Study Of Torque Optimization In Field-weakening Control On Electric Vehicle’s Asynchronous Motor

The petroleum is not the low-cost energy in2012.Electric car is being the mostpromising vehicle to solve the problem caused by fuel vehicles.As its good performance, vector control technology has been widely used inelectric vehicle. But when the system frequency increased to the based frequency, therotor speed can not increase with the limited of the battery voltage. It must reduce theflux level to increase the rotor speed. That is field-weakening.In the field weakening region, the torque capacity decrease with the increasingfrequency, the torque output capacity mainly depends on the filed-weakening strategy.In the traditional field-weakening method, as the speed is greater than its basedspeed,the flux level is proportion to1/ωr. Although it is simple, this open-loopfield-weakening method can not provide maximum output torque nor full utilization ofDC-link voltage. The voltage detection method is insensitive to motor parameters andcan get maximum torque, but it is too complex. This paper uses effective optimizationstrategy to increase the torque output capacity.Based on the mathematic model of asynchronous motor, this paper analyses thevoltage and current limitation. This paper analyses method adopted, in order to improvethe torque output and the dynamic characteristics in the field-weakening region, thepaper discussed the two key issues in field-weakening: one is the judge of the field–weakening region,the other one is the current distribution strategy.Then it uses the Matlab/Simulink built field oriented control system based onSVPWM inverter, simulates and verifies the contents of the above studies, and then itgets an effective control algorithm. This paper which uses the TI’s TMS320F28035asthe system control core designs the motor driver and vector control system used inelectric vehicle.After that it builds an experimental platform used to real-time monitorcontroller, to facilitate the debugging personnel on-line debugging and real-timemonitoring. About that it describes the system’s hardware structure and related modules’design. Finally the problem appeared in the simulation and debugging experiment onthe vehicle are present as well as the method to solve them. Experiment and simulationresults show that the method in this paper is effective for increasing the motor outputtorque.