Speed sensorless control of induction motor considering the flux saturation

When the air-gap flux of an induction motor is saturated, the conventional adaptive speed estimator cannot avoid the influence of the nonlinear inductance variation. In this paper, the authors propose a novel speed estimator having a hybrid architecture in order to estimate both the rotor speed and the inductance variation simultaneously. The proposed estimator consists of an error between the flux derived 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 error convergence of the proposed speed estimator is examined by performing the simulation. Furthermore, the experimental results show the validity of the proposed method