A New Hybrid Excitation Motor And It’s Controller For Electric Vehicle

The motor and controller for electric vehicles must be of the features such as high efficiency, large torque mass ratio and wide speed range. Resembling permanent magnet synchronous motors, hybrid excitation motors have the characters of high efficiency and adjustable air-gap flux by electrical excitation, which has obtained extensive attention. At present, domestic and foreign scholars in the field of hybrid excitation motor focus their research on basic theory, while little research in the field of motor speed control method, control strategy, design motor drive has been done. Although multiple prototypes of hybrid excitation motor have been brought up. but the common problem of complex magnetic excitation circuit and limited magnetic adjustment performance make them impossible to be used on electrica1cars which requires high magnetic adjustment ability. Therefore, according to the need of electric vehicles, in-depth research from following aspects are conducted for hybrid excitation motor and relevant control system in this paper.Firstly, this paper introduces the current research status and development trend of electric vehicle drive system and hybrid excitation motor control system, demonstrates the research significance of this topic, analyzes the structure and the magnetic adjustment principle of hybrid excitation motor, builds the mathematical model of the motor in stator and rotor coordinate axis system respectively.Secondly, the partition control strategy is put forward to meet the requirement of the hybrid excitation motor speed control. The control strategy and implementation of the methods at four regions of low speed standard area, low speed magnetic, high-speed standard area and weak magnetic area are explicitly elaborated. A non-turbulence current switching distributor for hybrid excitation motor between magnetic increasing, permanent magnet and weak magnetic states is also introduced in detail in this part.Thirdly, hardware and software design of the hybrid excitation controller based on partition control theory were conveyed, and various modules were analyzed in detail.Finally, a3-phase,8-pole,6kW hybrid excitation motor, as experimental subject, is used to test the performance of motor and controller, proved that the hybrid excitation motor drive system has good static and dynamic characteristics; By testing the driving system in increasing magnetic and weak magnetic conditions, the starting and dynamic response characteristics were proved to be satisfying. Making the motor work under fixed load, this paper compared the two states of the control system with permanent magnet and with increasing magnetic conditions as well as the power consumption. The analysis of experimental results showed that hybrid excitation motor control system was of superior characteristic performance for efficiency, dynamic response and with wider speed range.