• A novel small-signal admittance model for fuel cell circuits is developed. • Negative damping regions of fuel cell circuits are identified and analysed. • Causes of instability in DC grid-connected fuel cell circuits are assessed. • Sensitivity analysis guides converter design and control to enhance grid stability. • The model’s accuracy is validated via OPAL-RT hardware-in-the-loop simulations. Hydrogen fuel cells are attracting growing attention as controllable power sources in emerging DC-based multi-energy systems. When integrated through boost-type DC/DC converters, their fast dynamics can interact with grid resonances and compromise system stability. Device-specific small-signal models and frequency-domain analysis methods, among other tools, can contribute to understanding of these interactions. This paper develops an analytical small-signal admittance-based model of fuel cell circuits derived from state-space averaging. The model is used to characterise the resonance and damping frequency regions associated with the fuel cell circuit and to evaluate their impact on DC grid oscillatory stability. The positive-mode-damping stability criterion—based on resonance mode analysis—is applied to interpret stability concerns in the frequency domain and to identify critical parameter sensitivities. In contrast to electrolyser circuits, fuel cell circuits exhibit distinct energy-supplying dynamics and negative damping tendencies, which are compared and discussed. The validity of the proposed model and its stability predictions are confirmed by MATLAB/Simulink time-domain simulations and hardware-in-the-loop experiments conducted on an OPAL-RT4512 platform. These results provide practical insights into the role of fuel cell circuits in the stability of hydrogen-integrated DC grids and support the robust design of future multi-energy systems.
Cartiel et al. (Sun,) studied this question.