Date of Award

2013

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

Keywords

Applied sciences, Electrical machines, Fast-filled algorithm, Matrix converters, Switched reluctance motors, Torque ripple

Supervisor

Narayan C. Kar

Rights

info:eu-repo/semantics/openAccess

Abstract

The tangential component of electromagnetic force in switched reluctance motors (SRM) produces the desired torque which fluctuates with rotor position due to the doubly saliency in physical structure of SRM. The conventional methods are insufficient to completely compensate for the intrinsic behavior due to double saliency. This dissertation proposes a novel method of eliminating the torque ripple in the instantaneous torque profile of SRM and a method to generate the precise reference phase current waveforms for even open loop operational design through global optimization. For the purpose of implementation of the proposed method, a non-sinusoidal DC matrix converter is also proposed to generate such waveforms without using multiple source voltages and to be able to use the drive in electric vehicle applications where a battery system is available for DC voltage sources. The experimentally-obtained characteristics are used for finding the optimal solution for torque ripple reduction. FEA is used to investigate the accurate EM force and its radial and tangential components using volume integration method. The proposed global optimization method can give a precise solution for this non-linear problem. Therefore a modified fast-filled method is proposed to balance out the crests and troughs of the torque ripples throughout the operation of SRMs. A set of novel reference current waveforms are generated for feed-forward torque control. Comparative analyses with the torque and current profiles of conventional methods are performed to prove the elimination of ripple up to less than 1% by using the proposed method. Therefore, it is concluded that the advanced turn-on and delayed turn-off angles with gradual rise and fall significantly eliminate the ripple. Inverter topology requirement for SRM is geometry-dependent. A multi-level converter is more suitable to generate the required position-dependent phase current. Matrix converters can be used for finer control on flexible current profiling. Therefore, a non-sinusoidal DC matrix converter is proposed to generate the required phase current waveforms from a single DC source and to accommodate the changes if required accurately. Three reduced-switching states schemes were tested with matrix converter resulting in the ripple elimination between 0.9% - 2% where 0.45% reduction is possible.

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