Stability Analysis of Simultaneous Estimation of Speed and Stator Resistance for Sensorless Induction Motor Drives

(AFO) in the regenerative mode at low speeds without feedback gain is demonstrated. Design of the observer feedback gain to guarantee stability, especially in the regenerative mode at low speeds is proposed. Closed-loop control systems of the independent use of the two estimators are developed. All gains of the adaptive PI controllers, based on Root-Locus method, are selected to provide good tracking performance and fast dynamic response. Performance of AFO using the proposed feedback gain and adaptive PI controller gains, with a sensorless Indirect Field Oriented (IFO) controlled induction motor drive, is verified by simulation and experimental results. The results show a good improvement in both the convergence and stability, especially in the regenerative mode at low speeds, which support the validity of the proposed analysis.