Direct Torque Control Of AC Motor Based On Fuzzy Control

Direct torque control of AC motor (Direct torque control, DTC) is a kind of high perform ance of AC speed adjustment method developed after vector control. Compared with vector control, direct torque control eliminates need for cumbersome coordinate transformation. By employing stator-flux-oriented, system control performance out of influence of the changing rotor parameters. With the aid of flux and torque hysteresis controller, DTC has got a direct and optimal control to the state of the inverter switch. DTC has got a universal attention for its novel control ideas, simple system structure, and excellent static and dynamic performance. However, there are some disadvantages of DTC, such as strong of ripple torque, flux linkage and current, and too much of the zero voltage vector is associated with the stator flux linkage distortion.The paper takes cold rolling mill main drive AC, it first analysis of traditional direct torque control basic principle and on the foundation of basic structure, direct torque control model was constructed. In Simulink environment through established traditional direct torque control system Simulink model, indicated the disadvantages existing in the system. Then to design the fuzzy control direct torque control system, fuzzy control to replace the traditional hysteresis control in traditional direct torque control system, realize the torque, flux linkage error of precise control of space voltage vector selection and accurate, through Simulink test, show that the fuzzy direct torque control system has a good dynamic response, the magnitude of the stator flux linkage is stabilized basically, torque ripple is controlled in a small range.Finally, for direct torque control system exist the ripple of flux linkage and torque, and system with speed sensor has lower reliability and higher system cost. To solve these problems, an extended Kalman filter (EKF) direct torque control system was established. Thus speed senseless direct torque control system for AC was realized. Through Simulink test, rapid torque response and strong robustness of direct torque control method are still maintained. At the same time, solve the problem of the flux linkage and torque ripple, thus realize the high performance of motor control.