JPWO2019240004A1 - Failure diagnosis method, power conversion device, motor module and electric power steering device - Google Patents

Abstract

The failure diagnosis method of the present disclosure is a failure diagnosis method for diagnosing a failure of an H bridge, which is used in a power conversion device including at least one H bridge. The failure diagnosis method monitors the failure of the H bridge based on the first current sine wave of the phase current, the second current sine wave obtained by shifting the phase of the first current sine wave by 90 °, and the rotation speed of the motor. A step to generate a monitoring signal to generate a pre-failure signal, a step to generate a pre-failure signal based on a comparison result between the monitoring signal and a fault level threshold, a pre-failure signal, and enable or disable the pre-failure signal. This includes a step of generating a failure signal indicating whether or not the H bridge has failed by calculating the logical product of the activation signals to be generated.

Description

The present disclosure relates to failure diagnostic methods, power converters, motor modules and electric power steering devices.

In recent years, an electric motor (hereinafter, simply referred to as "motor"), an inverter and an ECU integrated with an electric motor have been developed. Especially in the in-vehicle field, high quality assurance is required from the viewpoint of safety. Therefore, a redundant design that can continue safe operation even if a part of the parts breaks down is adopted. As an example of the 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 as 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 has 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 has a second inverter unit, a power supply relay, a reverse connection protection relay, and the like. When the motor drive device has not failed, 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 released from the power supply to the failed system or the failure. The power supply to the system connected to the winding set is cut off. It is possible to continue the motor drive 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, the motor drive can be continued by the system that has not failed.

Japanese Publication No. 2016-34204 Japanese Publication No. 2016-32977 Japanese Publication No. 2008-132919

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

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

An exemplary failure diagnosis method of the present disclosure is used in a power conversion device comprising at least one H bridge that converts power from a power source into power supplied to a motor having at least one phase of windings. A fault diagnosis method for diagnosing a fault, 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 motor. A step of generating a monitoring signal for monitoring the failure of the H bridge based on the rotation speed of the above, a step of generating a pre-failure signal based on the result of comparison between the monitoring signal and the threshold value of the failure level, and a step of generating a pre-failure signal. Includes a step of generating a failure signal indicating whether or not the H bridge has failed by calculating the logical product of the pre-failure signal and an activation signal that enables or disables the pre-failure signal. do.

An exemplary power conversion device of the present disclosure is a power conversion device that converts power from a power source into power supplied to a motor having at least one phase of winding, and includes at least one H bridge and at least one of the above. A control circuit for controlling the switching operation of the switch element of the H bridge is provided, and the control circuit sets the phase of the first current sine wave of the phase current measured by the current sensor and the phase of the first current sine wave to 90 °. Based on the second current sine wave obtained by shifting and the rotation speed of the motor, a monitoring signal for monitoring the failure of the H bridge is generated, and the comparison result between the monitoring signal and the failure level threshold is obtained. A failure indicating whether or not the H bridge has failed by generating a pre-failure signal based on the above and calculating the logical product of the pre-failure signal and the activation signal that enables or disables the pre-failure signal. Generate a signal.

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

FIG. 1 is a block diagram schematically showing a typical block configuration of the motor module 2000 according to the exemplary embodiment 1. FIG. 2 is a circuit diagram schematically showing the circuit configuration of the inverter unit 100 according to the exemplary embodiment 1. FIG. 3 is a functional block diagram illustrating a functional block of the controller 340 for performing overall motor control. FIG. 4A is a functional block diagram illustrating a functional block of the monitoring signal unit 810A. FIG. 4B is a functional block diagram illustrating the functional blocks of the monitoring signal unit 810B. FIG. 4C is a functional block diagram illustrating the functional blocks of the monitoring signal unit 810C. FIG. 5 is a functional block diagram illustrating the functional blocks of the cutoff frequency unit 820, the threshold value unit 830, and the activation signal unit 840. FIG. 6 is a functional block diagram illustrating the pre-failure 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 phase A monitoring signal ω2Ia_Peek2 when the H bridge fails. FIG. 9 illustrates 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 converter 1000 is controlled according to the three-phase energization control. It is a graph to be done. 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 converter 1000 is controlled according to the two-phase energization control when the A-phase H bridge fails. It is a graph exemplifying. 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. It is a graph exemplifying. FIG. 10C shows a current waveform obtained by plotting the current values flowing in the A-phase and B-phase windings of the motor 200 when the power converter 1000 is controlled according to the two-phase energization control when the C-phase H bridge fails. It is a graph exemplifying. FIG. 11A is a graph showing the 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 the 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 the 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 the 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 the 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 the simulation result of the detection time with respect to the reference current Iq_ref when the motor is rotated at 1700 rpm. FIG. 12 is a schematic view showing a typical configuration of the electric power steering device 3000 according to the second embodiment.

