A new torque controller for Direct Torque Controlled Induction Machine drives

Hysteresis band control is one of the simplest and most popular techniques used in direct torque control (DTC) of induction machine drives. However the conventional fixed band hysteresis control has a variable switching frequency which causes serious problems in DTC. To solve these problems a new constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller in this paper. The technique, based on the same concept, but with the hysteresis band implemented with fuzzy logic is proposed to optimize the DTC drive performance. The proposed technique is verified by simulations. The system is first simulated by MATLAB/Simulink and tested by hardware in the loop. Then, it is implemented based on a TMS320C6711, 32-bit fixed point digital signal processor. Experimental results prove the feasibility of the proposed strategy as compared with the conventional method.