A fault diagnosis-free fault-tolerant control method based on a dual three-phase permanent magnet synchronous motor

Abstract

The application discloses a fault diagnosis-free fault-tolerant control method based on a double three-phase permanent magnet synchronous motor, and belongs to the field of multi-phase motor fault-tolerant control. Specifically, a proportional resonant controller is used to control fundamental plane currents, so that the fundamental rotating magnetic motive force is kept constant before and after motor failure, and the motor is ensured to operate in a minimum copper loss mode; in the alpha1-beta1 and alpha2-beta2 planes corresponding to the two sets of three-phase windings, respectively, harmonic components in phase currents are extracted, and the harmonic components are controlled to be zero through a harmonic current controller; phase voltage commands output by the fundamental current controller and the harmonic current controller are added to obtain final phase voltage commands, and the final phase voltage commands are used to drive the motor to operate in a fault-tolerant mode after being subjected to carrier pulse width modulation. The application does not need a fault diagnosis link and does not change the system control structure, and can realize self-fault-tolerant operation under normal conditions, arbitrary single-phase or two-phase open-circuit failure and switch tube open-circuit failure, and can effectively suppress current harmonics under normal and fault conditions and torque pulsation caused by failure.

Description

Technical Field

[0001] This invention relates to fault-tolerant control technology for multiphase motors, specifically to a fault-tolerant control method for dual three-phase permanent magnet synchronous motors that eliminates the need for fault diagnosis. Background Technology

[0002] With the increasing demands for high reliability, high efficiency, high dynamic performance, and steady-state performance in drive systems from fields such as new energy vehicles and aerospace, the application of multiphase permanent magnet synchronous motors has attracted widespread attention. Among them, the dual three-phase permanent magnet synchronous motor, as a typical multiphase motor topology, has advantages such as strong fault tolerance and low torque ripple. It can achieve stable operation under fault conditions without adding extra hardware through fault-tolerant control strategies.

[0003] Traditional fault-tolerant control strategies typically perform fault diagnosis after a fault occurs before switching to the corresponding fault-tolerant control algorithm. However, accurate fault diagnosis requires a certain amount of time, during which the motor remains in a faulty state. If load changes occur during this period, the motor operating in a faulty state will struggle to achieve high dynamic response, and in severe cases, may even be damaged. Furthermore, the fault diagnosis process relies on sensor accuracy and algorithm precision, inevitably introducing the risk of misdiagnosis and increasing the probability of secondary motor failures. In addition, traditional fault-tolerant control algorithms require reconfiguration of the system control structure, significantly increasing system design complexity. To address these technical issues, researching fault-tolerant control strategies that do not require fault diagnosis is of great significance for further improving the fault-tolerant operation performance of motors and meeting the drive requirements of high-end equipment.

[0004] The main reason for the limited fault tolerance of motors is the strong coupling between the α-β fundamental frequency space and the xy harmonic frequency space after a fault. Their control is mutually restrictive and difficult to adjust independently. To avoid the coupling effect between the fundamental and harmonic frequencies after a fault, existing fault-tolerant control strategies that do not require fault diagnosis typically prioritize stable torque control in the fundamental frequency space and then focus on harmonic frequency space control. Specifically, these strategies can be divided into open-loop and closed-loop control of the xy harmonic frequency space. The open-loop control strategy eliminates the control effect of the xy harmonic frequency space, directly avoiding coupling interference between the fundamental and harmonic frequencies and achieving self-fault-tolerant operation. However, the faulty motor model is no longer symmetrical, generating additional third, fifth, and seventh harmonic currents. The aforementioned open-loop control strategy does not consider the adverse effects of these harmonic currents on system operating efficiency and control performance. The closed-loop control strategy achieves closed-loop control by reasonably configuring the reference value of the xy current after a fault, but this reference value configuration depends on obtaining the fault current angle, essentially still involving related diagnostic steps and requiring a certain amount of fault diagnosis time. Therefore, the fault-tolerant performance of the above xy closed-loop control strategy is still affected by diagnostic accuracy and diagnostic delay. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the aforementioned background technology by proposing a fault-tolerant control method for a dual three-phase permanent magnet synchronous motor that eliminates the need for fault diagnosis. This method employs the same control strategy under conditions of normal motor operation, phase open-circuit faults, and inverter power device (switching transistor) open-circuit faults. When a fault occurs, the motor can enter a self-fault-tolerant operating state without fault diagnosis, and it precisely suppresses the main harmonic currents (third, fifth, and seventh) caused by the fault, ensuring the motor operates with minimum copper loss. Furthermore, this method eliminates the need for any fault diagnosis components and does not require changes to the control system structure, effectively avoiding the adverse effects of diagnostic delays and fault misjudgments on control system performance. It can meet the requirements of drive systems for high reliability, high efficiency, and high dynamic performance.

