Direct torque control of brushless doubly-fed reluctance machines
Theoretical and Experimental results of research on the Direct Torque Control (DTC) of the Brushless Doubly Fed Reluctance Machine (BDFRM) are presented in this thesis. The main motivation for this work has been found in the relative simplicity of the DTC strategy and attractive properties of the BDFRM drive, foremost its cost-effectiveness associated with the use of a partially rated power electronics, and reliability of brushless structure of the machine itself. It is hoped that the project outcomes will be extremely helpful to the further study of the machine in light of its application in wind power generation and/or large pump systems. The thesis is essentially divided into three main parts. The first part is the theory development, which involves the analysis of the fundamental principles of DTC and BDFRM operation. The second part presents the comprehensive simulation studies of the developed control scheme for the machine in both sensor and sensorless modes. The computer studies have been performed to examine the performance of the controller based on a linear (ideal) machine model. The parameters used for this model have been obtained by off-line testing of a small Axially Laminated BDFRM prototype at Northumbria University, UK. The third part of the thesis contains a comprehensive set of experimental results that have successfully verified the control algorithm for the machine. Based on the Simulink® program, a Digital Signal Processor (DSP) control board from dSPACE® has been used to control a conventional IGBT inverter bridge.