Hereinafter, embodiments of the H-bridge failure diagnosis method, the power conversion device, the motor module, and the electric power steering device of the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid unnecessarily redundant explanations below and facilitate understanding by those skilled in the art, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted.

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

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

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

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

The motor 200 is 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. Specifically, the first inverter 120 is connected to one end of the winding of each phase of the motor 200, and the second inverter 130 is connected to the other end of the winding of each phase.

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 circuit board). The control circuit 300 is connected to the inverter unit 100 and controls the inverter unit 100 based on the input signals from the current sensor 150 and the angle sensor 320. The control method includes, for example, vector control, pulse width modulation (PWM) or direct torque control (DTC). However, depending on the motor control method (for example, sensorless control), the angle sensor 320 may not be necessary.

The control circuit 300 can realize the closed loop control by controlling the position, rotation speed, current, and the like of the rotor of the motor 200, which are the objects. 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 includes, for example, a block configuration including a first control circuit for controlling the first inverter 120 and a second control circuit for controlling the second inverter 130. Can be done.

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

The angle sensor 320 is, for example, a resolver or a Hall IC. Alternatively, the angle sensor 320 is also realized by a combination of an MR sensor having a magnetoresistive (MR) element and a sensor magnet. The angle sensor 320 detects 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, may be referred to as “actual current value”), and sets the level of the actual current value to the input level of the controller 340 as necessary. It is converted and the actual current value is output 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 (turn-on or turn-off) of each switch element (typically a semiconductor switch element) in the first and second inverters 120 and 130 of the inverter unit 100. The controller 340 sets a target current value according to the actual current value, the rotation signal of the rotor, and the like, generates a PWM signal, and outputs the PWM signal to the drive circuit 350.

The drive circuit 350 is typically a pre-driver (sometimes referred to as 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 the control signal is generated at the gate of each switch element. give. When the drive target is a motor that can be driven at a low voltage, a pre-driver may not always be required. In that case, the function of the pre-driver may be implemented in the controller 340.

The ROM 360 is, for example, a writable memory (eg, PROM), a rewritable memory (eg, a flash memory), or a 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 device 1000. For example, the control program is temporarily expanded to RAM (not shown) at boot time.

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

FIG. 2 schematically shows the circuit configuration of the inverter unit 100 according to 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 supply 101 may be an AC-DC converter or a DC-DC converter, or may be a battery (storage battery). As shown in the figure, the power supply 101 may be a single power supply common to the first and second inverters 120 and 130, or for the first power supply (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 supply 101 and the first inverter 120, and between the power supply 101 and the second inverter 130. The coil functions as a noise filter and smoothes high-frequency noise included in the voltage waveform supplied to each inverter or high-frequency noise generated in each inverter so as not to flow out to the power supply 101 side. Further, 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 capacitance and the number of capacitors to be used are appropriately determined according to design specifications and the like.

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

As the switch element, for example, a field effect transistor (typically MOSFET) in which a parasitic diode is formed, or a combination of an insulated gate bipolar transistor (IGBT) and a freewheeling diode connected in parallel with the isolated gate bipolar transistor (IGBT) 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, for example, between the low-side switch element SW_A1L and the GND line GL. The first shunt resistor S_B1 is used to detect the B-phase current IB flowing through the B-phase winding M2, and is connected, for example, between the low-side switch element SW_B1L and the GND line GL. The first shunt resistor S_C1 is used to detect a C-phase current IC flowing through the C-phase winding M3, and is connected, for example, between the low-side switch element SW_C1L and the GND line GL. The three shunt resistors S_A1, S_B1 and S_C1 are commonly connected to the GND line GL of the first inverter 120.

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

The shunt resistor S_A2 is used to detect the A-phase current 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 to detect 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 commonly connected to the GND line GL of the second inverter 130.

