Fault Tolerant Topology Reconfiguration Control Method for Open Circuit Fault of Power Switch Devices in a Two-Motor System

Abstract

The present invention discloses a control method for fault-tolerant topology reconfiguration of an open-circuit fault of power switching devices in a two-motor system. The method includes: performing real-time fault diagnosis on the open circuit of power switching devices of a six-phase half-bridge two-level inverter in the two-motor system; using a normal control strategy, a fault-tolerant reconfiguration control strategy, and a fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or has a fault. The method of the present invention can achieve a fast and stable fault-tolerant topology reconfiguration process after an open-circuit fault of power switching devices in the two-motor system, and only by adjusting the duty cycle output by the control circuit, it can control the two-motor system under normal conditions and in the case of fault-tolerant topology reconfiguration. Without affecting the effectiveness of fault-tolerant topology reconfiguration, it shortens the transient process after a fault occurs, reduces the current impact during topology reconfiguration, and does not require strong accuracy for the results of fault diagnosis, which is beneficial to simplifying fault diagnosis and is convenient to implement in engineering.

Description

Technical Field

[0001] The present invention relates to a topology reconfiguration control method, and particularly to a fault-tolerant topology reconfiguration control method for an open-circuit fault of a power switching device in a two-motor system. Background Art

[0002] With the development of industrial automation, in the fields of heavy load, high-power drive and industrial robots, or in occasions with high reliability requirements, single-motor drive systems can no longer meet the needs, and multi-motor cooperative control is required. Among them, dual-motor systems are the most widely used. In the above-mentioned occasions, downtime caused by faults in the motor drive system will bring serious personal injuries and economic losses. The research results show that power device faults account for more than 30% of the motor drive system faults. Open-circuit faults of power devices are the most common type of faults in power converters, which will affect the operation performance of the motor system and cause harm to other normal devices in the system. Running for a long time in a fault state may cause secondary faults and lead to system collapse and shutdown. Therefore, timely and accurate fault-tolerant control is required after a fault occurs.

[0003] The existing fault-tolerant technologies for open-circuit faults of inverter power switching devices in three-phase motor drive systems generally focus on the control of inverter fault-tolerant topologies, without considering the influence of the fault diagnosis process and the topology reconfiguration process. Among the existing diagnostic technologies for open-circuit faults of power switching devices in motor drive system inverters, there is a lack of a method that can better balance the relationship between the implementation cost, complexity, accuracy and speed of diagnostic algorithms. In addition, there is still a lack of research on topology reconfiguration control after inverter faults. However, in actual situations, due to the existence of fault diagnosis and topology reconfiguration processes after a fault occurs, there will inevitably be a fault transient process during the period from the occurrence of the fault to fault-tolerant operation. During the transient process, the mismatch between the control strategy and the drive system topology will seriously affect the operation effect of the system and may cause other faults. Moreover, there will be a large current spike during the instant of topology reconfiguration, which will cause harm to normal devices. Summary of the Invention

[0004] In order to solve the problems in the background art, the present invention provides a fault-tolerant topology reconfiguration control method for an open-circuit fault of a power switching device in a two-motor system. After a single power device open-circuit fault occurs in the two-motor system, it completes fault diagnosis and performs fault-tolerant reconfiguration control in the shortest possible time, and can perform secondary verification on the fault diagnosis result, realizing a fast and reliable fault-tolerant reconfiguration process. At the same time, the fault diagnosis algorithm is very simple and easy to implement, saving the computing resources and storage resources of the controller.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The fault-tolerant topology reconfiguration control method of the present invention includes the following steps:

[0007] Step 1: Construct a two-motor system. The two-motor system includes two permanent magnet motors and a six-phase half-bridge two-level inverter. Drive the two-motor system to operate and perform real-time fault diagnosis on the open-circuit of the power switching devices of the six-phase half-bridge two-level inverter of the two-motor system.

[0008] Step 2: Use the normal control strategy, fault-tolerant reconstruction control strategy, and fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or a fault is diagnosed.

[0009] In the above-mentioned Step 1, the two-motor system further includes a topology reconstruction device, a sampling circuit, a control circuit, a three-phase AC power supply, an uncontrolled rectifier bridge, and a bus capacitor. The three-phase AC power supply outputs three-phase alternating current with adjustable amplitude, which is rectified by the uncontrolled rectifier bridge and used as the input of the six-phase half-bridge two-level inverter. The bus capacitor is connected in parallel between the uncontrolled rectifier bridge and the six-phase half-bridge two-level inverter.

[0010] The six-phase half-bridge two-level inverter is composed of two three-phase half-bridge two-level inverters with their DC sides connected in parallel. Each three-phase half-bridge two-level inverter is connected to one of the permanent magnet motors. The three bridge arms in each three-phase half-bridge two-level inverter are respectively connected to the three-phase windings of one of the permanent magnet motors. The A, B, and C bridge arms in the first three-phase half-bridge two-level inverter are respectively connected to the a1, b1, and c1 phase windings of the first permanent magnet motor, and the D, E, and F bridge arms in the second three-phase half-bridge two-level inverter are respectively connected to the a2, b2, and c2 phase windings of the second permanent magnet motor. Each bridge arm in the six-phase half-bridge two-level inverter is composed of a series-connected upper switch tube and a lower switch tube, and the series connection point is used as the output end of the bridge arm. Each switch tube is anti-parallel with a power diode.

[0011] The topology reconstruction device includes three topology reconstruction units. The three topology reconstruction units are respectively connected across the corresponding phase bridge arms of the first three-phase half-bridge two-level inverter and the second three-phase half-bridge two-level inverter. Specifically, the first reconstruction unit k A is connected across the A-phase bridge arm of the first three-phase half-bridge two-level inverter and the D-phase bridge arm of the second three-phase half-bridge two-level inverter. The second reconstruction unit k B is connected across the B-phase bridge arm of the first three-phase half-bridge two-level inverter and the E-phase bridge arm of the second three-phase half-bridge two-level inverter. The third reconstruction unit k C is connected across the C-phase bridge arm of the first three-phase half-bridge two-level inverter and the F-phase bridge arm of the second three-phase half-bridge two-level inverter. Each topology reconstruction unit of the topology reconstruction device is composed of two reversely connected switch tubes, and each switch tube is anti-parallel with a power diode, that is, it is composed of two IGBTs with anti-parallel diodes connected in reverse.

[0012] In the first step described above, the sampling circuit includes a voltage and current sampling circuit and a rotor position sampling circuit. The voltage and current sampling circuit includes a voltage sensor and six current sensors, and the rotor position sampling circuit includes two position sensors. The voltage sensor is connected in parallel across the bus capacitor and is used to measure the DC bus voltage U of the bus capacitor dc and input it into the control circuit. The DC bus voltage U dc is the DC voltage at the input of the six-phase half-bridge two-level inverter; the six current sensors are respectively connected in series with the six-phase windings of the two permanent magnet motors and are used to measure the six-phase currents between the six arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors and input them into the control circuit; the two position sensors are respectively coaxially connected to the rotors of the two permanent magnet motors and are used to measure the actual rotor positions of the two permanent magnet motors and input them into the control circuit.

[0013] The control circuit calculates the duty cycles of the switching actions of the six-phase half-bridge two-level inverter and the three topology reconstruction units based on the DC voltage at the input of the six-phase half-bridge two-level inverter, the six-phase currents of the two permanent magnet motors, and the positions and speeds of the rotors of the two permanent magnet motors fed back by the sampling circuit, and compares the duty cycles with the carrier wave generated by the control circuit itself to generate the PWM signal S A…F to drive the six-phase half-bridge two-level inverter to independently control the two permanent magnet motors.

[0014] The current sensor is specifically a Hall current sensor; the voltage sensor is specifically a Hall voltage sensor; the position sensor is specifically an incremental encoder or an absolute encoder.

[0015] In the first step described above, real-time fault diagnosis is performed on the open circuit of the power switching devices of the six-phase half-bridge two-level inverter of the two-motor system, specifically as follows:

[0016] 1.1) The control circuit calculates the actual rotor magnetic field positions and actual speeds of each permanent magnet motor based on the respective actual rotor positions measured by the position sensors of each permanent magnet motor, and at the same time calculates the speed deviations between the actual speeds and the preset reference speeds of each permanent magnet motor; inputs the speed deviations of each permanent magnet motor into their respective speed-loop PI controllers for processing and then outputs the q-axis reference currents of each permanent magnet motor respectively. The d-axis reference currents of each permanent magnet motor are preset values, and are preset to 0 in actual operation; according to the actual rotor magnetic field positions of each permanent magnet motor, the q-axis reference currents and d-axis reference currents of each permanent magnet motor are sequentially subjected to inverse Park transformation and inverse Clark transformation to obtain the three-phase reference currents of each permanent magnet motor, namely the a2-phase reference current, the b1-phase reference current, and the c1-phase reference current; the speed-loop PI controller serves as the speed regulator of the permanent magnet motor.

[0017] 1.2) The control circuit calculates the reference current magnitude of each permanent magnet motor based on the q-axis reference current and d-axis reference current of each permanent magnet motor, and normalizes the three-phase reference current according to the reference current magnitude of each permanent magnet motor to obtain the three-phase normalized reference current of the permanent magnet motor.

[0018] 1.3) The control circuit acquires the three-phase actual currents of the two permanent magnet motors measured by six current sensors. According to the actual rotor magnetic field position of each permanent magnet motor, the three-phase actual currents of each permanent magnet motor are sequentially transformed by Clark transformation and Park transformation to obtain the q-axis actual current and d-axis actual current of each permanent magnet motor. The actual current magnitude of each permanent magnet motor is calculated based on the q-axis actual current and d-axis actual current of each permanent magnet motor, and the three-phase actual currents of the permanent magnet motor are normalized according to the actual current magnitude of each permanent magnet motor to obtain the three-phase normalized actual current of the permanent magnet motor.

[0019] 1.4) The control circuit calculates the three-phase normalized current deviation between the three-phase normalized reference current and the three-phase normalized actual current of each permanent magnet motor.

