WO2019064725A1

WO2019064725A1 - Power conversion device, motor module, and electric power steering device

Info

Publication number: WO2019064725A1
Application number: PCT/JP2018/022912
Authority: WO
Inventors: 香織鍋師; 貴小池上; 雄飛中田
Original assignee: 日本電産株式会社
Priority date: 2017-09-29
Filing date: 2018-06-15
Publication date: 2019-04-04
Also published as: CN211830634U

Abstract

Provided is a power conversion device capable of detecting failure of switching elements in inverters in a shorter period of time. A power conversion device 1000 according to the present disclosure comprises: a first inverter 120; a second inverter 130; a failure detection device 340 for detecting the presence/absence of failure in switching elements in the first and second inverters; and a memory 341. The failure detection device acquires, for each predetermined period, at least one of an n-phase (n is an integer of 3 or more) current of a motor and a current/voltage represented by a dq coordinate system, writes data on the acquired current/voltage into the memory, and detects the presence/absence of failure of the switching elements in the first and second inverters on the basis of the result of comparison between data on the current/voltage acquired at a reference time for failure detection and a past data group including a plurality of data on currents/voltages acquired at times before the reference time.

Description

Power converter, motor module and electric power steering apparatus

The present disclosure relates to a power conversion device, a motor module, and an electric power steering device that convert power from a power supply into power to be supplied to an electric motor.

In recent years, a machine-electric integrated motor has been developed in which an electric motor (hereinafter simply referred to as "motor") and an ECU (Electrical Control Unit) are integrated. Particularly in the automotive field, high quality assurance is required from the viewpoint of safety. Therefore, a redundant design is adopted that can continue safe operation even if part of the part fails. As an example of redundant design, it is considered to provide two inverters for one motor. As another example, it is considered to provide a backup microcontroller on the main microcontroller.

Patent Document 1 discloses a power conversion device that includes a control unit and two inverters, and converts power from a power supply into power to be supplied to a three-phase motor. Each of the two inverters is connected to a power supply and a ground (hereinafter referred to as "GND"). One inverter is connected to one end of the three-phase winding of the motor, and the other inverter is connected to the other end of the three-phase winding. Each inverter has a bridge circuit composed of three legs, each of which includes a high side switch element and a low side switch element. The control unit switches motor control from normal control to abnormal control when it detects a failure of the switch element in the two inverters. In the normal control, for example, the motor is driven by switching switch elements of two inverters. In the control at the time of abnormality, for example, the motor is driven by the unfailed inverter using the neutral point of the winding in the broken inverter.

JP 2014-192950 A JP, 2017-063571, A

In a device that drives a motor using two inverters as described above, when a failure occurs in an inverter, it is required to identify the failure location in as short a time as possible.

Patent Document 2 discloses a device for driving a motor having a Y-connected winding by one inverter (hereinafter, referred to as “single inverter type device”). Patent Document 2 discloses that a signal detected in a predetermined energization pattern is collated with a predetermined abnormality type correspondence table to detect a disconnection and a short circuit of a wiring.

However, in the technique of Patent Document 2, since the failure detection such as disconnection of the wiring is performed using the measured current value and voltage value, more time is spent for the failure detection and the identification of the failure point.

An embodiment of the present disclosure provides a power converter capable of detecting a failure of a switch element of an inverter in a shorter time, a motor module including the power converter, and an electric power steering apparatus including the motor module.

An exemplary power converter of the present disclosure is a power converter that converts power from a power source to power supplied to a motor having n-phase (n is an integer of 3 or more) windings, A first inverter connected to one end of a winding of each phase, the first inverter having n legs each having a low side switching device and a high side switching device; and a winding of each phase of the motor A second inverter connected to the other end, the second inverter having n legs each having a low side switch element and a high side switch element, and presence or absence of a failure of the switch elements in the first and second inverters And a memory for storing processing data of the failure detection device, the failure detection device comprising an n-phase current of the motor and a dq coordinate system And at least one of the current and voltage represented is acquired every predetermined cycle, the data of the acquired current and voltage is written to the memory, and the data of the current and voltage acquired at the reference time of failure detection, The presence or absence of a failure of the switch element in the first and second inverters is detected based on a comparison result with a past data group including data of a plurality of current and voltage acquired at a time before the reference time.

According to an exemplary embodiment of the present disclosure, it is possible to detect a failure of a switch element of an inverter in a shorter time by referring to a past data group acquired before a reference time of failure detection. A converter, a motor module including the power converter, and an electric power steering apparatus including the motor module are provided.