The above-mentioned current sensor 150 includes, for example, shunt resistors S_A1, S_B1, S_C1, S_A2, S_B2, S_C2, and a current detection circuit (not shown) for detecting the current flowing through each shunt resistor.

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

The inverter unit 100 includes A-phase, B-phase, and C-phase H-bridges. The H-bridge of each phase has two low-side switch elements, two high-side switch elements and windings. 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 in the leg on the second inverter 130 side, a low-side switch element SW_A2L, and winding. It has a line M1.

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

For example, when the failed H bridge is identified, the control circuit 300 can switch to motor control that energizes the two-phase windings by using a two-phase H bridge other than the failed H bridge. In the present specification, energizing a three-phase winding is referred to as "three-phase energization control", and energizing a two-phase winding is referred to as "two-phase energization control".

[2. H-bridge failure diagnosis method]
With reference to FIGS. 3 to 8, for example, a specific example of a failure diagnosis method for diagnosing a failure of the H bridge used in the power conversion device 1000 shown in FIG. 1 will be described. 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 is usually equipped with a failure detection circuit that detects a short-circuit failure of a switch element in an inverter. For example, by comparing the measured source-drain voltage of the FET with the source-drain threshold voltage, a short-circuit failure of the switch element is detected. Therefore, the diagnosis of the short-circuit failure of the switch element can be performed by using the drive circuit 350 on which the failure detection circuit is mounted. On the other hand, the function of detecting an open failure is not implemented in the pre-driver. Therefore, a method for appropriately detecting an open failure of a switch element is desired.

In this embodiment, failure diagnosis is performed for each phase to diagnose whether or not at least one of the four switch elements of the H-bridge has an open failure based on the product of the rotation speed ω and the peak value Ipeak of the phase current. Provide a method.

The outline of the failure diagnosis method for diagnosing the failure of the H bridge 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 rotation 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 the rotation speed (rpm) at which the rotor of the motor rotates in a unit time (for example, 1 minute) or the rotation speed (rps) at which the rotor rotates in a unit time (for example, 1 second).

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

Step C: By calculating the logical product of the pre-failure signal and the activation signal that enables or disables the pre-failure signal, a failure signal indicating whether or not the H-bridge has failed is generated for each phase. The failure signal is, for example, a high-active signal, which is a signal 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, for example, in synchronization with a cycle in which each phase current is measured by the current sensor 150, that is, a cycle of AD conversion.

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

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

In the present 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 can be, for example, a module that constitutes a computer program for executing a specific process corresponding to each functional block. Such computer programs are stored, for example, in ROM 360. The controller 340 can read instructions from the ROM 360 and execute each process sequentially.

The controller 340 has, 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 into a series of processes of motor control.

The failure diagnosis unit 800 acquires the rotation speed ω of the motor, 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 the current command value. The failure diagnosis unit 800 generates phase 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 is failed.

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

In this specification, for convenience of explanation, each functional block may be referred to 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 on the controller 340, the execution subject of the software may be, for example, the core of the controller 340. As mentioned above, the controller 340 can be implemented by FPGA. In that case, all or part of the functional blocks may be implemented in hardware.

By distributing the processing using a plurality of FPGAs, the computing load of a specific computer can be distributed. In that case, all or part 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 data can be transmitted and received.

The failure diagnosis unit 800 includes monitoring signal units 810A, 810B, 810C, a cutoff frequency unit 820, a threshold value unit 830, an activation signal unit 840, a pre-failure signal unit 850, and a failure signal unit 860. The monitoring signal units 810A, 810B and 810C are composed of substantially the same functional blocks. Hereinafter, a processing flow for generating the A-phase monitoring signal ω2Ia_Peek2 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_Peek2 for monitoring the failure of the A-phase H-bridge. The input signal is the rotation speed ω and the phase A phase current IA measured by the current sensor 150. In the present embodiment, the current waveform of the phase current is a sine wave represented by the equation (1). Here, Ia_peak is the peak value of the phase current IA. The current sine wave represented by the equation (1) is referred to as a first current sine wave.
IA = Ia_peak · sin (ωt) Equation (1)

The monitoring signal unit 810A is, for example, a programmable low-pass filter (hereinafter referred to as “PLPF”) 801, 806, 808, 810, 813, square unit 802, 803, 807, 811, square root unit 805, multiplier 804, It has a differential unit 809 and an adder 812. For example, the square unit 802 squares a first current sine wave filtered by PLPF801. The multiplier 804 obtains ^{ω 2} Ia ² by multiplying ^{the output ω 2} of the squared unit 803 by the output Ia ^{2 of the squared unit 802.} The square root unit 805 calculates the square root ωIa of ^{ω 2} Ia ^{2, and the PLPF 806 filters ω Ia.} The squared unit 807 obtains the filtered ω ² Ia ² by squaring the filtered ω Ia again. By performing some low-pass filter processing in this way, noise of the phase current can be effectively removed.

