ESTIMATION OF STATOR RESISTANCE IN SENSOR-LESS INDUCTION MOTOR DRIVE USING MRAS

Abstract

Industrial motor drive applications are usually complex and expensive. Most industries invest time and effort to implement drives which are low-cost, reliable, energy efficient and require low maintenance. In this field, the Induction motor (IM) is popular for its superior performance compared to its counterparts. There are two types of IM- squirrel cage IM and wound rotor IM both widely used. The popularity of the squirrel cage induction machine is attributed to its ruggedness (high output power to size ratio) and simplicity of construction. Recent advances in power electronics such as the Voltage Source Inverter (VSI) based drives have enabled variable speed control of IM’s. VSI based drive converts DC voltage into three phase voltage of variable magnitude and frequency based on requirements for motor control. This thesis has its foundation on a certain form of control called Indirect Vector control based on frame transformations, estimators and error based controllers. This thesis work presents a new sensor less vector control scheme consisting on the one hand of a speed estimation algorithm which overcomes the necessity of the speed sensor and on the other hand of a stator resistance estimation algorithm. In this work, the design includes stator resistance estimation and rotor speed estimation from measured stator terminal voltages and currents. The estimated stator resistance is given to the speed estimation block. The rotor speed is used as feedback in an indirect vector control system achieving the speed control without the use of shaft mounted transducers. The scheme is simulated using a 1.5HP, 460V, 50Hz induction motor.