[0006] To achieve the above-mentioned objectives, this invention employs the following technical solution: a fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis, comprising the following steps:

[0007] Step 1: Acquire the six-phase current of the dual three-phase permanent magnet synchronous motor, and map it to the α-β stationary coordinate system through vector space decoupling (VSD) transformation to obtain the feedback current. ;

[0008] Step 2: Transform the current reference value on the dq synchronous rotating coordinate system to the α-β stationary coordinate system, calculate the difference between the current and the feedback current, and input the result into the quasi-proportional resonant controller to generate the fundamental voltage command in the α-β coordinate system. ;

[0009] Step 3: The fundamental voltage command is inversely transformed using VSD to obtain the six-phase fundamental phase voltage command. , , , , , ;

[0010] Step 4: Transform the three-phase currents corresponding to the two sets of windings to the corresponding α1-β1 and α2-β2 stationary coordinate systems, respectively; then extract the third, fifth, and seventh harmonic currents, respectively; then, use a second-order generalized integrator and a positive and negative sequence calculation module to extract the positive and negative sequence components of each harmonic current; finally, use a dual PI controller to perform closed-loop suppression on the above positive and negative sequence components and generate corresponding harmonic voltage commands. , , , , , ;

[0011] Step 5: The six-phase fundamental phase voltage command is superimposed with the harmonic voltage command to generate the final phase voltage command, which is then used to drive the motor to achieve fault-tolerant operation without fault diagnosis after carrier pulse width modulation.

[0012] The present invention has the following beneficial effects:

[0013] 1. This invention eliminates the need for any fault diagnosis process, effectively avoiding the adverse effects of fault diagnosis delays and misjudgments on system control performance; at the same time, it eliminates the need to reconfigure the control system structure after a fault, reducing the design complexity of the control system.

[0014] 2. The quasi-proportional resonant controller designed in this invention can effectively ensure the consistency of the fundamental space current before and after a fault, guarantee the constant fundamental rotating magnetomotive force before and after a fault, achieve stable torque output of the motor under fault conditions, and ensure the continuity and stability of the drive system operation. Simultaneously, it ensures that the fundamental space current is unaffected by the fault, ensuring that the current always changes according to a sinusoidal law before and after a fault (including during a fault), without interruption or jumps, achieving true seamless transition; furthermore, it ensures that the fault does not affect the motor output torque, and the motor torque is always smoothly output from normal to faulty operation, thus achieving imperceptible switching under fault conditions. Therefore, if a fault occurs during dynamic operation, it will not affect the dynamic response of the motor current and torque, thereby ensuring that its dynamic performance is unaffected.

[0015] 3. By eliminating the control effect of the harmonic space under the traditional vector space decoupling framework, this invention fundamentally avoids the coupling interference between the fundamental space and the harmonic space after a fault. At the same time, it realizes the extraction and control of harmonic current in the α1-β1 and α2-β2 planes of the two sets of three-phase windings, suppresses harmonic current, improves the sinusoidality of the phase current under normal and fault conditions, effectively suppresses current harmonics, reduces harmonic losses, and improves system operating efficiency.