FIG. 1 is a circuit diagram showing a circuit configuration of an inverter unit 100 according to an exemplary embodiment 1. FIG. 2 is a block diagram showing the block configuration of the motor module 2000 according to the exemplary embodiment 1, mainly showing the block configuration of the power conversion device 1000. As shown in FIG. FIG. 3 exemplifies a current waveform (sine wave) obtained by plotting current values flowing in the A-phase, B-phase, and C-phase windings of the motor 200 when the power conversion device 1000 is controlled according to three-phase energization control. Is a graph. FIG. 4 is a schematic view showing the configuration of the H bridge. FIG. 5 is a graph illustrating waveforms of simulation results of the three-phase currents Ia, Ib and Ic when the switch element L1 of the A-phase and H-bridge has an open failure. FIG. 6 is a diagram illustrating a table of data groups of three-phase currents recorded in the internal register 341 of the failure detection device 340. FIG. 7 shows a current waveform obtained by plotting current values flowing in the B-phase and C-phase windings of the motor 200 when the power conversion device 1000 is controlled according to the two-phase energization control when the winding M1 is broken. It is a graph which illustrates. FIG. 8 shows a current waveform obtained by plotting current values flowing in the A-phase and C-phase windings of the motor 200 when the power conversion device 1000 is controlled according to the two-phase energization control when the winding M2 is broken. It is a graph which illustrates. FIG. 9 shows a current waveform obtained by plotting the values of currents flowing through the A-phase and B-phase windings of the motor 200 when the power conversion device 1000 is controlled according to the two-phase energization control when the winding M3 is broken. It is a graph which illustrates. FIG. 10A is a graph showing waveforms of simulation results of three-phase current, d-axis current, q-axis current, and zero-phase current obtained when an open failure occurs in a switch element on the high side of the A-phase H bridge. FIG. 10B is a graph showing waveforms of simulation results of a three-phase current, a d-axis current, a q-axis current, and a zero-phase current obtained when a switch element on the high side of the A-phase H bridge fails. FIG. 10C is a graph showing waveforms of simulation results of a three-phase current, a d-axis current, a q-axis current, and a zero-phase current obtained when an open failure occurs in a switch element on the low side of the A-phase H bridge. FIG. 10D is a graph showing waveforms of simulation results of a three-phase current, a d-axis current, a q-axis current, and a zero-phase current, which are obtained when a switch element on the low side of the A-phase H bridge fails. FIG. 11 is a diagram exemplifying a table of data groups of d-axis current, q-axis current, zero-phase current and q-axis voltage recorded in the internal register 341. FIG. 12 is a schematic view showing a typical configuration of the electric power steering apparatus 3000 according to the second embodiment.

Embodiments of 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 facilitate the understanding of the person skilled in the art, the following description may be omitted unnecessarily to avoid redundant description. For example, detailed description of already well-known matters and redundant description of substantially the same configuration may be omitted.

In the present specification, the implementation of the present disclosure will be exemplified taking a power conversion device that converts power from a power supply into power supplied to a three-phase motor having three-phase (A-phase, B-phase, C-phase) windings. The form will be described. However, a power conversion device that converts power from a power supply to power supplied to an n-phase motor having n-phase (n is an integer of 4 or more) windings such as four-phase or five-phase is also within the scope of the present disclosure. .

Embodiment 1 [1-1. Structure of Inverter Unit 100] FIG. 1 schematically shows a circuit configuration of the inverter unit 100 according to the present embodiment.

The inverter unit 100 includes a power shutoff circuit 110, a first inverter 120 and a second inverter 130. The inverter unit 100 can convert the power from the

power supplies

101A and 101B into the power to be supplied to the motor 200. For example, the first and

second inverters

120, 130 can convert DC power into three-phase AC power which is pseudo-sinusoidal waves of A-phase, B-phase and C-phase.

The motor 200 is, for example, a three-phase alternating current 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. 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. In the present specification, “connection” between components (components) mainly means electrical connection.

The first inverter 120 has terminals A_L, B_L and C_L corresponding to the respective phases. The second inverter 130 has terminals A_R, B_R and C_R corresponding to the respective phases. The terminal A_L of the first inverter 120 is connected to one end of the A-phase winding M1, the terminal B_L is connected to one end of the B-phase winding M2, and the terminal C_L is connected to one end of the C-phase winding M3. Connected Similar to the first inverter 120, the terminal A_R of the second inverter 130 is connected to the other end of the A-phase winding M1, the terminal B_R is connected to the other end of the B-phase winding M2, and the terminal C_R is , C phase is connected to the other end of the winding M3. Such motor connections are different from so-called star connections and delta connections.

The power supply shutoff circuit 110 has first to

fourth switch elements

111, 112, 113 and 114. In the inverter unit 100, the first inverter 120 can be electrically connected to the power supply 101A and the GND by the power shutoff circuit 110. The second inverter 130 can be electrically connected to the power supply 101 B and the GND by the power shutoff circuit 110. Specifically, the first switch element 111 switches connection / non-connection between the first inverter 120 and GND. The second switch element 112 switches connection / non-connection between the power supply 101 and the first inverter 120. The third switch element 113 switches connection / disconnection between the second inverter 130 and GND. The fourth switch element 114 switches connection / disconnection between the power supply 101 and the second inverter 130.

