Direct Torque Control of Induction Machine Drives Using Adaptive Hysteresis Band for Constant Switching Frequency

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. In this paper, the adaptive hysteresis band control strategy is proposed, where the hysteresis band is controlled in real time as variation of applied voltage vectors. Thereby reducing the torque ripple whilst maintaining a constant torque switching frequency. The proposed adaptive hysteresis band control technique is verified by simulations. The system is first simulated by MATLAB 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.