Open-circuit fault-tolerant control method and system for three-level open-winding permanent magnet synchronous motor

Abstract

The invention discloses an open-circuit fault-tolerant control method and system for a three-level open-winding permanent magnet synchronous motor, and the method comprises the steps: collecting a non-fault phase current and the rotating speed and position of a motor rotor when the three-level open-winding permanent magnet synchronous motor has an open-circuit fault; according to the collected current of the non-fault phase and the rotating speed and the position of the motor rotor, current prediction is carried out by considering the stator voltage of the fault phase on the basis of using an original motor mathematical model when a fault occurs; selecting a space voltage vector and a corresponding switching state in a rhombus modulation range according to a current prediction result; and torque ripple is reduced through a quadrature-axis current injection method so as to realize open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor. According to the method, the effects of the fault phase fundamental wave back electromotive force and the three-time back electromotive force are considered, the voltage vector selection process of the three-level converter is optimized, the current prediction precision can be improved, accurate tracking of stator current is achieved, motor torque pulsation is reduced, and motor noise is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet synchronous motor control, and in particular relates to an open-circuit fault-tolerant control method and system for a three-level open-winding permanent magnet synchronous motor. Background Art

[0002] For high-power, high-reliability motor systems, the high-power characteristics of the three-level converter and the strong fault-tolerant operation capability of the open-winding motor can be used to form a high-power three-level converter-open-winding motor system. After a phase failure occurs in a three-level-common DC bus open-winding permanent magnet motor, the remaining two normal phases can continue to work to generate electromagnetic torque. Due to the existence of zero-sequence path and third-order back-EMF harmonics, the motor output torque produces a large torque pulsation, which affects the safe and stable operation of the motor. In order to solve the problem of fault-tolerant operation and torque pulsation after phase failure, the traditional method reconstructs a new coordinate transformation through current reconstruction to achieve vector control. Without considering the third-order back-EMF harmonics, a relatively stable torque can be generated. However, the new coordinate transformation constructed by this method is relatively complex, the motor mathematical model established is more complex, and the torque pulsation cannot be effectively suppressed when the third-order back-EMF is large. Another method can use the model before the open-circuit fault for fault-tolerant control, but it does not consider the influence of the stator voltage of the faulty phase, resulting in poor current tracking accuracy, and there is still room for improvement in torque pulsation suppression. Summary of the invention

[0003] The technical problem to be solved by the present invention is as follows: In view of the above-mentioned problems in the prior art, a three-level open-winding permanent magnet synchronous motor open-circuit fault-tolerant control method and system are provided. The present invention aims to address the problem of a high-power three-level common DC bus open-winding permanent magnet synchronous motor system under the premise of a phase failure. Under the condition that the original motor mathematical model remains unchanged, the effects of the fundamental back-electromotive force and the tertiary back-electromotive force of the fault phase are taken into account and the voltage vector selection process of the three-level converter is optimized, so as to improve the current prediction accuracy, realize the precise tracking of the stator current, reduce the motor torque pulsation, and reduce the motor noise.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A three-level open-winding permanent magnet synchronous motor open-circuit fault-tolerant control method comprises the following steps: S1, when an open circuit fault occurs in any phase of the three-level open-winding permanent magnet synchronous motor, the non-fault phase current and the motor rotor speed and position are collected; S2, based on the collected non-fault phase current and the motor rotor speed and position, current prediction is performed by considering the stator voltage of the fault phase based on the original motor mathematical model when a fault occurs; S3, selecting a space voltage vector and a corresponding switch state within the diamond modulation range according to the current prediction result; S4, reducing torque ripple by quadrature-axis current injection to achieve open-loop fault-tolerant control of a three-level open-winding permanent magnet synchronous motor.