The on / off of the first to

fourth switch elements

111, 112, 113 and 114 may be controlled by, for example, a microcontroller or a dedicated driver. The first to

fourth switch elements

111, 112, 113 and 114 can block bidirectional current. For example, semiconductor switches such as thyristors, analog switch ICs, or field effect transistors (typically MOSFETs) having parasitic diodes formed therein as the first to

fourth switch elements

111, 112, 113 and 114, and A mechanical relay or the like can be used. A combination of a diode and an insulated gate bipolar transistor (IGBT) may be used. In the drawings of this specification, an example in which MOSFETs are used as the first to

fourth switch elements

111, 112, 113 and 114 is shown. Thereafter, the first to

fourth switch elements

111 and 11 are provided.
2, 113 and 114 may be described as

SWs

111, 112, 113 and 114, respectively.

The SW 111 is arranged such that a forward current flows toward the first inverter 120 in an internal parasitic diode. The SW 112 is arranged such that a forward current flows in the parasitic diode toward the power supply 101A. The SW 113 is disposed such that a forward current flows to the second inverter 130 in the parasitic diode. The SW 114 is arranged such that forward current flows in the parasitic diode toward the power supply 101B.

The power shutoff circuit 110 preferably further includes fifth and

sixth switch elements

115 and 116 for reverse connection protection, as shown. The fifth and

sixth switch elements

115, 116 are typically semiconductor switches of a MOSFET having parasitic diodes. The fifth switch element 115 is connected in series to the SW 112, and is disposed such that a forward current flows toward the first inverter 120 in the parasitic diode. The sixth switch element 116 is connected in series to the SW 114, and is disposed such that a forward current flows toward the second inverter 130 in the parasitic diode. Even when the

power supplies

101A and 101B are connected in the reverse direction, the reverse current can be cut off by the two switch elements for reverse connection protection.

The number of switch elements to be used is not limited to the illustrated example, and is appropriately determined in consideration of design specifications and the like. Particularly in the on-vehicle field, high quality assurance is required from the viewpoint of safety, so it is preferable to provide a plurality of switch elements for each inverter.

The power supply may comprise a power supply 101A for the first inverter 120 and a power supply 101B for the second inverter 130. The power supplies 101A and 101B generate a predetermined power supply voltage (for example, 12 V). As a power supply, for example, a DC power supply is used. However, the power source may be an AC-DC converter and a DC-DC converter, or may be a battery (storage battery). In addition, the power supply 101 may be a single power supply common to the first and

second inverters

120 and 130.

A coil 102 is provided between the

power supplies

101A and 101B and the power shutoff circuit 110. The coil 102 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 side.

A capacitor 103 is connected to the power supply terminal of each inverter. The capacitor 103 is a so-called bypass capacitor, which suppresses voltage ripple. The capacitor 103 is, for example, an electrolytic capacitor, and the capacity and the number to be used are appropriately determined depending on design specifications and the like.

The first inverter 120 comprises a bridge circuit having three legs. Each leg has a low side switch element and a high side switch element. The A-phase leg has a low side switch element 121L and a high side switch element 121H. The B-phase leg has a low side switch element 122L and a high side switch element 122H. The C-phase leg has a low side switch element 123L and a high side switch element 123H. As a switch element, FET or IGBT can be used, for example. Hereinafter, an example using a MOSFET as a switch element will be described, and the switch element may be described as SW. For example, the

switch elements

121L, 122L and 123L are described as

SW

121L, 122L and 123L.

The first inverter 120 has three

shunt resistors

121R, 122R and 123R as a current sensor 150 (see FIG. 3) for detecting the current flowing in the winding of each phase A, B and C. Prepare. Current sensor 150 includes a current detection circuit (not shown) that detects the current flowing in each shunt resistor. For example, the

shunt resistors

121R, 122R and 123R are respectively connected between the three low side switch elements included in the three legs of the first inverter 120 and the GND. Specifically, shunt resistor 121R is electrically connected between SW121L and SW111, shunt resistor 122R is electrically connected between SW122L and SW111, and shunt resistor 123R is between SW123L and SW111. Electrically connected. The resistance value of the shunt resistor is, for example, about 0.5 mΩ to 1.0 mΩ.

Similar to the first inverter 120, the second inverter 130 includes a bridge circuit having three legs. The A-phase leg has a low side switch element 131L and a high side switch element 131H. The B-phase leg has a low side switch element 132L and a high side switch element 132H. The C-phase leg has a low side switch element 133L and a high side switch element 133H. The second inverter 130 includes three

shunt resistors

131R, 132R, and 133R. The shunt resistors are connected between the three low side switch elements included in the three legs and GND.

The number of shunt resistors is not limited to three for each inverter. For example, it is possible to use two shunt resistors for A phase and B phase, two shunt resistors for B phase and C phase, and two shunt resistors for A phase and C phase. The number of shunt resistors to be used and the arrangement of the shunt resistors are appropriately determined in consideration of product cost, design specifications and the like.

As described above, the second inverter 130 has substantially the same structure as the structure of the first inverter 120. In FIG. 1, the inverter on the left side of the drawing is described as a first inverter 120 and the inverter on the right side is described as a second inverter 130 for convenience of description. However, such notations should not be construed with the intention of limiting the present disclosure. The first and

second inverters

120 and 130 may be used as components of the inverter unit 100 without distinction.

