Small-Signal Modeling and Analysis of a Grid-Forming PEM Hydrogen Electrolyzer

Green hydrogen production using proton exchange membrane electrolyzers (PEMELs) is increasingly integrated with renewable energy resources to enhance sustainability, storage, and grid resilience. Analyzing the stability and dynamics of such systems is complex and requires comprehensive modeling. This paper develops a detailed multiphysics small-signal model of a grid-forming PEMEL employing a unidirectional DC/DC buck converter and a bidirectional DC/AC inverter for grid integration. The model captures electrical, electrochemical, thermal, and fluid dynamics, and is validated against a nonlinear time-domain multiphysics model. Key factors affecting eigenvalues and mode shifts include stack temperature, current consumption, gas pressures, short circuit ratio (SCR), PI controller gains, and converter LC sizing. It has been demonstrated that low SCR operation can hinder system stability due to the inherently slow dynamics of PEMELs, leading to intermittent hydrogen production. Furthermore, temperature variations are shown to influence system stability conditions. The proposed model not only supports PEMEL integration in grid dynamic studies, but provides insights toward temperature and mass-flow management, highlighting the importance of detailed modeling.