Droop-Based Hierarchical Power Management of Hybrid Hydrogen Electrolyzers Under Grid-Frequency Disturbances

Hydrogen electrolyzers, traditionally employed for hydrogen production, are increasingly being considered as dynamic assets for grid support. Hybridization of proton exchange membrane electrolyzers (PEME) and alkaline electrolyzers (AE) offers a balance between fast response and lower cost. However, droop-based power management for such hybrid electrolyzer systems (HES) remains largely underexplored. This paper proposes a novel droop-based hierarchical power management strategy for a grid-scale HES comprising PEME and AE units during grid-frequency disturbances. The strategy assigns distinct frequency-deviation dead-bands and droop slopes to each technology. The PEME, characterized by smaller dead-bands and steeper droop characteristics, is designated for primary frequency support. When PEME stack’s input power limits are exceeded under larger frequency deviations, AE units characterized by larger dead-bands and gentler droop slopes are activated to extend dynamic support within their limits. Both electrolyzers maintain constant-power operation for hydrogen production outside of frequency disturbance events. This hierarchical scheme enhances the dynamic range of grid-frequency support while preserving hydrogen output. Results demonstrate effective power sharing between the two electrolyzer types, leveraging their complementary strengths. Unlike prior hybrid approaches that broadly classify fast and slow components, the proposed hierarchical droop-based scheme explicitly links electrolyzer response to grid frequency using distinct dead-bands and droop slopes, ensuring coordinated participation of PEME and AE. This control-oriented approach is simpler, grid-compatible, and better suited for real-time ancillary service provision while maintaining hydrogen production.