Research On Key Techniques Of Permanent Magnet Synchronous Motor Drive System Using In Electric Vehicle

Because of the worldwide energy crisis and environmental deterioration, electric vehicles(EVs) have been the development direction of automobile industry. As the core component of energy conversion, the motor drive system used in EV is of important significance. Permanent-magnet synchronous motors(PMSMs), which have high efficiency and large torque-to-weight ratio, are widely used in electric vehicles(EVs), particularly in midsize and compact EVs. Therefore, this paper focuses on the PMSM drive system used in EV, and seeks the novel methods to improve system performance in perspectives of motor design and control. This paper mainly includes the following contents:The construction features of PMSM used in EV are dicussed and the models of PMSM in different coordinate systems are given. Two kinds of conventional PMSM direct torque control(DTC) methods are presented to analyze the disadvantages for EV usage and indicate the improvement direction. The stable operation region of PMSM DTC that considers the torque monotonicity, as well as voltage and current limits of both the motor and invertor, is discussed for safe operation.An improved DTC scheme based on torque angle for the EV PMSM drive systems is proposed. Detailed control structure and loops are dicussed after introducing the regulation principles of electromagnetic torque and stator flux linkage. The role of zero voltage vector and the reliable starting methods are also studied. Influence factors of torque performance are discussed and the nolinear deadtime effect caused by parasitic parameters of the power switches is studied, to solove which, an indirect dead time compensation method is introduced.For improving the reliability of PMSM control system, this paper proposes a novel rotor position signals estimation method of PMSM using phase inductance. The inductance characteristic of PMSM is studied and the common position signals extraction methods are given for comparing. On this basis, the proposed phase inductance vectors iteration method is obtained, and the the simplified method is also proposed. To obtain the sensorless control method in wide speed range, an estimation method of stator fluxlinkage using high frequency injection is introduced. And the mixed stator fluxlinkage is obtained by combining the normal fluxlinkage estimation method.To satisfy the high efficiency operation demand of EV, the change rule of electromagnetic loss for PMSM DTC method is analyzed. Based on this, a online efficiency optimization is proposed. To weaken the requirement of search algorithm, the proposed method sperates the serching progress in multithreading ways using the discretization idea.A kind of consequent pole in-wheel motor is proposed for EV. The fundamental, structural features and design rules of the motor are anazelied on the air gap flux density, leakage flux, slot-pole match,cogging torque and saliency. The influence of motor structural parameters to the leakage flux and cogging torque is emphasized by comparing with normal PM in-wheel motor. Besides, the change rule and corresponding solution methods are introduced,. The arc iron core pole is introduced to further optimize the cogging torque. The saliency formation reason of proposed motor is discussed, and the influence of the shape of arc iron core pole and the magnet thickness to saliency is also reasearched.