Thermal stress comparison in modular power converter topologies for smart transformers in the electrical distribution system

A Smart Transformer (ST) can cover an important managing role in the future electrical distribution grid. For the moment, the reliability and cost are not competitive with traditional transformers and create a barrier for its application. This work conduct detail designs and analysis for a promising modular ST solution, which is composed of Modular Multi-level converter, Quad Active Bridge DC-DC converters, and two-level voltage source converters. The focus is put on the loading conditions and thermal stress of power semiconductor devices in order to discover critical parts of the whole system when performing various mission profiles in the realistic distribution grid. It is concluded that the thermal stress for all stages is low during normal operation and especially the isolation stage is stressed least.