Study On Permanent Magnet Synchronous Motor And Its Drive System In Electric Vehicle Application

This dissertation is devoted to the study on the permanent magnet synchronous motor (PMSM) and its drive system in electric vehicle (EV) application. Four parts are included as follows:First of all, the phasor method is adopted to analyze the influence of the demagnetizing coefficient, saliency ratio and stator current control strategies of PMSM on the motor's voltage and current phasor loci and then the power capability and the flux-weakening level. The description of the PMSM's flux-weakening adjusting speed capability is worked out and expressed with the demagnetizing coefficient and saliency ratio, by which the radical method to enhance the PMSM's flux-weakening capability is concluded and the flux-weakening capability of PMSM with different magnet structures is compared.The design and calculation of PMSM used for EV are researched in the second part. Firstly, the calculating procedures are given to determinate the driven motor's performance parameters. Secondly, the influence of the rotor eccentric pole-arc is analyzed by finite element method (FEM) on no-load airgap permanent magnet flux density of PMSM with buried magnet. Simulated Annealing (SA) algorithm is employed to optimize the pole-arc in order to obtain sinusoidal no-load airgap permanent magnet flux-density distribution as well as possible, and the design rule to realize this target is presented which has been verified by calculation and experiment. Then, the parameter design and field-circuit coupled method of PMSM are studied deeply considering the EV drive demands. Finally, a 7.5kW PMSM prototype to drive mini electric bus is designed and manufactured.The third part concerns the winding switch of PMSM to compensate the shortage of flux-weakening capability of PMSM. The principle, method of winding switch in PMSM is given and the parameter change before and after the winding switch is analyzed. The transient process of winding switch and its effectiveness on the EV's climbing and initial acceleration are studied through simulation, and the efficiency improvement of the PMSM is verified by experiment when its winding connection is changed from parallel to series. The key points to the design of PMSM with winding switch are presented and the whole design method is given.In the forth part of this dissertation, the components of the control system of PMSM are introduced and studied, the hardware structure and the software procedure are given. The whole control system is completed, in which, the hardware system is realized with the single chip microcomputer (80C196KC) and other hardware circuits, and the control software is programmedwith the PL/M language. The whole system including the PMSM and the control unit is verified to be of well performances by experiment. At last, the digital simulation model of the EV driven by PMSM is given and the simulation software is programmed. Then simulation of the EV driven by the prototype PMSM is done considering the every operating condition.