CN211830634U

CN211830634U - Power conversion device, motor module, and electric power steering device

Info

Publication number: CN211830634U
Application number: CN201890001071.5U
Authority: CN
Inventors: 锅师香织; 小池上贵; 中田雄飞
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2017-09-29
Filing date: 2018-06-15
Publication date: 2020-10-30
Anticipated expiration: 2028-06-15
Also published as: WO2019064725A1

Abstract

Provided is a power conversion device capable of detecting a failure of a switching element of an inverter in a shorter time. The utility model discloses a power conversion device (1000) has 1 st inverter (120), 2 nd inverter (130), fault detection device (340) and memory (341), and wherein, this fault detection device (340) detects to the switching element in 1 st inverter and the 2 nd inverter has or not trouble. The fault detection device obtains at least 1 of n-phase (n is an integer of 3 or more) current of a motor and current/voltage represented in a dq coordinate system for each predetermined cycle, writes data of the obtained current/voltage into a memory, and detects the presence or absence of a fault in a switching element in a 1 st inverter and a 2 nd inverter based on a comparison result between the data of the current/voltage obtained at a reference time of fault detection and a past data group including data of a plurality of currents/voltages obtained at a time before the reference time.

Description

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

Technical Field

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

Background

In recent years, an electromechanical motor (hereinafter, simply referred to as a "motor") in which an electric motor and an ECU (Electrical control unit) are integrated has been developed. In particular, in the field of vehicle mounting, high quality assurance is required from the viewpoint of safety. Therefore, the following redundancy design is adopted: even if a part of the component is broken down, the safety operation can be continued. As an example of the redundant design, it is considered to provide 2 inverters for 1 motor. As another example, it is conceivable to provide a backup microcontroller in the main microcontroller.

Patent document 1 discloses a power conversion device having a control unit and 2 inverters, which converts power from a power supply into power to be supplied to a three-phase motor. The 2 inverters are connected to a power source and a ground (hereinafter, referred to as "GND") respectively. 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 3 legs including a high-side switching element and a low-side switching element, respectively. When a failure of a switching element in 2 inverters is detected, the control unit switches the motor control from normal control to abnormal control. In the normal control, for example, the motor is driven by switching the switching elements of 2 inverters. In the control at the time of abnormality, for example, the motor is driven by the inverter that has not failed, using the neutral point of the winding in the inverter that has failed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2014-192950

Patent document 2: japanese patent laid-open publication No. 2017 and 063571

SUMMERY OF THE UTILITY MODEL

Problem to be solved by utility model

In a device that drives a motor using 2 inverters as described above, when a failure occurs in an inverter, it is required to identify the failure site in as short a time as possible.

Patent document 2 discloses a device for driving a motor having Y-connected windings by 1 inverter (hereinafter, referred to as a "single inverter type device"). Patent document 2 discloses a method of: the signal detected in the predetermined energization pattern is compared with a predetermined abnormality type correspondence table, thereby detecting disconnection and short-circuit of the wiring.

However, in the technique of patent document 2, since a failure such as disconnection of a wiring is detected using the measured current value and voltage value, it takes much time to detect the failure and to specify a failure site.

An embodiment of the present invention provides a power conversion device capable of detecting a failure of a switching element of an inverter in a shorter time, a motor module having the power conversion device, and an electric power steering apparatus having the motor module.

Means for solving the problems

The present invention provides an exemplary power conversion device that converts power from a power supply into power to be supplied to a motor having an n-phase winding, where n is an integer of 3 or more, the power conversion device including: a 1 st inverter connected to one end of a winding of each phase of the motor, and having n branches each having a low-side switching element and a high-side switching element; a 2 nd inverter connected to the other end of the winding of each phase of the motor, and having n branches each having a low-side switching element and a high-side switching element; a failure detection device that detects whether or not a failure occurs in a switching element in the 1 st inverter and the 2 nd inverter; and a memory that stores processing data of the failure detection device, the failure detection device obtaining at least 1 of a current/voltage indicated in a dq coordinate system and an n-phase current of the motor for each predetermined cycle and writing data of the obtained current/voltage into the memory, the failure detection device detecting whether or not a failure occurs in a switching element in the 1 st inverter and the 2 nd inverter based on a comparison result between data of the current/voltage obtained at a reference time of failure detection and a past data group including data of a plurality of currents/voltages obtained at times before the reference time.

An exemplary motor module of the present invention includes a motor and a power conversion device described above.

The exemplary electric power steering apparatus of the present invention has the motor module described above.

Effect of the utility model

According to an exemplary embodiment of the present invention, there is provided a power conversion device capable of detecting a failure of a switching element of an inverter in a shorter time by referring to a past data set obtained before a reference time of failure detection, a motor module having the power conversion device, and an electric power steering device having the motor module.

Drawings

Fig. 1 is a circuit diagram showing a circuit configuration of an inverter unit 100 of exemplary embodiment 1.

Fig. 2 is a block diagram mainly showing the block structure of the power conversion device 1000, and shows the block structure of the motor module 2000 of the illustrated embodiment 1.

