ROTOR RESISTANCE ESTIMATION USING REACTIVE POWER BASED MRAS TECHNIQUE OF VECTOR CONTROL OF INDUCTION MOTOR

Abstract

The induction motors are the most famous and widely used machines in most of the industrial as well as in domestic applications due to its simplicity and low cost. When the variable speed applications are required the induction machines are used. For induction machines, variable speed drives requires both fast torque response as well as wide operating range of speed. Indirect vector control of induction motor is somewhat predictive method, where the speed of the rotor flux is predicted from slip speed and rotor speed. The rotor speed may be obtained either from the estimation method or from speed sensors. If due to a temperature change, there is any variation in the rotor time constant it may lead to uneven orientation of the flux and hence dynamic performance of the drive deteriorates. The continuous online estimation of rotor time constant or rotor resistance is very crucial for the flux orientation which subjected to the change of rotor time constant for variation in temperature. Due to lost in orientation of the flux, the coupling effect makes the performance of the induction motor drive slightly sluggish. Model reference adaptive system (MRAS) method is incorporated for the online estimation of the machine parameter. Model reference adaptive system controller using the reactive power (Q) is presented here, for the online estimation of the rotor resistance to maintain the flux orientation constant and fixed in an indirect vector control of induction motor drive. The formation of MRAS with the steady-state and instantaneous reactive power eliminates the estimation of flux. Reactive power based MRAS estimator is less prone to the integral problems like drift and saturation. Simulation results have presented to confirm the effectiveness of the technique.