Diagnosis-free self-fault-tolerant control method for dual three-phase permanent magnet synchronous motor

Abstract

The invention discloses a diagnosis-free self-fault-tolerant control method for dual three-phase permanent magnet synchronous motors, and relates to the technical field of motor fault-tolerant control. Six-phase current is sampled, d-axis current, q-axis current, xy-axis current and y-axis current are obtained based on a VSD decoupling transformation theory, when the motor is in a normal state, d-axis current given values, x-axis current given values and y-axis current given values are set to be 0, closed-loop control is conducted through a current loop PI controller, a q-axis current given value is given through output of a speed loop PI controller, and after a phase-loss fault occurs, the motor is controlled to be in a closed-loop mode. A fault-tolerant operation state is switched by reducing the degree of freedom of motor control, a second harmonic of q-axis current is extracted by adopting a high-order generalized integrator, a given value is set to be 0, a quasi-proportional resonance controller is used for controlling, and output is compensated to q-axis voltage as a feed-forward quantity. Conflicts between controllers are avoided by reducing the degree of freedom of motor control, secondary harmonics of q-axis current are suppressed in a mode of performing feed-forward compensation in combination with HOGI and QPR controllers, and the torque quality after a fault is improved.

Description

Technical Field

[0001] This invention relates to the field of fault-tolerant control technology for motors, specifically a diagnostic-free self-fault-tolerant control method for dual three-phase permanent magnet synchronous motors. Background Technology

[0002] Compared to traditional three-phase motors, dual three-phase permanent magnet synchronous motors have an increased number of phases, making it easier to achieve low-voltage, high-power operation, thereby reducing the voltage level of power devices and offering broad application prospects. Another major advantage of dual three-phase permanent magnet synchronous motors is their strong fault tolerance for phase loss faults. Without adding hardware redundancy, simply by configuring a reasonable software fault-tolerant control strategy, the torque output quality after a phase loss fault can be effectively improved.

[0003] However, the fault-tolerant control methods differ depending on the location and number of faulty phases. Therefore, fault-tolerant control strategies for dual three-phase permanent magnet synchronous motors typically rely on accurate fault diagnosis and location technology. Chinese invention patent CN110838808B discloses a self-repair method for open-circuit faults in a dual three-phase permanent magnet synchronous motor drive system, which optimizes the harmonic subspace current reference through deadbeat control to release the self-fault-tolerant capability of the dual three-phase permanent magnet synchronous motor. However, it requires real-time calculation of the phase and amplitude information of the x and y axis currents, increasing the complexity of the control algorithm and the computational burden on the main control chip.

[0004] To address this problem, this invention proposes a fault-tolerant strategy that actively reduces the degree of control freedom to simplify the diagnostic-free self-fault-tolerant control process. In addition, when a phase loss fault occurs in a dual three-phase permanent magnet synchronous motor, a large secondary torque pulsation will be generated. By suppressing the secondary torque pulsation, a torque output capability similar to that under normal conditions can be obtained. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a diagnostic-free, self-fault-tolerant control method for dual three-phase permanent magnet synchronous motors. This method avoids conflicts between controllers by reducing the motor's control degrees of freedom, and suppresses the second harmonic of the q-axis current by combining HOGI and QPR controllers for feedforward compensation, thereby improving torque quality after a fault.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor, comprising the following steps:

[0007] Step 1: Sample the six-phase current of the dual three-phase permanent magnet synchronous motor using six current sensors;

[0008] Step 2: Based on the VSD decoupling transformation theory, perform static coordinate transformation and rotating coordinate transformation on the collected six-phase currents to obtain the d-axis current i. d and q-axis current i qand x-axis current i x and y-axis current i y ;

[0009] Step 3: D-axis current setpoint under normal motor conditions x-axis current setpoint and y-axis current setpoint Set to 0, and then perform closed-loop control by the current loop PI controller, with the q-axis current setpoint... The speed is given by the output of the speed loop PI controller;

[0010] Step 4: After a phase loss fault occurs in any phase of the motor, the motor control degrees of freedom are reduced to switch to fault-tolerant operation. The harmonic subspace current closed loop is canceled, and the voltage reference value of the harmonic subspace is adjusted. and Set to 0;

[0011] Step 5: When the motor is in fault-tolerant operation, a high-order generalized integrator is used to extract the second harmonic i of the q-axis current. q2 Set the second harmonic value of the q-axis current. When set to 0, it is controlled by a quasi-proportional resonant controller, and the output is the q-axis voltage compensation quantity u. q2 Feedforward compensation to q-axis voltage u q The second harmonic of the q-axis current i q2 To suppress.

