Robust Controller Analysis and Design for Doubly Fed Induction Motor

Abstract

In this thesis, a model of the doubly fed induction motor system involving parametric uncertainties newlineand external disturbance is formulated. A Doubly fed induction motor(DFIM) newlineis essentially being as a nonlinear and unstable system for the torque tracking we have newlineadopted a novel approach to achieve sensorless control using measurement of only stator newlinecurrents. A Sliding Mode Control (SMC) is an effective approach to control nonlinear uncertain newlinesystems caused by its inherent insensitivity property to parameter variations and newlineexternal disturbances. A variant of the Discrete Sliding Mode Control (DSMC) known newlineas Multirate Output Feedback (MROF) was chosen to design the proposed controller newlinebecause the algorithm for MROF only makes use the output samples for designing the newlinecontroller. newlineWe proposed other various control schemes to DFIM for the analysis where first newlinestrategy proposed as deadbeat observer, which combined with a state feedback controller newlineconstitute a DFIM Deadbeat control, has faster response but could not attempt the newlinerobustness. In second implementation, We considered a novel strategy to achieve the newlinetorque and speed tracking via state reference tracking using the MROF based output newlinefeedback control in which state reference commands are used for computing it from newlinespeed and torque reference commands separately. newlineThen, we can estimate a nonlinear control which guarantees high performance tracking newlinein presence of input saturation. The output feedback is achieved using fast sampling of newlinethe output combined with a nonlinear control. The control is constrained to take values newlinewithin certain interval which can be scaled according to the motor rating. The tracking newlineperformance of the constrained is proved mathematically and via numerical simulations newlineboth in all the methods. newlineExtensive simulations were performed and the results show that the proposed robust newlineSMC-MROF controller has performed well in reducing the effect of matched uncertainty newlineand external disturbances. The proposed SMC-MROF generated better control performance newlinew