A bipolar fault-tolerant control method for a switched reluctance motor power converter

Abstract

The present invention provides a bipolar fault-tolerant control method for a switched reluctance motor power converter. The method adopts a current bidirectional excitation mode, connects two full-bridge power converters to one end of two groups of controllable single-pole double-throw switches respectively, and realizes system fault-tolerant operation by changing the state of the two groups of controllable single-pole double-throw switches. Each power conversion unit in the full-bridge power converter topology is connected to a controllable single-pole double-throw switch and then connected to one end of the winding. Under normal operation, each phase winding operates independently and alternately in the forward excitation and reverse excitation modes; in the event of a power switch tube failure in any power conversion unit, the corresponding controllable single-pole double-throw switch is actuated to cut off the faulty power conversion unit, and the corresponding phase winding connection mode is changed to a connection mode with a neutral line. The fault-tolerant control method of the present invention can be applied to motors with different phase numbers, and can ensure that the system still operates stably in the event of a multi-phase multi-switch tube failure.

Description

Technical Field

[0001] The present invention relates to the field of motor design, and in particular to a fault-tolerant control method for a switched reluctance motor power converter, and in particular to a bipolar fault-tolerant control method for a switched reluctance motor power converter. Background Art

[0002] As a new type of motor, the switched reluctance motor (SRM) has the advantages of high reliability, low manufacturing cost, fast response speed and simple structure. It is a double-salient structure motor with neither permanent magnets nor windings on the rotor, only concentrated windings on the stator, and does not contain any rare earth materials. It occupies a place in various industrial fields, especially in harsh environments such as aerospace and high dust at temperatures above 500°C, as well as electric vehicles, high-speed spindles and flywheel energy storage systems, which have great application potential in places with high reliability requirements. The direction of motor rotation is only related to the order in which each phase winding is energized, but not to the direction of the winding current, which makes the bipolar control method applicable.

[0003] The switched reluctance motor drive system (SRD) is mainly composed of SRM, power converter, detection unit and controller. Among them, the power converter is responsible for converting the energy provided by the power supply and providing it to the SRM. At present, the most widely used power converter is the asymmetric half-bridge power converter, which has the advantages of simple structure, good phase independence and low cost. However, since the semiconductor devices in the power converter work in the chopping state for a long time when running at low speed, open circuit or short circuit faults are prone to occur, which reduces the robustness of the system and affects the normal operation of the system. However, the asymmetric half-bridge power converter does not have good fault-tolerant operation capability, and it is difficult for the entire system to operate normally after a fault occurs. Therefore, in order to further improve the reliability of SRD, ensure that the electric traction system will not be paralyzed in the fault state, and minimize the damage to personnel and equipment caused by the fault, it is very necessary to propose a solution that can quickly realize fault-tolerant control for faults.

[0004] The Chinese invention patent with application publication number CN108988729 A sets the relay between the full-bridge power converter and the busbar, and cuts off the faulty part through the action of the relay. When the power switch tube is not faulty, the scheme performs bidirectional current excitation on the winding; when the power switch tube has an open circuit fault, the relay acts to cut off the faulty switch tube, and the working mode of the faulty phase becomes a unidirectional current excitation mode, and the working mode of the non-faulty phase is still a bidirectional current excitation mode; when the power switch tube short circuit fault occurs, the faulty switch tube is not cut off, and the fault-tolerant operation mode is realized by the relay action to change the three-phase winding into a star connection mode without a neutral line, and the three-phase winding becomes a two-two series conduction working mode during the entire conduction cycle. The wiring method of this scheme is simple, but different fault-tolerant schemes need to be implemented according to different fault locations and fault types. Therefore, the fault-tolerant control strategy can only be implemented on the basis of accurately identifying the fault type and location. Moreover, for the short-circuit fault of the switch tube, its fault-tolerant control scheme is relatively complicated. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, the present invention provides a bipolar fault-tolerant control method for a switched reluctance motor power converter.

[0006] The technical solution adopted by the present invention is:

[0007] A bipolar fault-tolerant control method for a switched reluctance motor power converter adopts a current bidirectional excitation mode and comprises two full-bridge power converters. The switched reluctance motor has m-phase windings. Each full-bridge power converter has m power conversion units. The midpoint of each power conversion unit is connected to one end of a winding via a controllable single-pole double-throw switch. Two controllable single-pole double-throw switches are connected to two different full-bridge power converters at both ends of each winding. Fault-tolerant control is achieved by changing the state of the single-pole double-throw switch.

[0008] Under normal operating conditions, each phase winding operates independently and alternately in forward excitation and reverse excitation modes; in the event of a power switch failure in any power conversion unit, it is not necessary to accurately identify the type and location of the failure, only the failed power conversion unit is located, and the corresponding controllable single-pole double-throw switch is actuated; for an even-phase motor, only the controllable single-pole double-throw switch connected to the failed power conversion unit is actuated, and only the failed power conversion unit is cut off, so that the failed phase winding and the fault side of the adjacent phase winding are connected; for an odd-phase motor, it is necessary to actuate the controllable single-pole double-throw switch connected to the failed power conversion unit and a controllable single-pole double-throw switch adjacent to it, and cut off the failed power conversion unit and its adjacent power conversion unit, so that the failed phase winding and the two adjacent phase windings are connected together in a star connection with a neutral line.

[0009] Detect the terminal voltage at both ends of the stator winding of the switched reluctance motor. If the tube voltage drop of the switch tube and the diode in the power conversion unit is ignored and the negative terminal voltage of the power supply is used as the reference voltage, the two terminal voltages U of one phase winding are Nk and U Nk+1 There are two values, namely bus voltage U S and reference voltage 0, k = 1, 2, ..., 2m-1; when it is detected that the voltage at one end is different from that in the normal state, it is determined that the power conversion unit connected to the end is faulty; at this time, the motor is operated in a fault-tolerant manner under the fault through the corresponding controllable single-pole double-throw switch;

[0010] When the full-bridge power converter is fault-free, each phase winding of the switched reluctance motor independently operates alternately in the forward excitation mode and the reverse excitation mode in two adjacent electrical cycles. At this time, each phase winding of the switched reluctance motor has 6 working states, namely, forward excitation state ST1, forward freewheeling state ST2, forward demagnetization state ST3, reverse excitation state ST4, reverse freewheeling state ST5 and reverse demagnetization state ST6. Under normal circumstances, the terminal voltage U Nk It is equal to the bus voltage Us in the forward excitation state ST1 and the reverse demagnetization state ST6, and equal to 0 in the forward freewheeling state ST2, the forward demagnetization state ST3, the reverse excitation state ST4 and the reverse freewheeling state ST5; the terminal voltage U Nk+1 It is equal to Us in the forward demagnetization state ST3 and the reverse excitation state ST4, and is equal to 0 in other states.