[0012] Furthermore, in step two, the formula for the static coordinate transformation of the six-phase current is as follows:

[0013]

[0014] In the formula, I A I B I C I D I E and I F These represent the currents in each phase, i α i β i x i y i o1 and i o2 These represent the currents along each axis in the transformed stationary coordinate system.

[0015] Furthermore, in step two, the formula for the rotation coordinate transformation is as follows:

[0016]

[0017] In the formula, θ e It is an electrical angle.

[0018] Furthermore, in step three, the motor speed setpoint... The difference between the actual motor speed n and the given speed is input to the speed loop PI controller. The output of the speed loop PI controller is the q-axis current setpoint. .

[0019] Furthermore, in step five, the second harmonic of the q-axis current under a phase loss fault is obtained through a high-order generalized integrator, and its transfer function is:

[0020]

[0021] In the formula, K1 and K2 are gain coefficients, and ω c The center frequency.

[0022] Furthermore, in step five, a quasi-proportional resonant controller is used to suppress the second harmonic, and its transfer function is:

[0023]

[0024] In the formula, K P K is the time constant of the proportional part. I ω is the resonance coefficient, and ω0 is the passband bandwidth.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention takes into account the problem that existing fault-tolerant control strategies typically require complex fault diagnosis and location steps, increasing computational burden and negatively impacting system reliability. First, it reduces the control degrees of freedom of the motor control system after a phase loss, avoiding control conflicts between the two sets of current controllers. Second, addressing the issue of torque ripple caused by the second harmonic of the q-axis current after a fault, it uses a feedforward compensation method combining a high-order generalized integrator and a quasi-proportional resonant controller to suppress the second harmonic of the q-axis current, thereby improving the torque quality after a fault. This invention can omit the phase loss fault location step, simplify the control algorithm, and is easy to implement in engineering. It has the advantages of requiring no complex fault diagnosis and location, low computational load, no change to the system control framework, and high reliability. Attached Figure Description

[0026] Figure 1 This is an overall control block diagram of the method of the present invention;

[0027] Figure 2 This is a control block diagram of the second harmonic suppression stage of the q-axis current in the method of the present invention;

[0028] Figure 3 It refers to the electromagnetic torque output by the motors before and after the fault-tolerant control when a phase loss fault occurs in phase F in Example 1;

[0029] Figure 4It refers to the electromagnetic torque output by the motors before and after the fault-tolerant control when a phase A failure occurs in Example 2. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] To reduce the complexity of fault-tolerant control algorithms, this invention aims to eliminate complex phase loss fault location steps, thereby forming a unified fault-tolerant control strategy that is easy to implement. Furthermore, theoretical derivation shows that when a single-phase loss fault occurs, the motor will experience secondary torque pulsation, the root cause of which is the second harmonic in the q-axis current. By suppressing this harmonic, the torque quality under fault-tolerant control conditions can theoretically be further improved.

[0032] like Figures 1-2 As shown, a diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor is presented, and its overall control block diagram is combined with... Figure 1 As shown, it includes the following steps:

[0033] Step 1: Sample the six-phase current of the dual three-phase permanent magnet synchronous motor using six current sensors.

[0034] Step 2: Based on the VSD decoupling transformation theory, perform static coordinate transformation and rotating coordinate transformation on the collected six-phase currents to obtain the d-axis current i in the dq subspace. d and q-axis current i q and the x-axis current i in the harmonic subspace x and y-axis current i y The transformation of the six-phase current coordinates to the stationary coordinate system is shown in the following formula:

[0035]

[0036] In the formula, I A I B I C I D I E and I F These represent the currents in each phase, i α i β i x i y i o1 and i o2 These represent the currents along each axis in the transformed stationary coordinate system.

[0037] The voltage or current of the dual three-phase permanent magnet synchronous motor is mapped to three pairwise orthogonal subspaces α-β, xy, and o1-o2 through coordinate transformation. The current in the α-β subspace is related to torque generation, the current in the xy subspace is a harmonic component and is not related to torque generation, and the current in the o1-o2 subspace is a zero-sequence component.

[0038] Since only the currents in the α-β subspace involve electromechanical energy conversion, the rotation transformation only needs to transform the currents in this subspace. Therefore, the currents in the α-β subspace can be transformed to the dq subspace, meaning the d-axis and q-axis currents are located in the dq subspace, and the x-axis and y-axis currents are located in the xy subspace. The rotation transformation process is as follows:

[0039]

[0040] In the formula, θ e It is an electrical angle.

