Three-phase permanent magnet motor system fault-phase fault-tolerant control method

Abstract

The invention relates to a fault-tolerant fault-tolerant control method for a three-phase permanent magnet motor system, and belongs to the technical field of fault-tolerant motor systems. Under a one-phase open-circuit fault, through a comprehensive design thought of a motor and a control algorithm, dependence of fault-tolerant control on motor parameters is reduced, a three-phase four-leg power topology design is simplified, power density is further improved, robustness of low-torque ripple control is further improved through a phase angle correction mode, and the method adapts to a working condition of a servo wide speed domain.

Description

Technical Field

[0001] The invention belongs to the technical field of fault-tolerant motor systems and relates to a phase-failure fault-tolerant control method for a three-phase permanent magnet motor system. Background Art

[0002] Three-phase motor systems, especially three-phase permanent magnet synchronous motor systems, are widely used in aerospace servo actuator systems due to their high torque density and other characteristics. As a key component for controlling the heading of an aircraft, the aerospace servo actuator system has high reliability requirements. In a three-phase motor system, motor windings and power devices are all electrical components, and there is a certain failure rate during operation. Once a motor winding or power device is broken, the three-phase motor system will become a two-phase system. The currents flowing through the two phases are equal in magnitude and opposite in direction, and the circular magnetic field required for normal motor control cannot be formed, causing the motor system to fail, and then leading to the failure of the aerospace servo actuator system and the aircraft mission. Therefore, this requires the motor system to have a certain fault tolerance capability. At present, conventional fault tolerance schemes include five-phase motor systems or six-phase motor systems. After a phase fails, due to the remaining more healthy phases, fault tolerance control can be completed more easily. However, this type of scheme requires the number of bridge arms of the power main circuit to be increased by at least two or three compared to the conventional three-phase motor system, which greatly reduces the power density of the motor control driver and is not suitable for aerospace servo actuator systems with high requirements for space size and weight. The fault-tolerant motor system formed on the basis of the three-phase motor system is a key research direction at present. The patent "Hybrid control method for phase-loss-tolerant operation of dual three-phase permanent magnet synchronous motor" (202111678446.6) proposes a hybrid control method after phase loss for dual three-phase motors, but dual three-phase motors are essentially multi-phase motors. Although they have high fault tolerance, their power density is low; the patent "A phase-loss control method for adaptively suppressing harmonic torque" (201910700813.4) proposes a fault-tolerant solution for permanent magnet motor systems based on three-phase four-bridge arms, but the feedforward algorithm introduced in the fault-tolerant algorithm of this solution is related to the motor resistance and inductance, which will change greatly with the motor working conditions, which is not conducive to the stable control of motor fault tolerance. Torque pulsation after phase loss is only applicable to a narrow speed range and cannot meet the requirements of wide speed range changes of servo actuator systems. Summary of the invention

[0003] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and propose a phase failure fault-tolerant control method for a three-phase permanent magnet motor system.

[0004] The solution of the present invention is:

[0005] A three-phase permanent magnet motor system phase failure fault tolerance control method, comprising:

[0006] The three-phase permanent magnet motor system adopts a three-phase four-bridge arm power topology, and the motor adopts a three-phase four-wire permanent magnet fault-tolerant motor, wherein three bridge arms are connected to the three-phase windings of the motor in a one-to-one correspondence, and the midpoint of the fourth bridge arm is connected to the star-connected neutral point of the three-phase four-wire permanent magnet fault-tolerant motor; the three-phase four-wire permanent magnet fault-tolerant motor is a surface-mounted type, and an isolation tooth structure is designed internally to reduce the mutual inductance between the motor phases to 0;

[0007] Assuming that one of the phases has a phase failure, the switch signal of the phase bridge arm is set to low, and the switch signal originally given to the phase bridge arm is assigned to the fourth bridge arm. At the same time, the output of the d-axis current controller is compensated. Compensation on the q-axis current controller output Phase-failure fault-tolerant control can be realized, where θ e is the electrical angle, ω is the electrical angular velocity, ψ m is the permanent magnet flux;

[0008] The d and q axis current loops are in the form of

[0009] The controller realizes the low torque ripple control in a wide speed range after the motor phase loss fault tolerance, where K P is the proportionality coefficient, K I is the integration coefficient, K r is the resonance coefficient, φ1 is the phase angle compensation value of the quadratic resonance controller, φ2 is the phase angle compensation value of the quadratic resonance controller, p is the number of motor pole pairs, and n is the real-time speed in rpm.

[0010] Preferably, in the three-phase four-wire permanent magnet fault-tolerant motor, the d-axis inductance=q-axis inductance.

