Transient Power Allocation Control Scheme for Hybrid Hydrogen Electrolyzer–Supercapacitor System With Autonomous Inertia Response

This paper proposes a hybrid hydrogen electrolyzer–supercapacitor system (HHESS) with a novel control strategy for renewable-dominant power grids. The HHESS consists of alkaline electrolyzers (AEL), proton exchange membrane electrolyzers (PEMEL), and supercapacitor (SC). The interfacing inverter between HHESS and power grid is regulated by an inertia emulation control strategy. Upon HHESS, AEL is with conventional V-P droop, whereas PEMEL and SC are designated with the proposed dynamic integral droop and capacitive integral droop, respectively. Benefitting from the coordination of three droops, within the HHESS, high-frequency transient power components are autonomously handled by SC, middle-frequency power components are regulated by PEMEL, and low-frequency steady-state power is addressed by AEL, characterized by low operational costs and longer lifespan. SC delivers immediate transient power, significantly alleviating dynamic stress on electrolyzers and achieving autonomous state-of-charge recovery without requiring additional communication. Implementing SOC recovery control enables the SC to withstand up to ten times more charge–discharge cycles compared to an SC without SOC recovery. Furthermore, a large-signal mathematical model based on mixed potential theory is established, providing clear stability boundaries for system parameters. Dynamic analyses theoretically verify system feasibility, and in-house hardware-in-the-loop experimental results fully validate the proposed HHESS along with the corresponding transient power allocation controls.