[0005] Optionally, step S2 includes: S2.1, calculate the estimated value of the AC and DC axis current at the next moment according to the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the AC and DC axis current slope when the zero voltage vector acts and the AC and DC axis current slope when two non-zero voltage vectors act in combination with the stator voltage of the fault phase; S2.2, according to the calculated AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act, the action time of each voltage vector is obtained: , , , In the above formula, is the action time of the zero voltage vector, is the sampling period, is the action time of the first non-zero voltage vector, is the action time of the second non-zero voltage vector, and are the reference values ​​of the AC and DC axis currents respectively, and are the estimated values ​​of the AC and DC axis currents at time k+1, and They are the AC and DC axis current slopes when the zero voltage vector acts, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, is the number of the first voltage vector selected, is the number of the second voltage vector selected, is an intermediate variable, and there are: ; S2.3, current prediction is performed according to the following formula: , In the above formula, and are the predicted values ​​of the AC and DC axis currents at time k+2, and They are the estimated values ​​of the AC and DC axis currents at time k+1 respectively.

[0006] Optionally, the function expression for determining the stator voltage of the faulty phase in step S2.1 is: , In the above formula, is the stator voltage of the fault phase, is the electrical angular velocity of the motor, is the permanent magnet flux, is the motor rotor position angle, is the tertiary flux linkage of the permanent magnet.

[0007] Optionally, in step S2.1, the function expressions for calculating the AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act in combination with the stator voltage of the faulty phase are: , , , In the above formula, and They are the AC and DC axis current slopes when the zero voltage vector acts, is the stator resistance, and are the AC and DC axis currents respectively, is the electrical angular velocity of the motor, is the stator voltage of the fault phase, is the permanent magnet flux, is the motor rotor position angle, and are the AC and DC axis inductances, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the components of the first selected voltage vector on the AC and DC axes, is the number of the first voltage vector selected, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, and are the components of the selected second voltage vector on the AC and DC axes, is the number of the second voltage vector selected.

[0008] Optionally, step S3 includes: S3.1, reconstructing the spatial voltage vector diagram of the three-level open-winding permanent magnet synchronous motor after an open-circuit fault occurs, and determining the switch state configuration with the least number of switching times in each small sector; S3.2, make a large sector judgment, traverse each large sector, predict the current through the large boundary vector, and determine the large sector by minimizing the preset cost function: S3.3, make a small sector judgment, traverse each small sector in the selected large sector, and select the selected vector according to the switch state configuration with the least number of switches in each small sector determined in S3.1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switch state.

[0009] Optionally, the function expression of the preset cost function is: , In the above formula, represents the preset cost function, and are the reference values ​​of the AC and DC axis currents respectively, and They are the predicted values ​​of the AC and DC axis currents at time k+2 respectively.

[0010] Optionally, when the torque ripple is reduced by a quadrature-axis current injection method in step S4 to achieve open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor, the function expression of the injected quadrature-axis current is: , In the above formula, is the injected quadrature-axis current, is the zero axis current, is the quadrature axis current, is the motor rotor position angle, is the motor electrical angular velocity, is the sampling period, is the tertiary flux of the permanent magnet, is the permanent magnet flux.

[0011] In addition, the present invention also provides a three-level-open-winding permanent magnet synchronous motor open-circuit fault-tolerant control system, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the three-level-open-winding permanent magnet synchronous motor open-circuit fault-tolerant control method.

[0012] In addition, the present invention also provides a computer-readable storage medium, which stores a computer program or instruction, and the computer program or instruction is programmed or configured to execute the open-circuit fault-tolerant control method of the three-level-open-winding permanent magnet synchronous motor through a processor.

[0013] In addition, the present invention also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the open-circuit fault-tolerant control method of the three-level-open-winding permanent magnet synchronous motor through a processor.

