Research on Direct Torque Control of Salient PM Brushless DC Motor

A novel direct torque control strategy of salient permanent magnetic brushless DC motor (BLDCM) without control for stator flux linkage amplitude was proposed combining with the characteristics of salient BLDCM and its operating mode with two phase conduction. This novel DTC adopts a single hysteresis-controlled torque loop to realize the rapid torque control by voltage vectors according to torque hysteresis comparison output and the position of stator flux linkage. The control theory of electromagnetic torque was set up using voltage vector in two phase conduction mode and the electromagnetic torque calculation mode was deduced in two phase static reference frame. A method of table lookup gaining the rotor back electromotive force (EMF) and flux linkage was applied to calculate torque as the BLDCM rotor back EMF is neither sinusoid nor trapezoid. Experimental results show that the proposed salient BLDCM DTC drive system has a quick dynamic response and good steady performance.