Design of a Modular Multilevel DC/DC Converter to Solid-State Transformer in a Green Hydrogen System

Green hydrogen (GH
2
) is conventionally produced using water electrolysis. The electrolyzer is integrated into the grid using a power supply. This paper introduces a two-stage medium-voltage solid-state transformer (SST) system for electrolyzer power supply. The DC/DC stage is a modular architecture in an input-series output-parallel (ISOP) configuration and the basic power electronics building block is composed of a medium-frequency isolated five-level LLC resonant converter. The paper focuses on the design of the modular DC/DC stage and the multilevel converter, with the aim of optimizing its efficiency and component count. Simulation results of a 1 MW system are presented to validate the theoretical analysis.