[0016] 4. The fault-tolerant control method without fault diagnosis proposed in this invention can ensure that the phase current amplitude is minimized under fault conditions, thereby achieving fault-tolerant operation with minimum copper loss.

[0017] 5. The fault-tolerant control method without fault diagnosis proposed in this invention has excellent universality and can be applied to the normal operation of dual three-phase permanent magnet motor drive systems, any single-phase or two-phase open-circuit faults, and self-fault-tolerant operation under switch tube open-circuit faults. It can fully meet the system's requirements for high reliability, high efficiency, and high dynamic performance. Attached Figure Description

[0018] Figure 1 This is a fault-tolerant control block diagram for a dual three-phase permanent magnet synchronous motor without fault diagnosis, according to an embodiment of the present invention.

[0019] Figure 2This is a block diagram of the harmonic current control structure according to an embodiment of the present invention;

[0020] Figure 3 The diagrams show the speed, torque, and current waveforms under the following conditions: phase A open circuit fault and phases A and F open circuit fault, respectively, according to an embodiment of the present invention. (a) represents phase A open circuit fault, and (b) represents phases A and F open circuit fault.

[0021] Figure 4 The figures are the torque and current waveforms under the following conditions: open circuit fault of the upper bridge arm switch tube of phase A, open circuit fault of the upper bridge arm of phase B and open circuit fault of the lower bridge arm of phase C in this embodiment of the invention. (a) is the open circuit fault of the upper bridge arm switch tube of phase A, and (b) is the open circuit fault of the upper bridge arm of phase B and the lower bridge arm of phase C.

[0022] Figure 5 The figures show the torque response waveforms under normal motor operation and phase A open circuit fault conditions according to an embodiment of the present invention, where (a) represents the normal operation condition and (b) represents the phase A open circuit fault condition.

[0023] Figure 6 The figure shows the torque response waveform of the motor under load step condition when the open circuit fault of phase A of the motor occurs in an embodiment of the present invention. (a) represents the load step condition when the load increases and (b) represents the load step condition when the load decreases. Detailed Implementation

[0024] The following will refer to the appendices in the embodiments of the present invention. Figures 1-6 The technical solutions in the embodiments of the present invention will be clearly and completely described herein. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0025] A fault-tolerant control method based on a dual three-phase permanent magnet synchronous motor without fault diagnosis includes the following steps:

[0026] Step 1: Use the Vector Space Decoupling (VSD) transformation matrix to transform the six-phase currents in the natural coordinate system to the α-β stationary coordinate system, resulting in:

[0027]

[0028] In the formula, , The current is in the α-β coordinate system; , , , , , It is a six-phase current;

[0029] Step 2: Use the Park inverse transformation matrix to convert the current reference value on the dq synchronous rotating coordinate system. Transforming to the α-β stationary coordinate system, we obtain:

[0030]

[0031] In the formula, , , This is the reference value for the current in the α-β coordinate system; , , This is the reference value for the current in the dq coordinate system; The rotor position angle; the current reference value With current feedback value The difference is then input into a quasi-proportional resonant controller. The transfer function of the quasi-proportional resonant controller is:

[0032]

[0033] In the formula, G QPR (s) is the transfer function of the quasi-proportional resonant controller; For proportional gain; The resonant coefficient; The cutoff frequency; The resonant frequency is set to the fundamental angular frequency of the motor. The quasi-proportional resonant controller generates the fundamental voltage command. The current in the α-β coordinate system before and after the motor fault is equal, ensuring that the fundamental rotating magnetomotive force of the motor remains constant before and after the fault, and effectively ensuring that the motor operates in a fault-tolerant mode with minimum copper loss. Taking an open-circuit fault in phase A as an example, its fault-tolerant current satisfies the following relationship:

[0034]

[0035] In the formula, i f B i f C i f D i f E and i f F These are the fault-tolerant currents for phases B, C, D, E, and F, respectively. The implementation process of the steps is as follows: Figure 1 The fundamental current control module is shown in the diagram.

