Adaptive hysteresis band control for constant switching frequency in DTC induction machine drives

摘要

It is fairly well known that direct torque control (DTC)exhibits fast dynamic torque response, a property that originates inthe fact that torque and flux is directly controlled by instantaneousspace voltage vector, unlike field-oriented control. For this reasondirect torque control gradually has been used in the field, elicitingquick response and high efficiency since its introduction in themid-1980s. Conventional fixed band hysteresis control has severalproblems. One of these is variable switching frequency, which causesserious problems in DTC. In this paper, an adaptive hysteresis bandcontrol strategy is proposed, where the hysteresis band is controlledin real time as variation of applied voltage vectors, thereby reducingthe torque ripple whilst maintaining a constant torque switchingfrequency. The proposed adaptive hysteresis band control technique isverified by simulations. The system is first simulated by using theprogram Matlab and tested by hardware in the loop. Then, it isimplemented in hardware based on a TMS320C6711, 32-bit fixed-pointdigital signal processor. Experimental results prove the feasibilityof the proposed strategy compared with conventional method.