Analysis of hysteresis band variations in DTC on the performance of IM drives

Abstract

Recently, Direct Torque Control (DTC) of AC motors is considered a significant method to attain torque control behavior compared to DC motors. However, it still suffers from some drawbacks such as the large torque and current ripples. Choice of hysteresis band amplitude is one of the initial difficulties involved in the technique since it determines ripple frequencies and amplitude error of control variables. This paper presents a comprehensive analysis of hysteresis band variations in DTC on the dynamic performance of induction motor (IM) drives. In this concern, effects of flux and torque hysteresis bands on switching frequency, torque and flux ripples as well as current distortion are explored. A simulation model is implemented by Matlab/Simulink. An experimental system of DTC for IM drives using DSP-DS1102 is built and tested. Experimental results are captured to prove the simulation results. The results show that the proposed DTC exhibits a good performance with minimum torque ripples and low current distortion under small hysteresis band amplitudes. However, small hysteresis band amplitudes produce high switching frequencies which cause high switching losses and high computation burden. To guarantee a high dynamic performance DTC of IM drives, a fuzzy logic controller (FLC) instead of a PI speed controller is designed.