Transformer Design for Solid-State Transformer (SST)-Based EV Charging Station Applications

Solid-state transformers (SSTs) are extensively studied nowadays to replace the line-frequency transformers (LFT) in various applications such as EV charging stations. The SST technology provides more controllability over the system, has the ability of power factor correction, and drastically reduces the size and weight of the whole system thanks to the medium-frequency transformer (MFT) used instead of LFT. In this paper, an optimized design tool is developed to design a 100 kW, 20 kHz transformer to be used in an SST-based EV charging station. The tool takes the system specifications as an input from the user then chooses the optimal core, number of turns, and Litz wire, to accelerate the design process. Two scaled-down 5 kW MFTs are implemented. The first was designed using the commonly used method in literature which ensures no saturation occurs in the core and limits the core losses to a certain value. Then, the transformer designed based on the developed tool is compared with the conventional design in terms of volume and efficiency. The transformer is also implemented and tested to compare the leakage inductance with the analytical and simulated values.