[0020] 1.5) The control circuit compares the magnitude of the absolute value of the three-phase normalized current deviation of each permanent magnet motor with the preset fault diagnosis threshold th. When the absolute value of the three-phase normalized current deviation of one phase of one of the permanent magnet motors is continuously greater than the preset fault diagnosis threshold th for N control cycles, it is diagnosed that there is a fault in this phase of this permanent magnet motor and it is used as the motor fault phase, and then a bridge arm fault of the six-phase half-bridge two-level inverter connected to the motor fault phase is determined and used as the fault bridge arm; the values of N and th need to be pre-tuned.

[0021] 1.6) Locate the position of the faulty power switch device in the fault bridge arm according to the polarity of the normalized current deviation of the fault phase. When the polarity of the normalized current deviation of the fault phase is positive, the faulty power switch device is the upper switch tube of the fault bridge arm. When the polarity of the normalized current deviation of the fault phase is negative, the faulty power switch device is the lower switch tube of the fault bridge arm.

[0022] In the second step described above, the two-motor system is controlled by using the normal control strategy, the fault-tolerant reconstruction control strategy, and the fault-tolerant control strategy when the two-motor system is operating normally or has a fault. Specifically, the two-motor system is controlled by switching the control strategy under different bases of the two-motor system as follows:

[0023] Basis 1: When no fault of the two-motor system is diagnosed or no fault is detected when switching back from the fault-tolerant reconstruction control strategy to the normal strategy, the two-motor system is controlled by the normal control strategy.

[0024] Basis 2: When diagnosing a fault in the two-motor system during control by the normal control strategy, the normal control strategy is switched to the fault-tolerant reconfiguration control strategy to control the two-motor system.

[0025] Basis 3: When controlling the two-motor system by the fault-tolerant reconfiguration control strategy and condition 1 is satisfied, the fault-tolerant reconfiguration control strategy is switched to the normal control strategy to control the two-motor system.

[0026] Basis 4: When controlling the two-motor system by the fault-tolerant reconfiguration control strategy and condition 1 is not satisfied, the fault-tolerant reconfiguration control strategy is maintained to control the two-motor system.

[0027] Basis 5: When controlling the two-motor system by the fault-tolerant reconfiguration control strategy and condition 2 is satisfied, the fault-tolerant reconfiguration control strategy is switched to the fault-tolerant control strategy to control the two-motor system.

[0028] The specific condition 1 is that the fault count value n d of the two-motor system is less than the first preset comparison value th Nd , and at the same time, the fault-phase current in the six-phase current between the six bridge arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors enters the range not affected by the fault, where the fault count value n d is the number of times the fault of the two-motor system is diagnosed; the specific condition 2 is that the fault count value n d is equal to the first preset comparison value th Nd .

[0029] In basis 3, the fault diagnosis result of the two-motor system is verified by obtaining the timing count value cnt through timing counting. The timing count value cnt is positively correlated with the continuous operation time of the two-motor system after switching from the fault-tolerant reconfiguration control strategy to the normal control strategy. The count value cnt is obtained through timing counting, the counting period is the control period Ts, and the value of cnt increases by 1 every time Ts passes. The time reflected by cnt is discrete; if no fault is detected in the two-motor system before the timing count value cnt reaches the second preset comparison value CNT, the values of the timing count value cnt and the fault count value n d are cleared; if the two-motor system diagnoses the same fault as the previously diagnosed fault before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the fault-tolerant reconfiguration control strategy and the value of the fault count value n d is incremented by 1; if a fault different from the previously diagnosed fault is diagnosed before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the reconfiguration control strategy and the value of the fault count value n d starts counting from zero again.

[0030] Whenever the control strategy switches from the reconstructed control strategy to the normal control strategy, the timing count value cnt starts counting from zero in steps of the control period Ts of the control circuit; to ensure the integrity of the verification of the fault diagnosis result, the time for the timing count value cnt to increase to the second preset comparison value CNT should be greater than one fundamental current period, that is, as follows:

[0031]

[0032] where p represents the number of pole pairs of the permanent magnet motor; n * represents the reference speed of the permanent magnet motor.

[0033] The non-fault-affected range of the fault phase current in the six-phase current between the six bridge arms of the six-phase half-bridge two-level inverter and the two three-phase windings of the permanent magnet motor is as follows:

[0034]

[0035]

[0036] where i a1 、i b1 and i c1 respectively represent the currents between the A, B, and C bridge arms in the first three-phase half-bridge two-level inverter and the a1, b1, and c1 phase windings of the first permanent magnet motor; i a2 、i b2 and i c2 respectively represent the currents between the D, E, and F bridge arms in the second three-phase half-bridge two-level inverter and the a2, b2, and c2 phase windings of the second permanent magnet motor.

[0037] The normal control strategy is as follows:

[0038] For each permanent magnet motor in the two-motor system, the control circuit calculates the d-axis current deviation between the actual d-axis current and the reference d-axis current of the permanent magnet motor, and calculates the q-axis current deviation between the actual q-axis current and the reference q-axis current of the permanent magnet motor. The d-axis current deviation and the q-axis current deviation are respectively input into the d-axis current loop PI controller and the q-axis current loop PI controller. The d-axis current loop PI controller and the q-axis current loop PI controller respectively output the reference d-axis voltage and the reference q-axis voltage of the permanent magnet motor;

[0039] For each permanent magnet motor of the two-motor system, the control circuit performs an inverse Park transformation on the d-axis reference voltage and the q-axis reference voltage according to the actual rotor magnetic field position of the permanent magnet motor, respectively obtaining the α-phase reference voltage and the β-phase reference voltage of the permanent magnet motor. According to the α-phase reference voltage and the β-phase reference voltage of the permanent magnet motor, the space vector pulse width modulation algorithm SVPWM is used to calculate the switching duty ratios of the three bridge arms of the three-phase half-bridge two-level inverter connected to the three-phase windings of the permanent magnet motor; the control circuit compares the switching duty ratios of the three bridge arms of each three-phase half-bridge two-level inverter with the carrier wave generated by itself to obtain the PWM signal S A…F Furthermore, it drives the six-phase half-bridge two-level inverter to operate.

[0040] The specific fault-tolerant reconfiguration control strategy is as follows:

[0041] When it is diagnosed that one of the bridge arms in the six-phase half-bridge two-level inverter is a faulty bridge arm, the control circuit selects the smallest switching duty ratio among the switching duty ratios of the three bridge arms of each three-phase half-bridge two-level inverter obtained under the normal control strategy as the maximum adjustment value of the bridge arm duty ratio of the three-phase half-bridge two-level inverter, corresponding to half of the zero vector duty ratio, where the maximum adjustment value of the bridge arm duty ratio of the three-phase half-bridge two-level inverter where the faulty bridge arm is located is used as the fault maximum adjustment value δ 1max , and the maximum adjustment value of the bridge arm duty ratio of the other three-phase half-bridge two-level inverter is used as the non-fault maximum adjustment value δ 2max ; calculate the switching duty ratio δ h of a non-faulty bridge arm connected to the faulty bridge arm through a reconfiguration unit and the switching duty ratio δ f of the faulty bridge arm, and take the difference between them and its absolute value as the duty ratio difference δ d and the absolute value of the duty ratio difference δ dabs .

[0042] Adjust the six-phase half-bridge two-level inverter according to the magnitude relationship among the fault maximum adjustment value δ 1max , the non-fault maximum adjustment value δ 2max , the duty ratio difference δ d and the absolute value of the duty ratio difference δ dabs , specifically as follows:

[0043] Case 1: When the duty ratio difference δ d is greater than or equal to 0, there is no need to adjust the duty ratios of the bridge arms in the six-phase half-bridge two-level inverter.

[0044] Case 2: When the duty ratio difference δ d is less than 0, and the absolute value of the duty ratio difference δ dabs is less than or equal to the fault maximum adjustment value δ 1max , the switching duty ratio δf and the duty ratios of the other two arms in the three-phase half-bridge two-level inverter where the faulty arm is located are each subtracted by the absolute value of the duty ratio difference δ dabs and then used as their respective duty ratios; keep the duty ratios of the three arms in the other three-phase half-bridge two-level inverter unchanged.

[0045] Case 3: When the duty ratio difference δ d is less than 0, and at the same time the absolute value of the duty ratio difference δ dabs is greater than the maximum fault adjustment value δ 1max and less than or equal to the sum of the maximum fault adjustment value δ 1max and the maximum non-fault adjustment value δ 2max subtract the maximum fault adjustment value δ f from the duty ratio of the faulty arm δ and the duty ratios of the other two arms in the three-phase half-bridge two-level inverter where the faulty arm is located, and then use them as their respective duty ratios; add the absolute value of the duty ratio difference δ 1max and the difference between the maximum fault adjustment value δ dabs to the duty ratios of the three arms in the other three-phase half-bridge two-level inverter, and then use them as their respective duty ratios. 1max

[0046] Case 4: When the duty ratio difference δ d is less than 0 and the absolute value of the duty ratio difference δ dabs is greater than the sum of the maximum fault adjustment value δ 1max and the maximum non-fault adjustment value δ 2max subtract the maximum fault adjustment value δ f from the duty ratio of the faulty arm δ and the duty ratios of the other two arms in the three-phase half-bridge two-level inverter where the faulty arm is located, and then use them as their respective duty ratios; add the maximum non-fault adjustment value δ 1max to the duty ratios of the three arms in the other three-phase half-bridge two-level inverter, and then use them as their respective duty ratios. 2max

[0047] Determine the conduction mode of the topology reconstruction device according to the duty ratios of each arm in the six-phase half-bridge two-level inverter adjusted according to the above four cases. Specifically, use the duty ratio δ f of the faulty arm and the switching signal of the faulty power switch device in the faulty arm as the switching duty ratio and switching signal of the switch tube of the topology reconstruction unit connected to the faulty arm, respectively, and then control the switch tube in the topology reconstruction unit.