[0011] According to an embodiment of the present application, the switched reluctance motor is a three-phase motor, including an A-phase winding, a B-phase winding and a C-phase winding. The full-bridge power converter is a three-phase full-bridge power converter, including a DC bus capacitor c and six power conversion units Part 1 to Part 6. Each module in the six power conversion units is composed of two switch tubes with anti-parallel diodes, and there are a total of 12 switch tubes S1 to S6 with anti-parallel diodes. 12 Specifically, the power conversion unit Part 1 is composed of a switch tube S1 and a switch tube S2 connected in series, the power conversion unit Part 2 is composed of a switch tube S3 and a switch tube S4 connected in series, the power conversion unit Part 3 is composed of a switch tube S5 and a switch tube S6 connected in series, the power conversion unit Part 4 is composed of a switch tube S7 and a switch tube S8 connected in series, and the power conversion unit Part 5 is composed of a switch tube S9 and a switch tube S10 connected in series. 10 The power conversion unit Part 6 consists of a switch tube S 11 And switch tube S 12 Series composition.

[0012] According to the embodiment of the present application, the switch tubes S1 to S 12 Using IGBT.

[0013] The collector of the upper switch tube in the power conversion unit Part 1 to Part 6 is connected to the positive electrode of the DC bus capacitor c, the emitter of the lower switch tube is connected to the negative electrode of the DC bus capacitor c, and the middle end is respectively connected to the controllable single-pole double-throw switches Q1 to Q6;

[0014] The normally closed end of the controllable single-pole double-throw switch Q1 is connected to the middle end of the power conversion unit Part 1, the normally open end of the controllable single-pole double-throw switch Q1 is connected to the common end of the controllable single-pole double-throw switch Q2, and the common end of the controllable single-pole double-throw switch Q1 is connected to one end of the A-phase winding; the normally closed end of the controllable single-pole double-throw switch Q2 is connected to the middle end of the power conversion unit Part 2, the normally open end of the controllable single-pole double-throw switch Q2 is connected to the common end of the controllable single-pole double-throw switch Q3, and the common end of the controllable single-pole double-throw switch Q2 is connected to one end of the B-phase winding; the normally closed end of the controllable single-pole double-throw switch Q3 is connected to the middle end of the power conversion unit Part 3, the normally open end of the controllable single-pole double-throw switch Q3 is connected to the common end of the controllable single-pole double-throw switch Q1, and the common end of the controllable single-pole double-throw switch Q3 is connected to one end of the C-phase winding; the normally closed end of the controllable single-pole double-throw switch Q4 is connected to the middle end of the power conversion unit Part 2. 4, the normally open end of the controllable single-pole double-throw switch Q4 is connected to the common end of the controllable single-pole double-throw switch Q5, and the common end of the controllable single-pole double-throw switch Q4 is connected to the other end of the A-phase winding; the normally closed end of the controllable single-pole double-throw switch Q5 is connected to the middle end of the power conversion unit Part 5, the normally open end of the controllable single-pole double-throw switch Q5 is connected to the common end of the controllable single-pole double-throw switch Q6, and the common end of the controllable single-pole double-throw switch Q5 is connected to the other end of the B-phase winding; the normally closed end of the controllable single-pole double-throw switch Q6 is connected to the middle end of the power conversion unit Part 6, the normally open end of the controllable single-pole double-throw switch Q6 is connected to the common end of the controllable single-pole double-throw switch Q4, and the common end of the controllable single-pole double-throw switch Q6 is connected to the other end of the C-phase winding.

[0015] When the switched reluctance motor system is in fault-tolerant operation under fault conditions, the power conversion units of the three-phase full-bridge power converter will be reduced from six to four. One end of the three-phase stator winding of the switched reluctance motor is connected to the middle ends of the three power conversion units after passing through the switch, and the other end is connected together after passing through the switch, and then connected to the middle end of the remaining power conversion unit, and the stator winding connection mode becomes a star connection mode with a neutral line. At this time, the system working intervals are: C phase forward conduction interval, CA phase forward commutation interval, A phase reverse conduction interval, AB phase reverse commutation interval, B phase forward conduction interval, BC phase forward commutation interval, C phase reverse conduction interval, CA phase reverse commutation interval, A phase forward conduction interval, AB phase forward commutation interval, B phase reverse conduction interval, BC phase reverse commutation interval, C phase forward conduction interval, CA phase reverse commutation interval, A phase forward conduction interval, AB phase forward commutation interval, B phase reverse conduction interval, BC phase reverse commutation interval, C phase forward conduction interval. Each phase winding of the motor has 12 working modes, namely single-phase winding forward excitation mode M1, single-phase winding forward freewheeling mode M2, two-phase winding forward series excitation mode M3, two-phase winding forward series freewheeling mode M4, one-phase winding forward demagnetization, one-phase winding reverse excitation mode M5, one-phase winding forward demagnetization, one-phase winding reverse freewheeling mode M6, single-phase winding reverse excitation mode M7, single-phase winding reverse freewheeling mode M8, two-phase winding reverse series excitation mode M9, two-phase winding reverse series freewheeling mode M10. 10 , one phase winding reverse demagnetization, one phase winding forward excitation mode M 11 , one phase winding reverse demagnetization, one phase winding forward freewheeling mode M 12 .

[0016] Controllable single-pole double-throw switch Q n It is at least one of an electromagnetic relay, a solid-state relay, a high-frequency relay, etc., or a controllable single-pole double-throw switch Q n Two power switching devices IGBT or MOSFET are connected in parallel through one pole and are driven by opposite signals to realize the single-pole double-throw switch function.

[0017] According to an embodiment of the present application, the switch tube S e The switch tube S e+1 A single pulse driving signal is passed; e=1,3,5,7,9,11, representing the number of switching tubes.

