A Family of New Multiport Power-Sharing Converter Topologies for Large Grid-Connected Fuel Cells

This paper presents a family of new multiport power-sharing converter (PSC) topologies for utility-scale fuel cell (FC) power generation. The proposed system connects multiple FC sources to a medium-voltage grid via a single multilevel neutral point clamp (NPC) inverter interface with high-frequency isolation. High-voltage series-connected inputs are achieved, despite safely referencing each source to ground. Also, unique power-sharing technology decouples series-connected source currents and enables control of each FCs individual power level. Multidimensional modeling and analysis of the proposed system´s PI- and PV-behavior is presented. Then, system topology and design considerations are discussed. Case study simulations show how this topology can operate four 250-kW FCs at separate power levels between 20% and 100%, while connecting to a single three-level NPC utility-interface. Correspondingly, a reduced-scale hardware prototype provides further proof of concept. Altogether, the proposed family of multiport PSC topologies realizes independent power control per source as well as increased output power, operational flexibility, thermal balancing, source availability, and cost effectiveness for utility FC power generation.