Comparison of aggregated and detailed large-scale hydrogen electrolyzer plant models for grid integration studies

This paper compares the aggregated model of a large-scale hydrogen electrolyzer plant, represented by a single electrolysis stack and converter system, to the detailed representation of the individual electrolyzer modules, each consisting of a converter system and electrolysis stack. The purpose of this study is to determine in which scenarios the aggregated model of a hydrogen electrolyzer plant can provide sufficient results for grid integration studies, specifically frequency control and small-signal studies. The response of the aggregated and detailed models to frequency events is evaluated through real-time electromagnetic transient (EMT) simulations. Impedance analysis is carried out to compare the plants small-signal characteristics over a broad frequency range. The models of the electrolysis stacks are parameterized using data obtained from a real 10 MW PEM electrolyzer plant. It is found that the aggregated model provides accurate response to frequency events under the assumption of an even set-point profile of the electrolyzer modules. The small-signal characteristics are accurately represented by the aggregated model for high frequencies, but can differ in the subsynchronous frequency range. The study is useful to determine the necessary modelling detail for frequency control and small-signal studies of large-scale hydrogen electrolyzer plants.