Fig. 3 is a graph illustrating a current waveform (sine wave) obtained by plotting current values flowing through the respective windings of the a-phase, B-phase, and C-phase of the motor 200 when the power conversion device 1000 is controlled according to three-phase energization control.

Fig. 4 is a schematic diagram showing the structure of an H-bridge.

Fig. 5 is a graph illustrating waveforms of simulation results of three-phase currents Ia, Ib, and Ic in the case where an open failure occurs in the switching element L1 of the a-phase H bridge.

Fig. 6 is a diagram illustrating a table of data sets of three-phase currents recorded in the internal register 341 of the fault detection device 340.

Fig. 7 is a graph illustrating current waveforms obtained by plotting current values flowing through the respective windings of the B-phase and C-phase of the motor 200 when the power conversion device 1000 is controlled by two-phase electrical control when the winding M1 is disconnected.

Fig. 8 is a graph illustrating current waveforms obtained by plotting current values flowing through the respective windings of the a-phase and C-phase of the motor 200 when the power conversion device 1000 is controlled by two-phase electrical control when the winding M2 is disconnected.

Fig. 9 is a graph illustrating a current waveform obtained by plotting current values flowing through the respective windings of the a-phase and the B-phase of the motor 200 when the power conversion device 1000 is controlled by two-phase electrical control when the winding M3 is disconnected.

Fig. 10A is a graph showing waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained when an open failure occurs in the switching element on the high side of the a-phase H-bridge.

Fig. 10B is a graph showing waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained when a short-circuit fault occurs in the switching element on the high side of the a-phase H-bridge.

Fig. 10C is a graph showing waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained when an open failure occurs in the switching element on the low side of the a-phase H-bridge.

Fig. 10D is a graph showing waveforms of simulation results of three-phase currents, D-axis currents, q-axis currents, and zero-phase currents obtained when a short-circuit fault occurs in the switching element on the low side of the a-phase H-bridge.

Fig. 11 is a diagram illustrating 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 diagram showing a typical configuration of an electric power steering apparatus 3000 according to exemplary embodiment 2.

Detailed Description

Embodiments of a power conversion device, a motor module, and an electric power steering device according to the present invention will be described in detail with reference to the drawings. However, in order to avoid unnecessarily long descriptions below, detailed descriptions above the necessary level may be omitted to make it easily understood by those skilled in the art. For example, detailed descriptions of the already commonly known matters and repetitive descriptions of substantially the same structures may be omitted.

In the present specification, an embodiment of the present invention will be described by taking as an example a power converter that converts power from a power supply into power to be supplied to a three-phase motor having windings of three phases (a phase, B phase, and C phase). However, a power converter that converts power from a power supply into power to be supplied to an n-phase motor having windings of four or five equal n phases (n is an integer of 4 or more) also belongs to the scope of the present invention.

(embodiment mode 1)

[ 1-1 ] Structure of inverter Unit 100 ]

Fig. 1 schematically shows a circuit configuration of an inverter unit 100 of the present embodiment.

The inverter unit 100 has a power supply cutoff circuit 110, a 1 st inverter 120, and a 2 nd inverter 130. The inverter unit 100 can convert electric power from the

power sources

101A, 101B into electric power to be supplied to the motor 200. For example, the 1 st and 2

nd inverters

120 and 130 can convert the dc power into three-phase ac power of analog sine waves of a phase, B phase, and C phase.

The motor 200 is, for example, a three-phase ac motor. The motor 200 has a winding M1 of a phase, a winding M2 of B phase, and a winding M3 of C phase, and the motor 200 is connected to the 1 st inverter 120 and the 2 nd inverter 130. Specifically, the 1 st inverter 120 is connected to one end of the winding of each phase of the motor 200, and the 2 nd inverter 130 is connected to the other end of the winding of each phase. In this specification, "connection" of components (structural elements) to each other mainly means electrical connection.

The 1 st inverter 120 has terminals a _ L, B _ L and C _ L corresponding to the respective terminals. The 2 nd inverter 130 has terminals a _ R, B _ R and C _ R corresponding to each. The terminal a _ L of the 1 st inverter 120 is connected to one end of the winding M1 of the a phase, the terminal B _ L is connected to one end of the winding M2 of the B phase, and the terminal C _ L is connected to one end of the winding M3 of the C phase. Like the 1 st inverter 120, the terminal a _ R of the 2 nd inverter 130 is connected to the other end of the winding M1 of the a phase, the terminal B _ R is connected to the other end of the winding M2 of the B phase, and the terminal C _ R is connected to the other end of the winding M3 of the C phase. Such motor wiring is different from so-called star wiring and delta wiring.

The power supply cutoff circuit 110 has 1 st to 4

th switching elements

111, 112, 113, and 114. In the inverter unit 100, the 1 st inverter 120 can be electrically connected to the power sources 101A and GND through the power source cutoff circuit 110. The 2 nd inverter 130 can be electrically connected to the power sources 101B and GND through the power source cutoff circuit 110. Specifically, the 1 st switching element 111 switches connection/disconnection between the 1 st inverter 120 and GND. The 2 nd switching element 112 switches connection/disconnection of the power source 101 to/from the 1 st inverter 120. The 3 rd switching element 113 switches connection/disconnection between the 2 nd inverter 130 and GND. The 4 th switching element 114 switches connection/disconnection of the power source 101 to/from the 2 nd inverter 130.

