Modeling and torque control implementtion for an 8/6 switched reluctance motor.
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Date
2005
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Abstract
This thesis begins with a brief introduction of the basic principles of operation of SRMs, and
explains how flux characteristics are derived from voltage and current measurements, and
presents results obtained from an 8/6 SRM. Torque characteristics are derived from these
flux characteristics using both the inductance and co-energy methods. Comparison of these
results with direct torque measurements shows that the co-energy method is significantly
more accurate than the inductance method. Electrical and mechanical simulation models are
derived from inductance and torque characteristics, and implemented in Matlab/Simulink.
Simulated results are shown to agree with measurements obtained from physical locked and
free rotor alignment experiments. These models are also used to illustrate the need for
sophisticated commutation strategies and high performance current control loops to achieve
low ripple torque control.
The Matlab/Simulink models are transferred to PSCAD to compare the current control
abilities, cost, complexity and robustness of the Asymmetrical Half Bridge (AHB), n+ 1
switch, and C-dump SRM converter topologies. The relatively high cost of the AHB
converter is justified in terms of its robustness, simplicity and superior capabilities for
current and torque control. The torque sharing function commutation strategy for low ripple
torque control is presented and simulated with hysteresis current control for the 8/6 SRM fed
from a four phase AHB converter.
A DSP implementation of the current and torque control loops is also presented and tested
under various dynamic speed and load conditions and recommendations are made for future
work.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006
Keywords
Theses--Electronic engineering.