Hydrogen-Supported Fractional Virtual Inertia: A Fixed-Time Control Strategy for Enhanced Frequency Stability in Smart Grids

The transition toward low-carbon energy systems has heightened the challenge of maintaining frequency stability due to declining system inertia. Traditionally, synchronous generators provided inherent rotational inertia that mitigated frequency deviations following disturbances. However, their displacement by converter-interfaced renewable energy sources (RESs) has reduced overall inertia, leading to sharper and faster frequency excursions. To address this challenge, this study proposes a hydrogen-supported fractional virtual inertia (FVI) control strategy that exploits the dynamic capabilities of hydrogen energy systems alongside conventional and renewable generation units. A fixed-time (FxT) control strategy is incorporated into the FVI framework to achieve rapid and robust frequency recovery with guaranteed convergence within a predefined time bound, independent of initial system conditions. The effectiveness of the developed FxT-FVI controller is rigorously validated through implementation on a two-area interconnected smart grid comprising thermal, hydro, and gas plants alongside wind, solar, electric vehicles, and a hydrogensubsystem combining electrolyzers, fuel cells, and storage units. Simulation results show that the FxT-FVI controller significantly enhances frequency stability, limits rapid frequency excursions, and improves tie-line regulation under load disturbances, generation outages, and high renewable penetration scenarios. Comparative analyses confirm that the hydrogen-supported FxT-FVI scheme consistently outperforms conventional VI and FVI controllers, underscoring its scalability and effectiveness for frequency regulation in low-inertia grids.