Small-signal admittance electrolyser circuit model for stability studies of multi-energy DC grid-connected hydrogen systems

Abstract

Renewable energies are increasingly being used as net-zero carbon power suppliers, replacing fossil fuels. Simultaneously, energy storage systems are emerging as complementary solutions to the intermittent and uncertain nature of these energies. In particular, hydrogen storage systems are being noticed as a promising option for future multi-energy DC power systems. One of the primary research topics regarding hydrogen storage systems is the prediction of system instabilities caused by interactions between DC grids and electrolyser and fuel cell DC/DC converters when hydrogen storage systems are connected. Frequency-domain methods are the most suitable to assess stability in large multi-energy DC power systems. Notably, the positive-mode-damping stability criterion is a friendly frequency-domain method that offers several benefits over techniques such as the generalised Nyquist criterion. The present paper contributes a small-signal admittance-based model of the electrolyser circuit of hydrogen storage systems. Using the proposed model, it analyses the resonance and the damping frequency regions of electrolyser circuits of hydrogen storage systems, and studies the influence of electrolyser circuit and multi-energy DC grid parameters on oscillatory instabilities by the positive-mode-damping stability criterion. The model and stability results are validated using MATLAB/Simulink time-domain and OPAL-RT (OPAL-RT4512) real-time simulations.