Modeling and Design of a Medium Frequency Transformer with High Isolation and High Power-Density

With the increasing applications of medium voltage high power conversion, solid state transformer (SST) has received extensive attention because of its high power-density, flexible control and the ability to realize AC/DC hybrid connection. The high frequency, high insulation and high power-density development direction of SST also brings new challenges for the design of medium frequency transformers, which is the core component of the SST system. The contradiction between insulation and power density is particularly obvious. Therefore, this paper proposes a high power-density design method for medium frequency transformer under high insulation requirements (35kV), with the multi-physical models for each part of medium frequency transformer and precise estimation of internal temperature considering multi-layers of insulation materials. Through this method, a transformer prototype with 60kw capacity and 35kV insulation is designed and tested, and the power density has reached 10.5kW/L.