Synthesis and Digital Implementation of a Reduced Order Rotor Flux Observer for IM Drive

This paper deals with the rotor flux detection in IM drives by means of reduced-order observers. The basic structure discussed by Verghese et al.[l] is slightly modified, and a novel observer class is proposed. A detailed stability analysis by Lyapunov approach is conducted, and the effect of rotor resistance variation is investigated. The discrete time implementation of the observer model is considered, and the Z-transform method is used to ensure the stability of the observer whichever is the adopted sampling period. Experimental investigations are conducted on a direct field oriented (DFO) IM drive to test the on-line behaviour of the proposed observer class.