Dual Estimation Method of Speed and Stator Resistance for DTC Controlled IM Drives

An 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 impact of the stator resistance change on the speedless DTC control system is at first verified by simulation and then by extensive experimentation. The result shows that the proposed stator resistance estimator has a better dynamic performance, and is capable of modifying the estimated speed effectively.