A Fault Self-Healing and Fault-Tolerant Control Method for Open-Phase Faults of a Multi-Mode Switching Dual-Three-Phase Motor

Abstract

The present invention discloses a self-healing fault-tolerant control method for open-phase faults of a multi-mode switching dual-three-phase motor, belonging to the technical field of motor control. The fault-tolerant control method includes mapping six-phase variables to different planes, adjusting the current in the fundamental plane through a PI controller, suppressing harmonic currents using a bidirectional PI controller, enabling the fundamental frequency component to flow through cascaded notch filters, and outputting to a voltage source inverter through SVPWM to achieve the control of the motor; after entering the fault-tolerant state, considering the stator copper loss and torque output ability of the motor comprehensively, it can automatically switch to the optimal operation mode according to the load condition. The present invention has the characteristics of no need for fault location and consistent control architecture. During the control process, there is no need to change the current reference through additional operations, avoiding secondary faults caused by incorrect references, simplifying the complexity of control implementation, eliminating the delay and error problems existing in the fault location process, and being able to keep the motor running stably before and after the occurrence of open-phase faults.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and particularly to a multi-mode switching dual three-phase motor open-phase fault self-healing fault-tolerant control method. Background Art

[0002] Most of the existing fault-tolerant control methods for dual three-phase motors rely on an accurate fault location process, that is, first locate the faulty phase and then switch the corresponding current reference value. However, this method has several significant drawbacks. First of all, the location process takes a certain amount of time, which may lead to a decline in the transient performance of the system. Especially in applications with high dynamic requirements, the delay may cause the system to fail to respond quickly. In addition, the location process depends on the accuracy of sensors and algorithms, and is easily affected by motor parameter fluctuations and external noise, thus causing judgment errors. Such errors will result in incorrect current reference value settings, thereby increasing torque ripple and even possibly causing the system to get out of control, affecting the safety and reliability of the equipment.

[0003] Traditional fault-tolerant control schemes also have a high degree of complexity, especially in the case where the current reference needs to be dynamically adjusted according to different faulty phases. Incorrect current references will lead to the occurrence of secondary faults. Since dual three-phase motors have more windings, compared with traditional three-phase motors, their control architectures and the adjustment of reference signals are more complex. This complexity not only increases the difficulty of implementing the control system, but also raises the design and maintenance costs. In the actual application in the industrial field, this complex fault location and adjustment process may lead to high maintenance requirements and system downtime, thereby affecting production efficiency.

[0004] To address these problems, the current dual three-phase motor control technology urgently needs a fault-tolerant control method that can eliminate the fault location process to improve the reliability of the system, can avoid complex adjustments of the control architecture, ensure that the motor can operate stably and continuously when a fault occurs, and at the same time, in order to meet the requirements of multi-load working conditions, it should have the ability to perform mode switching. The present invention proposes a multi-mode switching dual three-phase motor open-phase fault self-healing fault-tolerant control method to solve the above problems. This method maintains a consistent control architecture before and after a fault. Without changing the current reference, the motor can transition to a fault-tolerant state to achieve fault self-healing, eliminating the need for fault location and reference switching, thereby simplifying the control process, reducing the difficulty of system implementation, and significantly improving the fault-tolerant performance and stability. This method is applicable to multiple operating modes, comprehensively considering the stator copper loss and torque output capacity of the motor. Compared with traditional methods, it can achieve better fault-tolerant performance in a wide load range. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies in the above-mentioned background art, the present invention provides a multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method, which can achieve effective fault tolerance and self-healing without changing the control architecture and current reference value when an open-phase fault occurs, without locating the faulty phase, ensuring the continuous and stable operation of the motor. During the operation process, the fault-tolerant mode of the motor can be switched in real time according to different load torques, ensuring the optimal fault-tolerant performance of the motor when operating within a wide load range.

