High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis

The problem of state estimation in induction motors is considered in this paper. In most previous works, motor observers have been designed using standard models, neglecting the saturation and hysteretic effects in the machine magnetic circuit. As a matter of fact, these effects cannot be ignored especially when considering (speed, torque) control strategies involving wide range flux variations, necessary to meet optimal operation conditions when facing significant load torque changes. In this paper, a high gain observer is designed for induction motors based on a model that accounts for the nonlinear hysteretic nature of the magnetic circuit. The observer provides estimates of the magnetizing current and magnetic variables using available measurements i.e. stator currents and voltages, rotor speed. The observer is formally shown to enjoy nice convergence properties. The theoretical result is confirmed by simulation. 