The on/off of the 1 st to 4

th switching elements

111, 112, 113 and 114 can be controlled by a microcontroller or a dedicated driver, for example. The 1 st to 4

th switching elements

111, 112, 113 and 114 can cut off bidirectional current. As the 1 st to 4

th switching elements

111, 112, 113 and 114, for example, a thyristor, a semiconductor switch such as an analog switching IC or a field effect transistor (typically, MOSFET) having a parasitic diode formed therein, a mechanical relay, or the like can be used. A combination of diodes and Insulated Gate Bipolar Transistors (IGBTs) or the like may also be used. In the drawings in the present specification, an example of using MOSFETs as the 1 st to 4

th switching elements

111, 112, 113 and 114 is shown. Hereinafter, the 1 st to 4

th switching elements

111, 112, 113 and 114 may be referred to as SW111, 112, 113 and 114, respectively.

The SW111 is configured to flow a forward current in an internal parasitic diode toward the 1 st inverter 120. The SW112 is configured to cause a forward current to flow in the parasitic diode toward the power source 101A. The SW113 is configured to cause a forward current to flow in the parasitic diode toward the 2 nd inverter 130. SW114 is configured to cause a forward current to flow in the parasitic diode toward power source 101B.

As shown in the figure, the power cutoff circuit 110 preferably further includes 5 th and 6

th switching elements

115 and 116 for reverse connection protection. The 5 th and 6

th switching elements

115, 116 are typically semiconductor switches of MOSFETs with parasitic diodes. The 5 th switching element 115 is connected in series with the SW112 and configured to flow a forward current in the parasitic diode toward the 1 st inverter 120. The 6 th switching element 116 is connected in series with the SW114, and is configured to flow a forward current in the parasitic diode toward the 2 nd inverter 130. Even when the

power sources

101A and 101B are reversely connected, the reverse current can be cut by the 2 switching elements for reverse connection protection.

The number of switching elements to be used is not limited to the illustrated example, and may be determined as appropriate in consideration of design specifications and the like. In particular, in the field of vehicle mounting, it is preferable to provide a plurality of switching elements for each inverter in order to require high quality assurance from the viewpoint of safety.

The power supply can have a power supply 101A for the 1 st inverter 120 and a power supply 101B for the 2 nd inverter 130. The power supplies 101A and 101B generate a predetermined power supply voltage (for example, 12V). As the power supply, for example, a direct current power supply is used. However, the power source may be an AC-DC converter and a DC-DC converter, or may be a battery (secondary battery). Power source 101 may be a single power source common to 1 st and 2

nd inverters

120 and 130.

A coil 102 is provided between the

power supplies

101A and 101B and the power supply cutoff circuit 110. The coil 102 functions as a noise filter, and smoothes the high-frequency noise included in the voltage waveform supplied to each inverter or generated by each inverter so as not to flow out to the power supply side.

A capacitor 103 is connected to a power supply terminal of each inverter. The capacitor 103 is a so-called bypass capacitor, and suppresses voltage ripples. The capacitor 103 is, for example, an electrolytic capacitor, and the capacitance and the number to be used are appropriately determined in accordance with design specifications and the like.

The 1 st inverter 120 has a bridge circuit having 3 legs. Each branch has a low-side switching element and a high-side switching element. The a-phase branch has a low-side switching element 121L and a high-side switching element 121H. The B-phase leg has a low-side switching element 122L and a high-side switching element 122H. The C-phase leg has a low-side switching element 123L and a high-side switching element 123H. As the switching element, for example, an FET or an IGBT can be used. Hereinafter, an example in which a MOSFET is used as a switching element will be described, and the switching element may be referred to as SW. For example, the switching

elements

121L, 122L, and 123L are denoted as SW121L, 122L, and 123L.

The 1 st inverter 120 includes 3

shunt resistors

121R, 122R, and 123R as a current sensor 150 (see fig. 3) for detecting a current flowing through a winding of each of the a, B, and C phases. The current sensor 150 includes a current detection circuit (not shown) that detects a current flowing through each shunt resistor. For example, the

shunt resistors

121R, 122R, and 123R are respectively connected between the 3 low-side switching elements included in the 3 legs of the 1 st inverter 120 and GND. Specifically, the shunt resistor 121R is electrically connected between the SW121L and the SW111, the shunt resistor 122R is electrically connected between the SW122L and the SW111, and the shunt resistor 123R is electrically connected between the SW123L and the SW 111. The shunt resistor has a resistance value of, for example, about 0.5m Ω to 1.0m Ω.

Like the 1 st inverter 120, the 2 nd inverter 130 has a bridge circuit having 3 legs. The a-phase branch has a low-side switching element 131L and a high-side switching element 131H. The B-phase branch has a low-side switching element 132L and a high-side switching element 132H. The C-phase leg has a low-side switching element 133L and a high-side switching element 133H. The 2 nd inverter 130 has 3

shunt resistors

131R, 132R, 133R. These shunt resistors are connected between the 3 low-side switching elements included in the 3 branches and GND.