[0041] Step 3: D-axis current setpoint under normal motor conditions x-axis current setpoint and y-axis current setpoint Set to 0, and then perform closed-loop control by the current loop PI controller, with the q-axis current setpoint... The speed is given by the output of the speed loop PI controller. Specifically, the motor speed setpoint is... The difference between the actual motor speed n and the given speed is input to the speed loop PI controller. The output of the speed loop PI controller is the q-axis current setpoint. The current loop PI controller consists of two sets: the dq subspace current controller and the xy subspace current controller, which are used to control the current of each axis to reach the given value.

[0042] Step 4: After a phase loss fault occurs in the motor, regardless of which phase the fault occurs in, fault-tolerant control is achieved by reducing the motor control degrees of freedom. This is done by canceling the harmonic subspace current closed loop and adjusting the harmonic subspace voltage reference value. and Set to 0.

[0043] A phase loss fault can lead to two problems: First, because the faulty phase is open-circuited, its current is forced to zero, causing the current loop PI controller to fail in controlling the faulty phase. Second, after the fault, the currents in the α-β and xy subspaces are no longer independent and are now constrained. However, the original current loop PI controller still controls the two subspace currents independently, resulting in a conflict between the control objectives of the dq and xy subspace current controllers. Therefore, reducing the motor control degrees of freedom can be considered to mitigate this conflict.

[0044] When a single-phase loss fault occurs in the motor, the motor enters fault-tolerant operation. Regardless of which phase the fault occurs in, the xy subspace current controller actively relinquishes control of the current in the xy subspace, placing it in an open-loop state. .

[0045] Step 5: If the motor operates in a fault-tolerant mode, then the second harmonic of the q-axis current i q2 To suppress. Combined Figure 2 As shown, a high-order generalized integrator (HOGI) is used to control the second harmonic i of the q-axis current. q2 Extraction is performed, and the second harmonic of the q-axis current is given. When set to 0, it is controlled by a quasi-proportional resonant (QPR) controller, whose output is the q-axis voltage compensation amount u. q2 The q-axis voltage compensation amount u q2 Feedforward compensation to q-axis voltage u q This is used in conjunction with the diagnostic-free fault-tolerant strategy to suppress torque pulsation after a fault and improve torque quality.

[0046] When the motor is in normal operation, the current in each phase is:

[0047]

[0048] In the formula, I m The amplitude of the current in each phase.

[0049] Under the action of the current loop PI controller:

[0050]

[0051] At this point, the current of each axis can achieve stable tracking.

[0052] When a motor experiences a phase loss fault, the q-axis current becomes difficult to track effectively, resulting in frequency pulsation at double harmonics.

[0053]

[0054] In the formula, k is a constant.

[0055] This will exacerbate the secondary torque ripple after the fault. The second harmonic of the q-axis current under fault conditions is obtained through the high-order generalized integrator HOGI, and its transfer function is:

[0056]

[0057] In the formula, K1 and K2 are gain coefficients, and ω c The center frequency.

[0058] Because PI controllers have weak tracking ability and poor control performance for this type of AC signal, a quasi-proportional resonant QPR controller is used to suppress the second harmonic. Its transfer function is:

[0059]

[0060] In the formula, K P K is the time constant of the proportional part. I ω is the resonance coefficient, and ω0 is the passband bandwidth.

[0061] The second harmonic of the q-axis current i q2 After being extracted by a high-order generalized integrator HOGI, the voltage is fed into a quasi-proportional resonant QPR controller for control. The output of the quasi-proportional resonant QPR controller is used as the q-axis voltage setpoint. The feedforward compensation forms a diagnostic-free, self-tolerant control strategy that considers the suppression of secondary torque ripple.

[0062] Example 1

[0063] Step 1: Combining Figure 1 As shown, a four-dimensional vector control model of a dual three-phase permanent magnet synchronous motor is constructed.

[0064] Step 2: The motor is loaded with a load of 1.8 N·m, and the target speed is given as 240 r / min. The current sensor obtains the current of each phase of the motor, and the position sensor obtains the electrical angle and speed of the motor, which are used as feedback quantities for vector control.

[0065] Step 3: 0.4s A phase loss fault occurs in phase F of the motor.

[0066] Step 4: The motor enters fault-tolerant control mode in 0.6 seconds. (Combined with...) Figure 2 As shown, HOGI extracts the second harmonic of the q-axis current and combines it with a QPR controller for feedforward compensation. The controller reduces the control degrees of freedom, and the current in the xy subspace no longer participates in the closed loop, thus applying a fault-tolerant control strategy.