[0018] Specifically, in the forward excitation mode, the switch tubes S1, S3, and S5 are driven by chopper signals, and the switch tubes S8 and S9 are driven by chopper signals. 10 , the switch tube S 12 A single pulse drive signal is applied; in the reverse excitation mode, the switch tubes S7, S9, and S 11A chopping drive signal is applied, and a single pulse drive signal is applied to the switch tube S2 , the switch tube S4 , and the switch tube S6 .

[0019] m is an integer not less than 2.

[0020] The present invention is used to protect a switched reluctance motor speed control system based on a full-bridge power converter, the system comprising a switched reluctance motor, a voltage sensor, a position sensor, a controller, a PI module, a control mode selection module, a switch tube angle controller, a pulse signal generator and two full-bridge power converters: the switched reluctance motor has m-phase windings, each full-bridge power converter has m power conversion units, characterized in that the midpoint of each power conversion unit is connected to one end of a winding through a controllable single-pole double-throw switch, two ends of each winding are connected to two controllable single-pole double-throw switches, and the two controllable single-pole double-throw switches are connected to two different full-bridge power converters;

[0021] The voltage sensor is used to detect the voltage at the stator winding terminals of the switched reluctance motor;

[0022] The position sensor is used to detect the rotor position of the switched reluctance motor;

[0023] The controller is used to control the full-bridge power converter and the controllable single-pole double-throw switch to realize fault diagnosis and fault-tolerant control of the switched reluctance speed regulation system;

[0024] The PI module is a proportional-integral controller. It generates the corresponding reference quantity according to the set proportional and integral parameters. The output of the PI module is the set reference speed n. ref The difference between the actual speed n obtained by the speed calculation module;

[0025] The control mode selection module selects the corresponding control strategy according to the speed range of the motor; the control mode selection module selects the hysteresis controller to realize the current chopping control, the voltage PWM control (VPC) is realized through the PWM controller, and the angle position control (APC) is realized through the angle position controller;

[0026] The switch angle controller sets the switch angle according to the set opening angle θ. on and the turn-off angle θ off Determine whether the motor is in the conduction range;

[0027] The pulse signal generator generates a power converter drive signal according to the signals sent by the hysteresis controller, the PWM controller, the angle position controller, and the switch tube angle controller, and controls the on and off states of the power switch tube of the full-bridge power converter;

[0028] The full-bridge power converter is responsible for converting the energy provided by the power supply and providing it to the SRM.

[0029] According to the embodiments of the present application, in the fault-tolerant operation mode of the switched reluctance motor, a fixed switch tube that is passed with a chopping drive signal or a single-pulse drive signal is no longer set.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention discloses a bipolar fault-tolerant control method for a switched reluctance motor power converter. In a fault-free state, the motor windings alternately operate in a forward excitation mode and a reverse excitation mode within two adjacent electrical cycles, and each phase winding is independent of each other. In a fault-tolerant operation mode, the faulty power conversion unit and its adjacent power conversion units are cut off by a controllable single-pole double-throw switch, and the motor winding connection mode is changed to a connection mode with a neutral line. Whether in normal conditions or fault conditions, the entire system can work efficiently and reliably, effectively avoiding serious accidents caused by faults.

[0032] The fault-tolerant control method of the present invention has good scalability. For motors with different phase numbers, there is no need to change the controllable single-pole double-throw switch Q n The connection method only needs to increase or decrease the controllable single-pole double-throw switch Q according to the number of motor phases. n Specifically, for an m-phase motor, 2m controllable single-pole double-throw switches Q1 to Q 2m In addition, currently widely used controllable devices such as single-pole double-throw relays and power tubes can be used as the controllable single-pole double-throw switch Q of the present invention. n . BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of the three-phase SRD structure of an embodiment of the present application.

[0035] Figure 2 Schematic diagram of the structure of a three-phase SRM traditional asymmetric half-bridge power converter.

[0036] Figure 3 Schematic diagram of a three-phase full-bridge power converter and switch connection method.

[0037] FIG4( a ) is a schematic diagram of the forward excitation state ST1 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0038] FIG4( b ) is a schematic diagram of the forward freewheeling state ST2 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0039] FIG4( c ) is a schematic diagram of the forward demagnetization state ST3 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0040] FIG4( d ) is a schematic diagram of the reverse excitation state ST4 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0041] FIG4( e ) is a schematic diagram of the reverse freewheeling state ST5 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0042] FIG4( f ) is a schematic diagram of the reverse demagnetization state ST6 of the C-phase winding of the three-phase SRM according to an embodiment of the present application.

[0043] Figure 5 This is a simulation waveform diagram of the phase current, C-phase switch tube drive signal and total torque under normal operating conditions of the three-phase SRM in the embodiment of the present application.

[0044] Figure 6 This is a simulation waveform diagram of the phase current, C-phase switch tube drive signal and total torque under a C-phase switch tube short-circuit fault of the three-phase SRM in an embodiment of the present application.

[0045] Figure 7 This is a simulation waveform diagram of the phase current, C-phase switch tube drive signal and total torque under an open-circuit fault of the C-phase switch tube of the three-phase SRM in an embodiment of the present application.

[0046] Figure 8 The schematic diagram of the structure of the power converter is a fault-tolerant operation after the power conversion unit Part 5 or Part 6 fails.

[0047] Fig. 9 This is a schematic diagram of the power converter structure after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0048] FIG10( a ) is a schematic diagram of the forward excitation mode M1 of the C-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0049] FIG10( b ) is a schematic diagram of the forward freewheeling mode M2 ​​of the C-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0050] FIG11( a ) is a schematic diagram of the forward series excitation mode M3 of the CA phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0051] FIG11( b ) is a schematic diagram of the CA phase winding forward series freewheeling mode M4 after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0052] FIG11( c ) is a schematic diagram of a forward demagnetization mode M5 of a C-phase winding and a reverse excitation mode M5 of an A-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0053] FIG11( d ) is a schematic diagram of the forward demagnetization mode M6 of the C-phase winding and the reverse freewheeling mode M6 of the A-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0054] FIG12( a ) is a schematic diagram of the reverse excitation mode M7 of the C-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0055] FIG12( b ) is a schematic diagram of the reverse freewheeling mode M8 of the C-phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0056] FIG13( a ) is a schematic diagram of the reverse series excitation mode M9 of the CA phase winding after the three-phase SRM fault-tolerant operation according to an embodiment of the present application.

