Sensorless PMSM drive system based on direct torque control in M-T frame synchronized with stator flux-linkage vector

This paper proposes a direct torque controller in a rotating M-T reference frame that is synchronized with the stator flux-linkage vector. Both the torque and flux estimator and the controller operate in the M-T frame, whereas conventional estimators operate in the stationary α-β reference frame. The proposed controller is suitable for rotor speed and position sensorless control of permanent magnet synchronous motors. Thus, this paper also proposes a rotor speed and position sensorless drive system based on direct torque control in the M-T frame. In addition, control laws such as flux weakening and torque limiting derived from equations in the M-T frame can be easily applied to operation over a wide-speed range. Experimental results demonstrate the effectiveness of the proposed system.