[0006] The technical solution for achieving the object of the present invention is as follows:

[0007] A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method includes the following steps:

[0008] Step S1: Construct a mathematical model based on the vector space decoupling theory, and map the six-phase variables in the natural stationary coordinate system to the d-q fundamental wave plane, z1-z2 harmonic plane, and o1-o2 zero-sequence plane through decoupling transformation;

[0009] Step S2: For the fundamental wave plane, subtract the reference speed n * from the actual speed n collected by the rotary encoder, and calculate the current reference value of the q-axis through a PI controller Set the current reference value of the d-axis to 0; for the harmonic plane, always set the current reference value of the harmonic plane to 0, and no adjustment is required during the control process; the zero-sequence plane does not need to be controlled, and the overall current control dimension of the system is 4D;

[0010] Step S3: After an open-phase fault occurs, subtract from the harmonic plane currents i z1 , i z2 and suppress the harmonic plane currents through a bidirectional PI controller;

[0011] Step S4: Connect a notch filter in series at the output end of the bidirectional PI controller to allow the fundamental wave component during fault-tolerant operation to pass through;

[0012] Step S5: Discretize the transfer function of the notch filter using bilinear transformation for implementation in the digital control program;

[0013] Step S6: The current loop output plane reference voltage of the fundamental wave plane and the harmonic plane Obtain the reference voltage in the natural stationary coordinate system through vector space decoupling inverse transformation of the reference voltage Then obtain the duty cycle required for each phase of the switching tube through SVPWM and output it to the voltage source inverter to achieve motor control; the SVPWM is space vector pulse width modulation;

[0014] Step S7. During normal operation, i z1 , i z2 fluctuates slightly around 0; after entering the fault-tolerant state, the motor defaults to running in the minimum stator copper loss mode, and i z1 , i z2 is no longer 0;

[0015] Step S8. When the motor is in the fault-tolerant state, the operating mode is switched according to the torque derating coefficient K T detected in real time, including the minimum stator copper loss mode and the maximum torque output mode; the torque derating coefficient K T is equal to the actual load torque divided by the rated torque;

[0016] Step S9. When the torque derating coefficient K T exceeds a certain threshold, the motor is shut down to prevent overheating and damage.

[0017] Furthermore, in Step S1, the decoupling transformation is achieved through a decoupling transformation matrix, specifically as follows:

[0018]

[0019] where x represents the motor variables, and x d is the fundamental plane d-axis variable, x q is the fundamental plane q-axis variable, x z1 is the harmonic plane z1-axis variable, x z2 is the harmonic plane z2-axis variable, x o1 is the zero-sequence plane o1-axis variable, x o2 is the zero-sequence plane o2-axis variable, x A is the A-phase variable, x B is the B-phase variable, x C is the C-phase variable, x D is the D-phase variable, x E is the E-phase variable, x F is the F-phase variable; θ e is the stator electrical angle; the motor variables include voltage, current, and flux linkage.

[0020] Furthermore, in Step S4, the transfer function of the notch filter is:

[0021]

[0022] where ω e is the resonant angular frequency, which is set to the fundamental angular frequency, and k b is the adjustment coefficient related to the bandwidth;

[0023] Further, in the step S5, the transfer function of the notch filter after discretization by bilinear transformation is expressed in the z-domain as follows:

[0024]

[0025] The coefficients in the formula are as follows:

[0026]

[0027] Where, T s is the sampling period of the controller, ω e is the resonant angular frequency, and k b is the adjustment coefficient related to the bandwidth.

[0028] Further, in the step S7, a flag bit F n is constructed to mark whether the motor has entered the fault-tolerant state and is used to indicate subsequent mode switching. The expression of F n is as follows:

[0029]

[0030] In the formula, T is the fundamental wave period of the phase current, and i q is the actual current of the q-axis in the fundamental wave plane of the dual-three-phase motor; a threshold is set. When F n is greater than 1.5, it is considered that the motor has entered the fault-tolerant state.

[0031] Further, in the step S8, the standard for the motor operation mode is as follows: when K T is less than or equal to 0.555, the motor operates in the minimum stator copper loss mode; when K T is greater than 0.555 and less than or equal to 0.577, the motor operates in the maximum torque output mode; when the motor is in the fault-tolerant state, it defaults to operating in the minimum stator copper loss mode. When K T is less than or equal to 0.555, no additional operation is required; when K T is greater than 0.555 and less than or equal to 0.577, the amplitude of the phase current is detected, and the phase with unchanged amplitude before and after fault tolerance is disconnected through the circuit breaker or the drive signal is blocked, and the motor switches to the maximum torque output mode.

[0032] Further, in the step S9, the threshold of the torque derating coefficient K T for shutdown processing is set to 0.577.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention proposes a self-healing fault-tolerant control method for open-phase faults of a multi-mode switching dual-three-phase motor. Compared with traditional schemes, this method does not require fault location, avoiding negative problems such as increased torque ripple caused by location delay and inaccuracy.

