Design Trade-Offs for Medium- and High-Frequency Transformers for Isolated Power Converters in Distribution System Applications

Medium- and High-Frequency Transformers (MFTs/HFTs) are a fundamental component in many isolated power-converter topologies proposed for electric distribution applications (e.g., solid-state power substations). Previous work presented detailed transformer design methodologies and addressed core loss limitations of different core materials and operating frequencies. However, MFT/HFT designs become significantly challenging for high power levels that are typical of distribution systems (e.g., greater than 100 kVA). Furthermore, few references include specific requirements in the design methodology like desired leakage and/or magnetizing inductances (which are normally specified for high-power applications). A design methodology for MFTs/HFTs is presented in this paper that accounts for tradeoffs like having a given leakage inductance for maximum power transfer (e.g., in the case of dual-active bridges (DABs)) or a given magnetizing inductance (to either attain a certain power transfer or to limit the power semiconductor currents). The design methodology is verified via Finite-Element Analysis (FEA) using ANSYS™ and an experimental prototype.