[0057] FIG. 13( b ) is a diagram of the reverse series connection freewheeling mode M of the CA phase winding after the three-phase SRM fault-tolerant operation according to the present application. 10 Schematic diagram.

[0058] FIG. 13( c ) is a diagram showing the reverse demagnetization of the C-phase winding and the forward excitation mode of the A-phase winding after the three-phase SRM fault-tolerant operation according to the present application. 11 Schematic diagram.

[0059] FIG. 13( d ) is a diagram showing the reverse demagnetization of the C-phase winding and the forward freewheeling mode M of the A-phase winding after the three-phase SRM fault-tolerant operation according to the present application. 12 Schematic diagram.

[0060] Fig.14 This is a simulation waveform diagram of the phase current, C-phase switch tube drive signal and total torque after the three-phase SRM fault-tolerant operation of the embodiment of the present application. DETAILED DESCRIPTION

[0061] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments, but this is not intended to limit the scope of protection of the present application.

[0062] Figure 1 This is a schematic diagram of the SRD structure of the three-phase switched reluctance motor speed control system of the embodiment of the present application. Among them, the switched reluctance motor SRM is responsible for realizing electromechanical energy conversion; the voltage sensor is used to detect the midpoint voltage and provide the necessary voltage information for fault diagnosis; the encoder is used to detect the rotor position angle and provide the necessary position information for speed calculation; the speed calculation module calculates the motor speed according to the rotor angle information for subsequent speed closed-loop control;

[0063] The PI module is a proportional-integral controller, which generates the corresponding reference quantity according to the set proportional and integral parameters. The output of the PI module is the set reference speed n ref The difference between the actual speed n obtained by the speed calculation module;

[0064] The control mode selection module selects the corresponding control method according to the speed range of the motor; currently, the commonly used control methods include current chopping control (CCC), voltage PWM control (VPC) and angle position control (APC), which are respectively implemented by hysteresis controller, PWM controller and angle position controller, that is, the control mode selection module selects hysteresis controller to implement current chopping control, PWM controller to implement voltage PWM control (VPC), and angle position control (APC) by angle position controller;

[0065] The switch angle controller sets the switch angle according to the set opening angle θ. on and the turn-off angle θ off Determine whether the motor is in the conduction range;

[0066] The pulse signal generator generates a power converter drive signal according to the signals sent by the above four controllers (hysteresis controller, PWM controller, angle position controller, switch tube angle controller) to control the on and off state of the power switch tube.

[0067] The full-bridge power converter is responsible for converting the energy provided by the power supply and providing it to the SRM. It plays an important role in the SRD and its performance directly determines the performance of the SRD.

[0068] The most widely used power converter in the market is the asymmetric half-bridge power converter, whose topology is as follows: Figure 2 As shown. The asymmetric half-bridge power converter has the advantages of simple structure and good phase independence, but it does not have good fault-tolerant operation capability. After a fault occurs, the entire system is difficult to operate normally. Therefore, the present invention proposes a bipolar fault-tolerant control method for a switched reluctance motor power converter.

[0069] like Figure 3 As shown in FIG. 1 , the full-bridge power converter and the controllable single-pole double-throw switch connection diagram of the present invention are shown. The full-bridge power converter is a three-phase full-bridge power converter, including a DC bus capacitor c and six power conversion units Part 1 to Part 6. Each of the six power conversion units is composed of two switch tubes with anti-parallel diodes, and there are a total of 12 switch tubes S1 to S6 with anti-parallel diodes. 12 Specifically, the power conversion unit Part 1 is composed of a switch tube S1 and a switch tube S2 connected in series, the power conversion unit Part 2 is composed of a switch tube S3 and a switch tube S4 connected in series, the power conversion unit Part 3 is composed of a switch tube S5 and a switch tube S6 connected in series, the power conversion unit Part 4 is composed of a switch tube S7 and a switch tube S8 connected in series, and the power conversion unit Part 5 is composed of a switch tube S9 and a switch tube S10 connected in series. 10 The power conversion unit Part 6 consists of a switch tube S11 And switch tube S 12 Series composition.

[0070] The collector of the upper switch tube in the power conversion unit Part 1 to Part 6 is connected to the positive electrode of the DC bus capacitor c, the emitter of the lower switch tube is connected to the negative electrode of the DC bus capacitor c, and the middle end of the power conversion unit is respectively connected to the controllable single-pole double-throw switches Q1 to Q6. The normally closed end of the controllable single-pole double-throw switch Q1 is connected to the middle end N1 of the power conversion unit Part 1, the normally open end of the controllable single-pole double-throw switch Q1 is connected to the common end of the controllable single-pole double-throw switch Q2, and the common end of the controllable single-pole double-throw switch Q1 is connected to one end of the A phase winding; the normally closed end of the controllable single-pole double-throw switch Q2 is connected to the middle end N3 of the power conversion unit Part 2, the normally open end of the controllable single-pole double-throw switch Q2 is connected to the common end of the controllable single-pole double-throw switch Q3; the common end of the controllable single-pole double-throw switch Q2 is connected to one end of the B phase winding; the normally closed end of the controllable single-pole double-throw switch Q3 is connected to the middle end N3 of the power conversion unit Part 2. 3, the normally open end of the controllable single-pole double-throw switch Q3 is connected to the common end of the controllable single-pole double-throw switch Q1; the common end of the controllable single-pole double-throw switch Q3 is connected to one end of the C phase winding; the normally closed end of the controllable single-pole double-throw switch Q4 is connected to the middle end N2 of the power conversion unit Part 4, the normally open end of the controllable single-pole double-throw switch Q4 is connected to the common end of the controllable single-pole double-throw switch Q5; the common end of the controllable single-pole double-throw switch Q4 is connected to the other end of the A phase winding; the normally closed end of the controllable single-pole double-throw switch Q5 is connected to the middle end N4 of the power conversion unit Part 5, the normally open end of the controllable single-pole double-throw switch Q5 is connected to the common end of the controllable single-pole double-throw switch Q6; the common end of the controllable single-pole double-throw switch Q5 is connected to the other end of the B phase winding; the normally closed end of the controllable single-pole double-throw switch Q6 is connected to the power conversion unit Part 6, the normally open end of the controllable single-pole double-throw switch Q6 is connected to the common end of the controllable single-pole double-throw switch Q4; the common end of the controllable single-pole double-throw switch Q6 is connected to the other end of the C-phase winding.