[0011] Preferably, when the mutual inductance between the phases of the motor is reduced to 0, the zero-sequence inductance is equal to the DC value of the self-inductance.

[0012] Preferably, the inverter voltage vector of the three-phase permanent magnet motor system in a healthy state has eight states, which are 100, 101, 001, 011, 010, 110, 000, 111 in the order of Sa, Sb, and Sc. The phase voltages of the three phases A, B, and C are obtained from the voltage vectors of these eight states, and then the α and β voltages in the two-phase stationary coordinate system are obtained.

[0013] Preferably, the α and β voltages in the two-phase stationary coordinate system correspond to (0, 0), (0, 0); Vdc is the bus voltage.

[0014] Preferably, Sa, Sb, Sc sequentially refer to the switch states of the bridge arms connected to phases A, B, and C, Sx=1 means that the upper tube of the bridge arm connected to phase x is on and the lower tube is off, x=a, b, c.

[0015] Preferably, when a phase is shorted, the corresponding inverter bridge arm is separated from the motor, and the neutral point of the motor's star connection is connected to the midpoint of the fourth bridge arm. At this time, the power topology composed of the fourth bridge arm and two corresponding healthy bridge arms produces eight new switching states. The phase voltages of the two outer healthy phases are obtained from the voltage vectors of these eight states, and then the α and β voltages in the two-phase stationary coordinate system are obtained.

[0016] Preferably, the α and β voltages are consistent in a healthy state and after one phase is disconnected, and there is no need to reconstruct the switching vector after a fault. The midpoint of the fourth bridge arm is connected to the star-connected neutral point of the three-phase four-wire permanent magnet fault-tolerant motor, and the two bridge arms in normal operation are combined to provide a suitable voltage vector for the three-phase four-wire permanent magnet fault-tolerant motor to keep it in a normal operating state.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] (1) The present invention realizes a fault-tolerant system solution based on a three-phase four-bridge-arm power topology and a permanent magnet fault-tolerant motor. Compared with a three-phase permanent magnet motor system without fault-tolerant capability, this solution only adds one power bridge arm, and does not require additional large devices such as inductors between the midpoint of the bridge arm and the neutral point of the motor to improve current control stability. This improves the working reliability of the motor system without adding too many resources.

[0019] (2) The present invention realizes fault-tolerant control of a three-phase permanent magnet motor system based on a three-phase four-bridge arm power topology after one phase is disconnected. The fault-tolerant control strategy has greatly reduced dependence on motor parameters and only requires one parameter, the magnetic flux linkage of the motor permanent magnet. This parameter changes very little during the operation of the motor system, making the fault-tolerant control strategy highly adaptable to working conditions and stable.

[0020] (3) The present invention realizes low torque pulsation control operation of a three-phase permanent magnet motor system after one phase is disconnected, and has wide speed range adaptability, which can meet the wide speed range operation requirements of the servo actuator system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the system solution topology diagram;

[0022] Figure 2 This is the structure diagram of phase failure fault tolerance control of three-phase permanent magnet motor system;

[0023] Figure 3 This is a block diagram of wide speed range circuit breaker fault tolerance low torque ripple control;

[0024] Figure 4 This is the waveform diagram of 400rpm healthy, phase-failure fault tolerance and torque pulsation suppression test;

[0025] Figure 5 This is the waveform diagram of 1200rpm healthy, phase-failure fault tolerance and torque pulsation suppression test;

[0026] Figure 6 This is the waveform diagram of 3000rpm healthy, phase-failure fault tolerance and torque pulsation suppression test;

[0027] Figure 7 This is the waveform diagram of the 2400rpm non-phase angle compensation healthy, phase failure fault tolerance and torque pulsation suppression test;

[0028] Figure 8 This is the waveform diagram of the 2400rpm phase angle compensation, phase failure tolerance and torque pulsation suppression test;

[0029] Fig. 9 This is the speed transient test waveform under 1000 to 2400rpm phase-out torque pulsation suppression. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] like Figure 1 As shown, the present invention uses a system solution based on a three-phase four-bridge arm power topology and a three-phase four-wire permanent magnet synchronous motor, wherein the midpoint of the fourth bridge arm of the power topology is directly connected to the neutral point of the star connection of the three-phase four-wire permanent magnet fault-tolerant motor. Usually, in order to ensure the current stability after the fourth bridge arm is involved in the work, an inductor is connected in series between the midpoint of the fourth bridge arm and the neutral point of the motor, which will increase the size of the driver and is not conducive to achieving a high power density design. Therefore, the present invention proposes a three-phase four-wire permanent magnet synchronous motor for fault-tolerant design, and through the introduction of structures such as isolation teeth, the influence between the phases of the motor is minimized and the mutual inductance is 0. Such advantages are analyzed as follows:

[0032] Assume Laa is the self-inductance of phase A winding, Lab is the mutual inductance between phase A and phase B, and use d / q axis inductance L d , Lq and zero-sequence inductance L0 can be expressed as

[0033]

[0034]

[0035] in,

[0036] Can get L0=L a1 +2L m1

[0037] θ e The electrical angle.