[1-2. Structure of Power Conversion Device 1000 and Motor Module 2000] FIG. 2 schematically shows a block configuration of the motor module 2000 according to the present embodiment, and mainly shows a block configuration of the power conversion device 1000. As shown in FIG.

The motor module 2000 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 as an electromechanical integrated motor having, for example, a motor, a sensor, a driver and a controller. In addition, the power conversion device 1000 other than the motor 200 can be modularized and manufactured and sold.

The control circuit 300 includes, for example, a power supply circuit 310, an angle sensor 320, an input circuit 330, a controller 340, a drive circuit 350, and a ROM 360. The control circuit 300 is connected to the inverter unit 100, and drives the motor 200 by controlling the inverter unit 100.

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

The power supply circuit 310 generates DC voltages (for example, 3 V, 5 V) necessary for each block in the circuit. The angle sensor 320 is, for example, a resolver or a Hall IC. Alternatively, the angle sensor 320 is also realized by a combination of an MR sensor having a magnetoresistive (MR) element and a sensor magnet. The angle sensor 320 detects a rotation angle of the rotor (hereinafter referred to as “rotation signal”), and outputs a rotation signal to the controller 340.

The input circuit 330 receives the motor current value (hereinafter referred to as "actual current value") detected by the current sensor 150, converts the level of the actual current value to the input level of the controller 340 as necessary, The value is output to the controller 340. The input circuit 330 is, for example, an analog-to-digital converter.

The controller 340 is an integrated circuit that controls the entire power conversion apparatus 1000, and is, for example, a microcontroller or a field programmable gate array (FPGA).

The controller 340 controls the switching operation (turn on or off) of each SW 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, etc. to generate a PWM signal, and outputs it to the drive circuit 350. Further, the controller 340 can control on / off of each SW in the power shutoff circuit 110 of the inverter unit 100.

The controller 340 can further detect the presence or absence of a failure of the switch element in the first and

second inverters

120, 130. Therefore, when describing the operation of detecting the presence or absence of a failure of the switch element, in the present specification, "controller 340" may be described as "fault detection device 340" as the subject of the operation.

The drive circuit 350 is typically a gate driver (or pre-driver). The drive circuit 350 generates a control signal (gate control signal) for controlling the switching operation of the MOSFET of each SW in the first and

second inverters

120 and 130 in accordance with the PWM signal, and supplies the control signal to the gate of each SW. In addition, the drive circuit 350 can generate a control signal for controlling on / off of each SW in the power shutoff circuit 110 according to an instruction from the controller 340. When the drive target is a low voltage driveable motor, the gate driver may not be required. In that case, the function of the gate driver may be implemented in the controller 340.

The ROM 360 is electrically connected to the controller 340. The ROM 360 is, for example, a writable memory (for example, a PROM), a rewritable memory (for example, a flash memory), or a read only memory. The ROM 360 stores a control program including an instruction group for causing the controller 340 to control the power conversion apparatus 1000 and an instruction group for executing failure detection of a switch element described later. For example, the control program is temporarily expanded in a RAM (not shown) at boot time.

[1-3. Detection of Failure of Switch Element] First, a specific example of a control method at the time of normal operation of the power conversion device 1000 will be described. Normal means that each SW of the first inverter 120, the second inverter 130, and the power cut-off circuit 110 has not failed, and none of the three-phase windings M1, M2 and M3 of the motor 200 has failed. Point to the state. In the present specification, the

switches

115 and 116 for reverse connection protection of the power shutoff circuit 110 are always on.

At normal times, the control circuit 300 turns on all the

SWs

111, 112, 113 and 114 of the power shutoff circuit 110. Thereby, the power supply 101A and the first inverter 120 are electrically connected, and the power supply 101B and the second inverter 130 are electrically connected. In addition, the first inverter 120 and GND are electrically connected, and the second inverter 130 and GND are electrically connected. In this connected state, the control circuit 300 drives the motor 200 by energizing the windings M1, M2 and M3 using both the first and

second inverters

120, 130. In the present specification, energization of a three-phase winding is referred to as "three-phase energization control", and energization of a two-phase winding is referred to as "two-phase energization control".

FIG. 3 exemplifies a current waveform (sine wave) obtained by plotting current values flowing in the A-phase, B-phase, and C-phase windings of the motor 200 when the power conversion device 1000 is controlled according to three-phase energization control. doing. The horizontal axis indicates the motor electrical angle (deg), and the vertical axis indicates the current value (A). In the current waveform of FIG. 3, current values are plotted every 30 ° of electrical angle. I pk represents the maximum current value (peak current value) of each phase.

In the current waveform shown in FIG. 3, the sum of the currents flowing in the three-phase winding considering the direction of the current is "0" for each electrical angle. However, according to the circuit configuration of power conversion apparatus 1000, the currents flowing through the three-phase windings can be controlled independently, so it is also possible to perform control such that the sum of the currents does not become "0". For example, the control circuit 300 controls the switching operation of each switch element of the first and

second inverters

120 and 130 by PWM control that obtains the current waveform shown in FIG. 3.