[0071] When the power converter is fault-free, each phase winding of the switched reluctance motor independently operates alternately in the forward excitation mode and the reverse excitation mode in two adjacent electrical cycles. According to an embodiment of the present application, in the forward excitation mode, the switch tubes S1, S3, and S5 are connected with a chopping drive signal, and the switch tubes S8 and S9 are connected with a chopping drive signal. 10 , the switch tube S 12 A single pulse drive signal is applied; in the reverse excitation mode, the switch tubes S7, S9, and S11 A chopping drive signal is applied, and a single pulse drive signal is applied to the switch tube S2 , the switch tube S4 , and the switch tube S6 .

[0072] When the full-bridge power converter has no faults, under the current chopping control CCC or voltage PWM control, VPC control strategy, each phase winding of the switched reluctance motor has 6 working states. 12 When the switch is turned on, the current of phase C increases rapidly in the positive direction, which is the positive excitation state ST1, as shown in Figure 4(a). 12 When turned on, the current of phase C decreases slowly in the positive direction and is in the forward freewheeling state ST2, as shown in Figure 4(b). 12 When the switch is turned off, it is in the forward demagnetization state ST3, and the positive direction of the C phase current decreases rapidly, as shown in Figure 4(c). 11 When S6 is turned on, the current of phase C increases rapidly in the reverse direction, which is the reverse excitation state ST4, as shown in Figure 4(d). 11 When S6 is turned off and S6 is turned on, the current of phase C decreases slowly in the reverse direction and is in the reverse freewheeling state ST5, as shown in Figure 4(e). 11 When S6 is turned off, the C-phase current decreases rapidly in the reverse direction, which is the reverse demagnetization state ST6, as shown in Figure 4(f). Under the APC control strategy, there is no forward freewheeling state ST2 and reverse freewheeling state ST5. Figure 5 The simulation waveforms of the phase current, C-phase switch drive signal and total torque under the normal operation of the three-phase SRM under the current chopping control CCC are shown in Figure 1. A 、i B and i C are A phase, B phase and C phase current respectively; S5, S6, S 11 and S 12 are the driving signals of the corresponding switch tubes respectively; Te is the total torque, Figure 5 It can be seen that the current of each phase is turned on periodically in turn, and the torque waveform fluctuates slightly.

[0073] The fault types of full-bridge power converters mainly include switch short-circuit fault and switch open-circuit fault. Switch short-circuit fault will cause the phase current to increase sharply and cannot be reduced to zero, causing negative torque. Figure 6 As shown, the switch tube S 11 After the short circuit fault occurred at t=0.3325s, the current amplitude of phase C increased sharply and the torque pulsation increased significantly. The open circuit fault of the switch tube will cause the current of one phase to be lost, resulting in unbalanced output torque. Figure 7 As shown, the switch tube S 11After the open circuit fault occurred at t=0.3325s, the C phase current was lost in the reverse excitation mode, and the torque pulsation also increased significantly. Both of these faults will cause the torque pulsation to increase, seriously affecting the normal operation of the motor.

[0074] The voltage sensor is used to detect the terminal voltage at both ends of the stator winding of the switched reluctance motor. If the tube voltage drop of the switch tube and the diode is ignored and the negative terminal voltage of the power supply is used as the reference voltage, the two terminal voltages U of one phase winding are Nk and U Nk+1 (k=1~5) has two values, namely bus voltage U S and reference voltage 0. Under normal circumstances, the terminal voltage U Nk It is equal to Us in states ST1 and ST6, and equal to 0 in states ST2 to ST5; the terminal voltage U Nk+1 It is equal to Us in states ST3 and ST4, and equal to 0 in other states. When it is detected that the voltage of a certain terminal is different from that in normal conditions, it can be determined that the power conversion unit connected to this terminal is faulty. At this time, the corresponding single-pole double-throw switch is actuated to enable the motor to operate in a fault-tolerant manner under the fault. If only one phase of the power conversion unit fails, the controllable single-pole double-throw switch connected to the phase and its adjacent controllable single-pole double-throw switch are actuated to cut off the power conversion unit of the faulty phase and the adjacent phase. Taking Part 6 fault as an example, specifically, the switch tube S 11 When a short circuit fault occurs and it is detected that the potential of point N6 is equal to the bus voltage Us in both the excitation state and the freewheeling state in the reverse excitation mode, it means that a fault has occurred in the power conversion unit Part 6. At this time, the contacts of the controllable single-pole double-throw switches Q5 and Q6 need to be moved from the normally closed end to the normally open end to allow the motor to enter the fault-tolerant operation mode.

[0075] Figure 8 The schematic diagram of the power converter structure for fault-tolerant operation after the power conversion unit Part 5 or Part 6 fails. Fig. 9This is an equivalent structural diagram of fault-tolerant operation after the failure of power conversion unit Part 5 or Part 6. The power conversion units of the three-phase full-bridge power converter will be reduced from six to four. One end of the three-phase stator winding of the switched reluctance motor is connected to the middle end of the three power conversion units after passing through a single-pole double-throw switch, and the other end is connected together after passing through a single-pole double-throw switch, and then connected to the middle end of the remaining power conversion unit. The stator winding connection mode is changed to a star connection mode with a neutral line. At this time, each phase winding of the motor has 12 working modes, as shown in Figures 10 to 12. Unlike the asymmetric half-bridge power converter, which does not interfere with each other between phases, this fault-tolerant mode has the situation of two phases being connected in series during the commutation period. Taking phase C and phase A as an example, in the forward conduction interval of phase C, when the speed is too low, switches S5 and S8 are turned on, and the C phase winding enters the forward excitation mode M1, as shown in Figure 10(a); when the speed is too high, switch S5 is turned off, and only switch S8 is turned on, and the C phase winding enters the forward freewheeling mode M2, as shown in Figure 10(b). In this interval, under the closed-loop speed control, modes M1 and M2 are frequently switched.

