Parameterless rotor position estimation in a direct-torque controlled salient-pole PMSM without using additional test signals

Abstract

A vector controller is often applied to control a permanent-magnet synchronous machine (PMSM) at different operating points. A well-performing vector control method is the Direct Torque Control (DTC). From measurements of the stator phase currents only, the stator flux can be estimated and controlled in order to obtain the desired electromagnetic torque. To achieve accurate flux estimations in salient-pole machines the saliency should be taken into account for which the rotor position can be required. To avoid a position sensor in the DTC-PMSM, this paper discusses a rotor position estimator that computes the rotor position from the ripple in the stator current. For this purpose, the stator voltage, the stator current ripple and the relation of these variables to the rotor position is studied. The main advantage of this estimation method is that it can seamlessly be applied within existing direct torque controllers that operate in a broad speed range from standstill to high speed.