Frequency-Constrained Unit Commitment for Renewable-Dominated Grids Considering Electrolyzer Virtual Inertia and Primary Frequency Response

Abstract

The increasing penetration of inverter-based renewable energy sources significantly reduces power system inertia, posing severe challenges to dynamic frequency stability. Traditional frequency regulation heavily relies on the primary frequency response (PFR) of thermal units, which incurs high operational costs and limits renewable accommodation. To address these issues, this paper proposes a novel frequency-constrained unit commitment model that deeply integrates the flexible frequency support capabilities of power-to-hydrogen electrolyzers. By dynamically coupling the operational states of electrolyzers with the system total inertia and regulation capacity, the proposed model effectively utilizes electrolyzers to provide both virtual inertia and PFR. To overcome the computational intractability of the highly non-linear frequency security margin, a polyhedron-based piecewise linearization method is implemented, transforming the complex frequency dynamics into mixed-integer linear programming constraints. Case studies conducted on a modified IEEE 118-bus test system demonstrate that the active participation of electrolyzers successfully delays the frequency nadir time, mitigates the rate of change of frequency, and ensures strict frequency security. Specifically, under a severe 1000 MW power deficit, the proposed strategy elevates the frequency nadir to 49.727 Hz, strictly maintaining it above the 49.5 Hz security threshold, while simultaneously optimizing overall system scheduling economics and reserve allocations.