[0014] Compared with the prior art, the present invention mainly has the following advantages: the open-circuit fault-tolerant control method of the three-level open-winding permanent magnet synchronous motor of the present invention adopts a three-vector model prediction current control strategy after the motor has a phase failure. When the mathematical model of the motor remains unchanged, the influence of the opposite potential is considered, and the stator voltage of the fault phase is compensated in the control algorithm, which is equivalent to the opposite potential and the mutual inductance voltage acting together on the fault phase, so as to realize the decoupling control of the fault phase in the control process. In the model prediction current control with the unchanged mathematical model of the motor, the current tracking error caused by the coupling of the fault phase and the normal phase is eliminated, and the actual current of the motor is guaranteed to track the reference current through the injection of the quadrature axis current harmonics, thereby improving the torque pulsation suppression effect. The present invention reconstructs the voltage vector distribution of the three-level converters on both sides after the phase failure, and gives full play to the advantages of the three-level converter, realizes the five-level effect through the three-level converters on both sides, optimizes the voltage vector selection, performs voltage selection within the diamond modulation range, rather than just selecting within the regular hexagon range, utilizes all the voltage vectors, and configures the switching state of the voltage vector according to the principle of the minimum number of switching times, which greatly reduces the number of power device switching times. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the basic process of the present invention.

[0016] Figure 2 Schematic diagram of the open-winding motor control principle of the example method of the present invention.

[0017] Figure 3 Schematic diagram of the remaining normal phase space vector distribution of a three-level open-winding motor according to an example method of the present invention.

[0018] Figure 4 Schematic diagram of large sector division of normal phase space vector distribution in the example method of the present invention.

[0019] Figure 5 Schematic diagram of the first largest sector division of the normal phase space vector distribution of the example method of the present invention.

[0020] Figure 6 This is the motor output torque before and after considering the fault phase voltage in the example method of the present invention.

[0021] Figure 7 This is the Fourier analysis result of the motor output torque before considering the fault phase voltage in the example method of the present invention.

[0022] Figure 8 This is the Fourier analysis result of the motor output torque after considering the fault phase voltage in the example method of the present invention. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, the open-circuit fault-tolerant control method of the three-level open-winding permanent magnet synchronous motor in this embodiment includes the following steps: S1, when an open circuit fault occurs in any phase of the three-level open-winding permanent magnet synchronous motor, the non-fault phase current and the motor rotor speed and position are collected; S2, based on the collected non-fault phase current and the motor rotor speed and position, current prediction is performed by considering the stator voltage of the fault phase based on the original motor mathematical model when a fault occurs; S3, selecting a space voltage vector and a corresponding switch state within the diamond modulation range according to the current prediction result; S4, reducing torque ripple by quadrature-axis current injection to achieve open-loop fault-tolerant control of a three-level open-winding permanent magnet synchronous motor.

[0025] like Figure 2 As shown, the three-level open-winding permanent magnet synchronous motor of this embodiment is connected in a common DC bus mode, and each first end of the motor winding is connected to a set of three-level three-phase converters, and the two sets of converters share a DC power supply. Represents the motor direct-axis current, represents the motor quadrature axis current, Indicates the motor zero axis current, Indicates the direct axis current reference value, Indicates the quadrature axis current reference value, represents the injected harmonic current, S b1 , S c1 , S b2 , S c2Indicates the switching status of the two sets of windings of phases B and C. Compared with a normal motor, the open-winding motor opens the neutral point of the winding, providing a path for the zero-sequence current, so the tertiary magnetic flux of the motor will affect the operation of the motor. Since the three-phase windings of the open-winding motor are independent of each other, after a phase failure occurs, the faulty phase will not affect the remaining normal phases. Under the model prediction fault-tolerant control method considering the stator voltage of the faulty phase, this embodiment does not need to change the coordinate transformation and the mathematical model of the motor. The faulty phase voltage is considered under the original motor mathematical model to improve the current prediction accuracy, achieve accurate tracking of the stator current, improve the current control effect, and reduce the motor torque pulsation.

[0026] In step S1 of this embodiment, when collecting the non-fault phase current and the motor rotor speed and position, it is assumed that when phase a fails, the non-fault phases are phases b and c. In addition, the motor rotor speed and position are obtained by the motor encoder.