Each of PLPF801, 806, 808, 810 and 813 has a cutoff frequency fcut. The cutoff frequency unit 820 shown in FIG. 5 includes, for example, a gain unit 821 and an LPF822. The cutoff frequency unit 820 determines the cutoff frequency fcut based on the multiplication value of the rotation speed ω and the gain.

The monitoring signal unit 810A performs an operation to acquire a second current sine wave obtained by shifting the phase of the first current sine wave by 90 ° in parallel with the operation of ^{ω 2} Ia ^2. Shifting the phase by 90 ° means advancing or delaying the initial phase by 90 °. That is, the phase of the second current sine wave advances or lags 90 ° with respect to that of the first current sine wave.

A specific example of advancing the phase by 90 ° is the time derivative. As shown in FIG. 4A, the monitoring signal unit 810A acquires the second current sine wave by time-differentiating the first current sine wave. It is preferable that the monitoring signal unit 810A filters the phase current IA by the PLPF 808 before performing the differential operation in the differential unit 809. By this filter processing, it becomes possible to suppress the amplification of the noise superimposed on the phase current IA, which may be generated by the differential operation in the subsequent stage. The differentiation unit 809 time-differentiates the filtered first current sine wave to obtain the second current sine wave represented by the equation (2). That is, the second current sine wave is acquired by time-differentiating the first current sine wave after low-pass filtering. 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 with PLPF810. Further filtering makes it possible to more appropriately suppress the amplification of noise superimposed on the phase current IA, which may be caused by the differential operation. The squared unit 811 obtains ^{(dIA / dt) 2} by squaring the filtered second current sine wave. The adder 812 generates the A-phase monitoring signal ω2Ia_Peak ² by adding (dIA / dt) ^{2 to ω 2} Ia ² based on the 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 rotation 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 equation (3)

When obtaining the monitoring signal ω2Ia_Peek2 based on the equation (3), it is preferable that the magnitudes of the two signal peaks input to the adder 812 are about the same. In the lower branch (calculation path) including the differential operation of the adder 812 shown in FIG. 4A, the filtering process is performed twice. Along with this, the upper branch of the adder 812 is also filtered twice. This makes it possible to give the adder 812 two input signals having a peak corresponding ^{to Ia_peak 2.}

The monitoring signal unit 810A preferably filters the generated monitoring signal ω2Ia_Peak2 by PLPF813. This final stage of filtering makes it possible to improve the responsiveness of failure diagnosis, which will be described later. The B and C phase monitoring signals ω2Ib_Peek2 and ω2Ic_Peek2 are generated in the same manner as the A phase monitoring signals ω2Ia_Peek2. See FIGS. 4B and 4C.

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

The monitoring signal unit 810A may have 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_Peek2 by adding the output of the multiplier 804 filtered by PLPF806 to the square of the first current sine wave filtered by PLPF810 based on the equation (4). Can be done.
ω2Ia_Peak2 = IA ² + (ω∫IAdt) ² = Ia_peak ² equation (4)

When the monitoring signal unit 810A performs the differential calculation, the monitoring signal ω2Ia_Peek2 includes the rotation speed ω in the coefficient, so that the failure diagnosis is particularly easy at the time of high-speed rotation. When performing the integral calculation, the monitoring signal ω2Ia_Peek2 does not depend on the rotation speed ω, so that the failure diagnosis can be easily performed.

The failure level threshold FD_Level can be determined based on the average of the peak values Ia_Peak, Ib_Peak and Ic_Peak of the phase currents IA, IB and IC measured by the current sensor 150. The threshold unit 830 shown in FIG. 5 has an average value unit 831 and a gain unit 832. The threshold unit 830 determines the failure level threshold FD_Level based on ω2Ia_Peek2 output from the monitoring signal unit 810A, ω2Ib_Peak2 output from the monitoring signal unit 810B, and ω2Ic_Peek2 output from the monitoring signal unit 810C. 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 its average value by a variable gain. For example, the threshold unit 830 is realized using a look-up table to which a function of current and rotation speed is applied. The variable gain value is set, for example, in the range of 0.01 to 0.95. According to the threshold unit 830, it is not necessary to increase the variables for the failure diagnosis process in order to use the peak value of each phase.