[0048] Taking the open-circuit fault of the power switch of the upper arm of phase A of the inverter as an example, after the duty ratio adjustment, the faulty arm A and the reconstruction unit k A ​​Have the same switching state. When the power switch of the lower arm of phase A conducts, reconstruction unit k A Is in the off state. At this time, the current of phase a1 of the permanent magnet motor mainly flows through the lower arm of phase A, and the reconstruction unit and the faulty switch tube connected to the faulty arm have the same switching signal; when the power switch of the upper arm of phase A needs to conduct, reconstruction unit k A Is in the on state. At this time, the current of phase a1 of the permanent magnet motor mainly flows through the upper arm of phase D. Finally, the role of the switch tube of the faulty arm is replaced by the reconstruction unit and the non-faulty arm connected to the reconstruction unit.

[0049] Among them, the MCU transmits the adjusted duty cycle to the FPGA. In the FPGA, the duty cycle is compared with the carrier wave to obtain six PWM signals S for driving the six-phase half-bridge two-level inverter and three PWM signals for driving the reconstruction unit kA…C , and these PWM signals are processed by the CPLD to obtain the switching signals for driving the six-phase half-bridge two-level inverter and the reconstruction unit.

[0050] The described fault-tolerant control strategy is as follows:

[0051] When it is diagnosed that one of the arms in the six-phase half-bridge two-level inverter is a faulty arm, the control circuit blocks the driving signal of the faulty arm and keeps the topology reconstruction unit connected to the faulty arm conducting. One phase winding of the permanent magnet motor connected to the faulty arm is connected to one of the non-faulty arms through the topology reconstruction unit, and the remaining five non-faulty arms are used to control the two permanent magnet motors; the six-phase half-bridge two-level inverter is adjusted as follows:

[0052] Divide a control cycle T S Of the two-motor system into the front control cycle T1 and the back control cycle T2. In the front control cycle T1, keep the switching duty cycles of the three arms of the one-phase half-bridge two-level inverter where the faulty arm is located unchanged, and adjust the switching duty cycles of the three arms of the other one-phase half-bridge two-level inverter to be the same as the switching duty cycle δ f Of the faulty arm; in the back control cycle T2, keep the switching duty cycles of the three arms of the other one-phase half-bridge two-level inverter unchanged, and adjust the switching duty cycles of the three arms of the one-phase half-bridge two-level inverter where the faulty arm is located to be the same as the switching duty cycle δ h Of a non-faulty arm connected to the faulty arm through a reconstruction unit.

[0053] The duty ratios of each arm in the six-phase half-bridge two-level inverter adjusted according to the fault-tolerant control strategy are compared with the carrier wave generated by the control circuit, and the switching signals used to drive the six-phase half-bridge two-level inverter and the topology reconfiguration device are obtained. After blocking the switching signals of the faulty arm, the six-phase half-bridge two-level inverter and the topology reconfiguration device are controlled.

[0054] The beneficial effects of the present invention are as follows:

[0055] The method of the present invention can achieve a fast and stable fault-tolerant topology reconfiguration process after an open-circuit fault occurs in the power switching devices of the two-motor system, and can control the two-motor system under normal conditions and fault-tolerant topology reconfiguration conditions only by adjusting the duty ratio output by the controller without changing the control algorithm framework.

[0056] The method of the present invention can shorten the transient process after a fault occurs without affecting the effectiveness of the fault-tolerant topology reconfiguration, reduce the current impact during the topology reconfiguration moment, and achieve a stable inverter fault-tolerant topology reconfiguration process. At the same time, the proposed fault-tolerant reconfiguration control method does not have strong requirements for the accuracy of the fault diagnosis results, which is beneficial to simplifying the fault diagnosis algorithm and facilitating implementation in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is the overall system structure diagram;

[0058] Figure 2 is the control strategy block diagram;

[0059] Figure 3 is the fault-tolerant reconfiguration control flow chart;

[0060] Figure 4 is the schematic diagram of the circuit working state under fault-tolerant reconfiguration control;

[0061] Figure 5 is the schematic diagram of the strategy switching state;

[0062] Figure 6 is the schematic diagram of the simulation waveforms of two permanent magnet motors when an open-circuit fault occurs in the upper-arm power switching device of phase A in the positive half-cycle of the current in phase a1;

[0063] Figure 7 is the schematic diagram of the system operation when an open-circuit fault occurs in the upper-arm power switching device of phase A in the positive half-cycle of the current in phase a1;

[0064] Figure 8 is the schematic diagram of the simulation waveforms of two permanent magnet motors when an open-circuit fault occurs in the upper-arm power switching device of phase A in the negative half-cycle of the current in phase a1;

[0065] Figure 9Schematic diagram of the system operation when an open-circuit fault occurs in the upper-bridge-arm power switch device of phase A during the negative half-cycle of the a1-phase current;

[0066] Figure 10 Schematic diagram of the simulation waveforms of two permanent magnet motors when the drive protection of the upper-bridge-arm power switch device of phase A occurs during the positive half-cycle of the a1-phase current;

[0067] Figure 11 Schematic diagram of the system operation when the drive protection of the upper-bridge-arm power switch device of phase A occurs during the positive half-cycle of the a1-phase current. Specific embodiments

[0068] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0069] The fault-tolerant topology reconfiguration control method of the present invention includes the following steps:

[0070] Step 1: Construct a two-motor system, which includes two permanent magnet motors and a six-phase half-bridge two-level inverter. Drive the two-motor system to operate and perform real-time fault diagnosis on the open-circuit of the power switch devices of the six-phase half-bridge two-level inverter of the two-motor system.

[0071] In step 1, the two-motor system further includes a topology reconfiguration device, a sampling circuit, a control circuit, a three-phase AC power supply, an uncontrolled rectifier bridge, and a bus capacitor. The three-phase AC power supply outputs three-phase alternating current with adjustable amplitude, which is rectified by the uncontrolled rectifier bridge and used as the input of the six-phase half-bridge two-level inverter; the bus capacitor is connected in parallel between the uncontrolled rectifier bridge and the six-phase half-bridge two-level inverter.

[0072] The six-phase half-bridge two-level inverter is composed of two three-phase half-bridge two-level inverters with their DC sides connected in parallel. Each three-phase half-bridge two-level inverter is connected to one of the permanent magnet motors. The three bridge arms in each three-phase half-bridge two-level inverter are respectively connected to the three-phase windings of one of the permanent magnet motors; the A, B, and C bridge arms in the first three-phase half-bridge two-level inverter are respectively connected to the a1, b1, and c1 phase windings of the first permanent magnet motor, and the D, E, and F bridge arms in the second three-phase half-bridge two-level inverter are respectively connected to the a2, b2, and c2 phase windings of the second permanent magnet motor; each bridge arm in the six-phase half-bridge two-level inverter is composed of a series-connected upper switch tube and a lower switch tube, and the series connection point is used as the output end of the bridge arm. Each switch tube is anti-parallel with a power diode.

[0073] The topology reconfiguration device includes three topology reconfiguration units, and the three topology reconfiguration units are respectively connected across the corresponding phase bridge arms of the first three-phase half-bridge two-level inverter and the second three-phase half-bridge two-level inverter. Specifically, the first reconfiguration unit k AConnected between the A-phase arm of the first three-phase half-bridge two-level inverter and the D-phase arm of the second three-phase half-bridge two-level inverter, the second reconstruction unit k B Connected between the B-phase arm of the first three-phase half-bridge two-level inverter and the E-phase arm of the second three-phase half-bridge two-level inverter, the third reconstruction unit k C Connected between the C-phase arm of the first three-phase half-bridge two-level inverter and the F-phase arm of the second three-phase half-bridge two-level inverter; each topology reconstruction unit of the topology reconstruction device is composed of two switch tubes connected in series in reverse, and each switch tube is anti-parallel with a power diode, that is, it is composed of two IGBTs with anti-parallel diodes connected in series in reverse.

[0074] In step one, the sampling circuit includes a voltage and current sampling circuit and a rotor position sampling circuit. The voltage and current sampling circuit includes a voltage sensor and six current sensors, and the rotor position sampling circuit includes two position sensors. The voltage sensor is connected in parallel across the bus capacitor and is used to measure the DC bus voltage U of the bus capacitor dc and input it into the control circuit. The DC bus voltage U dc is the DC voltage at the input of the six-phase half-bridge two-level inverter; the six current sensors are respectively connected in series with the six-phase windings of the two permanent magnet motors and are used to measure the six-phase current between the six arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors and input it into the control circuit; the two position sensors are respectively coaxially connected to the rotors of the two permanent magnet motors and are used to measure the actual rotor positions of the two permanent magnet motors and input them into the control circuit.

[0075] The control circuit calculates the duty cycles of the switching actions of the six-phase half-bridge two-level inverter and the three topology reconstruction units through the DC voltage at the input of the six-phase half-bridge two-level inverter, the six-phase current of the two permanent magnet motors, and the positions and speeds of the rotors of the two permanent magnet motors fed back by the sampling circuit, and compares the duty cycles with the carrier wave generated by the control circuit itself to generate the PWM signal S A…F to drive the six-phase half-bridge two-level inverter to independently control the two permanent magnet motors.

[0076] The current sensor is specifically a Hall current sensor; the voltage sensor is specifically a Hall voltage sensor; the position sensor is specifically an incremental encoder or an absolute encoder.

[0077] The control circuit mainly consists of a Microcontroller Unit (MCU), a Field Programmable Gate Array (FPGA), and a Complex Programmable Logic Device (CPLD). Among them, the MCU is responsible for executing the control method, and the FPGA and CPLD are responsible for sampling the trigger sampling circuit and generating control signals for driving the fault-tolerant topology reconfiguration device, which is the two-motor system.