[0027] like Figure 3 As shown in the figure, the spatial voltage vector distribution of the converters on both sides under the motor phase failure is reconstructed, and the voltage vector selection method is optimized to utilize all voltage vectors. At the same time, the converter switching state is optimized to reduce the switching frequency as much as possible and reduce the number of power device switching times. In the figure, the N state represents the switching state of the four power devices as 0, 0, 1, 1, the O state represents the switching state as 0, 1, 1, 0, and the P state represents the switching state as 1, 1, 0, 0. For example, PN-OP represents that the B phase of the head-end converter is in the P state, the C phase is in the N state, and the B phase of the tail-end converter is in the O state and the C phase is in the P state.

[0028] When an open-winding motor has a phase failure (assuming that phase a fails), the output torque expression of the motor considering the third harmonic of the current is: , in, Represents the output torque of the motor, Indicates the number of motor pole pairs, Indicates the motor fundamental wave magnetic therapy, Represents the motor's tertiary flux, Represents the component of the motor fundamental current on the zero axis, is the motor rotor position. From the torque expression after phase failure, it can be seen that the torque pulsation is divided into two parts, namely the torque pulsation caused by the third-order zero-sequence current and the torque pulsation caused by the fundamental frequency zero-sequence component. This part of the torque pulsation has two forms, namely the second-order pulsation and the fourth-order pulsation. It can be seen that in order to suppress the torque pulsation, it is necessary to deal with this part of the torque pulsation.

[0029] , The torque expression of the open winding motor after phase failure can be derived by injecting a , the torque generated by this part of the injected current is used to offset the torque pulsation. The injection current size is as follows: , , Due to the one-shot delay of the controller, the injection current needs to be delayed to compensate. Considering that the control cycle is very short and It is the superposition of large DC flow and small AC flow, so it can be considered The amplitude of changes very little in a control cycle, and this part of the amplitude change has little effect on the motor control process, so the main consideration is the phase effect in the controller's one-shot delay. Therefore, the zero-sequence current correction in the injection current expression is: , Similarly, .

[0030] Model predictive control is designed based on the discretized mathematical model of the motor. In the synchronous rotating coordinate system, the current state equation of the open-winding motor is: , in represents the motor stator resistance, , , Respectively represent the quadrature, direct and zero axis inductances, , , Represent the quadrature, direct and zero axis voltages respectively. Assume the sampling period of the system is T s , discretize the above state equation to obtain the discretized current state equation: , Where k is the sampling period kT s The discrete value of k+1 is the sampling period (k+1)T s discrete value of .

[0031] In the actual control system, the motor-related information sampled at time k needs to go through a cycle of calculation and be issued at time k+1 to act on the motor. In predictive control, the voltage vector selected at time k is actually issued at time k+1, so it is necessary to compensate for one-beat delay in the control. The voltage vector acting at time k+1 is calculated based on the motor current and position information sampled at time k. It is necessary to calculate the predicted value of the current at time k+1 based on the voltage vector acting at time k, and calculate the voltage vector at time k+1 based on this predicted value. Taking into account the one-beat delay of the controller, the current sampling value at time k corresponds to the voltage value at time k-1. The above formula can be obtained by discretization: , Under normal operation of the open-winding motor, the AC-DQ axis current cannot affect the tertiary zero-sequence current due to the mutual decoupling of the AC-DQ axis and the zero axis. That is, under normal circumstances, the AC-DQ axis current control cannot affect the zero-sequence current. Therefore, under normal circumstances, additional zero-axis current control is required to suppress the zero-sequence current. In the case of a-phase fault, the zero axis (0 axis) and the AC-DQ axis are coupled with each other, so the AC-DQ axis current control will affect the zero-sequence current, and the degrees of freedom of current control are reduced to 2. At this time, only the AC-DQ axis current needs to be controlled. In addition: , In the model predictive current control, the action time of each voltage vector needs to be determined according to the voltage vector combination. Based on the current deadbeat control concept, three voltage vector predictive control is adopted in each control cycle. The predicted value of the AC-DC axis (DQ axis) current at the next moment is equal to the given value. The AC-DC axis (DQ axis) prediction formula is: , in, and are the predicted values ​​of the AC and DC axis currents at time k+2, and are the estimated values ​​of the AC and DC axis currents at time k+1, , , , , , It represents the slope of the direct-axis current when three voltage vectors act. , , represents the action time of the three voltage vectors, , is the reference value of the AC and DC axis current.