The number of shunt resistors is not limited to 3 for each inverter. For example, 2 shunt resistors for a phase and B phase, 2 shunt resistors for B phase and C phase, and 2 shunt resistors for a phase and C phase can be used. 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 2 nd inverter 130 has substantially the same configuration as that of the 1 st inverter 120. In fig. 1, for convenience of explanation, the inverter on the left side of the drawing is referred to as a 1 st inverter 120, and the inverter on the right side is referred to as a 2 nd inverter 130. However, such description should not be construed as limiting the invention. The 1 st and 2

nd inverters

120 and 130 can be used as the structural elements 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 structure of the motor module 2000 of the present embodiment, and mainly schematically shows a block structure of the power conversion device 1000.

The motor module 2000 has a power conversion device 1000 and a motor 200, and the power conversion device 1000 has an inverter unit 100 and a control circuit 300.

The motor module 2000 is modularized, and can be manufactured and sold as an electromechanically integrated motor having a motor, a sensor, a driver, and a controller, for example. The power conversion device 1000 other than the motor 200 may be manufactured and sold in a modular manner.

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 control the position, the rotational speed, the current, and the like of the target rotor of the motor 200 to realize closed-loop control. In addition, the control circuit 300 may have a torque sensor instead of the angle sensor 320. In this case, the control circuit 300 can control the target motor torque.

The power supply circuit 310 generates DC voltages (e.g., 3V, 5V) necessary for respective blocks in the circuit. The angle sensor 320 is, for example, a resolver or a hall IC. Alternatively, the angle sensor 320 may be implemented by a combination of a Magnetoresistive (MR) sensor having an MR element and a sensor magnet. The angle sensor 320 detects a rotation angle of the rotor (hereinafter, referred to as a "rotation signal"), and outputs the rotation signal to the controller 340.

The input circuit 330 receives a 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 an input level of the controller 340 as necessary, and outputs the actual current value to the controller 340. The input circuit 330 is, for example, an analog-digital conversion circuit.

The controller 340 is an integrated circuit that controls the entire power conversion device 1000, and is, for example, a microcontroller or an FPGA (Field Programmable Gate Array).

The controller 340 controls the switching operation (on or off) of each SW in the 1 st and 2

nd inverters

120 and 130 of the inverter unit 100. The controller 340 generates a PWM signal by setting a target current value based on the actual current value, the rotor rotation signal, and the like, and outputs the PWM signal to the drive circuit 350. In addition, the controller 340 can control on/off of each SW in the power shutoff circuit 110 of the inverter unit 100.

The controller 340 is also capable of detecting the presence or absence of a failure in the switching elements in the 1 st and 2

nd inverters

120 and 130. Therefore, when the operation of detecting whether or not there is a failure in the switching element is described, the "controller 340" may be referred to as "failure detection device 340" as the main body of the operation in this specification.

The driving 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 1 st and 2

nd inverters

120 and 130 based on the PWM signal, and supplies the control signal to the gate of each SW. The drive circuit 350 can generate a control signal for controlling on/off of each SW in the power shutoff circuit 110 in accordance with an instruction from the controller 340. When the driving target is a motor that can be driven at a low voltage, a gate driver may not be necessary. In this case, the function of the gate driver can be loaded in the controller 340.

The ROM 360 is electrically connected to the controller 340. The ROM 360 is, for example, a writable memory (e.g., PROM), a rewritable memory (e.g., flash memory), or a read-only memory. The ROM 360 stores control programs including a command set for causing the controller 340 to control the power conversion apparatus 1000 and a command set for performing failure detection of switching elements described later. For example, the control program is temporarily expanded into a RAM (not shown) at the time of startup.

[ 1-3 ] Fault detection of switching elements ]

First, a specific example of a normal-time control method of the power conversion device 1000 will be described. Normal refers to the following state: each SW of the 1 st inverter 120, the 2 nd inverter 130, and the power cutoff circuit 110 does not fail, and any one of the three-phase windings M1, M2, and M3 of the motor 200 does not fail. In this specification, it is assumed that the reverse connection protection SW115 and SW 116 of the power shutoff circuit 110 are always on.

In a normal state, the control circuit 300 turns on all of the SW111, 112, 113, and 114 of the power shutoff circuit 110. Thereby, power source 101A is electrically connected to 1 st inverter 120, and power source 101B is electrically connected to 2 nd inverter 130. In addition, the 1 st inverter 120 is electrically connected to GND, and the 2 nd inverter 130 is electrically connected to GND. In this connected state, the control circuit 300 drives the motor 200 by energizing the windings M1, M2, and M3 using both the 1 st and 2

nd inverters

120, 130. In this specification, a case where current is supplied to the three-phase windings is referred to as "three-phase current supply control", and a case where current is supplied to the two-phase windings is referred to as "two-phase current supply control".

Fig. 3 illustrates current waveforms (sine waves) obtained by plotting current values flowing through the respective windings of the a, B, and C phases of the motor 200 when the power conversion device 1000 is controlled according to three-phase energization control. The horizontal axis represents the motor electrical angle (deg) and the vertical axis represents the current value (A). In the current waveform of fig. 3, the current value is plotted at every 30 ° in electrical angle. Ipk represents the maximum current value (peak current value) of each phase.