[0078] In step 1, real-time fault diagnosis is performed on the open circuit of the power switch devices of the six-phase half-bridge two-level inverter of the two-motor system, specifically as follows:

[0079] 1.1) The control circuit calculates the actual rotor magnetic field position and actual speed of each permanent magnet motor based on the respective actual rotor positions measured by the position sensors of each permanent magnet motor, and at the same time calculates the speed deviation between the actual speed and the preset reference speed of each permanent magnet motor. The speed deviation of each permanent magnet motor is input into its respective speed-loop PI controller for processing, and then the q-axis reference current of each permanent magnet motor is output respectively. The d-axis reference current of each permanent magnet motor is a preset value, which is preset to 0 in actual operation. According to the actual rotor magnetic field position of each permanent magnet motor, the q-axis reference current and d-axis reference current of each permanent magnet motor are sequentially transformed by the inverse Park transform and inverse Clark transform to obtain the three-phase reference currents of each permanent magnet motor, namely the a2-phase reference current, b1-phase reference current, and c1-phase reference current. The speed-loop PI controller serves as the speed regulator of the permanent magnet motor.

[0080] 1.2) The control circuit calculates the reference current modulus value of the permanent magnet motor based on the q-axis reference current and d-axis reference current of each permanent magnet motor, and normalizes the three-phase reference currents according to the reference current modulus value of each permanent magnet motor to obtain the three-phase normalized reference currents of the permanent magnet motor.

[0081] 1.3) The control circuit obtains the three-phase actual currents of the two permanent magnet motors measured by six current sensors. According to the actual rotor magnetic field position of each permanent magnet motor, the three-phase actual currents of each permanent magnet motor are sequentially transformed by the Clark transform and Park transform to obtain the q-axis actual current and d-axis actual current of each permanent magnet motor. The actual current modulus value of each permanent magnet motor is calculated based on the q-axis actual current and d-axis actual current of each permanent magnet motor, and the three-phase actual currents of the permanent magnet motor are normalized according to the actual current modulus value of each permanent magnet motor to obtain the three-phase normalized actual currents of the permanent magnet motor.

[0082] 1.4) The control circuit calculates the three-phase normalized current deviation between the three-phase normalized reference current and the three-phase normalized actual current of each permanent magnet motor.

[0083] 1.5) The control circuit compares the magnitude of the absolute value of the three-phase normalized current deviation of each permanent magnet motor with a preset fault diagnosis threshold th. When the absolute value of the normalized current deviation of one phase of one of the permanent magnet motors is continuously greater than the preset fault diagnosis threshold th for N control cycles, it is diagnosed that there is a fault in this phase of this permanent magnet motor and it is used as the motor fault phase, and then a fault in one arm of the six-phase half-bridge two-level inverter connected to the motor fault phase is determined and used as the fault arm; the values of N and th need to be pre-tuned.

[0084] 1.6) Locate the position of the faulty power switch device in the fault arm according to the polarity of the normalized current deviation of the fault phase. When the polarity of the normalized current deviation of the fault phase is positive, the faulty power switch device is the upper switch tube of the fault arm. When the polarity of the normalized current deviation of the fault phase is negative, the faulty power switch device is the lower switch tube of the fault arm.

[0085] Step 2: Use the normal control strategy, fault-tolerant reconstruction control strategy, and fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or a fault is diagnosed.

[0086] In Step 2, use the normal control strategy, fault-tolerant reconstruction control strategy, and fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or has a fault. Specifically, the two-motor system is controlled by switching control strategies under different bases of the two-motor system as follows:

[0087] Basis 1: When no fault of the two-motor system is diagnosed or no fault is detected when switching back from the fault-tolerant reconstruction control strategy to the normal strategy, the two-motor system is controlled by the normal control strategy.

[0088] Basis 2: When controlling the two-motor system by the normal control strategy, if a fault of the two-motor system is diagnosed, the normal control strategy is switched to the fault-tolerant reconstruction control strategy to control the two-motor system.

[0089] Basis 3: When controlling the two-motor system by the fault-tolerant reconstruction control strategy and condition 1 is satisfied, the fault-tolerant reconstruction control strategy is switched to the normal control strategy to control the two-motor system.

[0090] Basis 4: When controlling the two-motor system by the fault-tolerant reconstruction control strategy and condition 1 is not satisfied, the fault-tolerant reconstruction control strategy is maintained to control the two-motor system.

[0091] Basis 5: When controlling the two-motor system through the fault-tolerant reconstruction control strategy and satisfying Condition 2, the fault-tolerant reconstruction control strategy is switched to the fault-tolerant control strategy to control the two-motor system.

[0092] The specific Condition 1 is that the fault count value n of the two-motor system d is less than the first preset comparison value th Nd , and at the same time, the fault-phase current in the six-phase current between the six bridge arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors enters the range not affected by the fault. Among them, the fault count value n d is the number of times the faults of the two-motor system are diagnosed; the specific Condition 2 is that the fault count value n d is equal to the first preset comparison value th Nd .

[0093] In accordance with Basis 3, the fault diagnosis result of the two-motor system is verified by obtaining the timing count value cnt through timing counting. The timing count value cnt is positively correlated with the continuous operation time of the two-motor system after switching from the fault-tolerant reconstruction control strategy to the normal control strategy. The count value cnt is obtained through timing counting, and the counting period is the control period T s , the value of cnt increases by 1 every time T s passes, and the time reflected by cnt is discrete; if no fault is detected in the two-motor system before the timing count value cnt reaches the second preset comparison value CNT, the values of the timing count value cnt and the fault count value n d are cleared; if the two-motor system diagnoses the same fault as the previously diagnosed fault before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the fault-tolerant reconstruction control strategy and the value of the fault count value n d increases by 1; if a fault different from the previously diagnosed fault is diagnosed before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the reconstruction control strategy and the value of the fault count value n d starts counting from zero again.

[0094] Whenever the control strategy is switched from the reconstruction control strategy to the normal control strategy, the timing count value cnt starts counting from zero with the control period Ts of the control circuit as the step size; to ensure the integrity of the verification of the fault diagnosis result, the time for the timing count value cnt to increase to the second preset comparison value CNT should be greater than a fundamental current period, that is, as follows:

[0095]

[0096] Among them, p represents the number of pole pairs of the permanent magnet motor; n * represents the reference speed of the permanent magnet motor.

[0097] The range of the fault-free phase current among the six-phase currents between the six bridge arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors is as follows:

[0098]

[0099]

[0100] Among them, i a1 , i b1 and i c1 respectively represent the currents between the A, B, and C bridge arms in the first three-phase half-bridge two-level inverter and the a1, b1, and c1 phase windings of the first permanent magnet motor; i a2 , i b2 and i c2 respectively represent the currents between the D, E, and F bridge arms in the second three-phase half-bridge two-level inverter and the a2, b2, and c2 phase windings of the second permanent magnet motor.

[0101] The specific normal control strategy is as follows:

[0102] For each permanent magnet motor in the two-motor system, the control circuit calculates the d-axis current deviation between the actual d-axis current and the reference d-axis current of the permanent magnet motor, and calculates the q-axis current deviation between the actual q-axis current and the reference q-axis current of the permanent magnet motor. The d-axis current deviation and the q-axis current deviation are respectively input into the d-axis current loop PI controller and the q-axis current loop PI controller, and the d-axis current loop PI controller and the q-axis current loop PI controller respectively output the reference d-axis voltage and the reference q-axis voltage of the permanent magnet motor.

[0103] For each permanent magnet motor in the two-motor system, the control circuit performs an inverse Park transformation on the reference d-axis voltage and the reference q-axis voltage according to the actual rotor magnetic field position of the permanent magnet motor to respectively obtain the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor. According to the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor, the space vector pulse width modulation algorithm SVPWM is used to calculate the switching duty ratios of the three bridge arms of the three-phase half-bridge two-level inverter connected to the three-phase windings of the permanent magnet motor; the control circuit compares the switching duty ratios of the three bridge arms of each three-phase half-bridge two-level inverter with its own generated carrier to obtain the PWM signal S A…F Furthermore, it drives the six-phase half-bridge two-level inverter to operate.

[0104] The specific fault-tolerant reconstruction control strategy is as follows:

[0105] When one of the bridge arms in a six-phase half-bridge two-level inverter is diagnosed as a faulty bridge arm, the control circuit selects the minimum switching duty cycle among the switching duty cycles of the three bridge arms of each three-phase half-bridge two-level inverter obtained under the normal control strategy as the maximum adjustment value of the bridge arm duty cycle of the three-phase half-bridge two-level inverter, corresponding to half of the zero-vector duty cycle. The maximum adjustment value of the bridge arm duty cycle of the three-phase half-bridge two-level inverter where the faulty bridge arm is located is used as the maximum fault adjustment value δ 1max , and the maximum adjustment value of the bridge arm duty cycle of the other three-phase half-bridge two-level inverter is used as the maximum non-fault adjustment value δ 2max ; Calculate the difference and its absolute value between the switching duty cycle δ h of a non-faulty bridge arm connected to the faulty bridge arm through a reconstruction unit and the switching duty cycle δ f of the faulty bridge arm, and use them as the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs respectively.

[0106] Adjust the six-phase half-bridge two-level inverter according to the magnitude relationship among the maximum fault adjustment value δ 1max , the maximum non-fault adjustment value δ 2max , the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs as follows:

[0107] Case 1: When the duty cycle difference δ d is greater than or equal to 0, there is no need to adjust the duty cycle of each bridge arm in the six-phase half-bridge two-level inverter.

[0108] Case 2: When the duty cycle difference δ d is less than 0, and the absolute value of the duty cycle difference δ dabs is less than or equal to the maximum fault adjustment value δ 1max , subtract the absolute value of the duty cycle difference δ f from the switching duty cycle δ dabs of the faulty bridge arm and the switching duty cycles of the other two bridge arms in the three-phase half-bridge two-level inverter where the faulty bridge arm is located respectively as their respective switching duty cycles; keep the switching duty cycles of the three bridge arms in the other three-phase half-bridge two-level inverter unchanged.

