Harmonic Current Injection Fault Tolerant Control Of Interior Permanent Magnet Synchronous Motor By Considering Reluctance Torque

The interior permanent magnet synchronous motors have been widely used in electric vehicle field due to its high efficiency,high power density and good field-weakening performance.The reliable operation of the motor drive system is an important guarantee for the safety of electric vehicles.Thus,it is of great reserch significance to improve the fault-tolerant operation performance of interior permanent magnet synchronous motor.This paper proposes the harmonic current injection fault-tolerant control strategy and maximum torque per ampere(MTPA)fault-tolerant control strategy for five-phase interior permanent magnet synchronous motor.The proposed fault-tolerant methods can reduce the torque ripple caused by harmonic back-EMFs and improve the output torque performance and efficiency of the interior permanent magnet synchronous motor under fault tolerant operation.The main research contents of this paper include the following aspects:(1)The fundamental reduced-order transformation matrices under single-phase and double-phases open-circuit faults are reconstructed.Based on the reduce-order transformation matrices,the decoupled models in fundamental synchronous frame of five-phase interior permanent magnet synchronous motors under single-phase and double-phase open-circuit fault are built.(2)The third-harmonic reduced-order transformation matrices are reconstructed under single-phase open-circuit.The constraints of the current components under lowest joule losses and equal joule losses are given.Based on the mathematical model of torque produced by the fundamental fault tolerant current under double-phase open-circuit fault,the reference third harmonic fault-tolerant currents are calculated.Considering the difficulty of extracting the third harmonic currents from the measured current,the method which realized the harmonic injection in reference current module is proposed.Combining with carrier-based pulse width modulation(CPWM),the harmonic current injection at a fixed switching frequency is achieved,and the torque ripples are effectively reduced.(3)The virtual signal injection based MTPA control method is introduced briefly.Based on the decoupled model of five-phase interior permanent magnet synchronous motor in synchronous frame and the computing method of the d-axis and q-axis voltages under various open-circuit faults,the virtual signal injection control can be applied to realize the MTPA under fault tolerant operation by post-fault field oriented control and CPWM.It can effectively reduce the amplitude of fault-tolerant currents.(4)The motor drive experimental platform based on d SPACE is built,and the design of the hardware is introduced.The proposed methods are verified by the experiments under various operating conditions.