[0032] In this embodiment, step S2 includes: S2.1, calculate the estimated value of the AC and DC axis current at the next moment according to the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the AC and DC axis current slope when the zero voltage vector acts and the AC and DC axis current slope when two non-zero voltage vectors act in combination with the stator voltage of the fault phase; S2.2, according to the calculated AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act, the action time of each voltage vector is obtained: , , , In the above formula, is the action time of the zero voltage vector (U0), is the sampling period, is the first non-zero voltage vector (U i ) action time, is the second non-zero voltage vector (U j ) action time, and are the reference values ​​of the AC and DC axis currents respectively, and are the estimated AC and DC axis currents at time k+1, and They are the AC and DC axis current slopes when the zero voltage vector acts, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, is the number of the first voltage vector selected, is the number of the second voltage vector selected, is an intermediate variable, and there are: ; S2.3, based on the motor mathematical model in the discretized synchronous rotating coordinate system, considering the delay of a control cycle, the prediction formula of the AC and DC (dq) axis current is obtained. Based on the current deadbeat control concept, three-voltage vector prediction control is adopted in each control cycle, and the predicted value of the AC and DC axis current at the next moment is equal to the given value. Therefore, the current prediction is performed according to the following formula in this embodiment: , In the above formula, and are the predicted values ​​of the AC and DC axis currents at time k+2, and are the estimated values ​​of the direct and quadrature axis currents at time k+1 respectively. Substituting the above vectors and their corresponding times into the formula, the current can be predicted.

[0033] Since the mutual inductance voltage amplitude is very small, the influence on the control of the motor is very small and can be ignored. Therefore, the function expression for determining the stator voltage of the fault phase in step S2.1 of this embodiment is: , In the above formula, is the stator voltage of the fault phase, is the electrical angular velocity of the motor, is the permanent magnet flux, is the motor rotor position angle, is the tertiary flux of the permanent magnet. The influence of the stator voltage of phase A on the model prediction current control is calculated by Park and Clark transformation. Considering the stator voltage of the fault phase, the function expression of the AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act in step S2.1 of this embodiment is calculated in combination with the stator voltage of the fault phase: , , , In the above formula, and They are the AC and DC axis current slopes when the zero voltage vector acts, is the stator resistance, and are the AC and DC axis currents respectively, is the electrical angular velocity of the motor, is the stator voltage of the fault phase, is the permanent magnet flux, is the motor rotor position angle, and are the AC and DC axis inductances, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the components of the first selected voltage vector on the AC and DC axes, is the number of the first voltage vector selected, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, and are the components of the selected second voltage vector on the AC and DC axes, is the number of the second selected voltage vector. Based on the DC axis current slope under the action of the zero voltage vector, the DQ axis current slope under the action of the two selected voltage vectors is calculated. The action time of the three voltage vectors is calculated by the DC axis current slope when the zero vector and the two selected voltage vectors act respectively, and finally the optimal vector is selected to act on the motor through the current cost function.

[0034] In this embodiment, the selection rule of the voltage vector is as follows: the spatial voltage vector of the remaining two normal phases is divided into eight large sectors, each large sector is further divided into a number of small sectors, and the vector action sequence and switching state corresponding to each small sector are determined by the minimum switching frequency. First, by traversing the large vectors of each large sector, the large sector is determined according to the selected optimal large vector, and then all small sectors in the selected large sector are traversed to obtain the small sector where the optimal voltage vector is located, and the switching state and action time of the voltage vector are determined at the same time. Specifically, step S3 in this embodiment includes: S3.1, reconstructing the spatial voltage vector diagram of the three-level open-winding permanent magnet synchronous motor after an open-circuit fault occurs, and determining the switch state configuration with the least number of switching times in each small sector; S3.2, make a large sector judgment, traverse each large sector, predict the current through the large boundary vector, and determine the large sector by minimizing the preset cost function: S3.3, make a small sector judgment, traverse each small sector in the selected large sector, and select the selected vector according to the switch state configuration with the least number of switches in each small sector determined in S3.1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switch state.

