An MRAS scheme for on-line rotor resistance adaptation of an induction machine

This paper presents a current model rotor flux observer based model reference adaptive control system (MRAS) scheme. The proposed MRAS scheme provides an attractive mean for achieving the rotor resistance adaptation for an indirect field oriented (IFO) induction motor drive system. The desired value of the rotor flux along the q-axis should ideally be zero. This condition acts as a reference model for the proposed MRAS scheme. The current model flux observer is an adjustable model. The machine parameters in the adjustable model are rotor inductance and resistance. Inductance does not change with temperature. Therefore, the only parameter which changes with temperature in the adjustable model is the rotor resistance. This resistance is adjusted such that the flux along the q-axis is driven to zero. The proposed method effectively adjusts the rotor resistance online and keeps the machine field oriented. The effectiveness of the proposed scheme is tested through simulation and is experimentally verified. Experimental results show that this scheme keeps the machine field oriented, provides faster and better speed/torque response and also improves the torque per amp output of the machine