[0036] Step 3, transmit the fundamental voltage command signal After VSD inverse transformation, the six-phase fundamental phase voltage command is obtained as follows:

[0037]

[0038] In the formula, , , , , , This is a six-phase voltage command; , Voltage command in the α-β coordinate system;

[0039] Step 4: Harmonic current extraction and suppression are performed on the two sets of three-phase windings respectively. The Clarke transformation matrix is ​​used to transform the ABC three-phase currents to the α1-β1 stationary coordinate system, resulting in:

[0040]

[0041] In the formula, , , Let be the current in the α1-β1 coordinate system; , , , For three-phase currents A, B, and C; based on Figure 2 The harmonic current control method shown first uses subtraction from The third, fifth, and seventh harmonic currents are separated from the sample; then, the precise third, fifth, and seventh harmonic components, as well as the quadrature components of each harmonic current, are extracted using a second-order generalized integrator (SOGI); finally, the positive and negative sequence components of each harmonic are obtained by arithmetic operations on the above harmonic components, i.e.:

[0042]

[0043]

[0044] In the formula, h represents the harmonic order 3, 5, or 7; It is a phase shift operator with a 90° lag; , , The positive sequence component of the h-th harmonic in the α1-β1 coordinate system; , , The negative-sequence component of the h-th harmonic in the α1-β1 coordinate system is given. The positive and negative-sequence components of the h-th harmonic are then transformed into positive and negative-sequence DC components in each harmonic plane. Finally, the difference between zero and these DC positive and negative-sequence components is input into a PI controller to obtain the corresponding positive and negative-sequence DC voltages in the third, fifth, and seventh harmonic planes. These are then converted into positive and negative-sequence AC voltages in the α1-β1 plane, and these positive and negative-sequence AC voltages are superimposed to obtain the third, fifth, and seventh harmonic voltage commands in the α1-β1 plane. , , After adding these signals together and transforming them to the ABC natural coordinate system, the harmonic voltage command for the first set of three-phase windings can be obtained as follows:

[0045]

[0046] In the formula, , , , This refers to the harmonic voltage command for phases ABC; , , The voltage command is in the α1-β1 coordinate system; through the same operation described above, the harmonic voltage command for the second set of three-phase windings can be obtained as follows:

[0047]

[0048] In the formula, , , , This is the harmonic voltage command for the DEF phase; , , The voltage command is in the α2-β2 coordinate system; the overall implementation process of the steps is as follows: Figure 1 The harmonic current control module and Figure 2 The block diagram of the harmonic current control structure is shown below;

[0049] Step 5: The six-phase fundamental phase voltage command is superimposed with the harmonic voltage command to generate the final phase voltage command, which is then used to drive the motor to achieve fault-tolerant operation without fault diagnosis after carrier pulse width modulation.

[0050] The overall control block diagram of the fault-tolerant control method for dual three-phase permanent magnet synchronous motors proposed in this invention is as follows: Figure 1As shown. First, a quasi-proportional resonant controller is used to control the α-β fundamental current to ensure that the fundamental rotating magnetomotive force remains constant before and after a motor fault, and to ensure that the motor operates in a fault-tolerant mode with minimum copper loss. Then, in the α1-β1 and α2-β2 planes corresponding to the two sets of windings, the harmonic components in the phase current are extracted respectively, and a harmonic current controller is used to suppress them to zero, as shown. Figure 2 As shown. Finally, the phase voltage commands output by the fundamental current controller and the harmonic current controller are superimposed to obtain the final phase voltage command, which is then modulated by carrier pulse width to drive the motor to run stably.