[0067] When a phase loss fault occurs in phase F, the electromagnetic torque output of the motors before and after the fault-tolerant control is combined. Figure 3 As shown, when a phase loss fault occurs in phase F, the motor torque ripple is significant, with a maximum value of approximately 2.59 N·m and a minimum value of approximately 1.2 N·m. Using the proposed fault-tolerant control strategy, the maximum torque ripple is reduced to approximately 1.91 N·m and the minimum to approximately 1.71 N·m. The motor torque ripple decreases by approximately 85%, thus improving torque quality.

[0068] Example 2

[0069] The difference between this embodiment and embodiment 1 is that a phase loss fault occurs in phase A of the motor at 0.4s, and the motor switches to fault-tolerant control state at 0.6s.

[0070] When a phase A loss fault occurs, the electromagnetic torque output of the motors before and after the fault-tolerant control is combined. Figure 4 As shown, when a phase loss fault occurs in phase A, the motor torque ripple is significant, with a maximum value of approximately 2.59 N·m and a minimum value of approximately 1.2 N·m. By employing the proposed fault-tolerant control strategy, the motor torque ripple decreases by approximately 85%, thus improving torque quality.

[0071] Through the two embodiments, it can be seen that the implementation steps of the proposed fault-tolerant control strategy do not need to be changed for faulty phases in different locations, thus avoiding the complex fault diagnosis and location process and effectively suppressing torque pulsation caused by phase loss faults.

[0072] In summary, this invention provides a detailed analysis of the fundamental principle of torque ripple in dual three-phase permanent magnet synchronous motors caused by a single-phase loss, delves into the conflicts between current controllers due to phase loss faults, and proposes a diagnostic-free, self-fault-tolerant control method for dual three-phase permanent magnet synchronous motors. Based on this, it combines HOGI and QPR controllers to suppress the second harmonic of the q-axis current, further improving torque quality after a fault. The proposed fault-tolerant control strategy omits complex fault diagnosis and location steps, exhibits good torque ripple suppression effects for faults at different locations, and finally verifies the effectiveness and feasibility of the method through simulation analysis.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0074] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor, characterized in that: Includes the following steps: Step 1: Sample the six-phase current of the dual three-phase permanent magnet synchronous motor using six current sensors; Step 2: Based on the VSD decoupling transformation theory, perform static coordinate transformation and rotating coordinate transformation on the collected six-phase currents to obtain the d-axis current i. d and q-axis current i q and x-axis current i x and y-axis current i y ; Step 3: D-axis current setpoint under normal motor conditions x-axis current setpoint and y-axis current setpoint Set to 0, and then perform closed-loop control by the current loop PI controller, with the q-axis current setpoint... The speed is given by the output of the speed loop PI controller; Step 4: After a phase loss fault occurs in any phase of the motor, the motor control degrees of freedom are reduced to switch to fault-tolerant operation. The harmonic subspace current closed loop is canceled, and the voltage reference value of the harmonic subspace is adjusted. and Set to 0; Step 5: When the motor is in fault-tolerant operation, a high-order generalized integrator is used to extract the second harmonic i of the q-axis current. q2 Set the second harmonic value of the q-axis current. When set to 0, it is controlled by a quasi-proportional resonant controller, and the output is the q-axis voltage compensation quantity u. q2 Feedforward compensation to q-axis voltage u q The second harmonic of the q-axis current i q2 To suppress.

2. The diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: In step two, the static coordinate transformation formula for the six-phase current is as follows: In the formula, I A I B I C I D I E and I F Let i represent the current in each phase. α i β i x i y i o1 and i o2 These represent the currents along each axis in the transformed stationary coordinate system.

3. The diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor according to claim 2, characterized in that: In step two, the formula for the rotation coordinate transformation is as follows: In the formula, θ e It is an electrical angle.

4. The diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: In step three, the motor speed setpoint The difference between the actual motor speed n and the given speed is input to the speed loop PI controller. The output of the speed loop PI controller is the q-axis current setpoint. .

5. The diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: In step five, the second harmonic of the q-axis current under phase loss fault is obtained through a high-order generalized integrator, and its transfer function is: In the formula, K1 and K2 are gain coefficients, ω c The center frequency.

6. The diagnostic-free, self-fault-tolerant control method for a dual three-phase permanent magnet synchronous motor according to claim 1, characterized in that: In step five, a quasi-proportional resonant controller is used to suppress the second harmonic, and its transfer function is: In the formula, K P K is the time constant of the proportional part. I ω is the resonance coefficient, and ω0 is the passband bandwidth.

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