In the current waveform shown in fig. 3, the sum of currents flowing in the windings of the three phases in consideration of the current direction is "0" in each electrical angle. However, according to the circuit configuration of the power conversion device 1000, since the currents flowing through the three-phase windings can be independently controlled, it is also possible to perform control in which the total sum of the currents is not "0". For example, the control circuit 300 controls the switching operation of each switching element of the 1 st and 2

nd inverters

120 and 130 by PWM control that can obtain the current waveform shown in fig. 3.

The fault detection device (i.e., controller) 340 can detect the presence or absence of a fault in the switching elements of the 1 st and 2

nd inverters

120 and 130 based on at least one of the current/voltage indicated in the dq coordinate system (which may also be referred to as dqz rotation coordinate system) and the three-phase current of the motor 200. The current/voltage of the dq coordinate system is, for example, a zero-phase current, which will be described in detail later.

The failure detection device 340 can detect the presence or absence of a failure in the switching elements in the 1 st and 2

nd inverters

120 and 130, for example, while driving the motor 200 by vector control. For example, when the power conversion apparatus 1000 turns on the power supply to start the motor control, the failure detection means 340 starts the failure detection of the switching element in response to the start. For example, the failure detection device 340 may continue to detect a failure of the switching element while controlling the motor 200, or may detect a failure of the switching element only for a predetermined period (e.g., periodically).

The failure of the switching element will be explained. The failure of the switching element refers to a failure of the switching element in the 1 st and 2

nd inverters

120 and 130. The failures of the switching elements are roughly classified into "open-circuit failures" and "short-circuit failures". The "open failure" refers to a failure in which the source-drain of the FET is open (in other words, the source-drain resistance rds is high impedance), and the "short failure" refers to a failure in which the source-drain of the FET is short-circuited.

When the power conversion apparatus 1000 is used for a long period of time, at least 1 of the plurality of SWs of the 2 inverters may malfunction. These failures are different from manufacturing failures that may occur at the time of manufacture. If 1 of the plurality of switching elements fails, the normal three-phase energization control cannot be performed. The failure detection device 340 detects a failure of the switching element.

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

The failure detection device (controller) 340 obtains at least one of the current/voltage indicated in the dq coordinate system and the three-phase current of the motor 200 for each predetermined period, and writes data of the obtained current/voltage into, for example, a register 341 (see fig. 2) inside the controller. The internal register 341 stores data to be subjected to arithmetic processing by the failure detection means 340. Fault detection device 340 detects the presence or absence of a fault in the switching elements in 1 st and 2

nd inverters

120 and 130 based on the result of comparison between current/voltage data obtained at a reference time of fault detection and a past data group including a plurality of current/voltage data obtained at a time before the reference time. The predetermined period is determined based on one period of the electrical angle of the motor and the number of points of the current/voltage data obtained during the one period. The predetermined period is, for example, 100 μ s.

< A. Fault detection of switching elements based on three-phase Current >

In this example, the failure detection device 340 obtains the three-phase current of the motor 200 for each predetermined cycle and writes the three-phase current into the internal register 341. The failure detection device 340 detects the presence or absence of a failure in the switching elements in the 1 st and 2

nd inverters

120 and 130 based on the result of comparison between the data of the three-phase currents obtained at the reference time and the data set of the plurality of three-phase currents obtained at the time before the reference time. In other words, the failure detection means 340 detects the presence or absence of a failure of the switching element based on the past data set relating to the three-phase current recorded in the internal register 341.

Fig. 4 schematically shows an H-bridge for each phase. The H-bridge of each phase includes a high-side switching element H1, a low-side switching element L1 of the 1 st inverter 120, a high-side switching element H2, a low-side switching element L2 of the 2 nd inverter 130, and a winding M.

The applicant conducted simulations in order to verify the behavior of the three-phase currents Ia, Ib, Ic after a failure of the switching elements of the H-bridge. The present simulation was performed under the condition that the time when the open failure occurred in the switching element L1 (corresponding to SW121L in fig. 1) of the a-phase H bridge was 0.01 ms.

Fig. 5 illustrates waveforms of simulation results of three-phase currents Ia, Ib, and Ic in the case of an open fault of the switching element L1 of the a-phase H bridge. The horizontal axis of the graphs above and below fig. 5 represents time [ s ], and the vertical axis represents current [ a ]. The upper graph illustrates waveforms of the three-phase currents Ia, Ib, and Ic of 0s to 0.02s, and the lower graph magnifies waveforms of portions of 9.6ms to 11ms of the waveforms of the three-phase currents Ia, Ib, and Ic of the upper graph.

The waveforms of the three-phase currents shown in fig. 5 are obtained based on the data of the three-phase currents Ia, Ib, and Ic obtained at a period of 0.1 ms. For example, when the switching element L1 of the a-phase H-bridge has an open fault, the phase current Ia of the a-phase fluctuates as shown in the drawing, and a period indicating the unusual behavior occurs. More specifically, when an open failure occurs in the low-side or high-side switching element of the H-bridge, the phase current becomes zero, and a period during which no change occurs can be observed. This is because the actual current or the actual voltage of the a-phase cannot follow the target current or the target voltage of PI (Proportional-Integral) control in vector control, for example. Since the B-phase and C-phase bridges are not broken, no specific change is observed in phase currents Ib and Ic.

