Adaptive Stator Resistance Estimation Method for Speed Sensorless DTC Controlled IM Drives

Accurate knowledge of stator resistance is of utmost importance for correct operation of a number of speed sensorless induction motor control schemes. Since stator resistance inevitably varies with operating conditions, stable and accurate operation of speed requires an appropriate online identification algorithm for the stator resistance. In this paper, a robust full-order adaptive flux observer is designed for a speed sensorless DTC-controlled induction motor drive in which the stator resistance value is updated during operation and a new speed-adaptive law is given. By using robust control theory, the constant observer gain is obtained by solving two bilinear matrix inequalities. The stability of the flux observer is ensured in a sufficiently large symmetric interval include zero point. Therefore, the sensorless drive system is capable of steadily working in whole speed range from very low speed to high speed and exhibits good dynamic and steady-state performance. The proposed speed estimator with parallelled stator resistance identification is at first verified by simulation. Extensive experimentation is conducted next.