The fault detection device (i.e., the controller) 340 is based on at least one of the three-phase current of the motor 200 and the current / voltage represented in the dq coordinate system (which may also be expressed as dqz rotational coordinate system). The presence or absence of a failure of the switch element in the two

inverters

120 and 130 can be detected. The current / voltage in the dq coordinate system is, for example, a zero-phase current, the details of which will be described later.

The failure detection device 340 can detect the presence or absence of a failure of the switch element in the first and

second inverters

120 and 130 while driving the motor 200 based on, for example, vector control. For example, when the power conversion device 1000 is powered on and motor control starts, the failure detection device 340 starts detecting a failure of the switch element in response to the start. For example, the failure detection device 340 may continue the detection of the failure of the switch element during the period of controlling the motor 200, or performs the detection of the failure of the switch element only during the designated period (for example, periodically). You may

The failure of the switch element will be described. The failure of the switch element means the failure of the switch element in the first and

second inverters

120 and 130. The failure of the switch element is roughly classified into “open failure” and “short failure”. "Open fault" refers to a fault in which the source-drain of FET is opened (in other words, resistance rds between source-drain becomes high impedance), and "short fault" is in the source-drain of FET Refers to a short circuit failure.

When the power converter 1000 is used for a long time, at least one of the plurality of SWs of the two inverters may fail. These failures are different from the manufacturing failures that can occur during manufacturing. If even one of the plurality of switch elements fails, normal three-phase conduction control becomes impossible. The failure detection device 340 detects a failure of the switch element.

The outline of the failure detection of the switch element is as follows.

The failure detection device (controller) 340 acquires at least one of the three-phase current of the motor 200 and the current / voltage represented in the dq coordinate system at a predetermined cycle, and acquires data of the acquired current / voltage, for example, in the controller Write to the register 341 (see FIG. 2) of The internal register 341 stores data that the failure detection device 340 performs arithmetic processing. The failure detection device 340 compares the current / voltage data acquired at the failure detection reference time with the past data group including data of a plurality of current / voltages acquired earlier than the reference time. Based on the detection, the presence or absence of a failure of the switch element in the first and

second inverters

120 and 130 is detected. The predetermined cycle is determined from the number of points at which current and voltage data are acquired during one cycle and one cycle of the electrical angle of the motor. The predetermined cycle is, for example, 100 μs.

<A. Detection of Failure of Switch Element Based on Three-Phase Current In this example, the failure detection device 340 acquires the three-phase current of the motor 200 for each predetermined cycle, and writes it in the internal register 341. The failure detection device 340 compares the data of the three-phase current acquired at the reference time with the data group of a plurality of three-phase currents acquired at a time earlier than the reference time, and the first and second inverters 120. , 130 detects the presence or absence of a failure of the switch element. In other words, the failure detection device 340 detects the presence or absence of a failure of the switch element based on the past data group related to the three-phase current recorded in the internal register 341.

FIG. 4 schematically shows the H bridge of each phase. The H bridge of each phase includes the switch element H1 on the high side of the first inverter 120, the switch element L1 on the low side, the switch element H2 on the high side of the second inverter 130, the switch element L2 on the low side, and the winding M. Have.

The inventor conducted a simulation to verify the behavior of the three-phase currents Ia, Ib and Ic after a failure occurs in the switch element of the H bridge. This simulation was performed under the condition that the time when the open failure of the switch element L1 (corresponding to the SW121L in FIG. 1) of the A phase H bridge is 0.01 ms.

FIG. 5 exemplifies waveforms of simulation results of the three-phase currents Ia, Ib and Ic when the switch element L1 of the A-phase H bridge has an open failure. The horizontal axis of the upper and lower graphs in FIG. 5 indicates time [s], and the vertical axis indicates current [A]. The upper graph illustrates the waveforms of the three-phase currents Ia, Ib and Ic from 0s to 0.02s, and the lower graph shows the waveforms of the three-phase currents Ia, Ib and Ic in the upper graph. The waveform of the portion from 6 ms to 11 ms is shown enlarged.

The waveforms of the three-phase current shown in FIG. 5 are based on data of the three-phase currents Ia, Ib and Ic acquired in a cycle of 0.1 ms. For example, assuming that the switch element L1 of the A-phase H bridge is open failure, as shown in the figure, the phase current Ia of the A-phase fluctuates to generate a period in which a peculiar behavior is exhibited. More specifically, when an open failure occurs in the low side or high side switch element of the H bridge, it is possible to observe a period in which the phase current becomes zero and does not change. This is because, for example, the actual current or voltage of phase A can not follow the target current or voltage of PI (Proportional-Integral) control in vector control. In addition, since the B-phase and C-phase bridges are not broken, no particular change is observed in the phase currents Ib and Ic.

FIG. 6 illustrates a table of three-phase current data groups recorded in the internal register 341 of the failure detection device 340. The table of FIG. 6 shows the values of the phase currents Ia and Ib of A-phase and B-phase for 14 points acquired between 9.6 ms and 11 ms in the graph of FIG. The value of the phase current Ic of the C phase is not shown.

