Enhanced Control Strategy for Hydrogen PEM Electrolyzers Providing Frequency Support in Low-Inertia Isolated Microgrids

Abstract

Maintaining frequency stability is a major challenge in low-inertia systems due to the penetration of renewable energy sources (RESs). Hydrogen Proton Exchange Membrane (PEM) electrolyzers emerged as viable resources for ancillary service provision, providing flexible frequency support through dynamic adjustment of power consumption. This paper proposes a coordinated hybrid control strategy for PEM electrolyzers integrating rate of change of frequency (RoCoF)-based control with sustained droop control within a unified primary frequency regulation framework. A weighted-sum multi-objective optimization based on the slime mould algorithm is developed to determine the optimized controller parameters by minimizing the maximum absolute frequency deviation, the maximum absolute RoCoF, and the integral squared error. Trade-offs between transient and steady-state performance indices are investigated using Pareto-based analysis. The proposed strategy is extensively evaluated for a 60 Hz isolated low-inertia microgrid under challenging scenarios, including load disturbances, fluctuations and variations of RESs, and parameter uncertainty. Overall, the proposed strategy achieved the most balanced response, simultaneously delivering satisfactory frequency deviation, short settling time, and effective reduction in maximum RoCoF. Under the severe 20% load increase, for example, the proposed control strategy achieved the largest frequency nadir of 59.784 Hz among all investigated controllers, indicating superior frequency-support capability. It decreased settling time by 61.1% and maximum RoCoF by 46.4% compared with the basic droop controller. It reduced settling time by 55.9% relative to the RoCoF controller while maintaining a similar maximum RoCoF. Compared with the sustained controller, it lowered the maximum RoCoF by 52.5% while retaining a comparable settling time.