[0038] When designing a permanent magnet motor, the permanent magnet is designed to be surface mounted, and the d / q axis inductance is equal, then L a2 =0, and the mutual inductance DC quantity L m1 =0, then L q =L d =L a1 , L0=L a1 Therefore, the zero-sequence inductance is equal to the self-inductance DC value. After the fourth bridge arm participates in the work, it is equivalent to connecting an inductor with a value of the self-inductance DC value in series between the midpoint of the bridge arm and the neutral point of the motor, which can ensure the stability of the current and avoid the problem of increasing the large-size physical inductor and causing the power density to decrease.

[0039] The inverter voltage vector of the permanent magnet fault-tolerant motor system in a healthy state has eight states, namely (in the order of Sa, Sb, Sc) 100, 101, 001, 011, 010, 110, 000, 111. The voltage vectors of these eight states can be used to obtain the phase voltages of the three phases A, B, and C, and then the α and β voltages in the two-phase stationary coordinate system can be deduced to correspond to (0, 0), (0, 0). When phase A is disconnected, the inverter bridge arm corresponding to A is separated from the motor, and the motor neutral line is connected to the midpoint of the fourth bridge arm. At this time, the power topology composed of the fourth bridge arm and two healthy corresponding bridge arms can generate eight new switch states, which are (in the order of Sn, Sb, Sc) 100, 101, 001, 011, 010, 110, 000, 111. The voltage vectors of these eight states can be used to obtain the phase voltages of phases B and C, and then the voltages of α and β in the two-phase stationary coordinate system can be deduced to be (0, 0), (0, 0). It can be obtained that the α and β voltages are consistent in the healthy state and after one phase (taking phase A as an example) is disconnected, so there is no need to reconstruct the switch vector. After the fault, the motor neutral line is connected to the fourth bridge arm, and the two bridge arms in normal operation can provide the permanent magnet fault-tolerant motor with a suitable voltage vector, so that it can maintain the normal operating state.

[0040] According to the above analysis, the present invention adopts the following fault-tolerant strategy for the phase failure of the permanent magnet fault-tolerant motor: when the phase failure of phase A occurs, the switch signal originally given to the corresponding bridge arm of phase A is assigned to the fourth bridge arm, and the conventional PI control is adopted in the current loop control, and the switch signal is generated in conjunction with the SVPWM algorithm. Due to the absence of phase A, the above control will inevitably lead to a large fluctuation in the motor torque. In order to ensure the normal operation of the motor, the voltage compensation amount is derived based on the analysis of the difference between the voltage output by the inverter after reconstruction and the phase voltage in the actual motor, thereby realizing the fault-tolerant control of the permanent magnet fault-tolerant motor after phase failure. Specifically, Figure 2 As shown, the motor phase voltage u an、u bn 、u cn It can be obtained by CLARK transformation u α is the α voltage, u β is the β voltage. The inverter output voltage can be obtained through CLARK transformation

[0041] Because u 1n =0,u 2n =u bn ,u 3n =u cn ,get is the α voltage converted at the inverter output end, It is the β voltage converted at the inverter output.

[0042] After PARK transformation, we get

[0043] u d for u α and u β The d-axis voltage obtained by PARK transformation, u q for u α and u β The q-axis voltage obtained by PARK transformation is: for and The d-axis voltage obtained by PARK transformation is for and The q-axis voltage obtained by PARK transformation is:

[0044] Since in the case of phase A disconnection,

[0045] And through the motor fault tolerance design, the mutual inductance is zero, m ab (θ e )、m ac (θ e ) are the mutual inductance between phase A and phase B, and the mutual inductance between phase A and phase C. b 、i c are the currents of phase B and phase C respectively, e a A is the opposite potential.

[0046] Then there is u an =e a =-ωψ m sinθ e ,but

[0047] θ e is the electrical angle, ω is the electrical angular velocity, ψ m is the permanent magnet flux. By compensating the above two equations into the d / q axis forward channel, the phase failure fault tolerance control can be realized, in which only ψ m The permanent magnet flux is related to the motor parameters, and the permanent magnet flux changes very little during the operation of the motor, which can ensure the stable operation of the motor system with phase-failure tolerance.

