A drive system for six-phase switched reluctance motors

Abstract

Switched Reluctance Motor (SRM) drives have been developed for decades. They are advantageous because of their simple structure, low manufacturing cost, high system reliability and wide speed range. They are one of the types of traction drive system employed for electric vehicles and are also used in the aviation industry. In this thesis, a novel six-phase SRM is selected to be the research object. Two converters with fewer switches are proposed which are a circle converter and a circle converter with extra diodes. Conventional control methods are modified to suit the selected SRM and applied with the proposed converters. Simulation results are compared with the conventional Asymmetric Half Bridge (AHB) converter and show that the proposed converters can work effectively as the conventional converter. In order to further reduce the torque ripple of the six-phase SRM, a Direct Torque Control (DTC) method is developed and applied to the AHB converter and the proposed converters. Simulation results show that the DTC method can reduce torque ripple throughout the whole speed range compared with traditional control methods. The effects of winding connections on performance of the six-phase SRM are discussed to find the optimum winding connection type. The effects are first studied from a single-phase excitation. Subsequently five different winding connection types are proposed and analysed. Both torque performance and mutual inductance distribution are discussed through multi-phase excitation simulations and an optimum winding connection type is proposed. A 4.0kW SRM test rig is built and commissioned in Newcastle University. Experimental results validate the optimum decoupled winding connection type, demonstrate the feasibility of the proposed circle converters, and verify the highly effective torque ripple reduction performance of the DTC method throughout the whole speed range.