Physics-Based Design Optimization of High Frequency Transformers for Solid State Transformer Applications

The use of solid state transformers (SST) is fast becoming an attractive alternative to conventional low frequency transformers. For adequate galvanic isolation, the use of high frequency transformer (HFT) is of great importance to achieving high efficiency and high power-density SST. This paper proposes an physics-based design and multi-objective optimization of HFT for SST applications. A multi objective optimization algorithm that minimizes the volume of the core (maximizes the power density), the total transformer losses as well as the overall cost of the HFT is developed. A case study of a 20kHz, 10kW HFT is investigated, and the Pareto-optimal solution are presented. The results shows the dependencies of the objective functions on the various design variables. The results also show that, with careful selection of the design variables based on the developed method, the size, efficiency and cost of the HFT can be effectively optimized. Many of the Pareto-Optimal solutions show that an efficiency above 97% can be achieved in the HFT design for SST applications.