Speed sensorless control of saturated induction motor using a hybrid speed estimator

When the air-gap flux is saturated, the conventional adaptive speed estimator cannot remove the influence of the nonlinear inductance variation. Without speed sensors, it is difficult to identify inductance variation using a reactive power model because the model contains a rotor speed term in itself In this paper, we propose a novel speed estimator having hybrid architecture in order to estimate both the rotor speed and the inductance variation simultaneously when the induction motor is operated under the saturation condition. The proposed estimator consists of the error between the flux induced from the stator voltage equation and the flux estimated from the rotor flux observer. Introducing the correction term into the estimator increases the estimation ability of the conventional speed estimator even though the motor flux is saturated. The convergence of the speed estimation error is examined by simulation. Furthermore, the experimental results show the validity of the proposed method