[0076] When entering the CA phase forward commutation interval, the switch tubes S2 and S5 are turned on, entering the CA phase winding forward series excitation mode M3, the C phase and A phase currents are equal in magnitude and opposite in direction, as shown in Figure 11(a); when the speed is too high, the switch tube S2 is turned off, and only the switch tube S5 is turned on, entering the CA phase winding forward series freewheeling mode M4, the C phase and A phase currents are equal in magnitude and opposite in direction, as shown in Figure 11(b). In this interval, under the speed closed-loop control, the modes M3 and M4 are frequently switched. When entering the C phase disconnection zone and the C phase current has not dropped to zero, if the speed is too low, the switch tubes S2 and S7 are turned on, entering the C phase winding forward demagnetization and A phase winding reverse excitation mode M5, as shown in Figure 11(c); if the speed is too low, the switch tube S2 is turned off, and only the switch tube S7 is turned on, entering the C phase winding forward demagnetization and A phase winding reverse freewheeling mode M6, as shown in Figure 11(d). In this range, the mode M5 and M6 are frequently switched. After the C phase current drops to zero, the A phase and B phase working ranges are entered in turn.

[0077] When entering the C phase reverse conduction interval, when the speed is too low, the switch tubes S6 and S7 are turned on, and the C phase winding reverse excitation mode M7 is entered, as shown in Figure 12(a); when the speed is too high, the switch tube S6 is turned off, and only the switch tube S7 is turned on, and the C phase winding reverse freewheeling mode M8 is entered, as shown in Figure 12(b). In this interval, the speed closed-loop control is also used, switching back and forth between modes M7 and M8.

[0078] When entering the CA phase reverse commutation interval, the switch tubes S1 and S6 are turned on, entering the CA phase winding reverse series excitation mode M9, and the C phase and A phase currents are equal in magnitude and opposite in direction, as shown in Figure 13(a); when the speed is too high, the switch tube S1 is turned off, and only the switch tube S6 is turned on, entering the CA phase winding reverse series freewheeling mode M9. 10 , the currents of phase C and phase A are equal in magnitude and opposite in direction, as shown in Figure 13(b). In this interval, the system is in modes M9 and M 10 When the C phase current has not dropped to zero, if the speed is too low, the switches S1 and S8 are turned on, and the C phase winding is reversely demagnetized and the A phase winding is forwardly excited. 11 , as shown in Figure 13(c); if the speed is too low, the switch tube S1 is turned off, and only the switch tube S8 is turned on, entering the C-phase winding reverse demagnetization and A-phase winding forward freewheeling mode M 12 , as shown in Figure 13(d). In this range, the same speed closed-loop control is used. 11 and M 12 Switch back and forth between.

[0079] The current flowing into the neutral point is positive, and the current flowing out of the neutral point is negative. In M1 and M2 modes, only phase C is turned on, and the current direction of phase C is positive. In M3~M6 modes, phase C and phase A are turned on, the current direction of phase C is positive, and the current direction of phase A is negative. In M7 and M8 modes, only phase C is turned on, and the current direction of phase C is negative. In M9~M 12 In this mode, the current direction of phase C is negative and the current direction of phase A is positive. The operation modes of the A-phase and B-phase separate conduction intervals, the AB-phase commutation interval, and the BC-phase commutation interval are similar to the above-mentioned operation modes.

[0080] According to the embodiments of the present application, in the fault-tolerant operation mode of the switched reluctance motor, a fixed switch tube that is passed with a chopping drive signal or a single-pulse drive signal is no longer set. Fig.14 The following are the simulated waveforms of phase current, C-phase switch drive signal and total torque after the three-phase SRM fault-tolerant operation. It can be seen from the figure that the torque pulsation degree of the motor in the fault-tolerant operation mode is almost the same as that in the normal condition.

[0081] The present invention discloses a bipolar fault-tolerant control method for a switched reluctance motor power converter. In the fault-tolerant control scheme of the embodiment, a three-phase full-bridge power converter is connected to six controllable single-pole double-throw switches, and the system fault-tolerant operation is realized by changing the state of the controllable single-pole double-throw switches. In the case of no fault, each phase winding of the motor operates alternately in a forward excitation mode and a reverse excitation mode in two adjacent electrical cycles, and each phase winding is independent of each other, and the phase independence is good. After a fault occurs in the system, it is not necessary to accurately identify the type and location of the fault, and only the power conversion unit where the fault occurs is located to implement the corresponding fault-tolerant control strategy. In the fault-tolerant operation mode, after the position of the power conversion unit where the fault occurs is located, the faulty power conversion unit and its adjacent power conversion units are cut off by the controllable single-pole double-throw switch. At this time, the controllable single-pole double-throw switch after the power conversion unit is cut off is connected to the neutral point of the power conversion unit that has not been cut off, and the motor winding connection mode becomes a star connection mode with a neutral line. At this time, each phase winding works independently during the non-commutation period, and the phase windings are connected in series during the commutation period. The motor system can still work stably using the remaining power switch tubes without faults. The fault-tolerant control method of the switched reluctance motor power converter proposed by the present invention can be applied to motors with different phase numbers, and can ensure that the system can still operate stably under the condition of multi-phase and multi-switch tube faults.

[0082] The fault-tolerant control method proposed in the present invention does not need to change the motor body structure, so it has universality and can fully ensure that the motor system can still work stably after a fault. In addition, the fault-tolerant method of the present invention also has good scalability, and does not need to change the connection mode. It can be realized by simply increasing or decreasing the controllable single-pole double-throw switch Q n The quantity can be applied to motors with other phase numbers.