[0109] Case 3: When the duty cycle difference δ d is less than 0, and at the same time the absolute value of the duty cycle difference δ dabs is greater than the maximum fault adjustment value δ 1max and less than or equal to the sum of the maximum fault adjustment value δ 1max and the maximum non-fault adjustment value δ 2max , subtract the absolute value of the duty cycle difference δ fThe switching duty cycles of the other two arms in the three-phase half-bridge two-level inverter where the faulty arm is located are each subtracted by the maximum fault adjustment value δ 1max and then used as their respective switching duty cycles; the switching duty cycles of the three arms in the other three-phase half-bridge two-level inverter are each added by the absolute value of the duty cycle difference δ dabs and the maximum fault adjustment value δ 1max and the differences are then used as their respective switching duty cycles.

[0110] Case 4: When the duty cycle difference δ d is less than 0 and the absolute value of the duty cycle difference δ dabs is greater than the sum of the maximum fault adjustment value δ 1max and the non-fault maximum adjustment value δ 2max , the switching duty cycle δ f of the faulty arm and the switching duty cycles of the other two arms in the three-phase half-bridge two-level inverter where the faulty arm is located are each subtracted by the maximum fault adjustment value δ 1max and then used as their respective switching duty cycles; the switching duty cycles of the three arms in the other three-phase half-bridge two-level inverter are each added by the non-fault maximum adjustment value δ 2max and then used as their respective switching duty cycles.

[0111] Determine the conduction mode of the topology reconstruction device according to the duty cycles of each arm in the six-phase half-bridge two-level inverter adjusted according to the above four cases. Specifically, the switching duty cycle δ f of the faulty arm and the switching signals of the faulty power switch devices in the faulty arm are respectively used as the switching duty cycle and switching signal of the switch tube of the topology reconstruction unit connected to the faulty arm, and then the switch tube in the topology reconstruction unit is controlled.

[0112] Taking the open-circuit fault of the power switch of the upper arm of phase A of the inverter as an example, after the duty cycle adjustment, the faulty arm A and the reconstruction unit k A have the same switching state. When the power switch of the lower arm of phase A conducts, the reconstruction unit k A is in the off state. At this time, the current of phase a1 of the permanent magnet motor mainly flows through the lower arm of phase A, and the reconstruction unit and the faulty switch tube connected to the faulty arm have the same switching signal; when the power switch of the upper arm of phase A needs to conduct, the reconstruction unit k A is in the on state. At this time, the current of phase a1 of the permanent magnet motor mainly flows through the upper arm of phase D. Finally, the function of the switch tube of the faulty arm is realized by the reconstruction unit and the non-faulty arm connected to the reconstruction unit.

[0113] Among them, the MCU transmits the adjusted duty cycle to the FPGA. In the FPGA, the duty cycle is compared with the carrier wave to obtain six PWM signals S for driving the six-phase half-bridge two-level inverter and three PWM signals for driving the reconstruction unitkA…C These PWM signals are processed by the CPLD to obtain switching signals for driving the six-phase half-bridge two-level inverter and the reconfiguration unit.

[0114] The fault-tolerant control strategy is as follows:

[0115] When it is diagnosed that one of the bridge arms in the six-phase half-bridge two-level inverter is a faulty bridge arm, the control circuit blocks the driving signal of the faulty bridge arm and keeps the topology reconfiguration unit connected to the faulty bridge arm conducting. One phase winding of the permanent magnet motor connected to the faulty bridge arm is connected to one of the non-faulty bridge arms through the topology reconfiguration unit, and the remaining five non-faulty bridge arms are used to control the two permanent magnet motors; the six-phase half-bridge two-level inverter is adjusted as follows:

[0116] Divide a control period T of the two-motor system S into two equal parts to obtain the front control period T1 and the rear control period T2. In the front control period T1, keep the switching duty ratios of the three bridge arms of the one-phase half-bridge two-level inverter where the faulty bridge arm is located unchanged, and adjust the switching duty ratios of the three bridge arms of the other one-phase half-bridge two-level inverter to be the same as the switching duty ratio δ f of the faulty bridge arm; in the rear control period T2, keep the switching duty ratios of the three bridge arms of the other one-phase half-bridge two-level inverter unchanged, and adjust the switching duty ratios of the three bridge arms of the one-phase half-bridge two-level inverter where the faulty bridge arm is located to be the same as the switching duty ratio δ h of a non-faulty bridge arm connected to the faulty bridge arm through a reconfiguration unit.

[0117] The duty ratios of each bridge arm in the six-phase half-bridge two-level inverter adjusted according to the fault-tolerant control strategy are compared with the carrier wave generated by the control circuit to obtain switching signals for driving the six-phase half-bridge two-level inverter and the topology reconfiguration device. After blocking the switching signals of the faulty bridge arms, the six-phase half-bridge two-level inverter and the topology reconfiguration device are controlled.

[0118] The specific embodiments of the present invention are as follows:

[0119] Drive the two-motor system to operate and perform real-time fault diagnosis on the open circuit of the power switching devices of the six-phase half-bridge two-level inverter of the two-motor system. Assume that the upper power switching device of the A-phase bridge arm connected to the a-phase winding of the first permanent magnet motor in the six-phase half-bridge two-level inverter has an open circuit fault, as follows:

[0120] 1.1) The control circuit calculates the actual rotor magnetic field position and actual speed of each permanent magnet motor according to the respective actual rotor positions measured by the position sensors of each permanent magnet motor, as follows:

[0121]

[0122]

[0123] Among them, θ e1 and ω r1 respectively represent the actual rotor magnetic field position and the actual rotational speed of the first permanent magnet motor, and θ e2 and ω r2 respectively represent the actual rotor magnetic field position and the actual rotational speed of the second permanent magnet motor; θ r1 and θ r2 respectively represent the actual rotor positions of the two permanent magnet motors; t represents the moment within a control period.

[0124] Meanwhile, the rotational speed deviation between the actual rotational speed and the preset reference rotational speed of each permanent magnet motor is calculated and obtained; the rotational speed deviation of each permanent magnet motor is input into its respective rotational speed loop PI controller, and after processing, the q-axis reference current of each permanent magnet motor is output, and the d-axis reference current is preset to 0; according to the actual rotor magnetic field position of each permanent magnet motor, the q-axis reference current and the d-axis reference current of each permanent magnet motor are successively subjected to inverse Park transformation and inverse Clark transformation to obtain the three-phase reference current of each permanent magnet motor, specifically as follows:

[0125]

[0126]

[0127] Among them, and respectively represent the a1-phase reference current, the b1-phase reference current, and the c1-phase reference current of the first permanent magnet motor; and respectively represent the a2-phase, b2-phase, and c2-phase reference currents of the second permanent magnet motor; and respectively represent the d-axis reference current and the q-axis reference current of the first permanent magnet motor; and respectively represent the d-axis reference current and the q-axis reference current of the second permanent magnet motor.

[0128] 1.2) The control circuit calculates and obtains the reference current modulus value of the permanent magnet motor according to the q-axis reference current and the d-axis reference current of each permanent magnet motor, and normalizes the three-phase reference current according to the reference current modulus value of each permanent magnet motor to obtain the three-phase normalized reference current of the permanent magnet motor, specifically as follows:

[0129]

[0130]

[0131] Among them, and respectively represent the reference current magnitude values of two permanent magnet motors; and respectively represent the normalized reference currents of phase a1, phase b1, and phase c1 of the first permanent magnet motor; and respectively represent the normalized reference currents of phase a2, phase b2, and phase c2 of the second permanent magnet motor.

[0132] 1.3) The control circuit obtains the three-phase actual currents of the two permanent magnet motors measured by six current sensors. According to the actual rotor magnetic field position of each permanent magnet motor, the three-phase actual currents of each permanent magnet motor are sequentially transformed by Clark transformation and Park transformation to obtain the q-axis actual current and d-axis actual current of each permanent magnet motor. The actual current magnitude of each permanent magnet motor is calculated based on the q-axis actual current and d-axis actual current of each permanent magnet motor. The three-phase actual currents of the permanent magnet motor are normalized based on the actual current magnitude of each permanent magnet motor to obtain the three-phase normalized actual currents of the permanent magnet motor, as follows:

[0133]

[0134]

[0135] where, |i s1 | and |i s2 | respectively represent the actual current magnitude values of the two permanent magnet motors; i na1 , i nb1 and i nc1 respectively represent the normalized actual currents of phase a1, phase b1, and phase c1 of the first permanent magnet motor; i na2 , i nb2 and i nc2 respectively represent the normalized actual currents of phase a2, phase b2, and phase c2 of the second permanent magnet motor.

[0136] 1.4) The control circuit calculates the three-phase normalized current deviation between the three-phase normalized reference current and the three-phase normalized actual current of each permanent magnet motor, as follows:

[0137]

[0138] where, |e na1 |, |e nb1 |, |e nc1 |, |e na2 |, |e nb2 | and |e nc2 | respectively represent the absolute values of the normalized current deviations of phase a1, phase b1, phase c1, phase a2, phase b2, and phase c2 of the two permanent magnet motors.

[0139] 1.5) The control circuit compares the magnitude of the absolute value of the three-phase normalized current deviation of each permanent magnet motor with a preset fault diagnosis threshold th. When the absolute value of the normalized current deviation of one phase of one of the permanent magnet motors is greater than the preset fault diagnosis threshold th for N consecutive control cycles, it is diagnosed that there is a fault in this phase of the permanent magnet motor, which is regarded as the motor fault phase. Furthermore, a fault in one arm of the six-phase half-bridge two-level inverter connected to the motor fault phase is determined as the fault arm; the values of N and th need to be pre-tuned. In specific implementation, the preset fault diagnosis threshold th is set to 0.1, and the value of N is set to 5;

[0140] 1.6) Locate the position of the faulty power switch device in the fault arm according to the polarity of the normalized current deviation of the fault phase. When the polarity of the normalized current deviation of the fault phase is positive, the faulty power switch device is the upper switch tube of the fault arm. When the polarity of the normalized current deviation of the fault phase is negative, the faulty power switch device is the lower switch tube of the fault arm. It is diagnosed that the upper power switch device in the A-phase arm connected to the a1-phase winding of the permanent magnet motor has an open-circuit fault. The a1-phase current of the permanent magnet motor is zero in the positive half-cycle of its reference current and can normally follow the reference current in the negative half-cycle of its reference current. Therefore, the a1-phase current deviation of the permanent magnet motor will increase in the positive half-cycle of the current and return to the normal level in the negative half-cycle.

