This paper describes a new control scheme for direct flux and torque control of an induction machine using integral variable structure control (IVSC). The conventional direct torque controllers show some undesirable torque responses due to utilization of finite number of voltage vectors or linear control scheme. For good torque responses, a new direct torque controller with nonlinear control scheme and space vector PWM is required.
The proposed controller has been designed on the basis of the stator flux field-orientation method and all the terms related to slip frequency have been considered as disturbances. To solve reaching phase and chattering problems, integral variable structure control with saturation function has been used. Consequently, a good torque response with no overshoot and no steady-state error has been obtained. The proposed control scheme has been implemented using DSP-based hardware and verified through simulations and experiments.