For example, the fault detection device 340 writes the latest data group of the three-phase current acquired every 0.1 ms during one cycle of the electrical angle of the motor into the internal register 341, and the data group recorded in the internal register 341 Update every cycle of electrical angle. For example, as the failure detection device 340, a microcontroller having an internal register with a data width of 8 bits can be used. Alternatively, instead of the internal register 341, a dedicated buffer (not shown) can be used. The buffer may have a capacity capable of recording the latest data group of the three-phase current acquired during one cycle of the electrical angle.

For example, the failure detection device 340 may write the data group of three-phase current acquired during a part of one period of the electrical angle of the motor as the latest data group in the internal ranger. In that case, the predetermined period is determined from the partial period and the number of points for acquiring current / voltage data in the period.

The reference time is a time at which the latest data in the latest data group is acquired or calculated. In other words, the reference time is the latest time at which the latest data is acquired or calculated in the failure detection of the switch element, and changes with the passage of time. However, the reference time can be arbitrarily set in the latest data group. The time when certain data in the latest data group is acquired can be used as a reference time, and the data group acquired before the reference time can be treated as a past data group.

For example, let's look at when the reference time of failure detection is at time 11 ms (corresponding to point No. 13). A past data group including data of a plurality of current and voltage acquired at a time prior to the reference time has point No. It consists of data groups of three-phase currents acquired at a total of 13 points from 0 to 12 (9.6 ms to 10.9 ms). This past data group is included in the above-mentioned latest data group (data group for one period of electrical angle). In other words, the past data group is a part of the latest data group.

The failure detection device 340 compares the data of the reference time (point No. 13) with the past (point No. 0 to 12) data group. In the table of FIG. 6, it is observed that the phase current of A phase continues to be zero during a period of 8 points from the reference time to the past 7 points. The failure detection device 340 identifies the failure of the A-phase H bridge when the phase current of A-phase is continuously zero during a predetermined point (for example, 8 points) going back from the reference time. The failure of the H bridge refers to the open failure of at least one of the four switch elements H1, L1, H2 and L2.

The failure detection device 340 can determine the failure at the reference time (11 ms) after an open failure occurs in the low-side switch element 121L of the A-phase H bridge. On the other hand, based on the data group of B phase and C phase (not shown) in the past data group, the failure detection device 340 determines that the failure of the B bridge and the C phase H bridge has not occurred. Time is determined.

In the conventional failure detection of a switch element, failure detection of the switch element has been performed in response to a trigger notifying that start of the failure detection of the switch element, for example. In that case, data necessary for failure detection of the switch element is acquired in response to the trigger, and failure detection of the switch element is performed based on the acquired data. Therefore, much time has been spent on failure detection of the switch element. In the case where failure detection of switch elements is performed in parallel during control of the motor, it is desirable to make the detection time as short as possible so as not to affect motor control.

According to the present embodiment, failure detection of the switch element is performed based on a past data group acquired at a time prior to the failure detection reference time. Data may not be newly acquired to detect a failure of the switch element. Therefore, it becomes unnecessary to acquire new data, and failure detection of the switch element can be performed in a shorter time. As a result, for example, it becomes possible to quickly switch the motor control from the three-phase energization control to the two-phase energization control described later.

When the open failure of the switch element is detected, the failure detection device 340 can switch the control mode of the motor from normal three-phase current control to abnormal two-phase current control. In the present specification, energization of a three-phase winding is referred to as "three-phase energization control", and energization of a two-phase winding is referred to as "two-phase energization control".

For example, when the failure detection device 340 detects a failure in the A-phase H bridge, it performs two-phase energization control of energizing the windings M2 and M3 using the B-phase and C-phase H bridges other than the A phase. it can. When the failure detection device 340 detects a failure in the B-phase H bridge, the failure detection device 340 can perform two-phase energization control of energizing the windings M1 and M3 using the A-phase and C-phase H bridges other than the B phase. When the failure detection device 340 detects a failure in the C-phase H bridge, the failure detection device 340 can perform two-phase energization control of energizing the windings M1 and M2 using the A-phase and B-phase H bridges other than the C phase.

FIG. 7 is a current waveform obtained by plotting current values flowing in the B-phase and C-phase windings of motor 200 when power converter 1000 is controlled in accordance with two-phase energization control when A-phase H bridge fails. Is illustrated. FIG. 8 is a current waveform obtained by plotting the values of currents flowing through the A-phase and C-phase windings of motor 200 when power converter 1000 is controlled according to two-phase energization control when the B-phase H bridge fails. Is illustrated. FIG. 9 is a current waveform obtained by plotting current values 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. Is illustrated. The horizontal axis indicates the motor electrical angle (deg), and the vertical axis indicates the current value (A). In the current waveforms of FIG. 7 to FIG. 9, current values are plotted at every electrical angle of 30 °. I pk represents the maximum current value (peak current value) of each phase during energization control of each phase.

<B. Failure detection of switch element based on current and voltage of dq coordinate system> A configuration in which two inverters as shown in FIG. 1 are respectively connected to one end and the other end of a winding, that is, a circuit configuration including an H bridge for each phase In this case, it is possible to control the current flowing through the three-phase winding independently, in which case zero-phase current may flow. The zero phase current is also called z phase current. In the dq coordinate system, an axis corresponding to the zero phase is represented as the z axis. The fault detection device 340 can monitor, for example, the zero phase current, and detect a fault of the switch element in the first and

second inverters

120 and 130 according to a change in the current.

