Design,Analysis And Control Of Fault-Tolerant Permanent Magnet Assisted Synchronous Reluctance Motor

Energy crisis and environmental degradation gave become recent worldwide concerns,which has aroused great attention from governments of various countries.The development of electric vehicles(EVs)is conducive to energy saving and emissions reduction.Due to the advantages of low price,wide speed range,high power density and overload capacity,the permanent magnet assisted synchronous reluctance(PMa Syn R)motors have good application prospect in the field of EVs.However,the large torque ripple,insufficient reliability and lack of control methods limit the application of the PMa Syn R motor with distributed winding.The PMa Syn R motor with segmented stator and modular winding is proposed to achieve both high reluctance torque and high fault tolerance.Then,the torque analysis models of the PMa Syn R motor with single-layer and two-layer flux barrier are established.Meanwhile,the relationship between the specific torque harmonics and position of rotor flux barrier is obtained and the reason that produces the torque ripple is revealed.In addition,in order to solve the shortcoming of large torque ripple of PMa Syn R motor,the methods of rotor flux barrier asymmetric deisgn and stator slot shifting are proposed.The torque expressions of PMa Syn R motors are derived after using the rotor asymmetric deisgn and stator slot shifting.Besides,the maximum torque per ampere(MTPA)control of the constant-frequency space vector signal injection is proposed to maximize the output torque of the motor.The research content of this paper includes the high fault tolerance performance analysis and evaluation,electromagnetic performance analysis and evaluation,torque ripple mechanism analysis,low torque ripple design,MTPA control and experimental verification and so on.The main research results of this paper include the following aspects:1.The reason for the low fault tolerance performance of the PMaSynR motor with distributed winding is studied.A modular PMa Syn R motor with high reliability and high torque density has been established,and the isolation of physical,electrical,magnetic,thermal between the winding modules is realized.Moreover,the electromagnetic performance and coupling between windings under open circuit,short circuit and inter-turn short circuit faults are analyzed.2.The torque analysis method suitable for PMa Syn R motors is proposed,and the analytical formula of torque generated by the interaction of stator and rotor magnetomotive force is derived.Based on the torque analysis expression,the specific angle of the flux barrier end is accurately calculated,then the specific torque harmonics are eliminated.The analytical method greatly shortens the calculation time and improves the optimization efficiency significantly.3.Based on the cogging effect of a single magnetic pole and a single stator slot,the basic equation of the total cogging torque is derived.The effect of the asymmetric rotor and stator slot offset on the torque harmonics is studied,and an analytical model of asymmetric design is established.In addition,this paper proposes the design of the end slot of the offset module to suppress the torque ripple caused by the modular design.The key structural parameters that affect the torque ripple are determined,which provides a theoretical basis and reference for the low torque ripple design of the PMa Syn R motor.4.Firstly,the mathematical model of the fault tolerant PMa Syn R motor is established,and the working principle of MTPA control is analyzed.On the basis,a MTPA control of fixed frequency signal injection method is proposed.The basic idea of the control strategy is to inject a small high frequency signal into the voltage vector,which causes high-frequency fluctuations in the amplitude of the flux linkage and stator current.Then,it can control the inverter and motor after passing through the signal processing module and space vector pulse width modulation(SVPWM)module.5.An experimental platform for fault tolerant PMa Syn R motor was established.The experimental study of the electromagnetic performance,fault tolerance and control strategy for fault tolerant PMa Syn R motor was tested.