[0141] As Figure 4 shown, diagnose the open-circuit fault of the power switch device in the arm of each phase according to the deviation between the actual current and the reference current of each phase of the permanent magnet motor. For example, after the upper switch of the A-phase of the three-phase half-bridge two-level inverter is open-circuited, the positive current cannot flow normally. Therefore, when the upper switch of the A-phase of the three-phase half-bridge two-level inverter needs to be turned on, the deviation between the A-phase reference current and the A-phase actual current is positive; similarly, after the lower switch of the A-phase of the three-phase half-bridge two-level inverter is open-circuited, the deviation between the A-phase reference current and the A-phase actual current is negative when the lower switch is turned on. After diagnosing the fault, the faulty device can be located based on this.

[0142] As Figure 5 shown, use the normal control strategy, the fault-tolerant reconfiguration control strategy, and the fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or a fault is diagnosed.

[0143] In this embodiment, to minimize the fault-tolerant reconfiguration control process and ensure the verification effect of the validity of the fault diagnosis result, the comparison value of the fault count value n d is selected as 2, and the value of CNT is the count value corresponding to one fundamental period of the phase current. In the control circuit, according to the control period T sDetermine the count value CNT based on the reference speed of the motor. The specific calculation formula is as follows:

[0144]

[0145] The normal control strategy is as follows:

[0146] For each permanent magnet motor in the two-motor system, the control circuit calculates the d-axis current deviation between the actual d-axis current and the reference d-axis current of the permanent magnet motor, and calculates the q-axis current deviation between the actual q-axis current and the reference q-axis current of the permanent magnet motor. The d-axis current deviation and the q-axis current deviation are respectively input into the d-axis current loop PI controller and the q-axis current loop PI controller. The d-axis current loop PI controller and the q-axis current loop PI controller respectively output the reference d-axis voltage and the reference q-axis voltage of the permanent magnet motor Set the reference d-axis currents of the two permanent magnet motors and to be 0.

[0147] For each permanent magnet motor in the two-motor system, the control circuit performs an inverse Park transformation on the reference d-axis voltage and the reference q-axis voltage according to the actual rotor magnetic field position of the permanent magnet motor, and respectively obtains the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor According to the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor, use the space vector pulse width modulation algorithm SVPWM to calculate the switching duty ratios of the three bridge arms of the three-phase half-bridge two-level inverter connected to the three-phase windings of the permanent magnet motor; the control circuit compares the switching duty ratios of the three bridge arms of each three-phase half-bridge two-level inverter with the carrier wave generated by itself to obtain the PWM signal S A…F Furthermore, drive the six-phase half-bridge two-level inverter to operate.

[0148] The fault-tolerant reconstruction control strategy is as follows:

[0149] Assume that the A-phase bridge arm in the six-phase half-bridge two-level inverter is diagnosed as a faulty bridge arm, and an open-circuit fault occurs in the upper power switching device of the A-phase bridge arm. The control circuit selects the smallest switching duty ratio among the switching duty ratios of the three bridge arms of each three-phase half-bridge two-level inverter obtained under the normal control strategy as the maximum adjustment value of the bridge arm duty ratio of the three-phase half-bridge two-level inverter, corresponding to half of the zero vector duty ratio; the maximum adjustment value of the bridge arm duty ratio of the three-phase half-bridge two-level inverter where the faulty bridge arm is located is used as the maximum fault adjustment value δ 1max , and the maximum adjustment value of the bridge arm duty ratio of the other three-phase half-bridge two-level inverter is used as the maximum non-fault adjustment value δ 2max , as follows:

[0150] δ 1max= max{δ A , δ B , δ C}

[0151] δ 2max = max{δ D , δ E , δ F}

[0152] Wherein, δ A , δ B , δ C , δ D , δ E , δ F respectively represent the switching duty cycles of phase A, phase B, phase C, phase D, phase E, and phase F of a six-phase half-bridge two-level inverter.

[0153] Calculate the difference between the switching duty cycle δ h of a non-faulty phase D bridge arm connected to the faulty phase A bridge arm through a reconstruction unit and the switching duty cycle δ f of the faulty bridge arm, and take their absolute values as the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs respectively, as follows:

[0154]

[0155] According to the magnitude relationship between the maximum fault adjustment value δ 1max , the maximum non-fault adjustment value δ 2max , the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs , adjust the six-phase half-bridge two-level inverter, as shown in Figure 3 below, specifically as follows:

[0156] Case 1: When the duty cycle difference δ d is greater than or equal to 0, there is no need to adjust the duty cycles of each bridge arm in the six-phase half-bridge two-level inverter.

[0157] Case 2: When the duty cycle difference δ d is less than 0 and the absolute value of the duty cycle difference δ dabs is less than or equal to the maximum fault adjustment value δ 1max , subtract the absolute value of the duty cycle difference δ f from the switching duty cycle δ dabs of the faulty bridge arm and the switching duty cycles of the other two bridge arms in a three-phase half-bridge two-level inverter where the faulty bridge arm is located, and take them as their respective switching duty cycles respectively, as follows:

[0158]

[0159] Among them, δ A ′, δ B ′, and δ C ′ respectively represent the switching duty cycles of the adjusted phase A, B, and C bridge arms.

[0160] At the same time, keep the switching duty cycles of the three bridge arms in another three-phase half-bridge two-level inverter unchanged.

[0161] Case 3: When the duty cycle difference δ d is less than 0, and at the same time the absolute value of the duty cycle difference δ dabs is greater than the maximum fault adjustment value δ 1max and less than or equal to the sum of the maximum fault adjustment value δ 1max and the non-fault maximum adjustment value δ 2max , subtract the maximum fault adjustment value δ f from the switching duty cycle δ 1max of the phase A fault bridge arm and the switching duty cycles of the phase B and C bridge arms respectively to be their respective switching duty cycles; add the difference between the absolute value of the duty cycle difference δ dabs and the maximum fault adjustment value δ 1max to the switching duty cycles of the phase C, D, and E bridge arms in another three-phase half-bridge two-level inverter respectively to be their respective switching duty cycles, specifically as follows:

[0162]

[0163] Among them, δ′ D , δ′ E , and δ′ F respectively represent the switching duty cycles of the adjusted phase D, E, and F bridge arms.

[0164] Case 4: When the duty cycle difference δ d is less than 0 and the absolute value of the duty cycle difference δ dabs is greater than the sum of the maximum fault adjustment value δ 1max and the non-fault maximum adjustment value δ 2max , subtract the maximum fault adjustment value δ f from the switching duty cycle δ 1max of the phase A fault bridge arm and the switching duty cycles of the phase B and C bridge arms respectively to be their respective switching duty cycles; add the non-fault maximum adjustment value δ 2max to the switching duty cycles of the phase C, D, and E bridge arms in another three-phase half-bridge two-level inverter respectively to be their respective switching duty cycles, specifically as follows:

[0165]

[0166] Determine the conduction mode of the topology reconstruction device according to the duty cycle of each arm in the six-phase half-bridge two-level inverter adjusted according to the above four cases. Specifically, the switching duty cycle δ of the faulty arm f and the switching signal of the faulty power switch device in the faulty arm are respectively used as the switching duty cycle and switching signal of the switch tube of the topology reconstruction unit connected to the faulty arm, so as to control the switch tube in the topology reconstruction unit.

[0167] The fault-tolerant control strategy is as follows:

[0168] When it is diagnosed that one of the arms in the six-phase half-bridge two-level inverter is a faulty arm, the control circuit blocks the drive signal of the faulty arm and keeps the topology reconstruction unit connected to the faulty arm conducting. Connect one phase winding of the permanent magnet motor connected to the faulty arm to one of the non-faulty arms through the topology reconstruction unit, and control the two permanent magnet motors through the remaining five non-faulty arms. Adjust the six-phase half-bridge two-level inverter as follows:

[0169] Divide a control period T of the two-motor system S into the first-stage control period T1 and the second-stage control period T2. In the first-stage control period T1, keep the switching duty cycles of the three arms of the one-phase half-bridge two-level inverter where the faulty arm is located unchanged, and adjust the switching duty cycles of the three arms of the other-phase half-bridge two-level inverter to be the same as the switching duty cycle δ of the faulty arm f ; In the second-stage control period T2, keep the switching duty cycles of the three arms of the other-phase half-bridge two-level inverter unchanged, and adjust the switching duty cycles of the three arms of the one-phase half-bridge two-level inverter where the faulty arm is located to be the same as the switching duty cycle δ of a non-faulty arm connected to the faulty arm through a reconstruction unit h ; Compare the duty cycle of each arm in the six-phase half-bridge two-level inverter adjusted according to the fault-tolerant control strategy with the carrier wave generated by the control circuit to obtain the switching signal for driving the six-phase half-bridge two-level inverter and the topology reconstruction device, and block the switching signal of the faulty arm therein, and then control the six-phase half-bridge two-level inverter and the topology reconstruction device.

[0170] To verify the effectiveness of the open-circuit fault-tolerant topology reconstruction control method for power switch devices of the two-motor system proposed in the present invention, a simulation model of the above-mentioned open-circuit fault-tolerant topology reconstruction device and control method for power switch devices of the two-motor system was built on the Matlab / Simulink platform. The detailed parameters of the permanent magnet synchronous motor used in the simulation are shown in Table 1.

[0171] Table 1 Motor parameters

[0172]

[0173] The calculation period T of the control algorithm in the simulation s is 200 μs, and the calculation period of the simulation model except the control algorithm is 2 μs. The reference speed of the permanent magnet motor 1 is 600 r / min, and the reference speed of the permanent magnet motor 2 is 300 r / min. The fault-tolerant reconfiguration control method proposed by the present invention is verified through the following three fault conditions.