The fault detection device 340 can monitor the current / voltage represented in the dq coordinate system. The current / voltage in the dq coordinate system indicates at least one of d-axis current, q-axis current, zero-phase current, d-axis voltage, q-axis voltage and z-phase voltage. The current / voltage of the dq coordinate system to be monitored preferably includes a zero-phase current. In the present embodiment, an example will be described in which a zero-phase current is mainly used as the current / voltage in the dq coordinate system.

The failure detection device (i.e., the controller) 340 acquires the current and voltage represented in the dq coordinate system at predetermined intervals. The predetermined cycle is, for example, 0.1 ms. The failure detection device 340 has, for example, a failure detection unit that performs failure detection. For example, the failure detection unit converts the currents Ia, Ib and Ic into the d-axis current Id, the q-axis current Iq, and the zero-phase current Iz in the dqz rotational coordinate system, using a conversion matrix. Alternatively, the controller 340 typically has a control unit that performs vector control. The fault detection unit may also receive necessary data from the control unit among the d-axis current, q-axis current, zero-phase current, d-axis voltage, q-axis voltage and z-phase voltage. Thus, the fault detection device 340 acquires at least one of these currents and voltages in the dq coordinate system.

The inventor conducted a simulation to verify the behavior of the three-phase currents Ia, Ib, Ic, d-axis current, q-axis current, and zero-phase current after a failure occurs in the switch element of the H bridge. This simulation was performed under the condition that the time when the switch element H1 or L1 (corresponding to the

SW

121H or 121L in FIG. 1) of the A-phase H bridge is open or shorted is 0.015 s.

FIG. 10A shows waveforms of simulation results of three-phase current, d-axis current, q-axis current, and zero-phase current obtained when an open failure occurs in a switch element on the high side of the A-phase H bridge. FIG. 10B shows waveforms of simulation results of a three-phase current, a d-axis current, a q-axis current, and a zero-phase current, which are obtained when the switch element on the high side of the A-phase H bridge fails. FIG. 10C shows waveforms of simulation results of three-phase current, d-axis current, q-axis current, and zero-phase current obtained when an open failure occurs in a switch element on the low side of the A-phase H bridge. FIG. 10D shows waveforms of simulation results of a three-phase current, a d-axis current, a q-axis current, and a zero-phase current, which are obtained when the switch element on the low side of the A-phase H bridge fails. The horizontal axis of the graph indicates time (s), and the vertical axis indicates current (A).

In this simulation, it can be seen that, after the switch element has failed, the phase current Ia of the three-phase current fluctuates to generate a period in which a peculiar behavior is exhibited. In particular, in the case of an open failure, it is possible to observe a period in which the phase current is zero and does not change. This is as already explained. Even in the case of the short failure, the fluctuation of the phase current Ia can be confirmed.

Focus on the d-axis current, q-axis current and zero-phase current in the dq coordinate system. Since the current in the dq coordinate system can be regarded as a DC component, it does not change in normal three-phase conduction control. However, when the switch element fails, fluctuations in d-axis current, q-axis current, and zero-phase current can be observed. This is due to the fluctuation of the phase current Ia of the A phase. This phenomenon is not limited to the fluctuation of the phase current Ia of the A phase, and is also observed due to the fluctuation of the phase current Ib of the B phase or the phase current Ic of the C phase. Thus, by monitoring changes in current (or voltage) in the dq coordinate system, failure of at least one switch element in two inverters can be detected. The d-axis voltage and the q-axis voltage in the dq coordinate system are calculated based on the abc phase voltage.

The failure detection device 340 acquires, for example, d-axis current, q-axis current, zero-phase current and q-axis voltage in the dq coordinate system based on the three-phase current, and writes the acquired data to the internal register 341. The failure detection device 340 detects a failure of the switch element in the first and

second inverters

120 and 130 based on the comparison result between the data acquired at the reference time and a plurality of data groups acquired at a time earlier than the reference time. To detect the presence or absence of

FIG. 11 illustrates a table of data groups of d-axis current, q-axis current, zero-phase current, and q-axis voltage, which are recorded in the internal register 341. The table shows data of 5 points in the latest data group acquired. The failure detection device 340 refers to the table to monitor the current / voltage fluctuation of the dq coordinate system, for example, monitors the fluctuation of the zero phase current. The failure detection device 340 detects a failure of the switch element in the first and

second inverters

120 and 130 when the point value at the reference time deviates from the value of the past data group.

When the reference time for failure detection is at point T + 3, the failure detection device 340 determines that the Iz value “20” of the reference time is a past data group acquired earlier than the reference time: point T, T + 1, T + 2 It is determined that the values are out of the Iz values “6.8”, “5”, and “7” in For this determination, for example, a threshold value stored in advance in the ROM 360 can be used. If the difference between the Iz value at the reference time and each Iz value included in the past data group is equal to or less than the threshold value, the failure detection device 340 does not detect a failure of the switch element. On the other hand, when the difference is larger than the threshold, the failure detection device 340 can determine that at least one switch element in the first and

second inverters

120 and 130 is open failure or short failure.

