An improved flux regulation using a controlled hysteresis toque band for DTC of induction machines

This paper presents a dynamic hysteresis toque band strategy for improving flux regulation at low and zero speeds in a direct torque control (DTC)-look-up-table-based induction machine. The hysteresis torque band is controlled based on speed variation to solve the stator flux magnitude droops which normally occur at low frequency. The main benefit of the proposed approach is its simplicity, since it only requires a minor modification to the hysteresis band value and does not require an alteration on the lookup table. The simulation results of the proposed system showed a significant enhancement in speed and torque estimations at very low and zero speed and at the same time removes the problem of flux droop in the conventional hysteresis based DTC.