ROTOR RESISTANCE ESTIMATION FOR INDUCTION MOTOR USING MODEL REFERENCE ADAPTIVE CONTROLLER

Abstract

Induction motors are widely used machines in domestic and industrial applications due to its simple, low cost and rugged construction. There are many where speed operation of motor is required. Variable speed drives for induction motor cause both fast torque response and wide operating range of speed. Indirect vector control of induction motor is a predictive method, where the speed of the rotor flux is predicted from rotor speed and slip speed variation. The rotor speed may be obtained either from speed sensors or from the estimation method. Any variation in the rotor time constant due to increase in winding temperature may lead to improper flux orientation and hence deterioration of dynamic performance of the drive. Online estimation of rotor time constant is very essential for the flux orientation which subjected to the change of rotor time constant for variation in temperature. Due to changes in flux orientation and the coupling of flux and torque, the performance of the induction motor drive become sluggish. The estimation of machine parameters using model reference adaptive controller (MRAC) is described and analysed through simulation in MATLAB/Simulink. Model reference adaptive system controller utilizing the reactive power is presented for the online estimation of the rotor resistance to maintain the flux orientation in an indirect vector control of induction motor drive. The effect of sudden and slow variation in rotor resistance on performance of the indirect vector controlled induction motor (IVCIM). The formation of MRAC with the instantaneous and steady-state reactive power eliminates the estimation of flux. Reactive power based MRAC estimator is less sensitive to integral problems like saturation and drift. Simulation and analytical analysis have been presented in MATLAB/Simulink to validate the capability of the technique.