Quantifying Grid-Forming Requirement for Electrolyzer-Based Hydrogen Production in Off-Grid Systems

Off-grid renewable power-to-hydrogen (ReP2H) systems face stability and economic constraints driven by the variability of renewable resources. This paper presents a comparative analysis of grid-forming (GFM) service requirements under three approaches, i.e., centralized GFM battery energy storage system (BESS), GFM electrolyzers and coordinated multi-source GFM strategies. We first establish detailed GFM models for off-grid ReP2H systems under each approach and then conduct hardware-in-the-loop (HIL) real-time simulations. By evaluating both dynamic performance and cost, we identify the strengths and limitations of the three strategies and quantify the GFM capacity needed to ensure stable off-grid hydrogen production.