Design And Simulation Of Direct Torque Control System For AC Motor Of Electric Vehicle

With the rapid increase number of fuel cars, the problems of oil resources shortages and environmental pollution have become increasingly serious。The electric car has received increasing attention due to its energy saving and environmental protection. It has be trend to make the transformation in the transport sector energy and power systems.Powered system is the core and key components of pure electric vehicles, it determines the power and economy of pure electric vehicles, even determines the industry, market competitiveness and development prospects of the pure electric vehicles. Therefore, the study of electric vehicle motor drive system has an important significance. Direct Torque Control is more simple and fast by using the stator flux and torque as control variable directly without field-oriented, vector conversion and current control. Currently, it has become one of the most widely studied and the most widely used method of AC motor speed control. In order to achieve overall performance requirements, this paper has studied the direct torque control of three-phase induction motor using in electric vehicles. Direct torque control is a new type of variable frequency speed control technology, which is developed after vector control and is suitable for the control of electric vehicle drive system.Aiming at the problem of flux overflow and torque ripple spill in the traditional direct torque control, the three-phase induction motor direct torque control was studied in the paper. New control method based on voltage space vector PWM was proposed. First of all, the target electromagnetic torque was generated by the amount of change of speed. Then, the magnitude of the voltage vector was calculated according to the amount of change of stator flux. The direction of the voltage vector was determined using the amount of change of torque. The three-phase input voltage was gained through the voltage vector PWM inverter to complete the overall control. The method overcame the shortcomings in traditional methods. The stator flux was controlled quantitatively, and the better circular flux trajectory control was achieved. At last, a system model was built based on Matlab/Simulink software. The results indicate that the system has stable flux magnitude, low torque ripple, fast response speed, short transient time, and can demonstrate the feasibility, advantages and effectiveness of direct torque control system.