The increasing share of renewable energy sources necessitates demand-side flexibility. Given the pivotal role of green hydrogen in the future energy landscape, integrating large-scale water electrolyser plants into electric grids could provide valuable support. This integration into ancillary markets offers dual benefits: grid stabilization and reduced costs for renewable hydrogen.

Current studies on grid connections for electrolysers often use simplified dynamic models that fail to account for the physical characteristics of the stacks. The balance of plant (BoP) equipment in an electrolyser plant which governs the temperature and gas pressure dynamics within the stacks are often overlooked in these simplified models. These temperature and gas pressure dynamics are on a much slower timescale compared to power electronics dynamics and are not adequately captured in simplified models. However, these are important to assess the suitability of the electrolyser plant for a given balancing services market.

In this work, we present a Simulink model that integrates both power electronics and process dynamics of an electrolyser plant, including BoP equipment. This model is employed to evaluate the performance of the electrolyser plant in balancing markets in Germany. Furthermore, operating tests described by German TSOs to satisfy prequalification conditions in German market are performed using this Simulink model and results compare the performance of electrolyser plant in FCR, aFRR and mFRR markets.

Our study demonstrates that electrolyser plants are particularly suited for the aFRR market in Germany, achieving setpoint changes within 5 minutes and meeting prequalification conditions set by German TSOs. This research highlights the importance of detailed dynamic modeling in optimizing the performance and economic viability of electrolyser plants in balancing markets.