Application of observer system to nonlinearly controlled induction motor fed by voltage source inverter

A nonlinear observer for an induction motor, taking the saturation effect into account, is presented. The observer is applied to a drive system with the induction motor linearized by nonlinear changes of variables and nonlinear feedback. The main problem in application of the observer to the induction motor is processing the output current and voltage signals of the inverter. Filtering of the signals must be performed without phase shifting. Two inverter control systems are considered and methods of signal processing are analysed. The two systems were investigated by simulation and results are compared. A signal processor was applied to realise the observer and control algorithm in real-time.