Design And Fault-Tolerant Control Of Permanent Magnet Synchronous Machine With Open Windings For Starter-Generator System

Multiphase motors have many advantages,such as more phases,good fault tolerance and small electromagnetic torque ripple.They are widely used in low voltage,high power and high reliability situations.Multiphase motors with open-end winding can eliminate the electrical coupling between windings,improve the utilization ratio of DC voltage,and further highlight its advantages in low voltage,high power and reliability.In this paper,a five-phase fault-tolerant permanent magnet synchronous machine(FTPMSM)with open windings is designed for the aerospace starter-generator system,and the control system of the motor is researched.Firstly,according to the requirements of motor design parameters and low-temperature operation conditions,the motor structure is designed.On the basis of the motor with open windings,small teeth are added to the stator core,which eliminates the physical contact and electromagnetic coupling between the windings and improves the fault tolerance of the motor.By optimizing the angle of small teeth,the motor fundamental winding coefficient is improved,and the power density is increased.Maxwell software is used to simulate and analyze the electromagnetic field of the motor,the size of the motor is refined and adjusted according to the simulation results,and the design size is determined.Then,in order to check the mechanical structure strength and vibration characteristics,the stress and mode of the motor are simulated and analyzed by ANSYS software.According to the structural parameters,the prototype is built.The experimental results of the prototype are basically in agreement with the simulation analysis.Secondly,according to the physical characteristics of the motor,the mathematical model is established.In view of the high content of third harmonic in back EMF,a scheme of injecting third harmonic current is proposed in the vector control system,and the simulation results are compared with the control strategy without injecting the third harmonic current.When choosing the basic space voltage vector for SVPWM pulse generation,the zero sequence current is effectively suppressed by choosing the space voltage vector without common mode voltage.Finally,the expression of residual four-phase winding current is deduced in order to realize the fault-tolerant control strategy in which the magnetomotive generated by windings remains unchanged when one-phase winding is open circuit.Two PWM pulse generation control algorithms,SPWM and SVPWM,are proposed for the fault-tolerant control strategy,which solve the problem of uncontrollable switching frequency in hysteresis control that widely used at present.The simulation results show that the two control algorithms are feasible.