[0083] The above is an explanation based on a three-phase switched reluctance motor. For motors with other phases, there is no need to change the controllable single-pole double-throw switch Q n The connection method only needs to increase or decrease the controllable single-pole double-throw switch Q according to the number of motor phases. nSpecifically, for a two-phase motor, four controllable single-pole double-throw switches Q1 to Q4 are required, which are respectively connected between the power conversion unit Part 1 to Part 4 and the A-phase and B-phase windings. When it is detected that the voltage at one end is inconsistent with the normal state, it can be determined that the power conversion unit connected to the end is faulty, and only the controllable single-pole double-throw switch connected to the end point is actuated to cut off the faulty power conversion unit. At this time, the faulty side of the two-phase winding is connected to the neutral line; for a four-phase motor, eight controllable single-pole double-throw switches Q1 to Q8 are required, which are respectively connected between the power conversion unit Part 1 to Part 8 and the A-phase, B-phase, C-phase, and D-phase windings. When a power conversion unit is detected to be faulty, only the controllable single-pole double-throw switch of the faulty power conversion unit is actuated. At this time, the faulty phase and the faulty side of the adjacent phase winding are connected to the neutral line, and the connection mode of the remaining two-phase windings does not change, which is the same as the connection mode in the case of no fault. For a five-phase motor, after the faulty power conversion unit is determined, the controllable single-pole double-throw switch connected to the faulty power conversion unit and the controllable single-pole double-throw switch adjacent to it need to be operated to cut off the faulty power conversion unit and the power conversion unit adjacent to it, so that the three phase windings of the motor are connected together in a star connection with a neutral line, where the three phase windings are the faulty phase winding and the two phase windings adjacent to it, and the connection mode of the remaining two phase windings remains unchanged. The above situation can be summarized as follows: For an m-phase motor, the number of controllable single-pole double-throw switches required can be defined as 2m. If m is an even number, only the controllable single-pole double-throw switch connected to the faulty power conversion unit is activated, and the faulty phase is connected to the faulty side of the adjacent phase winding. The faulty side of the adjacent phase winding is the location of the neutral line, and the connection mode of the remaining windings does not change; if m is an odd number, the controllable single-pole double-throw switch connected to the faulty power conversion unit and the controllable single-pole double-throw switch adjacent to it are activated, and the faulty phase winding and the two adjacent phase windings are connected together to form a star connection with a neutral line, and the connection mode of the remaining windings does not change. At this time, if the faulty phase winding has only one adjacent phase winding, the adjacent phase windings are found in sequence so that the three can form a star connection with a neutral line. If the faulty phase winding has two adjacent phase windings, the two adjacent phase windings are directly selected to form a star connection with a neutral line when encountering the faulty phase. The controllable single-pole double-throw switch Q described in this scheme n It can be a controllable device with on / off capability such as an electromagnetic relay, a solid-state relay, or a high-frequency relay. In addition, two power switch devices IGBT or MOSFET are connected in parallel through one pole and are driven by opposite signals, and can also be used as the single-pole double-throw switch Q described in this solution. n .

[0084] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A bipolar fault-tolerant control method for a switched reluctance motor power converter, using a current bidirectional excitation mode, comprising two full-bridge power converters, the switched reluctance motor having m-phase windings, each full-bridge power converter having m power conversion units, characterized in that: The midpoint of each power conversion unit is connected to one end of a winding through a controllable single-pole double-throw switch, and the two ends of each winding are connected to two controllable single-pole double-throw switches, and the two controllable single-pole double-throw switches are connected to two different full-bridge power converters; fault-tolerant control is achieved by changing the state of the single-pole double-throw switch; Under normal operating conditions, each phase winding operates independently and alternately in forward excitation and reverse excitation modes; in the event of a power switch failure in any power conversion unit, it is not necessary to accurately identify the type and location of the failure, only the failed power conversion unit is located, and the corresponding controllable single-pole double-throw switch is actuated; for an even-phase motor, only the controllable single-pole double-throw switch connected to the failed power conversion unit is actuated, and only the failed power conversion unit is cut off, so that the failed phase winding and the fault side of the adjacent phase winding are connected; for an odd-phase motor, it is necessary to actuate the controllable single-pole double-throw switch connected to the failed power conversion unit and a controllable single-pole double-throw switch adjacent to it, and cut off the failed power conversion unit and its adjacent power conversion unit, so that the failed phase winding and the two adjacent phase windings are connected together in a star connection with a neutral line.

2. The fault-tolerant control method according to claim 1, characterized in that: Detect the terminal voltage at both ends of the stator winding of the switched reluctance motor. If the tube voltage drop of the switch tube and the diode in the power conversion unit is ignored and the negative terminal voltage of the power supply is used as the reference voltage, the two terminal voltages U of one phase winding are Nk and U Nk+1 There are two values, namely bus voltage U S and reference voltage 0, k=1, 2, ..., 2m-1; when it is detected that the voltage at one end is different from that in normal conditions, it is determined that the power conversion unit connected to the end is faulty; at this time, the motor is operated in a fault-tolerant manner under fault conditions through the corresponding controllable single-pole double-throw switch; When the full-bridge power converter is fault-free, each phase winding of the switched reluctance motor independently operates alternately in the forward excitation mode and the reverse excitation mode in two adjacent electrical cycles. At this time, each phase winding of the switched reluctance motor has 6 working states, namely, forward excitation state ST1, forward freewheeling state ST2, forward demagnetization state ST3, reverse excitation state ST4, reverse freewheeling state ST5 and reverse demagnetization state ST6. Under normal circumstances, the terminal voltage U Nk It is equal to the bus voltage Us in the forward excitation state ST1 and the reverse demagnetization state ST6, and equal to 0 in the forward freewheeling state ST2, the forward demagnetization state ST3, the reverse excitation state ST4 and the reverse freewheeling state ST5; the terminal voltage U Nk+1 It is equal to Us in the forward demagnetization state ST3 and the reverse excitation state ST4, and equal to 0 in other states.