[0048] Generally speaking, in a healthy state, the fourth bridge arm does not work, and it is difficult for the third harmonic current to obtain a closed loop, so it is difficult for the third harmonic space to form torque. However, when a permanent magnet motor has a phase failure, although fault-tolerant operation is achieved through voltage compensation, the third harmonic current is formed due to the participation of the neutral line. The third harmonic current and the fundamental back electromotive force, the third back electromotive force and the fundamental current will form secondary and fourth torque components, which will increase the motor torque after the fault. To solve this problem, the third harmonic current can be injected into the healthy phase to offset the secondary and fourth torques. The third harmonic current in the three-phase rotating coordinate system contains secondary and quartic AC components in the d / q axis coordinate system. The PI controller can be used in the conventional current loop to track the DC quantity, but there will be a large deviation in the tracking of the AC quantity. Therefore, it is necessary to introduce a resonant controller to track the AC quantity. The ideal resonant controller has infinite gain only at a fixed resonant frequency, but the actual speed of the motor is not a constant value during operation. The frequency of the actual harmonic current deviates from the fixed resonant frequency, and the control effect is weakened or unstable. Therefore, the resonant frequency of the denominator of the ideal resonant controller is set to the real-time harmonic frequency of the three-phase fault-tolerant motor. The current harmonics during actual operation can be adaptively tracked to achieve wide speed range control. The current loop control adopts the controller form of PI and PR in parallel. Where n is the real-time speed in rpm. P is the proportionality coefficient, K I is the integration coefficient, K r is the resonance coefficient, and p is the number of motor pole pairs. Based on the above method, when the resonant frequency is high, phase lag will occur, and at high frequencies, the delay of the digital system will also cause phase lag, and the higher the frequency, the more obvious the phase lag, causing instability. In order to further adapt to the low torque pulsation operation in a wide speed range after the motor phase failure, a resonant control method based on phase angle compensation is proposed. The phase angle is increased on the basis of the resonant controller to improve the system phase margin. The control block diagram is shown in the figure. Figure 3 As shown, the controller form used is It can realize wide speed range low torque ripple control operation after motor phase loss fault tolerance. φ1 is the phase angle compensation value of the secondary resonance controller, and φ2 is the phase angle compensation value of the fourth resonance controller.

[0049] Therefore, the present invention provides a three-phase permanent magnet motor system phase failure fault tolerance control method, which specifically includes the following steps:

[0050] (1) A system solution based on a three-phase four-bridge-arm power topology and a three-phase four-wire permanent magnet synchronous motor is adopted. The permanent magnet synchronous motor is designed as a surface-mount type, and an isolation tooth structure is introduced to reduce the mutual inductance between the motor phases to 0, thereby making the zero-sequence inductance equal to the DC value of the motor's self-inductance, avoiding the additional increase of the neutral line inductance, and creating conditions for reducing the dependence of fault-tolerant control on motor parameters.

[0051] (2) Assuming that one of the phases has a phase failure, the switch signal of the bridge arm of that phase is set to low, and the switch signal originally given to the bridge arm of that phase is assigned to the fourth bridge arm. At the same time, the output of the d-axis current controller is compensated Compensation on the q-axis current controller output Phase-failure fault-tolerant control can be realized, where θ e is the electrical angle, ω is the electrical angular velocity, ψ m is the permanent magnet flux;

[0052] (3) In view of the second and fourth harmonic torque problems after the fourth bridge arm is involved in the work and the instability of pulsation suppression control at high frequency, the current loop adopts the form of The controller can realize low torque ripple control in a wide speed range after the motor fails to tolerate phase loss.

[0053] like Figure 4 , 5 6 are torque waveform diagrams of the three-phase motor system at 400rpm, 1200rpm and 3000rpm, respectively, from healthy state to phase-failure fault tolerance and then to phase-failure torque pulsation suppression. It can be seen that the torque pulsation rate can be significantly suppressed in a wide speed range after adopting the method proposed by the present invention. Figure 7 The torque waveform of the conventional torque pulsation suppression method is shown. It can be seen that the torque suddenly increases and causes loss of control. Figure 8 The torque waveform of the same working condition using the method of the present invention is shown in the test. The test shows that the method can achieve phase failure tolerance and pulsation suppression in a wide speed range. Fig. 9 The speed tracks the transient command (1000rpm to 2400rpm) when the motor is in the state of phase loss and torque pulsation suppression. The experiment shows that this method has good adaptability to transient conditions in a wide speed range.