Fig. 6 illustrates a table of data sets of three-phase currents recorded in the internal register 341 of the fault detection apparatus 340. Fig. 6 is a table showing values of phase currents Ia and Ib of the a-phase and the B-phase at 14 points obtained between 9.6ms and 11ms in the graph of fig. 5. In addition, the value of the phase current Ic of the C phase is not shown.

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

The failure detection device 340 may write a data group of three-phase currents obtained during a part of one cycle of the electrical angle of the motor, for example, as the latest data group in the internal register. In this case, the predetermined period is determined based on the partial period and the number of points of the current/voltage data obtained during the partial period.

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

For example, the reference time when trying to observe the failure detection is at time 11ms (corresponding to point number 13). The past data group including a plurality of current/voltage data obtained at a time before the reference time is composed of data groups of three-phase currents obtained at 13 points in total of point numbers 0 to 12(9.6ms to 10.9 ms). The past data group is included in the latest data group (data group in one cycle of the electrical angle). In other words, the past data set is a part of the latest data set.

The failure detection device 340 compares the data at the reference time (point number 13) with the past data sets (point numbers 0 to 12). In the table of fig. 6, it is observed that the phase current of the a phase is continuously zero for 8 points from the reference time to the past 7 points. When the phase current of the a-phase is continuously zero during a predetermined point (for example, 8 points) from the reference time, the failure detection device 340 determines that the H-bridge of the a-phase is failed. The failure of the H-bridge means that at least 1 of the 4 switching elements H1, L1, H2, and L2 has an open failure.

After the open failure of the low-side switching element 121L of the H-bridge of the a-phase, the failure detection means 340 can determine the failure thereof at the reference timing (11 ms). On the other hand, the failure detection device 340 determines that the H-bridge of the B-phase and the C-phase (not shown) is not failed at the reference time from the data group of the B-phase and the C-phase in the past data group.

In conventional failure detection of a switching element, for example, failure detection of the switching element is performed in response to a trigger for notifying the start of failure detection of the switching element. In this case, data necessary for detecting a failure of the switching element is acquired in response to the trigger, and the failure of the switching element is detected based on the acquired data. Therefore, more time is spent on the failure detection of the switching element. When the failure detection of the switching elements is performed simultaneously in parallel during the period in which the motor is controlled, it is preferable to shorten the detection time as much as possible so as not to affect the motor control.

According to the present embodiment, the failure detection of the switching element is performed based on the past data set acquired at the time before the reference time of the failure detection. The failure of the switching element can be detected without retrieving data. Therefore, it is possible to detect a failure of the switching element in a shorter time without requiring new data acquisition. As a result, for example, the motor control can be quickly switched from the three-phase energization control to the two-phase energization control described later.

When detecting an open failure of the switching element, the failure detection device 340 can switch the control mode of the motor from the normal three-phase energization control to the abnormal two-phase energization control. In this specification, a case where current is supplied to the three-phase windings is referred to as "three-phase current supply control", and a case where current is supplied to the two-phase windings is referred to as "two-phase current supply control".

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

Fig. 7 illustrates current waveforms obtained by plotting current values flowing through the respective windings of the B-phase and C-phase of the motor 200 when the power conversion device 1000 is controlled according to two-phase electrical control in the case where a failure occurs in the a-phase H-bridge. Fig. 8 illustrates current waveforms obtained by plotting current values flowing through the respective windings of the a-phase and C-phase of the motor 200 when the power conversion device 1000 is controlled according to two-phase electrical control in the case where a failure occurs in the B-phase H-bridge. Fig. 9 illustrates current waveforms obtained by plotting current values flowing through the respective windings of the a-phase and the B-phase of the motor 200 when the power conversion device 1000 is controlled according to two-phase electrical control in the case where a failure occurs in the C-phase H-bridge. The horizontal axis represents the motor electrical angle (deg) and the vertical axis represents the current value (A). In the current waveforms of fig. 7 to 9, the current values are plotted at electrical angles of every 30 °. Ipk represents a maximum current value (peak current value) of each phase at the time of energization control of each phase.

< B. Fault detection of Current/Voltage switching elements based on dq coordinate System >

In a configuration in which 2 inverters shown in fig. 1 are connected to one end and the other end of a winding, respectively, that is, a circuit configuration having an H-bridge for each phase, currents flowing through windings for three phases can be independently controlled, and in this case, a zero-phase current can flow. The zero phase current is also referred to as the z-phase current. In the dq coordinate system, an axis corresponding to zero is represented as a z-axis. The fault detection device 340 can monitor, for example, a zero-phase current and detect a fault of a switching element in the 1 st and 2

nd inverters

120 and 130 from a change in the current.