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 the equation (5). abs is an absolute value operator.
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 the d-axis reference current in the dq coordinate system, and Iq_req is the q-axis reference current in the dq coordinate system. Iz_ref is the z-phase reference current. The minimum value I_min of the reference current is set to, for example, about 10 mA.

For example, the activation signal Zero_Level is a highly 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 a state of level change of the A-phase monitoring signal ω2Ia_Peak2 when an open failure occurs in the switch element of the H bridge. When H-bridge is normal, the level of the monitoring signal ω2Ia_Peak2 shows ω ² Ia_peak ^2. When an open failure occurs in the switch element of the H-bridge, the level of the monitoring signal ω2Ia_Peek2 drops to a level close to zero below the failure level threshold FD_Level. Its signal level is much lower than the normal signal level. In the present specification, the time required for this change in signal level is referred to as "Detection Time". The earlier the detection time, the better the sensitivity or responsiveness to detect the failure. As described above, the responsiveness can be improved by filtering the generated monitoring signal ω2Ia_Peak2 by PLPF.

The pre-failure signal unit 850 shown in FIG. 6 has three comparators 851. The three comparators 851 generate phase A, B and C phase pre-failure signals A_Level_FD, B_Level_FD and C_Level_FD, respectively. For example, when the phase A monitoring signal ω2Ia_Peak2 is less than the failure level threshold FD_Level, the phase A comparator 851 generates a pre-failure signal A_Level_FD indicating that the H-bridge is in a failed state. When the monitoring signal ω2Ia_Peek2 is greater than or equal to the failure level threshold FD_Level, the Phase A comparator 851 generates a pre-failure signal A_Level_FD indicating that the H-bridge is not in a fault state.

For example, the pre-failure signal A_Level_FD is a highly 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 also generates pre-failure signals B_Level_FD and C_Level_FD of the B and C phases in the same manner as the A phase.

The fault signal unit 860 shown in FIG. 6 has three AND units 861. The AND unit 861 calculates the logical product of the pre-failure signal and the activation signal Zero_Level to generate a failure signal indicating whether or not the H-bridge has failed for each phase. For example, the phase A AND unit 861 calculates the logical product of the phase A pre-failure signal A_Level_FD and the activation signal Zero_Level to indicate whether or not the phase A H-bridge is faulty. To generate. The failure signal unit 860 also generates failure signals PhaseB_FD and PhaseC_FD of the B and C phases 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-failure signal A_Level_FD is generated. In that case, the pre-failure signal A_Level_FD is masked by the activation signal Zero_Level even in the asserted state. For example, when driving a motor under normal conditions, 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_Peek2 can be less than the failure level threshold FD_Level. The pre-failure signal A_Level_FD is asserted even if the H-bridge is not faulty. In order to avoid this, the failure signal PhaseA_FD can be maintained in the negated state by masking the pre-failure signal A_Level_FD with the activation signal Zero_Level.

FIG. 9 illustrates 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 converter 1000 is controlled according to the three-phase energization control. is doing. FIG. 10A shows a current obtained by plotting the current values flowing in the B-phase and C-phase windings of the motor 200 when the power converter 1000 is controlled according to the two-phase energization control when the A-phase H bridge fails. The waveform is illustrated. The horizontal axis represents the motor electric angle (deg), and the vertical axis represents the current value (A). In the current waveforms of FIGS. 9 and 10A, the current values are plotted for each electric angle of 30 °. 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 obtained current waveform is illustrated. FIG. 10C shows a current obtained by plotting the current values 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. The waveform is illustrated.

For example, the motor control unit 900 performs three-phase energization control at normal times, 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. As a result, even if the H-bridge of one of the three phases fails, the power converter 1000 can continue to drive the motor.

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

The detection times for the reference current Iq_ref in the range 0A to 20A were verified when the motors were rotated at 250, 500, 750, 1000, 1500 and 1700 rpm, respectively.

11A to 11F show the simulation results of the detection time 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 shows the detection time (ms), and the horizontal axis shows the reference current Iq_ref (A).