[0035] In this embodiment, the function expression of the preset cost function is: , In the above formula, represents the preset cost function, and are the reference values ​​of the AC and DC axis currents respectively, and are the predicted values ​​of the AC and DC axis currents at time k+2 respectively. The phase voltage of the open-winding motor is generated by the converters on both sides. When the motor phase A fails, it no longer participates in the modulation of the motor voltage. At this time, the voltage vector of the motor is generated by phases B and C. The voltage vector diagram in the two-phase stationary coordinate system is as follows Figure 4As shown, the horizontal axis is the α axis and the vertical axis is the β axis. The voltage vector is divided into eight small sectors. When selecting a vector, firstly make a large sector judgment, traverse each large sector, select the large sector where the required voltage vector is located, and then traverse all the small sectors in the corresponding large sector. When the voltage vector combination that meets the requirements is obtained, the loop is exited. At the same time, the selected vector must meet the basic characteristics of the three-level converter. The switching state of each phase cannot be directly from N to P or from P to N.

[0036] On the basis of satisfying the cost function of minimum current error, the switch state is further configured according to the principle of minimum switching times of power devices. Taking the first sector as an example, the switch state corresponding to the voltage vector is configured. First, the first step is to determine the large sectors, traverse each large sector, and select the voltage vector as two large vectors (two red boundary vectors in the figure) in the first large sector. In order to reduce the number of switching times, it is selected to start and end with a zero vector. U1 is the first vector, U2 is the second vector, and the vectors are arranged as follows Figure 5, where Uref represents the reference voltage vector, and U1-U5 are the five non-zero vectors in the first large sector. The switch state corresponding to U1 is selected as ON-OP, and the switch state corresponding to U2 is selected as NN-PP. It is worth noting that this part of the calculation is only used to obtain the large sector where the voltage vector is located, and has no actual effect on the motor. After determining that the voltage vector is in the first large sector, traverse each small sector in the large sector. When the voltage vector is located in small sectors 1 and 2, select U3 as the first vector and U4 as the second vector, where the switch state corresponding to U3 is selected as ON-OO, and the switch state corresponding to U2 is selected as NN-OO. At this time, only two sets of power device switch states change during the cycle; when the voltage vector is located in small sector 3, select U4 as the first vector and U5 as the second vector, where the switch state corresponding to U4 is selected as NN-OO, and the switch state corresponding to U5 is selected as NN-OP. At this time, only three sets of power device switch states change during the cycle; when the voltage vector is located in small sector 4, select U3 as the first vector and U5 as the second vector, where the switch state corresponding to U3 is selected as ON-OO, The switch state corresponding to U5 is selected as NN-OP or ON-PP. At this time, only three sets of power device switch states change in the cycle; when the voltage vector is located in the 5th small sector, U5 is selected as the first vector and U2 is the second vector, wherein the switch state corresponding to U5 is selected as NN-OP or ON-PP, and the switch state corresponding to U2 is NN-PP. At this time, the switch states of four sets of power devices change in the cycle; when the voltage vector is located in the 6th small sector, U1 is selected as the first vector and U5 is the second vector, wherein the switch state corresponding to U1 is selected as ON-OP, and the switch state corresponding to U5 is NN-OP or ON-PP. At this time, only three sets of power device switch states change in the cycle. The switch states in the remaining sectors are similar. Through the above voltage vector selection optimization and corresponding switch state optimization, a maximum of 8+5=13 cycles can be executed in each cycle, which greatly reduces the calculation speed and improves the selection speed. At the same time, by utilizing the redundancy of the dual three-level converter, a voltage vector may correspond to multiple switch states. By optimizing the selection of the switch state, the number of switch switching is greatly reduced, and the switching frequency and loss are reduced.