[0054] The present invention provides a fault-tolerant control method for a three-phase permanent magnet motor system. Under a single-phase circuit breaker fault, the dependence of fault-tolerant control on motor parameters is reduced through a comprehensive design approach of the motor and control algorithm, and the three-phase four-bridge arm power topology design is simplified to further achieve an improvement in power density. The robustness of low-torque pulsation control is further improved through phase angle correction to adapt to the working conditions of a wide servo speed range.

[0055] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A three-phase permanent magnet motor system phase failure fault tolerance control method, characterized in that: include: The three-phase permanent magnet motor system adopts a three-phase four-bridge arm power topology, and the motor adopts a three-phase four-wire permanent magnet fault-tolerant motor, wherein three bridge arms are connected to the three-phase windings of the motor in a one-to-one correspondence, and the midpoint of the fourth bridge arm is connected to the star-connected neutral point of the three-phase four-wire permanent magnet fault-tolerant motor; the three-phase four-wire permanent magnet fault-tolerant motor is a surface-mounted type, and an isolation tooth structure is designed internally to reduce the mutual inductance between the motor phases to 0; Assuming that one of the phases has a phase failure, the switch signal of the phase bridge arm is set to low, and the switch signal originally given to the phase bridge arm is assigned to the fourth bridge arm. At the same time, the output of the d-axis current controller is compensated. Compensation on the q-axis current controller output Phase-failure fault-tolerant control can be realized, where θ e is the electrical angle, ω is the electrical angular velocity, ψ m is the permanent magnet flux; The d and q axis current loops are in the form of The controller can realize the low torque ripple control in a wide speed range after the motor phase loss fault tolerance, where K P is the proportionality coefficient, K I is the integration coefficient, K r is the resonance coefficient, φ1 is the phase angle compensation value of the quadratic resonance controller, φ2 is the phase angle compensation value of the quadratic resonance controller, p is the number of motor pole pairs, and n is the real-time speed in rpm.

2. A three-phase permanent magnet motor system phase failure fault tolerance control method according to claim 1, characterized in that: In the three-phase four-wire permanent magnet fault-tolerant motor, the d-axis inductance = q-axis inductance.

3. A three-phase permanent magnet motor system phase failure fault tolerance control method according to claim 2, characterized in that: When the mutual inductance between motor phases decreases to 0, the zero-sequence inductance is equal to the DC value of the self-inductance.

4. The method for controlling a three-phase permanent magnet motor system in phase failure tolerance according to claim 1, characterized in that: The inverter voltage vector of the three-phase permanent magnet motor system in a healthy state has eight states, which are 100, 101, 001, 011, 010, 110, 000, 111 in the order of Sa, Sb, and Sc. The phase voltages of the three phases A, B, and C are obtained from the voltage vectors of these eight states, and then the α and β voltages in the two-phase stationary coordinate system are obtained.

5. A three-phase permanent magnet motor system phase failure fault tolerance control method according to claim 4, characterized in that: The voltages of α and β in the two-phase stationary coordinate system are (0, 0), (0, 0); Vdc is the bus voltage.

6. A three-phase permanent magnet motor system phase failure fault tolerance control method according to claim 5, characterized in that: The sequence of Sa, Sb, Sc refers to the switching state of the bridge arm connected to phases A, B, and C. Sx=1 means that the upper tube of the bridge arm connected to phase x is on and the lower tube is off, x=a, b, c.

7. The method for controlling a three-phase permanent magnet motor system in phase failure tolerance according to claim 5, characterized in that: When a phase is broken, the corresponding inverter bridge arm is separated from the motor, and the neutral point of the motor's star connection is connected to the midpoint of the fourth bridge arm. At this time, the power topology composed of the fourth bridge arm and two corresponding healthy bridge arms produces eight new switching states. The voltage vectors of these eight states are used to obtain the phase voltages of the two outer healthy phases, and then the α and β voltages in the two-phase stationary coordinate system are obtained.

8. A three-phase permanent magnet motor system phase failure fault tolerance control method according to claim 7, characterized in that: In the healthy state and after one-phase circuit breaker, the α and β voltages are consistent. There is no need to reconstruct the switching vector after a fault. The midpoint of the fourth bridge arm is connected to the star-connected neutral point of the three-phase four-wire permanent magnet fault-tolerant motor. Combined with the two normally operating bridge arms, a suitable voltage vector is provided for the three-phase four-wire permanent magnet fault-tolerant motor to keep it in a normal operating state.

Images