[0035] (2) The fault-tolerant control method proposed by the present invention adopts a unified control architecture before and after fault tolerance. It does not need to repeatedly switch the current reference value according to different fault phases, simplifies the complexity of control implementation, realizes fault self-healing, saves control resources, and avoids secondary faults caused by incorrect references.

[0036] (3) The fault-tolerant control method proposed by the present invention can switch between the minimum stator copper loss mode and the maximum torque output mode according to different load conditions, ensuring good fault-tolerant performance within a wide load range. Description of the Drawings

[0037] Figure 1 is the block diagram of the self-healing fault-tolerant control system for open-phase faults of the dual-three-phase motor proposed by the present invention;

[0038] Figure 2 is the drive topology diagram of the dual-three-phase motor adopted by the present invention;

[0039] Figure 3 is the control block diagram of the bidirectional PI controller proposed by the present invention;

[0040] Figure 4 is the Bode diagram of the notch filter proposed by the present invention;

[0041] Figure 5 is the schematic diagram of the mode switching of the motor of the present invention in the fault-tolerant state;

[0042] Figure 6 is the schematic diagram of the mode switching principle of the motor of the present invention in the fault-tolerant state;

[0043] Figure 7 is the six-phase current waveform diagram of the motor of the present invention in the minimum stator copper loss mode when phase B is open;

[0044] Figure 8 is the experimental diagram of the dq-axis current waveform, speed waveform, and harmonic plane current waveform of the motor of the present invention in the minimum stator copper loss mode when phase B is open;

[0045] Figure 9 is the experimental diagram of the six-phase current waveform of the motor of the present invention during mode switching when phase B is open;

[0046] Figure 10 is the experimental diagram of the dq-axis current waveform, speed waveform, and harmonic plane current waveform of the motor of the present invention during mode switching when phase B is open. Detailed Embodiments

[0047] The present invention will be described based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail. Those skilled in the art can fully understand the present invention without the description of these details.

[0048] A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method includes the following steps:

[0049] Step S1: Construct a mathematical model based on the vector space decoupling theory, and map the six-phase variables in the natural stationary coordinate system to the d-q fundamental wave plane, z1-z2 harmonic plane, and o1-o2 zero-sequence plane through decoupling transformation.

[0050] Step S2: For the fundamental wave plane, subtract the reference speed n * from the actual speed n calculated by the rotary encoder, and obtain the current reference value of the q-axis after passing through the PI controller The d-axis current does not participate in torque output, so the current reference value of the d-axis is set to 0. For the harmonic plane, the control structure proposed by the present invention always makes the current reference value of the harmonic plane be 0 whether in normal operation or fault-tolerant operation, and there is no need to additionally locate the fault phase to switch different current reference values. Due to neutral point isolation, the zero-sequence plane does not need to be controlled, and the overall current control dimension of the system is 4D.

[0051] Step S3: After an open-phase fault occurs, in order to improve the suppression effect and reduce the harmonic content in the phase current, subtract from the harmonic plane current i z1 and i z2 and suppress the harmonic plane current through a bidirectional PI controller, as shown in Figure 2 . Its principle uses the rotating coordinate transformation to convert the positive and negative sequence harmonic currents into direct currents for control. Considering the low-order harmonic content after open-phase, let k = 3, 5, 7, and use multiple bidirectional PI controllers for parallel output.

[0052] Step S4: In order not to interfere with the necessary fundamental frequency components in the harmonic plane current during fault-tolerant operation, a notch filter is connected in series at the output end of the bidirectional PI controller to suppress the low-order harmonics in the harmonic plane current during fault-tolerant operation.

[0053] Step S5: Discretize the transfer function of the notch filter using bilinear transformation for implementation in the digital control program.

[0054] Step S6: The current loop output plane reference voltage of the fundamental wave plane and the harmonic plane The reference voltage is subjected to a vector space decoupling inverse transformation to obtain the reference voltage in the natural stationary coordinate system. Then, through SVPWM (Space Vector Pulse Width Modulation), the duty cycle required for each phase of the switch tube is obtained and output to the voltage source inverter to achieve motor control; the SVPWM is Space Vector Pulse Width Modulation; the overall control block diagram of the final system is as Figure 4 shown.

[0055] Step S7: During normal operation, i z1 , i z2 fluctuates slightly near 0; after entering the fault-tolerant state, the motor defaults to running in the stator copper loss minimum mode, and i z1 , i z2 is no longer 0.