[0037] In step S4 of this embodiment, when the torque ripple is reduced by the quadrature-axis current injection method to realize the open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor, the zero-axis current is obtained by coordinate transformation according to the S1 sampling current, and the harmonic current to be injected into the quadrature axis is obtained from the motor torque expression, and a cycle delay is considered. The function expression of the injected quadrature-axis current is: , In the above formula, is the injected quadrature-axis current, is the zero axis current, is the quadrature axis current, is the motor rotor position angle, is the motor electrical angular velocity, is the sampling period, is the tertiary flux of the permanent magnet, The above current is injected into the quadrature axis current reference value, and the torque generated by this part of the injected current is used to offset the torque ripple.

[0038] Figure 6 The simulation results of the motor output torque before and after considering the fault phase voltage in this example. The fault phase voltage was not considered before 0.2s, and the torque pulsation was large at this time; the fault phase voltage was considered from 0.2s onwards, and the motor torque pulsation was effectively suppressed. Figure 7 This is the Fourier analysis result of the motor output torque before considering the fault phase voltage in the example method of the present invention. Figure 8 This is the Fourier analysis result of the motor output torque after considering the fault phase voltage in the example method of the present invention. Figure 7 and Figure 8 It can be seen that after considering the fault phase voltage, the total harmonic distortion rate of the output torque is reduced and the motor torque pulsation is significantly suppressed.

[0039] In summary, the open-circuit fault-tolerant control method of the three-level open-winding permanent magnet synchronous motor in this embodiment adopts a three-vector model to predict the current control strategy after a phase failure occurs in the three-level common DC bus open-winding motor. When the mathematical model of the motor remains unchanged, the influence of the opposite potential and the mutual inductance voltage is considered, and the stator voltage of the fault phase is compensated in the control algorithm, which is equivalent to the opposite potential and the mutual inductance voltage acting together on the fault phase, thereby realizing decoupling control of the fault phase in the control process. In the model predictive current control with the unchanged mathematical model of the motor, the current tracking error caused by the stator voltage coupling of the fault phase is eliminated, and the accurate tracking of the stator current is realized by injecting the Q-axis current harmonics, thereby improving the torque pulsation suppression effect. The voltage vector distribution of the three-level converters on both sides after phase failure is reconstructed, and the advantages of the three-level converter are fully utilized. The five-level effect is achieved through the three-level converters on both sides, and the voltage vector selection is optimized. The voltage is selected within the diamond modulation range instead of just within the regular hexagon range. All voltage vectors are utilized. At the same time, the switching state of the voltage vector is configured according to the principle of minimum switching times, which greatly reduces the switching times of power devices.

[0040] In addition, this embodiment also provides a three-level-open-winding permanent magnet synchronous motor open-circuit fault-tolerant control system, including a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the three-level-open-winding permanent magnet synchronous motor open-circuit fault-tolerant control method.

[0041] This embodiment also provides a computer-readable storage medium, in which a computer program or instruction is stored. The computer program or instruction is programmed or configured to execute the open-circuit fault-tolerant control method of the three-level-open-winding permanent magnet synchronous motor through a processor.

[0042] This embodiment also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the open-circuit fault-tolerant control method of the three-level-open-winding permanent magnet synchronous motor through a processor.

[0043] Those skilled in the art should understand that the technical solutions provided by the embodiments of the present application may be in the form of methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0044] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A three-level open-winding permanent magnet synchronous motor open-circuit fault-tolerant control method, characterized in that: The steps include: S1, when an open circuit fault occurs in any phase of the three-level open-winding permanent magnet synchronous motor, the non-fault phase current and the motor rotor speed and position are collected; S2, based on the collected non-fault phase current and the motor rotor speed and position, current prediction is performed by considering the stator voltage of the fault phase based on the original motor mathematical model when a fault occurs; S3, selecting a space voltage vector and a corresponding switch state within the diamond modulation range according to the current prediction result; S4, reducing torque ripple by quadrature-axis current injection to achieve open-loop fault-tolerant control of a three-level open-winding permanent magnet synchronous motor.

2. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that: Step S2 includes: S2.1, calculate the estimated value of the AC and DC axis current at the next moment according to the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the AC and DC axis current slope when the zero voltage vector acts and the AC and DC axis current slope when two non-zero voltage vectors act in combination with the stator voltage of the fault phase; S2.2, according to the calculated AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act, the action time of each voltage vector is obtained: ， ， ， In the above formula, is the action time of the zero voltage vector, is the sampling period, is the action time of the first non-zero voltage vector, is the action time of the second non-zero voltage vector, and are the reference values ​​of the AC and DC axis currents respectively, and are the estimated values ​​of the AC and DC axis currents at time k+1, and They are the AC and DC axis current slopes when the zero voltage vector acts, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, is the number of the first voltage vector selected, is the number of the second voltage vector selected, is an intermediate variable, and there are: ； S2.3, current prediction is performed according to the following formula: ， In the above formula, and are the predicted values ​​of the AC and DC axis currents at time k+2, and They are the estimated values ​​of the AC and DC axis currents at time k+1 respectively.

3. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 2, characterized in that: The function expression for determining the stator voltage of the fault phase in step S2.1 is: ， In the above formula, is the stator voltage of the fault phase, is the electrical angular velocity of the motor, is the permanent magnet flux, is the motor rotor position angle, is the tertiary flux linkage of the permanent magnet.

4. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 2, characterized in that: In step S2.1, the function expressions for calculating the AC and DC axis current slopes when the zero voltage vector acts and the AC and DC axis current slopes when two non-zero voltage vectors act are combined with the stator voltage of the fault phase as follows: ， ， ， In the above formula, and They are the AC and DC axis current slopes when the zero voltage vector acts, is the stator resistance, and are the AC and DC axis currents respectively, is the electrical angular velocity of the motor, is the stator voltage of the fault phase, is the permanent magnet flux, is the motor rotor position angle, and are the AC and DC axis inductances, and are the AC and DC axis current slopes when the first non-zero voltage vector acts, and are the components of the first selected voltage vector on the AC and DC axes, is the number of the first voltage vector selected, and are the AC and DC axis current slopes when the second non-zero voltage vector acts, and are the components of the selected second voltage vector on the AC and DC axes, is the number of the second voltage vector selected.

5. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that: Step S3 includes: S3.1, reconstructing the spatial voltage vector diagram of the three-level open-winding permanent magnet synchronous motor after an open-circuit fault occurs, and determining the switch state configuration with the least number of switching times in each small sector; S3.2, make a large sector judgment, traverse each large sector, predict the current through the large boundary vector, and determine the large sector by minimizing the preset cost function: S3.3, make a small sector judgment, traverse each small sector in the selected large sector, and select the selected vector according to the switch state configuration with the least number of switches in each small sector determined in S3.

1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switch state.

6. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 5, characterized in that: The function expression of the preset cost function is: ， In the above formula, represents the preset cost function, and are the reference values ​​of the AC and DC axis currents respectively, and They are the predicted values ​​of the AC and DC axis currents at time k+2 respectively.

7. The open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that: When the torque ripple is reduced by the quadrature-axis current injection method in step S4 to realize the open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor, the function expression of the injected quadrature-axis current is: ， In the above formula, is the injected quadrature-axis current, is the zero axis current, is the quadrature axis current, is the motor rotor position angle, is the motor electrical angular velocity, is the sampling period, is the tertiary flux of the permanent magnet, is the permanent magnet flux.

8. A three-level open-winding permanent magnet synchronous motor open-circuit fault-tolerant control system, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program or instruction stored therein, characterized in that: The computer program or instruction is programmed or configured to execute the open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor as described in any one of claims 1 to 7 through a processor.

10. A computer program product comprising a computer program or instructions, characterized in that The computer program or instruction is programmed or configured to execute the open-circuit fault-tolerant control method of a three-level open-winding permanent magnet synchronous motor as described in any one of claims 1 to 7 through a processor.

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