Optimized Nine-Switch Converter-Fed Flux-Modulated Doubly-Salient Reluctance Motor Drive With Integrated ZSC Regulation Ability Considering Efficiency Improvement

Owing to the significant torque ripple and vibration reduction ability, flux-modulated doubly-salient reluctance motor (FMDRM) drives have been widely investigated. However, the parallel dual-inverter is commonly utilized in conventional FMDRM drives, where the power switch number is doubled compared to conventional ac motor drives. In this article, to reduce the utilization of power switches, an optimized nine-switch converter-fed FMDRM drive is proposed to achieve integrated zero-sequence current (ZSC) regulation ability. First, the winding connection is developed, and the equivalent vectors of the nine-switch converter are analyzed for the dc-biased sinusoidal current excitation. Then, a carrier-based space vector modulation (SVM) strategy is put forward, where the regulations of the rotating and zero-sequence voltage components are achieved, ensuring the dc-biased sinusoidal current excitation. Moreover, to further improve the converter efficiency and release the power stress of the middle switches, the modulation index clamping method is developed, where the switching actions of middle switches can be effectively reduced without sacrificing current regulation accuracy. With the proposed drive, the number of power switches is reduced by one-fourth, and a similar linear modulation region is achieved. Finally, the feasibility of the proposed FMDRM drive is proved by the corresponding experiments based on a three-phase FMDRM prototype.