[0051] Figure 3 The figures show the speed, torque, and current waveforms under A-phase open-circuit fault and A-phase / F-phase open-circuit fault conditions provided in this embodiment of the invention. As can be seen from the figures, regardless of whether the motor experiences a single-phase open-circuit fault or a two-phase open-circuit fault, its speed and torque waveforms show no significant pulsation and are consistent with normal conditions. The current waveform also exhibits good sinusoidal characteristics. Therefore, the fault-tolerant control strategy proposed in this invention enables the motor to instantly enter a self-fault-tolerant operating state after a phase open-circuit fault occurs, without the need for fault diagnosis. Figure 4 The figures show torque and current waveforms under the following conditions: fault in the upper bridge arm of phase A, and faults in the upper bridge arm of phase B and the lower bridge arm of phase C, as provided in this embodiment of the invention. As can be seen from the figures, regardless of whether the motor experiences a single switch failure or a failure in both switches, the torque waveform shows no significant pulsation and remains consistent with normal conditions. This demonstrates that the fault-tolerant control strategy proposed in this invention can enable the motor to quickly enter a self-fault-tolerant operating state without fault diagnosis after an open-circuit fault occurs in the switch. Figure 5 The figure shows the torque response waveforms under normal motor operation and phase A open circuit fault conditions provided in this embodiment of the invention. As can be seen from the figure, the response time for the torque to jump from 3 N·m to 6 N·m under normal operating conditions is 2.1 ms, and the response time under fault-tolerant operating conditions is also 2.1 ms, indicating that the fault-tolerant control strategy proposed in this invention ensures the same dynamic performance before and after the fault. Figure 6 The figure shows the torque response waveform of a motor with an open-circuit fault in phase A under a step load condition, as provided in an embodiment of the present invention. As can be seen from the figure, the torque response time is 2.1 ms when the open-circuit fault in phase A occurs under an upward step load condition, and 1.9 ms when the fault occurs under a downward step load condition. This demonstrates that the fault-tolerant control strategy proposed in this invention ensures high dynamic response performance during the fault occurrence period.

[0052] As described above, the fault-tolerant control method for a dual three-phase permanent magnet synchronous motor proposed in this invention can quickly enable the motor to enter a self-fault-tolerant operating state after a fault occurs and effectively suppress the harmonic current caused by the fault. At the same time, this method does not require any fault diagnosis link and does not require any change to the original control structure of the system, effectively avoiding the adverse effects of fault diagnosis delay and fault misjudgment on the system control performance, and can meet the requirements of the drive system for high reliability, high efficiency and high dynamic performance.

[0053] While the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the invention. Any equivalent changes or modifications made without departing from the spirit and scope of the invention are within the scope of protection defined by the appended claims.

Claims

1. A fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis, characterized in that, Includes the following steps: Step 1: Acquire the six-phase current of the dual three-phase permanent magnet synchronous motor, and map it to the α-β stationary coordinate system through vector space decoupling transformation to obtain the feedback current. ; Step 2: Transform the current reference value on the dq synchronous rotating coordinate system to the α-β stationary coordinate system, calculate the difference between the current and the feedback current, and input the result into the quasi-proportional resonant controller to generate the fundamental voltage command in the α-β coordinate system. ; Step 3: The fundamental voltage command is decoupled and inversely transformed in vector space to obtain the six-phase fundamental phase voltage command. , , , , , ; Step 4: Transform the three-phase currents corresponding to the two sets of windings to the corresponding α1-β1 and α2-β2 stationary coordinate systems, respectively; then extract the third, fifth, and seventh harmonic currents, respectively; then, use a second-order generalized integrator and a positive and negative sequence calculation module to extract the positive and negative sequence components of each harmonic current; finally, use a dual PI controller to perform closed-loop suppression on the above positive and negative sequence components and generate corresponding harmonic voltage commands. , , , , , ; Step 5: The six-phase fundamental phase voltage command is superimposed with the harmonic voltage command to generate the final phase voltage command, which is then used to drive the motor to achieve fault-tolerant operation without fault diagnosis after carrier pulse width modulation.

2. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, The specific process of step 1 is as follows: By using a vector space decoupling transformation matrix to transform the six-phase currents in the natural coordinate system to the α-β stationary coordinate system, we obtain: ； In the formula, , The current is in the α-β coordinate system; , , , , , It is a six-phase current.

3. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, The specific process of step 2 is as follows: The Park inverse transformation matrix is ​​used to transform the current reference value in the dq synchronous rotating coordinate system. Transforming to the α-β stationary coordinate system, we obtain: ； In the formula, , , This is the reference value for the current in the α-β coordinate system; , , This is the reference value for the current in the dq coordinate system; The rotor position angle; the current reference value With current feedback value The difference is then input into a quasi-proportional resonant controller. The transfer function of the quasi-proportional resonant controller is: ； In the formula, G QPR (s) is the transfer function of the quasi-proportional resonant controller; For proportional gain; The resonant coefficient; The cutoff frequency; The resonant frequency is set to the fundamental angular frequency of the motor. ; The quasi-proportional resonant controller generates a fundamental voltage command. The current in the α-β coordinate system before and after the motor fault is equal, ensuring that the fundamental rotating magnetomotive force of the motor remains constant before and after the fault, and effectively ensuring that the motor operates in a fault-tolerant mode with minimum copper loss. Taking an open-circuit fault in phase A as an example, its fault-tolerant current satisfies the following relationship: ； In the formula, i f B i f C i f D i f E and i f F These are the fault-tolerant currents for phases B, C, D, E, and F, respectively. .

4. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, The specific process of step 3 is as follows: fundamental voltage command After vector space decoupling and inverse transformation, the six-phase fundamental phase voltage command is obtained as follows: ； In the formula, , , , , , This is a six-phase voltage command; , This refers to the voltage command in the α-β coordinate system.

5. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, The specific process of step 4 is as follows: Step 4.1: Use the Clarke transformation matrix to transform the three-phase currents ABC to the α1-β1 stationary coordinate system, and obtain: ； In the formula, , , Let be the current in the α1-β1 coordinate system; , , , The currents are for the three phases A, B, and C. Step 4.2: Use subtraction from The third, fifth, and seventh harmonic currents are separated from the current; then, the precise third, fifth, and seventh harmonic components, as well as the orthogonal components of each harmonic current, are extracted by a second-order generalized integrator. Step 4.3: Obtain the positive and negative sequence components of each harmonic by performing arithmetic operations on the above harmonic components, that is: ， ； In the formula, h represents the harmonic order 3, 5, or 7; It is a phase shift operator with a 90° lag; , , The positive sequence component of the h-th harmonic in the α1-β1 coordinate system; , , The negative sequence component of the h-th order harmonic in the α1-β1 coordinate system is given; and the positive and negative sequence components of the above h-th order harmonic are transformed into positive and negative sequence DC components of each harmonic plane. Step 4.4: Input the difference between zero and the positive and negative sequence DC components of each harmonic plane into the PI controller to obtain the corresponding positive and negative sequence DC voltages of the third, fifth, and seventh harmonic planes. Convert these voltages to positive and negative sequence AC voltages of the α1-β1 plane, and then superimpose these positive and negative sequence AC voltages to obtain the command for the α1-β1 plane. , , After adding these signals together, and further transforming them to the ABC natural coordinate system, the harmonic voltage command for the first set of three-phase windings is obtained as follows: ； In the formula, , , , This refers to the harmonic voltage command for phases ABC; , , The voltage command is in the α1-β1 coordinate system; Step 4.5: Through the same operation described above, the harmonic voltage command for the second set of three-phase windings is obtained as follows: ； In the formula, , , , This is the harmonic voltage command for the DEF phase; , , The voltage command is in the α2-β2 coordinate system.

6. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, The control method is applicable to both single-phase and two-phase open-circuit faults in dual three-phase permanent magnet synchronous motors and to self-fault-tolerant operation under open-circuit faults of switching transistors.

7. The fault-tolerant control method for a dual three-phase permanent magnet synchronous motor without fault diagnosis according to claim 1, characterized in that, Steps 1-5 are also applicable to the normal operation of dual three-phase permanent magnet synchronous motors.

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