[0174] It is defined that the fault bridge arm numbers 1 to 6 in the fault diagnosis result respectively correspond to the faults of the A arm to the F arm of the six-phase half-bridge two-level inverter, and the fault bridge arm number 0 represents no fault; it is defined that the fault device number 1 in the fault diagnosis result corresponds to the fault of the upper switch tube of the fault bridge arm, the fault device number 2 corresponds to the fault of the lower switch tube of the fault bridge arm, and the fault device number 0 represents no fault. It is defined that the control strategy flag 1 indicates the normal operation of the control strategy; the control strategy flag 2 indicates the operation of the fault-tolerant control strategy; the control strategy flag 3 indicates the operation of the fault-tolerant reconfiguration control strategy.

[0175] The first case is that an open-circuit fault of the power switch device on the upper arm of phase A in the six-phase half-bridge two-level inverter occurs in the positive half-cycle of the a1-phase current of motor 1. The current, speed, and torque waveforms of motor 1 and motor 2 before and after the fault are as Figure 6 shown; the system operation conditions are as Figure 7 shown. It can be seen from the current, speed, and torque of the two motors before and after the fault that the three-phase current of motor 1 has no large impact during the topology reconfiguration process, the torque and speed do not fluctuate significantly, and the fault of inverter 1 has no obvious impact on the operating state of motor 2. In this fault condition, the maximum speed drop of motor 1 during the reconfiguration process is 30 r / min, which is about 5% of the normal operating speed.

[0176] The second case is that an open-circuit fault of the power switch device on the upper arm of phase A in the six-phase half-bridge two-level inverter occurs in the negative half-cycle of the a1-phase current of motor 1. The current, speed, and torque waveforms of motor 1 and motor 2 before and after the fault are as Figure 8 shown; the system operation conditions are as Figure 9 shown. It can be seen from the current, speed, and torque of the two motors before and after the fault that the three-phase current of motor 1 has no large impact during the topology reconfiguration process, the torque and speed do not fluctuate significantly, and the fault of inverter 1 has no obvious impact on the operating state of motor 2. In this fault condition, the maximum speed drop of motor 1 during the reconfiguration process is 4 r / min, which is about 0.67% of the normal operating speed.

[0177] The third case is that the drive protection of the power switch device on the upper arm of phase A in the six-phase half-bridge two-level inverter occurs in the positive half-cycle of the a1-phase current of motor 1. The current, speed, and torque waveforms of motor 1 and motor 2 before and after the misdiagnosis are as Figure 10 shown; the system operation conditions are as Figure 11As shown in. From Figure 11 It can be seen that the misdiagnosis does not cause the system to enter the five-bridge-arm fault-tolerant mode of operation, which proves that the fault-tolerant reconstruction control strategy proposed in this chapter can effectively avoid the influence of misdiagnosis caused by drive protection and other reasons on the system operation performance.

[0178] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many variations without departing from the purpose of the present invention, and all of these are within the protection scope of the present invention.

Claims

1. A fault-tolerant topology reconfiguration control method for open-circuit faults of power switching devices in a two-motor system, characterized in that: The method includes the following steps: Step 1: Construct a two-motor system. The two-motor system includes two permanent magnet motors and a six-phase half-bridge two-level inverter. Drive the two-motor system to operate and perform real-time fault diagnosis on the open-circuit of the power switch devices of the six-phase half-bridge two-level inverter of the two-motor system. Step 2: Use the normal control strategy, fault-tolerant reconstruction control strategy, and fault-tolerant control strategy to control the two-motor system when the two-motor system is operating normally or a fault is diagnosed. In the above-mentioned Step 1, the two-motor system further includes a topology reconstruction device, a sampling circuit, a control circuit, a three-phase AC power supply, an uncontrolled rectifier bridge, and a bus capacitor. The three-phase AC power supply outputs three-phase alternating current with adjustable amplitude, which is rectified by the uncontrolled rectifier bridge and used as the input of the six-phase half-bridge two-level inverter. The bus capacitor is connected in parallel between the uncontrolled rectifier bridge and the six-phase half-bridge two-level inverter. The six-phase half-bridge two-level inverter is composed of the parallel connection of the DC sides of two three-phase half-bridge two-level inverters. Each three-phase half-bridge two-level inverter is connected to one of the permanent magnet motors respectively. The three bridge arms in each three-phase half-bridge two-level inverter are respectively connected to the three-phase windings of one of the permanent magnet motors. The A, B, and C bridge arms in the first three-phase half-bridge two-level inverter are respectively connected to the a1, b1, and c1 phase windings of the first permanent magnet motor, and the D, E, and F bridge arms in the second three-phase half-bridge two-level inverter are respectively connected to the a2, b2, and c2 phase windings of the second permanent magnet motor. Each bridge arm in the six-phase half-bridge two-level inverter is composed of an upper switch tube and a lower switch tube connected in series. The topology reconstruction device includes three topology reconstruction units, and the three topology reconstruction units are respectively connected across the corresponding phase bridge arms of the first three-phase half-bridge two-level inverter and the second three-phase half-bridge two-level inverter. Specifically, the first reconstruction unit k A is connected across the A-phase bridge arm of the first three-phase half-bridge two-level inverter and the D-phase bridge arm of the second three-phase half-bridge two-level inverter. The second reconstruction unit k B is connected across the B-phase bridge arm of the first three-phase half-bridge two-level inverter and the E-phase bridge arm of the second three-phase half-bridge two-level inverter. The third reconstruction unit k C is connected across the C-phase bridge arm of the first three-phase half-bridge two-level inverter and the F-phase bridge arm of the second three-phase half-bridge two-level inverter; In the first step described above, the sampling circuit includes a voltage and current sampling circuit and a rotor position sampling circuit. The voltage and current sampling circuit includes a voltage sensor and six current sensors, and the rotor position sampling circuit includes two position sensors. The voltage sensor is connected in parallel across the bus capacitor and is used to measure the DC bus voltage U of the bus capacitor dc and input it into the control circuit. The DC bus voltage U dc is the DC voltage at the input of the six-phase half-bridge two-level inverter; the six current sensors are respectively connected in series with the six-phase windings of the two permanent magnet motors and are used to measure the six-phase currents between the six bridge arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors and input them into the control circuit; the two position sensors are respectively coaxially connected to the rotors of the two permanent magnet motors and are used to measure the actual rotor positions of the two permanent magnet motors and input them into the control circuit; The control circuit calculates the duty ratios of the switching actions of the six-phase half-bridge two-level inverter and the three topology reconstruction unit switches based on the DC voltage at the input of the six-phase half-bridge two-level inverter, the six-phase currents of the two permanent magnet motors, and the position and speed of the rotors of the two permanent magnet motors fed back by the sampling circuit, and compares the duty ratios with the carrier wave generated by the control circuit itself to generate PWM signals to drive the six-phase half-bridge two-level inverter to independently control the two permanent magnet motors.

2. A fault-tolerant topology reconfiguration control method for open-circuit faults of power switching devices in a two-motor system according to claim 1, characterized in that: In the above-mentioned Step 1, the real-time fault diagnosis of the open-circuit of the power switch devices of the six-phase half-bridge two-level inverter of the two-motor system is as follows: 1.1) The control circuit calculates the actual rotor magnetic field position and actual speed of each permanent magnet motor according to the actual rotor position measured by the position sensor of each permanent magnet motor, and at the same time calculates the speed deviation between the actual speed and the preset reference speed of each permanent magnet motor. The speed deviation of each permanent magnet motor is input into the respective speed-loop PI controller for processing, and the q-axis reference current of each permanent magnet motor is output respectively. The d-axis reference current of each permanent magnet motor is a preset value. According to the actual rotor magnetic field position of each permanent magnet motor, the q-axis reference current and d-axis reference current of each permanent magnet motor are sequentially subjected to inverse Park transformation and inverse Clark transformation to obtain the three-phase reference current of each permanent magnet motor. 1.2) The control circuit calculates the reference current magnitude of each permanent magnet motor based on the q-axis reference current and d-axis reference current of each permanent magnet motor, and normalizes the three-phase reference current according to the reference current magnitude of each permanent magnet motor to obtain the three-phase normalized reference current of the permanent magnet motor; 1.3) The control circuit acquires the three-phase actual currents of the two permanent magnet motors measured by six current sensors. According to the actual rotor magnetic field position of each permanent magnet motor, the three-phase actual currents of each permanent magnet motor are sequentially transformed by Clark transformation and Park transformation to obtain the q-axis actual current and d-axis actual current of each permanent magnet motor. The actual current magnitude of each permanent magnet motor is calculated based on the q-axis actual current and d-axis actual current of each permanent magnet motor, and the three-phase actual currents of the permanent magnet motor are normalized according to the actual current magnitude of each permanent magnet motor to obtain the three-phase normalized actual current of the permanent magnet motor; 1.4) The control circuit calculates the three-phase normalized current deviation between the three-phase normalized reference current and the three-phase normalized actual current of each permanent magnet motor; 1.5) The control circuit compares the magnitude of the absolute value of the three-phase normalized current deviation of each permanent magnet motor with the preset fault diagnosis threshold th. When the absolute value of the three-phase normalized current deviation of one phase of one of the permanent magnet motors is continuously greater than the preset fault diagnosis threshold th for N control cycles, it is diagnosed that there is a fault in this phase of this permanent magnet motor, which is used as the motor fault phase, and then a bridge arm fault of the six-phase half-bridge two-level inverter connected to the motor fault phase is determined and used as the fault bridge arm; 1.6) Locate the position of the faulty power switch device in the fault bridge arm according to the polarity of the normalized current deviation of the fault phase. When the polarity of the normalized current deviation of the fault phase is positive, the faulty power switch device is the upper switch tube of the fault bridge arm. When the polarity of the normalized current deviation of the fault phase is negative, the faulty power switch device is the lower switch tube of the fault bridge arm.

