Research On Electric Vehicle Permanent Magnet Synchronous Reluctance Motor And Inhibition Of Torque Ripple

The advantages of Permanent Magnet-assisted Synchronous Reluctance Motor(PMASyn RM) in electric vehicles(EV) and hybrid electric vehicles(HEV) include high torque/power density, a wide speed range, high efficiency, and low cost, which make the motor become hotspot recent years. There are some critical issues of PMASyn RM to be addressed in the paper, such as the magnetic circuit analysis, mathematical modeling, the study about parameters of inductances and saliency ratio, the optimitzation of rotor structure, the volume of permanent magnet flux and the suppression of torque ripple. This paper will provide theoretical guidance for the design PMASyn RM.The different types of PMASyn RM has been given and the transversally-laminated rotor has been chosen in the research. The mathematical model, phasor diagram as well as theoretical analysis has been presented. After that, in order to obtain the wide constant power speed range, the effect of the inductance parameters on the electromagnetic torque within the full speed range has been studied. Thus the principle of selecting inductance parameters has been given. According to the principle and the dq axis equivalent magnetic circuit model, the relationship between the dq axis inductances, saliency ratio, reluctance torque, magnetic torque and the permanent magnet layers as well as the main dimensions of the rotor has been provided. Besides, the conclusions is validated with the finite element(FE) simulation.The rotor structure of the PMASyn RM for applications in Electric Vehicle is deeply studied in order to obtain high saliency ratio. The effects of different shapes of magnetic barriers on the inductance parameters and assembled magnetic effect is researched with theoretical analysis and FE simulation. The number of the layers is also been studied. Therefore, the principle of selecting the shape and the number of layers of magnetic barrier is given. Additionally, the proposed rotor geometry and related microscopic and macroscopic parameter definition for Syn RM is built. The effect of the main design parameters on the inductance parameters and reluctance torque is researched in order to give the optimal rotor structure.The high torque at low speed and minimal volume of permanent magnet is required for EV PMASyn RM. Therefore, the effect of the permanent magnet flux on the d-q axis current and electromagnetic torque for the ideal motor as well as the actual motor is presented respectively. Considering the actual control strategy, the optimal permanent magnet flux to get the maximum torque at low speed is shown, which is verified by the FE simulation.The low noise and vibration is required for EV PMASyn RM, so the study about the suppression of torque ripple is given in the paper. The precise equivalent magnetic network model is built at first. Then, the Fourier expression of the air-gap flux density produced by the armature current is obtained with flux continuity theorem. The Fourier expressions of the air-gap flux density produced by the permanent magnet and both effects are respectively obtained with superposition theorem. The Fourier expression of the electromagnetic torque considering harmonic is theoretically analyzed and simulated. In that way, two asymmetric rotor structure which can suppress the torque ripple is proposed. The effect of the barrier angle on the electromagnetic torque and torque ripple is theoretically studied and simulated. Finally, the optimal barrier angle is given.