Research on Hysteresis Bandwidth Adaptive Algorithms in DTC Systems

The bandwidth of the conventional hysteresis controller for the Bang-Bang control is constant in the direct torque control (DTC) systems of induction motors, thus the ripple of the tuned flux and torque is stronger in low speed. In order to improve the torque and flux response, a hysteresis bandwidth adaptive control algorithm is proposed on the basis of conventional hysteresis comparator. By the comprehensive comparison of the current sample value, historical sample value of the torque error or flux linkage error as well as the historical output values of the hysteresis comparator, the current hysteresis control signal is achieved, and the zero voltage vector and the backward voltage vector are used fully to achieve satisfactory control effect. The simulation result shows that the new hysteresis control algorithm can not only effectively reduce the stator flux and torque ripple, but also can effectively reduce the switching frequency, and improve the efficiency of the inverter.