A PS-SWM strategy for isolated modular multilevel DC/DC converter with reduced passive component size and low total device rating

The isolated modular multilevel dc/dc converter (IM2DC) based on modular multilevel converter (MMC) is a promising dc/dc power conversion topology in HVDC/MVDC applications. In this paper, a novel phase-shifted square wave modulation strategy (PS-SWM) is proposed for IM2DC. Compared to the conventional modulation methods, the proposed technique achieves a smaller dc inductance due to higher equivalent switching frequency. In addition, the required capacitor energy can be reduced, which decreases the capacitor size without total device rating (TDR) penalty. The operation principles of the proposed method are presented. The passive components are designed and compared with those using other modulation methods. The experimental results are provided to validate the proposed modulation strategy.