Fault-tolerant Db-dtfc Of Five-phase Permanent-magnet Synchronous Motor Based On SVPWM

Deadbeat direct torque and flux control(DB-DTFC)retains the advantages of simple structure and fast dynamic response of direct torque control(DTC).DB-DTFC solves the problems of large torque and flux ripple and high current harmonic content existing in DTC,and effectively improves the control performance when it is applied to permanent magnet synchronous motor(PMSM).Open circuit fault is the most common fault of PMSM,which not only affects the normal operation of the motor,but also causes harm to the motor structure.Therefore,an improved DB-DTFC strategy of five-phase PMSM is proposed to realize the undisturbed operation under open-circuit fault in this paper.The main contents of the paper are as follows:(1)Aiming at the problems of traditional DB-DTFC strategy,such as unsatisfactory mathematical model and large calculation amount,the paper proposes an improved DB-DTFC strategy based on the PMSM discretized mathematical model.The proposed strategy focuses on analyzing the influence of the voltage vector on the torque and flux linkage errors in a single control cycle,and solves the stator voltage that satisfies both torque and flux linkage requirements.A space vector pulse width modulation(SVPWM)based on adjacent four vectors is used to synthesize the target voltage vector.Considering the delay problem in the digital system,the current and flux observers are designed to compensate for the delay.The proposed strategy reduces the computational burden,realizes the decoupling control of torque and stator flux linkage,and better suppress the torque and flux linkage ripple and the third harmonic current.(2)When a single-phase open-circuit fault occurs in PMSM,the reduced-order transformation matrix after the fault is derived according to the principle that the stator magnetomotive force remains unchanged before and after the fault.The voltage compensation strategy is used to solve the offset problem of the neutral point voltage,and the space voltage vector is re-divided.An improved DB-DTFC strategy suitable for the single-phase open circuit of the five-phase PMSM is designed.(3)When the non-adjacent two-phase open circuit and adjacent two-phase open circuit faults occur in the PMSM,the reduced order transformation matrix is deduced to ensure that the stator magnetomotive force is consistent with that before the fault,and the rotor flux of the non-fault phase after fault correction is positive circle.An improved DB-DTFC strategy suitable for the two-phase open circuit fault of five-phase PMSM is designed.(4)The five-phase PMSM control experiment platform was built to carry out experimental research.The steady-state and dynamic performance of the motor controlled by the improved DB-DTFC strategy and the traditional DB-DTFC strategy are compared to prove its superiority.Furthermore,single-phase and two-phase open-circuit fault experiments are carried out by using the proposed open-circuit fault-tolerant strategy to realize the stable operation of the motor.