The fault detection device 340 can set the current/voltage indicated in the dq coordinate system as the object of monitoring. The current/voltage of the dq coordinate system refers to at least 1 of d-axis current, q-axis current, zero-phase current, d-axis voltage, q-axis voltage, and z-phase voltage. Preferably, the current/voltage of the dq coordinate system to be monitored includes a zero-phase current. In this embodiment, an example in which a zero-phase current is mainly used as a current/voltage of a dq coordinate system will be described.

The fault detection means (i.e., controller) 340 obtains the current/voltage represented in the dq coordinate system at every prescribed period. The predetermined period 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 fault detection unit converts the currents Ia, Ib, and Ic into a d-axis current Id, a q-axis current Iq, and a zero-phase current Iz in dqz rotational coordinate system using a transformation matrix. Alternatively, the controller 340 typically has a control unit that performs vector control. The fault detection unit may also receive required data from the control unit in the d-axis current, the q-axis current, the zero-phase current, the d-axis voltage, the q-axis voltage and the z-phase voltage. In this way, the fault detection device 340 obtains at least 1 of these currents/voltages of the dq coordinate system.

The applicant conducted simulations in order to verify the behavior of the three-phase currents Ia, Ib, Ic, d-axis current, q-axis current, and zero-phase current after the switching elements of the H-bridge failed. The present simulation was performed under the condition that the timing of occurrence of an open or short-circuit failure in the switching element H1 or L1 (corresponding to SW121H or 121L of fig. 1) of the a-phase H bridge was set to 0.015 s.

Fig. 10A shows waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained in the case where an open failure occurs in the switching element on the high side of the a-phase H bridge. Fig. 10B shows waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained in the case where a short-circuit fault occurs in the switching element on the high side of the a-phase H-bridge. Fig. 10C shows waveforms of simulation results of three-phase currents, d-axis currents, q-axis currents, and zero-phase currents obtained in the case where an open failure occurs in the switching element on the low side of the a-phase H bridge. Fig. 10D shows waveforms of simulation results of three-phase currents, D-axis currents, q-axis currents, and zero-phase currents obtained in the case where a short-circuit fault occurs in the switching element on the low side of the a-phase H-bridge. The horizontal axis of the graph represents time(s) and the vertical axis represents current (a).

In the present simulation, it is found that, after the switching element has failed, the phase current Ia in the three-phase current fluctuates, and a period indicating a peculiar behavior occurs. In particular, in the case of an open circuit fault, the phase current becomes zero, and a period during which no change occurs can be observed. The reason for this is as already explained. Even in the case of a short-circuit fault, the fluctuation of phase current Ia can be checked.

Attention is directed to 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 the three-phase energization control at a normal time. However, when the switching element fails, variations in the d-axis current, the q-axis current, and the zero-phase current can be observed. This is caused by the fluctuation of phase current Ia of phase a. This phenomenon is observed not only by the fluctuation of phase current Ia of phase a but also by the fluctuation of phase current Ib of phase B or phase current Ic of phase C. By monitoring the change in current (or voltage) in the dq coordinate system in this way, it is possible to detect a failure of at least 1 switching element in 2 inverters. In addition, a d-axis voltage and a q-axis voltage in a dq coordinate system are calculated from the abc phase voltages.

The fault detection means 340 obtains a d-axis current, a q-axis current, a zero-phase current, and a q-axis voltage in the dq coordinate system, for example, from the three-phase currents, and writes the obtained data to the internal register 341. The failure detection device 340 detects the presence or absence of a failure in the switching elements in the 1 st and 2

nd inverters

120 and 130 based on the result of comparison between the data obtained at the reference time and the plurality of data sets obtained at the time before the reference time.

Fig. 11 illustrates 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. The data of 5 points in the latest data set obtained are shown in the table. The fault detection device 340 refers to the table to monitor the current/voltage fluctuation in the dq coordinate system, for example, the zero-phase current fluctuation. When the value at the reference time point deviates from the value of the past data group, the failure detection device 340 detects that the switching elements in the 1 st and 2

nd inverters

120 and 130 have failed.

When the reference time of the failure detection is at point T +3, the failure detection device 340 determines that the Iz value "20" at the reference time is deviated from the past data set acquired at the time before the reference time: the Iz values at points T, T +1, T +2 are "6.8", "5", "7". For this determination, for example, a threshold value held in advance in the ROM 360 can be used. When 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 that the switching element has failed. On the other hand, when the difference is larger than the threshold value, the failure detection device 340 can determine that an open failure or a short-circuit failure has occurred in at least 1 switching element in the 1 st and 2

nd inverters

120 and 130.

For example, when the value "3" is used as the threshold value, the failure detection device 340 does not detect that the switching element has failed when the reference time is at the point T +2, and can primarily determine that the switching element has failed when the reference time moves to the point T + 3. In this way, the failure detection device 340 can detect a failure of the switching element by monitoring a change in current/voltage of the dq coordinate system as the DC component.

The fault detection unit of the controller 340 may also generate and output a motor control off signal to the control unit, for example, when a short-circuit fault or an open-circuit fault of the switching element is detected. The control unit may also turn off the three-phase energization control in response to the signal. Thus, for example, in an Electric Power Steering (EPS) device, the control mode can be switched from the torque assist mode to the manual steering mode.

