An improved DTC of three-level voltage source inverter fed induction motor

Abstract

Three-level inverter fed induction motor (IM) drives are very popular in high power industrial applications. Different control techniques are being used to ensure good performance of these motor drives. Direct Torque Control (DTC) is one of the most renowned control techniques applied in IM drive systems to obtain high performance torque control. The aim of this thesis is to present an improved DTC technique for a three-level voltage source inverter (VSI) fed IM drive. A simple and unique three-level switching vector table (SVT) is developed to implement the DTC drive. The SVT is obtained by observing the most significant space vectors which reflect changes of motor flux and torque in the space vector region. The entire space vector region is symmetrically divided into 36 triangles and the instantaneous position of flux in each of the triangles is considered to investigate the effect of space vectors on increasing or decreasing the flux and torque of the motor. The proposed switching table is simple and gives proper selection of space vectors. As a result, an improved DTC which gives fast torque and flux responses in modern medium or high power IM drives. This thesis also reports a sliding mode direct torque control (SM-DTC) drive which contributes enhanced performance of the drive through reducing torque, flux, and current ripples. A comparative study of SM-DTC drive with existing DTC drive is also reported in this thesis. The system is simulated using MATLAB/ SIMULINK toolbox. Simulation results are used to point out the dynamic behavior of the improved DTC technique for IM drive.

Date of Award	2013
Original language	American English
Supervisor	Abdul Rahiman Beig (Supervisor)