Parameter estimation of vector controlled induction machine

Abstract

This thesis deals with the modeling and control of induction machine under indirect vector control with parameter estimation in order to get better field oriented performance. Because of its excellent decoupled control, wide flux weakening region and operation at low speed, indirect vector control is becoming popular. But as the rotor time constant varies the detuning of the control system occurs. Without exact rotor time constant the slip frequency calculation becomes inexact. In this thesis most of the existing methods of determining rotor time constant are discussed, and a novel approach for estimating the parameter using direct measurement is recommended. Instead of injecting high frequency disturbance in the inverter, an extended zero crossing period for a smaller amount of time is created. A complete model of the inverter and the machine is developed to assist the approach. Hysteresis and space vector modulation switching schemes have been compared. The new switching scheme requires the measurement of the back emf (electromotive force) through a transducer. Simulated results validate the claim.