Modeling and Control of a 5-Phase Switched Reluctance Drive for Low-Torque-Ripple and Wide-Speed-Range Operation

The Switched Reluctance Machine (SRM) is widely recognized for its robust, magnet-free construction and cost-effectiveness, making it a compelling alternative to Permanent Magnet (PM) and Induction Machine (IM) in a variety of applications. However, its widespread adoption is often restricted by inherent high torque ripple and acoustic noise, particularly in conventional 3-phase topologies. This thesis addresses such limitations by investigating the mathematical modeling and control of an unsaturated 5-phase SRM drive. The 5-phase architecture is deliberately selected for its superior capability to provide continuous torque production and smoother commutation compared to standard designs. A comprehensive mathematical framework is established to derive current profiling strategies specifically designed for ripple minimization. Initially, a Half-Sinusoidal Supply (HSS) strategy is developed to theoretically ensure constant instantaneous torque. To overcome the voltage constraints inherent to this method at higher speeds, a new Extended-Speed-Range (ESR) strategy is proposed. This approach utilizes a state-machine controller to maximize DC bus voltage utilization. Furthermore, a Balanced Torque Sharing (BTS) strategy is introduced to address unbalanced thermal and mechanical loading at low speeds by enforcing equal torque sharing between phases. The electromagnetic characteristics of the machine, including static inductance profiles, are obtained and validated using Finite Element Analysis (FEA) in the JMAG software environment. The proposed control strategies are then implemented and analyzed through detailed dynamic simulations in the PLECS software environment. Simulation results demonstrate that the proposed strategies can achieve significantly low torque ripple in comparison to classical 3-phase SRMs, while permitting an extended operational speed range. The ESR strategy is shown to more than double the base speed achievable by the HSS strategy while retaining very good ripple performance. The BTS strategy is proven effective in balancing phase loads without compromising dynamic performance. Overall, the outcome of the research activity developed proves that SRMs featuring the selected 5-phase topology can indeed provide very good performance when properly controlled, for example, according to the proposed strategies.