For example, according to the standard of the EPS system mounted on the vehicle, a detection time of 20 ms or less is required. From the simulation results, it can be seen that a detection time that sufficiently satisfies the market demand 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 the switch element of the 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. Further, even when the H bridge is functioning normally, since the phase current is a sine wave, its current value becomes zero periodically. This made it even more difficult to accurately detect open failures.

According to this embodiment, a 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. This makes it possible to easily diagnose the failure of the H-bridge without considering the fluctuation of the phase current due to time dependence. Further, by low-pass filtering the generated monitoring signal, the responsiveness or sensitivity of failure detection can be improved.

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

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

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522, a universal shaft joint 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, and knuckle 528A. It may consist of 528B and the left and right steering wheels 529A and 529B.

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

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

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

The embodiments of the present disclosure can be widely used in various devices including various motors, such as vacuum cleaners, dryers, sealing fans, washing machines, refrigerators and electric power steering devices.

Claims (16)

Converts power from a power source into power to supply to a motor with at least one phase of winding,
A failure diagnosis method for diagnosing a failure of an H bridge used in a power conversion device including at least one H bridge.
Failure of the 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. And the steps to generate a monitoring signal to monitor
A step of generating a pre-failure signal based on the result of comparison between the monitoring signal and the failure level threshold value,
A step of generating a failure signal indicating whether or not the H-bridge has failed by calculating the logical product of the pre-failure signal and the activation signal that enables or disables the pre-failure signal.
Failure diagnosis method including. The failure diagnosis method according to claim 1, wherein in the step of generating the monitoring signal, the second current sine wave is acquired by time-differentiating the first current sine wave. The failure diagnosis method according to claim 2, wherein the second current sine wave is acquired by time-differentiating the first current sine wave after low-pass filtering. The claim that the monitoring signal is generated by adding the square of the second current sine wave to the multiplication value obtained by multiplying the square of the first current sine wave by the rotation speed in the step of generating the monitoring signal. The failure diagnosis method according to 2 or 3. The failure diagnosis method according to claim 1, wherein the second current sine wave is acquired by time-integrating the first current sine wave in the step of generating the monitoring signal. The claim that the monitoring signal is generated by adding the square of the multiplication value obtained by multiplying the second current sine wave by the rotation speed to the square of the first current sine wave in the step of generating the monitoring signal. The failure diagnosis method according to 5. The failure diagnosis method according to claim 6, further comprising a step of low-pass filtering the generated monitoring signal. The failure diagnosis method according to any one of claims 1 to 7, 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. In the step of generating the pre-failure signal, when the monitoring signal is less than the threshold value of the failure level, the H bridge generates the pre-failure signal indicating a failure state, and the monitoring signal is the failure. The failure diagnosis method according to claim 8, wherein when the value is equal to or higher than the threshold value of the level, the H bridge generates the pre-failure signal indicating that the H bridge is not in a failure state. The failure diagnosis method according to claim 9, wherein when the absolute value of the peak value of the reference current is less than the minimum value of the reference current, the activation signal that invalidates the pre-failure signal is generated. The failure diagnosis method according to any one of claims 1 to 10, further comprising a step of outputting the failure signal to a motor control unit that controls the motor. The n-phase H-bridge 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 n-phase (n is an integer of 3 or more) windings. It is a failure diagnosis method that diagnoses failures phase by phase.
A failure diagnosis method for diagnosing a failure of an H-bridge for each phase by executing the failure diagnosis method according to any one of claims 1 to 11 on the H-bridge of each phase. The failure diagnosis method according to claim 12, wherein the failure level threshold value is determined based on an average value of peak values of phase currents of each phase measured by a current sensor. A power conversion device that converts power from a power source into power supplied to a motor having at least one phase of winding.
With at least one H-bridge
A control circuit that controls the switching operation of the switch element of at least one H-bridge, and
With
The control circuit
Failure of the 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. Generate a monitoring signal to monitor
A pre-failure signal is generated based on the comparison result between the monitoring signal and the fault level threshold value.
A power conversion device that generates a failure signal indicating whether or not the H-bridge has failed by calculating the logical product of the pre-failure signal and the activation signal that enables or disables the pre-failure signal. With the motor
The power conversion device according to claim 14,
Motor module with. An electric power steering device including the motor module according to claim 15.

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