Research On DTC System Of Permanent Magnet Synchronous Motor For Electric Vehicle

With the energy exhaustion and the increasing serious environmental issues, thenew energy, non-pollution characteristics of Electric Vehicle make it become not onlyan important development direction to improve environment and ease energy crisisbut also a hot research topic for scholars home and abroad. Motor control and drivesystem is one of the core components of Electric Vehicle. The currenthigh-performance motor control techniques mainly contain Vector Control (VC) andDirect Torque Control (DTC). Direct Torque Control is another AC speed regulationcontrol technology after the Vector Control, it abandons the decoupling idea of VectorControl, simplifies the complex coordinate transformation, has simple controlstructure, fast torque response, good dynamic and static performance, so is widelyused in the motor control system of Electric Vehicle.This paper takes three-phase sine wave permanent magnet synchronous motor(PMSM) of Electric Vehicle as the research object, Direct Torque Control as the basiccontrol method. It first introduces the structure of PMSM and establishs themathematical model, on this basis, analyses the basic structure and implementationmethods of PMSM DTC system.The control to PMSM in Electric Vehicle is actually the control to motor torqueand rotate speed in the driving process. The speed closed-loop of PMSM DTC systemconsists of outer speed ring and inner torque ring, the output of outer speed ring is theinput of inner torque ring, so the speed loop affects the system’s overall controlperformance to a large extent. The traditional DTC system uses speed PI control, fluxand torque hysteresis control, so it exists the problems of poor speed performance andlarge torque ripple which lead by nonlinear and strong coupling control object,operating condition variations in the motor as well as the variation of system load. Inorder to solve the above problems, this paper focuses on the speed fuzzy adaptive PIcontrol method of PMSM DTC system, introduces fuzzy control theory to thetraditional DTC system, adjusts Kpand Kiparameters of the speed PI controlleraccording to the speed error and error rate to improve the motor speed controlperformance in different operating conditions; adopts SVPWM control technology torealize the continuous adjustment of the voltage vector to reduce torque ripple. InMatlab7.1/Simulink environment, simulation studies of PMSM DTC system based on speed fuzzy PI control and SVPWM control are conducted.Finally, the system hardware and software are designed based ondsPIC30F6010A control chip and experimental researches are conducted on ElectricVehicle also. The hardware part mainly includes main circuitry, detection circuitry,communication circuitry, resolver interface circuitry and so on. The software partincludes the main procedure of control system and function procedure of each part.Human-machine interface controller is designed based on CAN Fieldbus in order tofacilitate the information exchange with DTC system. Simulation and experimentalresults show that the PMSM DTC system based on speed fuzzy PI control andSVPWM control has good static and dynamic speed performance, improves theproblems of large torque ripple and speed performance degradation of traditional DTCsystem when speed is affected by the external disturbance. The method has somepractical value in the Electric Vehicle.