MRAS based Speed Estimator with Rotor Resistance Adaptation for Vector Controlled Induction Motor Drive

摘要

Presence of a speed encoder in the drive increases itssize, cost and decreases the reliability. Alternatively, rotor speedinformation can be gathered by the help of speed estimators whichutilizes the motor terminal voltages/currents. However, the speedestimation is adversely affected by the motor parameter variation. Itis well observed that rotor flux MRAS based speed-sensorless drivecan suffer from instability problem especially due to the variation inthe stator and rotor resistances of the machine. In this paper, effect ofrotor resistance variation on the speed estimation is studied. Also,online rotor resistance estimation is incorporated in the conventionalModel Reference Adaptive System (MRAS) based speed estimator.For rotor resistance estimation a comparison between the referencerotor flux and the adaptive rotor flux is made as the error in theadaptive system depends directly on the variation of value of rotorresistance. The rotor resistance adaptation loop a proportionalintegral controller is used which converges the rotor resistance valueexponentially to the true value. In the presented method the rotorresistance is capable of adapting any change in the rotor resistance.The stability of the system is also checked by introducing the error inthe rotor resistance without the adaptation method and with theadaptation mechanism. The complete simulation model is developedin MATLAB/SIMULINK environment.