[0056] Step S8: When the motor is in the fault-tolerant state, according to the torque derating coefficient K T detected in real time, the operating mode is switched, including the stator copper loss minimum mode and the maximum torque output mode; the torque derating coefficient K T is equal to the actual load torque divided by the rated torque.

[0057] Step S9: When the torque derating coefficient K T exceeds a certain threshold, it is output that the load exceeds the limit that the motor can withstand during fault-tolerant operation, and the motor is shut down to prevent the motor from overheating and being damaged.

[0058] Furthermore, in step S1, the decoupling transformation is realized through a decoupling transformation matrix, specifically as follows:

[0059]

[0060] Among them, x represents the motor variable, x d is the fundamental wave plane d-axis variable, x q is the fundamental wave plane q-axis variable, x z1 is the harmonic plane z1-axis variable, x z2 is the harmonic plane z2-axis variable, x o1 is the zero-sequence plane o1-axis variable, x o2 is the zero-sequence plane o2-axis variable, x A is the A-phase variable, x B is the B-phase variable, x C is the C-phase variable, x D is the D-phase variable, x E is the E-phase variable, x F is the F-phase variable; θ e is the stator electrical angle; the motor variables include voltage, current, and flux linkage.

[0061] Furthermore, in step S4, the transfer function of the notch filter is:

[0062]

[0063] where ω e is the resonant angular frequency, which is set to the fundamental angular frequency, and k b is an adjustment coefficient related to the bandwidth; taking ω e as 50π rad / s and k b as 1 for example, the Bode plot of the notch filter is plotted as Figure 3 shown. The gain of the notch filter at the fundamental frequency component is very small, and the harmonic plane current reference value is 0. Cooperating with the bidirectional PI controller can suppress the low-order harmonics that generate additional losses without affecting the passage of the fundamental frequency component.

[0064] Furthermore, in the step S5, the expression of the transfer function of the notch filter after discretization by bilinear transformation in the z-domain is as follows:

[0065]

[0066] The coefficients in the formula are as follows:

[0067]

[0068] where T s is the sampling period of the controller, ω e is the resonant angular frequency, and k b is an adjustment coefficient related to the bandwidth.

[0069] Furthermore, in the step S7, a flag bit F n is constructed to mark whether the motor has entered the fault-tolerant state and is used to indicate subsequent mode switching. The expression of F n is as follows:

[0070]

[0071] In the formula, T is the fundamental period of the phase current, and i q is the actual current of the q-axis in the fundamental plane of the dual-three-phase motor; a threshold is set, and when F n is greater than 1.5, it is considered that the motor has entered the fault-tolerant state.

[0072] Furthermore, in the step S8, the standard for the motor operation mode is as follows: when K T is less than or equal to 0.555, the motor operates in the minimum stator copper loss mode, which can ensure the highest operating efficiency of the motor; when K T is greater than 0.555 and less than or equal to 0.577, the motor operates in the maximum torque output mode, which can ensure a stronger load-carrying capacity; when the motor is in the fault-tolerant state, it defaults to operating in the minimum stator copper loss mode. When KT When it is less than or equal to 0.555, no additional operation is required; when K T is greater than 0.555 and less than or equal to 0.577, the amplitude of the phase current is detected, the phases with unchanged amplitude before and after fault tolerance are disconnected through the circuit breaker or the drive seal signal is blocked, and the motor switches to the maximum torque output mode.

[0073] Further, in the step S9, the torque derating coefficient K of the shutdown process T is set to 0.577.

[0074] Further, the experimental waveforms of the embodiment are as Figures 7 to 10 shown. Before and after fault tolerance, the torque and speed of the motor can both remain stable. Effective fault tolerance can be achieved without additional changing of the current reference value, and the mode switching can be realized.