For example, when the value “3” is used as the threshold value, the failure detection device 340 does not detect a switch element failure when the reference time is at point T + 2, shifts the reference time to point T + 3 for the first time It can be decided. As described above, the failure detection device 340 can detect the failure of the switch element by monitoring the variation of the current / voltage of the dq coordinate system which is the DC component.

The failure detection unit of the controller 340 may generate, for example, a motor control shutdown signal and output it to the control unit when it detects a short failure or an open failure of the switch element. The control unit may shut down the three-phase conduction control in response to the signal. Thereby, for example, in the electric power steering (EPS) apparatus, the control mode can be switched from the assist mode of torque to the manual steering mode.

According to the present embodiment, by monitoring the signal change in the dq coordinate system which is the DC component, the comparison between the data acquired at the reference time and the plurality of data groups acquired at the time before the reference time is more It becomes easy to do. Therefore, for example, an advantage such as circuit scale reduction or memory size reduction can be obtained in the implementation on a microcontroller. Furthermore, by performing failure detection based on the past data group, failure detection can be performed in a shorter time.

Second Embodiment FIG. 12 schematically shows a typical configuration of an electric power steering apparatus 3000 according to this embodiment.

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

The steering system 520 includes, for example, a steering handle 521, a steering shaft 522,

free shaft joints

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

tie rods

527A and 527B,

knuckles

528A, 528B, and left and

right steering wheels

529A, 529B.

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, an electronic control unit (ECU) 542 for a car, a motor 543, and a reduction mechanism 544. The steering torque sensor 541 detects a steering torque in the steering system 520. The ECU 542 generates a drive signal based on a 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 assist torque 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 is built around an ECU. 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 unit.

Embodiments of the present disclosure can be widely used in a variety of devices equipped with various motors, such as vacuum cleaners, dryers, ceiling fans, washing machines, refrigerators, and electric power steering devices.

Claims

A power converter that converts power from a power supply into power supplied to a motor having n-phase (n is an integer of 3 or more) windings,

A first inverter connected to one end of a winding of each phase of the motor, the first inverter having n legs each having a low side switch element and a high side switch element;

A second inverter connected to the other end of the winding of each phase of the motor, the second inverter having n legs each having a low side switch element and a high side switch element;

A failure detection device for detecting the presence or absence of a failure of a switch element in the first and second inverters;

A memory for storing data to be processed by the failure detection device;

Equipped with

The failure detection device is

At least one of the n-phase current of the motor and the current / voltage represented in the dq coordinate system is acquired for each predetermined cycle, and the acquired current / voltage data is written to the memory.

The first and the second are based on the comparison result of current / voltage data acquired at a reference detection time of failure detection and a past data group including data of a plurality of current / voltage acquired at a time before the reference time. The power converter device which detects the existence of failure of the switch element in the 2nd inverter.
The power conversion device according to claim 1, wherein the failure detection device acquires the current / voltage represented in the dq coordinate system for each predetermined cycle based on the n-phase current of the motor, and writes the current / voltage in the memory. .
The power converter according to claim 2, wherein the current / voltage of the dq coordinate system is at least one of d-axis current, q-axis current, zero-phase current, d-axis voltage, q-axis voltage and z-phase voltage.
The failure detection device may be configured to compare the first and second data based on the comparison result of the zero-phase current data acquired at the reference time and a plurality of zero-phase current data groups acquired at times earlier than the reference time. The power converter according to claim 3, wherein presence or absence of a failure of a switch element in two inverters is detected.
The power conversion device according to claim 1, wherein the failure detection device acquires the n-phase current of the motor for each of the predetermined cycles and writes the n-phase current in the memory.
The failure detection device compares the first and the second on the basis of the comparison result of data of n-phase current acquired at the reference time and data groups of a plurality of n-phase currents acquired at time before the reference time. The power converter according to claim 5, wherein presence or absence of a failure of the switch element in the two inverters is detected.
The failure detection device writes the latest data group of the current and voltage acquired during one cycle of the electric angle of the motor in the memory, and the data group recorded in the memory is in each cycle. Updated,

The power converter according to any one of claims 1 to 6, wherein the past data group is included in the latest data group.
The power conversion device according to claim 7, wherein the predetermined cycle is determined from the number of points for acquiring data of the current and voltage during the one cycle of the electrical angle and the one cycle.
The power conversion device according to claim 8, wherein the reference time is a time at which latest data in the latest data group is acquired.
A first switch element for switching connection / disconnection between the first inverter and the ground;

A second switch element for switching connection / disconnection between the first inverter and the power supply;

A third switch element for switching connection / disconnection between the second inverter and the ground;

A fourth switch element for switching connection / disconnection between the second inverter and the power supply;

The power converter according to any one of claims 1 to 9, further comprising:
Motor,

The power converter according to any one of claims 1 to 10,

, A motor module.
An electric power steering apparatus comprising the motor module according to claim 11.