Study On Induction Motor Vector Control System Based On State Parameter Estimation

Induction motors are found great use in industry field because of its simple structure, reliable function and convenient maintenance. The emergence of vector control technology makes possibility for their applications in high performance control field. The vector control technology can be divided into indirect vector control system with open-loop flux and direct vector control with closed loop flux. Aim at the problems exist in induction motor vector control system such as time-varying parameters, unknown load change, uncertain disturbance and so on, this dissertation gives deep analysis and research on states and parameter estimation as well as speed compensation in vector control systems.Firstly, based on the Extended Kalman Filter technology, the rotor resistance is estimated according to the mathematical model of induction motor on two-phase static frame. The estimated result makes real-time compensation of rotor parameter change in vector control equations, so that the induction motor indirect vector control system with rotor resistance on-line compensation is realized, and the corresponding system performance is improved. The simulation results proved the validity of this method.Secondly, according to current model of induction motor rotor flux, taking consideration of the influences of process noise and measure noise, the rotor flux is identified in this paper using the Extended Kalman Filter technology. Meanwhile, since the speed sensor has problems associated with installation, connection, malfunction and so on, the motion equation of induction motor is added to the state equations of Extended Kalman Filter, so that the speed and load torque can be estimated on-line at the same time. Finally, the traditional speed controller is improved in this dissertation. The speed variation caused by load changes is reduced by taking load torque as feedforward input of speed control loop. The simulation results prove that the Extended Kalman Filter arithmetic can accurately estimate rotor flux, speed and load torque in whole speed range, also, the speed controller based on load torque feedforward compensation strategy can improve the dynamic response performance of the direct vector control system effectively.