A new stator flux calculating approach for direct torque control based on multi-rate sampling

The flux estimating techniques currently used in the variable speed motor control are based on dynamic equations. It leads to the concern about the stable, fastness and error accumulation problems. In this paper, a new stator flux calculation method based on the multi-rate output sampling is proposed. By arranging the current sampling speed twice as fast as the control voltage updating speed, we can develop a multi-rate strategy to perform a static calculation of the stator flux in a direct torque control system. This paper introduces the methodology to get the relate equations and the multi-rate direct torque control system structure. Simulation results have shown the effectiveness of the proposed method.