Design of Medium-Voltage and Medium-Frequency Transformer for Solid State Transformers

This paper presents a design guideline of medium-voltage (MV) and medium-frequency (MF) transformer for the isolated dc/ dc stage in the solid state transformer (SST). A dedicated leakage inductance can be integrated inside the transformer to get rid of the extra auxiliary inductor for phase-shift based power control. Therefore, the circuit prototype could be more compact. The design guideline includes transformer topologies comparison, core material selection, winding type considerations, and power loss & thermal calculations. Some of the design parameters are further illustrated by finite element analysis (FEA). This transformer was fabricated and measured. Finally, the transformer was demonstrated in a 7-kV 10-kW 60-kHz dc/dc converter.