Adaptive observation of stator flux and resistance for speed sensorless DTC controlled IM drives

This paper presents the synthesis of an adaptive observer which is used for the improvement of the Direct Torque Control (DTC) of induction motor drives. The observer detects the stator flux components in the two-phase stationary reference frame, the rotor speed and the stator resistance by the measure of the stator terminal voltages and currents. The observer is adapted using a simple algorithm which does not imply a high computational load. Stability analysis based on Lyapunov theory is performed in order to guarantee the closed loop stability. Simulation tests under load disturbance and stator resistance variation are provided to evaluate the consistency and performance of the proposed control technique in the low and high speeds.