According to the present embodiment, by monitoring the signal change in the dq coordinate system as the DC component, it is easier to perform comparison of data obtained at the reference time with a plurality of data groups obtained at times before the reference time. Therefore, for example, in mounting to a microcontroller, there is an advantage that the circuit scale and the memory size can be reduced. Further, it is possible to perform failure detection based on a past data set, and to perform failure detection in a shorter time.

(embodiment mode 2)

Fig. 12 schematically shows a typical configuration of an electric power steering apparatus 3000 according to the present embodiment.

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

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

universal joints

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

tie rods

527A and 527B,

knuckles

528A and 528B, and left and right steered

wheels

529A and 529B.

The assist torque mechanism 540 includes, for example, a steering torque sensor 541, an automobile Electronic Control Unit (ECU)542, a motor 543, and a speed reduction mechanism 544. The steering torque sensor 541 detects a steering torque in the steering system 520. ECU 542 generates a drive signal based on the detection signal of steering torque sensor 541. The motor 543 generates an assist torque corresponding to the steering torque in accordance with the drive signal. The motor 543 transmits the generated assist torque to the steering system 520 via the speed reduction mechanism 544.

The ECU 542 includes, for example, the controller 340 and the drive circuit 350 of embodiment 1. An electronic control system with an ECU as a core is built in an automobile. In the electric power steering apparatus 3000, for example, a motor drive unit is configured by the ECU 542, the motor 543, and the inverter 545. In this unit, the motor module 2000 of embodiment 1 can be preferably used.

Industrial applicability

The embodiment of the utility model can be widely applied to various devices with various motors, such as dust collectors, hair dryers, ceiling fans, washing machines, refrigerators, electric power steering devices and the like.

Claims

1. A power conversion device for converting power from a power source into power to be supplied to a motor having n-phase windings, n being an integer of 3 or more,

the power conversion device includes:

a 1 st inverter connected to one end of a winding of each phase of the motor, and having n branches each having a low-side switching element and a high-side switching element;

a 2 nd inverter connected to the other end of the winding of each phase of the motor, and having n branches each having a low-side switching element and a high-side switching element;

a failure detection device that detects whether or not a failure occurs in a switching element in the 1 st inverter and the 2 nd inverter; and

a memory that stores data for the failure detection device to perform arithmetic processing,

the failure detecting means obtains at least 1 of a current/voltage indicated in a dq coordinate system and an n-phase current of the motor every prescribed period, and writes data of the obtained current/voltage in the memory,

the fault detection device detects the presence or absence of a fault in the switching element in the 1 st inverter and the 2 nd inverter based on a comparison result between current/voltage data obtained at a reference time of fault detection and a past data set including a plurality of current/voltage data obtained at a time before the reference time.

2. The power conversion apparatus according to claim 1,

the failure detection device obtains the current/voltage indicated in the dq coordinate system for each predetermined period based on the n-phase current of the motor, and writes the current/voltage in the memory.

3. The power conversion apparatus according to claim 2,

the current/voltage of the dq coordinate system is at least 1 of a d-axis current, a q-axis current, a zero-phase current, a d-axis voltage, a q-axis voltage, and a z-phase voltage.

4. The power conversion apparatus according to claim 3,

the fault detection device detects the presence or absence of a fault in the switching element in the 1 st inverter and the 2 nd inverter based on a result of comparison between the data of the zero-phase current obtained at the reference time and a data set of a plurality of zero-phase currents obtained at times before the reference time.

5. The power conversion apparatus according to claim 1,

the failure detection device obtains an n-phase current of the motor for each of the predetermined periods, and writes the n-phase current into the memory.

6. The power conversion apparatus according to claim 5,

the failure detection device detects the presence or absence of a failure in the switching elements in the 1 st inverter and the 2 nd inverter based on a result of comparison between data of the n-phase current obtained at the reference time and a data set of a plurality of n-phase currents obtained at times before the reference time.

7. The power conversion apparatus according to claim 1,

the failure detection means writes the latest data set of the current/voltage obtained during one cycle of the electrical angle of the motor into the memory, and updates the data set recorded in the memory every time the one cycle elapses,

the past data set is included in the latest data set.

8. The power conversion apparatus according to claim 7,

the predetermined period is determined based on the one period of the electrical angle and the number of points at which the data of the current/voltage is obtained during the one period.

9. The power conversion apparatus according to claim 8,

the reference time is a time at which the latest data in the latest data group is obtained.

10. The power conversion apparatus according to claim 1,

the power conversion device further includes:

a 1 st switching element that switches connection/disconnection of the 1 st inverter to/from ground;

a 2 nd switching element that switches connection/disconnection of the 1 st inverter to/from the power supply;

a 3 rd switching element that switches connection/disconnection of the 2 nd inverter to/from the ground; and

a 4 th switching element that switches connection/disconnection of the 2 nd inverter to/from the power source.

11. A motor module is characterized in that a motor module is provided,

the motor module has:

a motor; and

the power conversion device of claim 1.

12. An electric power steering apparatus, characterized in that,

the electric power steering apparatus has the motor module according to claim 11.