THE INVESTIGATION OF SENSORLESS CONTROL METHODS OF INDUCTION MACHINES FOR LOW SPEED OPERATION

Abstract

This dissertation report describes the investigation of sensor less control methods of Induction machines for low speed operation. Requirement of low cost, low maintenance, robust electrical motors has resulted in the emergence of the AC Induction motor as the industry leader. Induction motors have been used more in the industrial variable speed drive system with the development of vector control technology. This method requires a speed sensor such as shaft encoder for speed control. Sensors used in electric drives degrade the reliability of the system especially in hostile environments and require special attention to electrical noise. Moreover, it is difficult to mount sensors in certain applications in addition to extra expenses involved. The induction motor drives without mechanical speed sensors have low cost and size and high reliability. IM is mathematically modelled to get an approximate idea of the actual plant model. The vector control of IM is implemented by using PI controller. To make the system sensor less, we go for rotor speed estimation using MRAS technique along with Popov’s hyper stability criteria. MRAS identification is performed with three methods based on rotor flux, back emf and reactive power as the state variables. The different simulation results are observed and studied and the analysis of the different simulated results are presented. The dynamic performance of the estimators is analysed for parameter variations with particular focus on low speed operation. The Reactive power based MRAS method is observed to be the best method and tested with experimental setup on 400V test bench.