Sensorless Stator Flux Observer for Direct Torque Controlled Interior Permanent Magnet Synchronous Motor Drives using the Current Derivative Approach

This paper proposes a sensorless stator flux observer for the direct torque control (DTC) scheme of interior permanent magnet synchronous motors (IPMSMs) drives in the very low speed region including standstill. The stator flux observer comprises the voltage model augmented by the current model. The position information required by the current model is obtained by a separate rotor position estimator that utilizes the current derivative of the machine. Due to inherent machine saliency, the stator current excites different responses during the application of the active and zero voltage vectors which in turn, can be analysed to retrieve the rotor position information. Unlike the signal injection method, the proposed method utilizes only the applied voltage vectors to the machine stator windings. The simulation results presented verify the effectiveness of the proposed approach.