Comprehensive Overview of Power Electronic Converters for Electrolyzer Systems

The growing demand for green hydrogen has driven the development of efficient and grid-compatible power electronic converters for electrolyzer systems. In this context, this work provides a comprehensive overview of ac-dc and dc-dc converter topologies applicable to electrolyzers. Conventional multipulse rectifiers remain dominant in large-scale plants due to their robustness and low cost, although traditional 12-pulse rectifiers typically exhibit a current total harmonic distortion (THD) around 15%, failing to meet power-quality standards. Alternative solutions include hybrid and active front-end (AFE) rectifiers, which can improve power quality and controllability, with AFE configurations achieving near-unity power factor and current THD below 5% in the reviewed studies, enabling flexible operation and integration with renewable energy sources. Furthermore, non-isolated high step-down dc-dc converters can extend the conversion range and mitigate low-frequency current ripple. They can reduce dc-current ripple from typical values above 10% in six-pulse rectifiers to below 1% in AFE-based configurations, thereby enhancing electrolyzer lifetime and efficiency. A comparative analysis highlighting trade-offs among cost (ranging from approximately 85 to 160 €/kVA across the reviewed case studies), complexity, and performance is presented. In addition, emerging trends such as modular multilevel structures, interleaved topologies, and wide-bandgap semiconductor devices are identified as key enablers for future systems.