Power Loss Comparison of Different Operation Modes of a Medium Voltage Solid-State Transformer

This paper focuses on optimized operation modes to reduce the overall power losses of a modular three-phase SolidState Transformer (SST) for an AC-DC grid coupling. The topology of the investigated SST is a Cascaded H-Bridge structure, consisting of a series connection of Dual Active Bridges (DAB) to provide a multilevel phase voltage. This structure inherently has several degrees of freedom to distribute the transmitted power between the modules. Using different approaches to distribute power among the DABs offers significant potential for reducing power losses. Extrapolated values for an SST phase, derived from experimental results of a 450 kW,720 V to 1800 V DAB, indicate a possible reduction of up to 20%.