Vector control for a three-phase induction motor based on optimal regulator theory

A new technique for the speed control of a three-phase induction motor (IM), based on the improved optimal regulator theory is synthesized in this paper. The proposed technique comprises a new error system, vector control of IMs and a preview feedforward control loop. This is to enhance the transient response of the controlled system and to increase its robustness. The IM is described as a three-input, three-output controlled object. The state equations of the IM, suitable for current control, are derived based on the vector method. In addition, a field-oriented control system is constructed by deriving the state equations in a synchronously rotating reference frame, and trying to maximize the developed torque over the whole control range. In the synthesized control system, speed control and field-oriented control with constant flux are attained simultaneously. The design procedure of the optimal regulator technique with preview feedforward steps and the new error system technique are investigated. Computer simulation results are obtained to demonstrate the reliability and effectiveness of this controlled method