Research And Simulation On Direct Torque Control For Induction Asynchronous Motor On Vehicle

Direct Torque Control(DTC) technique of asynchronous motor, which is a new high-powered AC driving control technique after the Vector Control(VC) technique, has been developed rapidly in the recent decades. It is an excellent AC driving control technique which has high static and dynamic performance for its novel control method, simple structure and direct control mean.In the consideration of the characteristic of electric vehicle, asynchronous motor control system has been researched and DTC system of asynchronous motor on electric vehicle has been designed in this paper. Main research and work are described as follow.First, basic principle of DTC theory has been introduced briefly, and mathematic model has been analyzed. Driving system of electric vehicle based on DTC is researched according to the actual control condition of the electric vehicle.Second, problems of DTC system at low speed are analyzed in this paper. Anew method of observing and compensating stator flux based on U-I model has been puts forward to improve the performance at low speed. Integration of traditional U-I model is replaced by low-pass filter and problems about bias and DC initial can be restrained by using this method.Third, model of DTC system has been designed in MATLAB/SIMULINK environment, and the result of simulation has been analyzed. It shows that the improved DTC is better than the traditional DTC through comparison of the two control system at low speed.Last, According to the requirement, hardware system of DTC system has been designed. TMS320LF2407A DSP which is specialized in motor control system is used in the system. The software design of DTC system of electric vehicle is developed through embedding Assemble Language in C program.Through the research on AC motor driving system of electric vehicle, method on DTC and DSP control technique are combined perfectly. This method has practical value of application.