wherein the activation signal is generated based on a comparison result between a peak value of a reference current used for controlling the motor and a minimum value of the reference current.
9. In the step of generating the pre-failure signal, if the monitoring signal is less than the failure level threshold, the H-bridge generates the pre-failure signal indicating a failure condition, and the monitoring signal is the failure signal. 9. The fault diagnosis method according to claim 8, wherein when the level is equal to or higher than a threshold level, the pre-failure signal is generated to indicate that the H-bridge is not in a fault state.
10. 10. The fault diagnosis method according to claim 9, wherein when the absolute value of the peak value of the reference current is less than a minimum value of the reference current, the activation signal that invalidates the pre-fault signal is generated.
11. 11. The failure diagnosis method according to claim 1, further comprising a step of outputting the failure signal to a motor control unit that controls the motor.
12. The n-phase H bridge is used in a power conversion device including an n-phase H bridge that converts power from a power source into power supplied to a motor having an n-phase (n is an integer of 3 or more) winding. A failure diagnosis method for diagnosing a failure for each phase,
    A failure diagnosis method for diagnosing a failure of an H bridge for each phase by executing the failure diagnosis method according to claim 1 on an H bridge of each phase.
13. The failure diagnosis method according to claim 12, wherein the threshold value of the failure level is determined based on an average value of a peak value of a phase current of each phase measured by a current sensor.
14. A power conversion device that converts electric power from a power source into electric power to be supplied to a motor having at least one phase winding,
    At least one H-bridge;
    A control circuit for controlling a switching operation of the at least one H-bridge switch element;
    With
    The control circuit includes:
    Based on the first current sine wave of the phase current measured by the current sensor, the second current sine wave obtained by shifting the phase of the first current sine wave by 90 °, and the rotational speed of the motor, the H-bridge failure Generate a monitoring signal to monitor
    Generating a pre-failure signal based on a comparison result between the monitoring signal and a failure level threshold;
    The power converter which produces | generates the failure signal which shows whether the H bridge has failed by calculating the logical product of the pre-failure signal and the activation signal which validates or invalidates the pre-failure signal.
15. A motor,
    The power conversion device according to claim 14,
    A motor module comprising:
16. An electric power steering apparatus comprising the motor module according to claim 15.

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