3. The fault-tolerant control method according to claim 1, characterized in that: The switched reluctance motor is a three-phase motor, and the full-bridge power converter is a three-phase full-bridge power converter, including a DC bus capacitor c and six power conversion units Part 1 to Part 6; each of the six power conversion units is composed of two power switch tubes with anti-parallel diodes, and there are a total of 12 power switch tubes S1 to S6 with anti-parallel diodes. 12 ; The collector of the upper switch tube in the power conversion unit Part 1 to Part 6 is connected to the positive electrode of the DC bus capacitor c, the emitter of the lower switch tube is connected to the negative electrode of the DC bus capacitor c, and the middle end is respectively connected to the controllable single-pole double-throw switch Q1 to Q6; The normally closed end of the controllable single-pole double-throw switch Q1 is connected to the middle end of the power conversion unit Part 1, the normally open end of the controllable single-pole double-throw switch Q1 is connected to the common end of the controllable single-pole double-throw switch Q2, and the common end of the controllable single-pole double-throw switch Q1 is connected to one end of the A-phase winding; the normally closed end of the controllable single-pole double-throw switch Q2 is connected to the middle end of the power conversion unit Part 2, the normally open end of the controllable single-pole double-throw switch Q2 is connected to the common end of the controllable single-pole double-throw switch Q3, and the common end of the controllable single-pole double-throw switch Q2 is connected to one end of the B-phase winding; the normally closed end of the controllable single-pole double-throw switch Q3 is connected to the middle end of the power conversion unit Part 3, the normally open end of the controllable single-pole double-throw switch Q3 is connected to the common end of the controllable single-pole double-throw switch Q1, and the common end of the controllable single-pole double-throw switch Q3 is connected to one end of the C-phase winding; the normally closed end of the controllable single-pole double-throw switch Q4 is connected to the middle end of the power conversion unit Part 2. 4, the normally open end of the controllable single-pole double-throw switch Q4 is connected to the common end of the controllable single-pole double-throw switch Q5, and the common end of the controllable single-pole double-throw switch Q4 is connected to the other end of the A-phase winding; the normally closed end of the controllable single-pole double-throw switch Q5 is connected to the middle end of the power conversion unit Part 5, the normally open end of the controllable single-pole double-throw switch Q5 is connected to the common end of the controllable single-pole double-throw switch Q6, and the common end of the controllable single-pole double-throw switch Q5 is connected to the other end of the B-phase winding; the normally closed end of the controllable single-pole double-throw switch Q6 is connected to the middle end of the power conversion unit Part 6, the normally open end of the controllable single-pole double-throw switch Q6 is connected to the common end of the controllable single-pole double-throw switch Q4, and the common end of the controllable single-pole double-throw switch Q6 is connected to the other end of the C-phase winding.

4. The fault-tolerant control method according to claim 3, characterized in that: When the switched reluctance motor is in fault-tolerant operation under fault conditions, the power conversion units of the three-phase full-bridge power converter will be reduced from six to four, one end of the three-phase stator winding of the switched reluctance motor is connected to the middle ends of the three power conversion units after passing through single-pole double-throw switches, and the other end is connected together after passing through single-pole double-throw switches, and then connected to the middle end of the remaining power conversion unit, and the stator winding connection mode is changed to a star connection mode with a neutral line; at this time, each phase of the motor works alternately in the forward and reverse excitation modes, and during the two-phase commutation period There is a series conduction working mode between the two phases; each phase winding has 12 working modes, namely: single-phase winding forward excitation mode M1, single-phase winding forward freewheeling mode M2, two-phase winding forward series excitation mode M3, two-phase winding forward series freewheeling mode M4, one-phase winding forward demagnetization, one-phase winding reverse excitation mode M5, one-phase winding forward demagnetization, one-phase winding reverse freewheeling mode M6, single-phase winding reverse excitation mode M7, single-phase winding reverse freewheeling mode M8, two-phase winding reverse series excitation mode M9, two-phase winding reverse series freewheeling mode M 10 , one phase winding reverse demagnetization, one phase winding forward excitation mode M 11 , one phase winding reverse demagnetization, one phase winding forward freewheeling mode M 12 .

5. The fault-tolerant control method according to claim 1, characterized in that: Controllable single-pole double-throw switch Q n It is at least one of an electromagnetic relay, a solid-state relay, a high-frequency relay, or a controllable single-pole double-throw switch Q n Two power switching devices IGBT or MOSFET are connected in parallel through one pole and are driven by opposite signals to realize the single-pole double-throw switch function.

6. The fault-tolerant control method according to any one of claims 1 to 5, characterized in that: m is an integer not less than 2.

7. A switched reluctance motor speed control system based on a full-bridge power converter, the system comprising a switched reluctance motor, a voltage sensor, a position sensor, a controller, a PI module, a control mode selection module, a switch tube angle controller, a pulse signal generator and two full-bridge power converters: the switched reluctance motor has m-phase windings, each full-bridge power converter has m power conversion units, characterized in that: The midpoint of each power conversion unit is connected to one end of a winding through a controllable single-pole double-throw switch, and two ends of each winding are connected to two controllable single-pole double-throw switches, and the two controllable single-pole double-throw switches are connected to two different full-bridge power converters; The voltage sensor is used to detect the voltage at the stator winding terminals of the switched reluctance motor; The position sensor is used to detect the rotor position of the switched reluctance motor; The controller is used to control the full-bridge power converter and the controllable single-pole double-throw switch to realize fault diagnosis and fault-tolerant control of the switched reluctance speed regulation system; The PI module is a proportional-integral controller, which generates the corresponding reference quantity according to the set proportional and integral parameters. The output of the PI module is the set reference speed n ref The difference between the actual speed n obtained by the speed calculation module; The control mode selection module selects the corresponding control strategy according to the speed range of the motor; the control mode selection module selects the hysteresis controller to realize the current chopping control, the voltage PWM control (VPC) is realized through the PWM controller, and the angle position control (APC) is realized through the angle position controller; The switch angle controller sets the switch angle according to the set opening angle θ. on and the turn-off angle θ off Determine whether the motor is in the conduction range; The pulse signal generator generates a power converter drive signal according to the signals sent by the hysteresis controller, the PWM controller, the angle position controller, and the switch tube angle controller, and controls the on and off states of the power switch tube of the full-bridge power converter; The full-bridge power converter is responsible for converting the energy provided by the power supply and providing it to the SRM; Under normal operating conditions, each phase winding operates independently and alternately in forward excitation and reverse excitation modes; in the event of a power switch failure in any power conversion unit, it is not necessary to accurately identify the type and location of the failure, only the failed power conversion unit is located, and the corresponding controllable single-pole double-throw switch is actuated; for an even-phase motor, only the controllable single-pole double-throw switch connected to the failed power conversion unit is actuated, and only the failed power conversion unit is cut off, so that the failed phase winding and the fault side of the adjacent phase winding are connected; for an odd-phase motor, it is necessary to actuate the controllable single-pole double-throw switch connected to the failed power conversion unit and a controllable single-pole double-throw switch adjacent to it, and cut off the failed power conversion unit and its adjacent power conversion unit, so that the failed phase winding and the two adjacent phase windings are connected together in a star connection with a neutral line.

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