Speed sensorless control of induction motor based on sliding-mode observer and MRAS

In this paper, the rotor speed of induction motor (IM) is estimated with a combined observation structure consisting of a sliding-mode observer (SMO) and a model reference adaptive system (MRAS) in series. In this algorithm extended magnetizing currents, referring to Γ-type representation of IM, are defined, and their actual values are feasible to be calculated from the voltage equations. Based on the intermediate variables, a SMO is constructed. The equivalent control components of the corresponding sliding-mode functions are further used as reference mode in the MRAS to estimate the rotor speed. As shown by simulation results, both the robustness to the rotor resistance and the dynamic performance are improved.