[0075] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing specific embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing specific embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method, characterized in that The method includes the following steps: Step S1: Construct a mathematical model based on the vector space decoupling theory, and map the six-phase variables in the natural stationary coordinate system to the d-q fundamental wave plane, the z1-z2 harmonic plane, and the o1-o2 zero-sequence plane through decoupling transformation; Step S2: For the fundamental wave plane, subtract the reference speed n * from the actual speed n collected by the rotary encoder, and calculate the current reference value of the q-axis through a PI controller Set the current reference value of the d-axis to 0; for the harmonic plane, always set the current reference value of the harmonic plane to 0, and no adjustment is required during the control process; the zero-sequence plane does not need to be controlled, and the overall current control dimension of the system is 4D; Step S3, after a phase loss fault occurs, subtract it from the harmonic plane current i z1 , i z2 , and then suppress the harmonic plane current through a bidirectional PI controller; Step S4: Connect a notch filter in series at the output end of the bidirectional PI controller to allow the fundamental wave component during fault-tolerant operation to pass through; Step S5: Discretize the transfer function of the notch filter using bilinear transformation for implementation in the digital control program; Step S6: The current loop output plane reference voltage in the fundamental wave plane and the harmonic wave plane The reference voltage is subjected to a vector space decoupling inverse transformation to obtain the reference voltage in the natural stationary coordinate system Then, the duty cycle required for each phase of the switching tube is obtained through SVPWM and output to the voltage source inverter to achieve motor control; the SVPWM is space vector pulse width modulation Step S7, during normal operation, i z1 、i z2 fluctuates slightly around 0; after entering the fault-tolerant state, the motor defaults to running in the mode of minimum stator copper loss, and i z1 、i z2 is no longer 0; Step S8: When the motor is in a fault-tolerant state, according to the torque derating coefficient K detected in real time T switch the operation mode, including the minimum stator copper loss mode and the maximum torque output mode; the torque derating coefficient K T is equal to the actual load torque divided by the rated torque; Step S9: When the torque derating factor K T exceeds a certain threshold, the motor is shut down to prevent overheating and damage of the motor.

2. The self-healing fault-tolerant control method for open-phase faults of a multi-mode switching dual-three-phase motor according to claim 1, wherein In Step S1, the decoupling transformation is realized through a decoupling transformation matrix, specifically as follows: Among them, x represents the motor variable, x d is the fundamental plane d-axis variable, x q is the fundamental plane q-axis variable, x z1 is the harmonic plane z1-axis variable, x z2 is the harmonic plane z2-axis variable, x o1 is the zero-sequence plane o1-axis variable, x o2 is the zero-sequence plane o2-axis variable, x A is the phase A variable, x B is the phase B variable, x C is the phase C variable, x D is the phase D variable, x E is the phase E variable, x F is the phase F variable; θ e is the stator electrical angle; the motor variables include voltage, current, and flux linkage.

3. A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method according to claim 1, characterized in that, In Step S4, the transfer function of the notch filter is: where ω e is the resonant angular frequency, which is set to the fundamental angular frequency, and k b is an adjustment coefficient related to the bandwidth.

4. A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method according to claim 1, characterized in that, In Step S5, the expression of the transfer function of the notch filter after discretization by bilinear transformation in the z-domain is as follows: The coefficients in the formula are as follows: Among them, T s is the sampling period of the controller, ω e is the resonant angular frequency, and k b is the adjustment coefficient related to the bandwidth.

5. A multi-mode switching dual-three-phase motor open-phase fault self-healing fault-tolerant control method according to claim 1, characterized in that In the step S7, a flag bit F is constructed n to mark whether the motor has entered a fault-tolerant state and is used to indicate subsequent mode switching. The expression of F n is as follows: where T is the fundamental period of the phase current, and i q is the actual current of the q-axis in the fundamental plane of the dual three-phase motor; Set a threshold value. When F n is greater than 1.5, it is considered that the motor has entered the fault-tolerant state.

6. A self-healing fault-tolerant control method for open-phase faults of a multi-mode switching dual-three-phase motor according to claim 1, characterized in that In step S8, the criteria for the motor operation mode are as follows: when K T is less than or equal to 0.555, the motor operates in the minimum stator copper loss mode; when K T is greater than 0.555 and less than or equal to 0.577, the motor operates in the maximum torque output mode; when the motor is in the fault-tolerant state, it defaults to the minimum stator copper loss mode. When K T is less than or equal to 0.555, no additional operation is required; when K T is greater than 0.555 and less than or equal to 0.577, the amplitude of the phase current is detected, and the phases with unchanged amplitude before and after fault tolerance are disconnected through the circuit breaker or the drive signal is blocked, and the motor switches to the maximum torque output mode.

7. A self-healing fault-tolerant control method for open-phase faults of a multi-mode switching dual-three-phase motor according to claim 1, characterized in that In the step S9, the torque derating coefficient K for shutdown processing T is set with a threshold value of 0.577.

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