Design of high gain controller for part-load performance optimization of variable voltage induction motor drive

Improved performance of a lightly loaded induction motor, in terms of energy saving, is usually achieved by keeping the motor slip at an optimum value, which is obtained using stator voltage control. A PI-controller is normally employed to attain best steady state and dynamic responses of an induction motor. However, an induction motor is a nonlinear device and the parameters vary as the operating point changes. This requires a variable gain PI-controller, which has to be tuned according to the change in operating condition, which is very difficult to achieve. In this paper, a high-gain controller is intentionally introduced in the feedback path to obtain performance optimization, nullify the effect of parameter variation and reject external disturbance. A linearized incremental model of an induction motor is derived and is used for the design of a high-gain controller. The complete drive system is simulated in SIMULINK. Encouraging results are obtained and presented.