Feasibility Study of High-Frequency Transformer with High-Voltage Insulation Structure for SST Based Medium-Voltage Multi-Level Converter

Due to the rapid spread of EVs, the demand for fast chargers is increasing at a faster pace. High- power density multiport EV fast charger by utilizing SST based multi-level converter has been proposed. The high-frequency transformer mounted in SST is key component to realize high power density considering medium-voltage insulation between grid side and EV side. Then, this paper presents high-frequency transformer design including winding specification and insulation structure design for solid-state transformer (SST) based medium- voltage multi-level converter. The winding specification for tens kW level is studied by experimental evaluation. The proposed transformer design can reduce electric field between core and high-voltage side coil by shield plate and potential fixing plate. Therefore, proposed transformer can achieve features of both high-voltage insulation and suppressing the increasing of volume compared to a conventional structure. This paper also shows the electric field simulation results and experimental results of developed transformer.