3. A fault-tolerant topology reconfiguration control method for an open-circuit fault of a power switch device in a two-motor system according to claim 1, characterized in that: In the second step described above, the two-motor system is controlled by using the normal control strategy, fault-tolerant reconstruction control strategy, and fault-tolerant control strategy when the two-motor system is operating normally or has a fault. Specifically, the two-motor system is controlled by switching the control strategy under different bases of the two-motor system as follows: Basis 1: When no fault of the two-motor system is diagnosed or no fault is detected when switching back from the fault-tolerant reconstruction control strategy to the normal strategy, the two-motor system is controlled by the normal control strategy; Basis 2: When a fault of the two-motor system is diagnosed while the two-motor system is being controlled by the normal control strategy, the normal control strategy is switched to the fault-tolerant reconstruction control strategy to control the two-motor system; Basis 3: When the two-motor system is being controlled by the fault-tolerant reconstruction control strategy and condition 1 is satisfied, the fault-tolerant reconstruction control strategy is switched to the normal control strategy to control the two-motor system; Basis 4: When the two-motor system is being controlled by the fault-tolerant reconstruction control strategy and condition 1 is not satisfied, the fault-tolerant reconstruction control strategy is maintained to control the two-motor system; Basis 5: When the two-motor system is controlled by the fault-tolerant reconstruction control strategy and Condition 2 is satisfied, the fault-tolerant reconstruction control strategy is switched to the fault-tolerant control strategy to control the two-motor system; The specific condition 1 is the fault count value n of the two-motor system d is less than the first preset comparison value th Nd , and at the same time, the fault-phase current in the six-phase current between the six bridge arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors enters the range not affected by the fault, where the fault count value n d is the number of times the fault of the two-motor system is diagnosed; the specific condition 2 is that the fault count value n d is equal to the first preset comparison value th Nd ; At time 3, the fault diagnosis result of the two-motor system is verified by obtaining the timing count value cnt through timing counting; if no fault is detected in the two-motor system before the timing count value cnt reaches the second preset comparison value CNT, the timing count value cnt and the fault count value n d are cleared; if the two-motor system diagnoses the same fault as the previously diagnosed fault before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the fault-tolerant reconfiguration control strategy and the fault count value n d is incremented by 1; if a fault different from the previously diagnosed fault is diagnosed before the timing count value cnt reaches the second preset comparison value CNT, the normal control strategy is switched to the reconfiguration control strategy and the fault count value n d is reset to zero and starts counting again.

4. A fault-tolerant topology reconfiguration control method for open-circuit faults of power switching devices in a two-motor system according to claim 3, characterized in that: The range of the fault-free phase current among the six-phase currents between the six arms of the six-phase half-bridge two-level inverter and the three-phase windings of the two permanent magnet motors is as follows: Among them, i a1 , i b1 and i c1 respectively represent the currents between the A, B, and C arms of the first three-phase half-bridge two-level inverter and the a1, b1, and c1 phase windings of the first permanent magnet motor; i a2 , i b2 and i c2 respectively represent the currents between the D, E, and F arms of the second three-phase half-bridge two-level inverter and the a2, b2, and c2 phase windings of the second permanent magnet motor.

5. A fault-tolerant topology reconfiguration control method for an open-circuit fault of a power switch device in a two-motor system according to claim 1, characterized in that: The specific normal control strategy is as follows: For each permanent magnet motor of the two-motor system, the control circuit calculates the d-axis current deviation between the actual d-axis current and the reference d-axis current of the permanent magnet motor, and the control circuit calculates the q-axis current deviation between the actual q-axis current and the reference q-axis current of the permanent magnet motor. The d-axis current deviation and the q-axis current deviation are respectively input into the d-axis current loop PI controller and the q-axis current loop PI controller. The d-axis current loop PI controller and the q-axis current loop PI controller respectively output the reference d-axis voltage and the reference q-axis voltage of the permanent magnet motor; For each permanent magnet motor of the two-motor system, the control circuit performs an inverse Park transformation on the reference d-axis voltage and the reference q-axis voltage according to the actual rotor magnetic field position of the permanent magnet motor to respectively obtain the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor. According to the reference α-phase voltage and the reference β-phase voltage of the permanent magnet motor, the space vector pulse width modulation algorithm SVPWM is used to calculate the switching duty ratios of the three arms of the three-phase half-bridge two-level inverter connected to the three-phase windings of the permanent magnet motor; The control circuit compares the switching duty ratios of the three arms of each three-phase half-bridge two-level inverter with the carrier wave generated by itself to obtain a PWM signal and then drives the six-phase half-bridge two-level inverter to operate.

6. A fault-tolerant topology reconfiguration control method for open-circuit faults of power switch devices in a two-motor system according to claim 5, characterized in that: The specific fault-tolerant reconstruction control strategy is as follows: When one of the bridge arms in a six-phase half-bridge two-level inverter is diagnosed as a faulty bridge arm, the control circuit selects the smallest switching duty cycle among the switching duty cycles of the three bridge arms of each three-phase half-bridge two-level inverter obtained under the normal control strategy as the maximum adjustment value of the bridge arm duty cycle of the three-phase half-bridge two-level inverter. The maximum adjustment value of the bridge arm duty cycle of the three-phase half-bridge two-level inverter where the faulty bridge arm is located is used as the maximum fault adjustment value δ 1max , and the maximum adjustment value of the bridge arm duty cycle of the other three-phase half-bridge two-level inverter is used as the maximum non-fault adjustment value δ 2max ; Calculate the difference and its absolute value between the switching duty cycle δ h of a non-faulty bridge arm connected to the faulty bridge arm and the switching duty cycle δ f of the faulty bridge arm, and use them as the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs respectively; According to the maximum fault adjustment value δ 1max , the maximum non-fault adjustment value δ 2max , the duty cycle difference δ d and the absolute value of the duty cycle difference δ dabs , the six-phase half-bridge two-level inverter is adjusted according to the magnitude relationship among them as follows: Case 1: When the duty cycle difference δ d is greater than or equal to 0, there is no need to adjust the duty cycle of each arm in the six-phase half-bridge two-level inverter; Case 2: When the duty cycle difference δ d is less than 0, and the absolute value of the duty cycle difference δ dabs is less than or equal to the maximum fault adjustment value δ 1max , subtract the absolute value of the duty cycle difference δ f from the switching duty cycle δ of the faulty leg and the switching duty cycles of the other two legs in a three-phase half-bridge two-level inverter where the faulty leg is located, and then use them as their respective switching duty cycles; dabs ​ Keep the switching duty ratios of the three arms in the other three-phase half-bridge two-level inverter unchanged; Case 3: When the duty cycle difference δ d is less than 0, and at the same time the absolute value of the duty cycle difference δ dabs is greater than the maximum fault adjustment value δ 1max and less than or equal to the sum of the maximum fault adjustment value δ 1max and the non-fault maximum adjustment value δ 2max , the switching duty cycle δ f of the faulty arm and the switching duty cycles of the other two arms in a three-phase half-bridge two-level inverter where the faulty arm is located are each subtracted by the maximum fault adjustment value δ 1max and then used as their respective switching duty cycles; Add the absolute value of the duty cycle difference δ and the maximum fault adjustment value δ to the switching duty cycles of the three arms in another three-phase half-bridge two-level inverter, respectively, and use them as their respective switching duty cycles; dabs and the maximum fault adjustment value δ 1max after the difference, and use them as their respective switching duty cycles; Case 4: When the duty cycle difference δ d is less than 0 and the absolute value of the duty cycle difference δ dabs is greater than the maximum fault adjustment value δ 1max and the sum of the maximum non-fault adjustment value δ 2max the switching duty cycle δ of the faulty arm f and the switching duty cycles of the other two arms in a three-phase half-bridge two-level inverter where the faulty arm is located are each subtracted by the maximum fault adjustment value δ 1max and then used as their respective switching duty cycles; Add the non - fault maximum adjustment value δ to the switching duty ratios of the three arms in another three - phase half - bridge two - level inverter, respectively, and then use them as their respective switching duty ratios; 2max ​ Determine the conduction mode of the topology reconstruction device according to the duty cycle of each bridge arm in the six-phase half-bridge two-level inverter adjusted according to the above four cases. Specifically, the switching duty cycle δ f of the faulty bridge arm and the switching signal of the faulty power switching device in the faulty bridge arm are respectively used as the switching duty cycle and switching signal of the switching tube of the topology reconstruction unit connected to the faulty bridge arm, so as to control the switching tube in the topology reconstruction unit.

7. A fault-tolerant topology reconfiguration control method for open-circuit faults of power switching devices in a two-motor system according to claim 6, characterized in that: The specific fault-tolerant control strategy is as follows: When it is diagnosed that one of the arms in the six-phase half-bridge two-level inverter is a faulty arm, the control circuit blocks the drive signal of the faulty arm and keeps the topology reconstruction unit connected to the faulty arm conducting. One phase winding of the permanent magnet motor connected to the faulty arm is connected to one of the non-faulty arms through the topology reconstruction unit, and the two permanent magnet motors are controlled by the remaining five non-faulty arms; The six-phase half-bridge two-level inverter is adjusted as follows: Divide a control period T of the two-motor system S into a front-stage control period T1 and a rear-stage control period T2. In the front-stage control period T1, keep the switching duty ratios of the three arms of a phase half-bridge two-level inverter where the faulty arm is located unchanged, and adjust the switching duty ratios of the three arms of the other phase half-bridge two-level inverter to be the same as the switching duty ratio δ of the faulty arm f ; In the rear-stage control period T2, keep the switching duty ratios of the three arms of the other phase half-bridge two-level inverter unchanged, and adjust the switching duty ratios of the three arms of a phase half-bridge two-level inverter where the faulty arm is located to be the same as the switching duty ratio δ of a non-faulty arm connected to the faulty arm h ; The duty ratios of the arms in the six-phase half-bridge two-level inverter adjusted according to the fault-tolerant control strategy are compared with the carrier wave generated by the control circuit to obtain the switching signals for driving the six-phase half-bridge two-level inverter and the topology reconstruction device. After blocking the switching signals of the faulty arms, the six-phase half-bridge two-level inverter and the topology reconstruction device are controlled.

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