Analytical frequency-domain impedance modelling of large converter-interfaced electrolyser for grid stability assessment.

P.K.S Ayivor 1

1.TenneT TSO B.V, Netherlands

Flexibility needs in Europe, are projected to double by 2030[1], as renewable energy penetration targets aim for 42.5% penetration by 2030. Demand-side solutions are gaining prominence in the search for new sources for flexibility, as traditional supply side sources are phased out. Large converter-interfaced loads, such as electrolyser plants are increasingly being seen as potential sources of flexibility in the future grid [2]. This potentially rapid increase in large converter-interfaced loads (CIL) being applied for purposes of grid flexibility, presents both opportunities (ancillary services) and risks (potentially adverse interactions between converters and the grid, over a broad range of frequencies) [3]. It is therefore critical that these interactions are well understood to integrate large CILs into the power system while maintaining adequate stability margins. The impedance-based stability criterion [4] provides an adequate framework to support the assessment of small signal stability for such large converter-interfaced loads, however, adequate small signal impedance models of large electrolyzers, tailored for system level stability analysis, are not readily available. Bridging this knowledge gap is crucial.

This analytical study is an original analysis which will demonstrate the feasibility of creating a generic analytical small signal sequence impedance model of a PEM electrolyser system. The paper will provide an overview of the electrolyser plant, how impedance models are developed for each subsystem and how the subsystem models are combined into a unit level model and aggregated into a large-scale plant model. A case study will demonstrate the impact of operating points and converter control parameters on the overall impedance of the system at the grid interface and the impact on stability margins. This model can support system‑level parametric studies, offering a foundation for impedance‑aware control tuning, stability screening, and integration of large flexible loads into future renewable‑dominated grids.

References

[1] European Commission. (2025). Renewable energy targets. Energy Directorate-General. https://energy.ec.europa.eu/topics/renewable-energy/renewable-energy-directive-targets-andrules/renewable-energy-targets_en

[2] European Parliament. (2025). Increasing flexibility in the EU energy system – Technologies and policies to enable the integration of renewable electricity sources (Study No. 769347). Committee on Industry, Research and Energy.

[3] GridLab. (2025). Practical guidance & considerations for large load interconnections. https://gridlab.org/wp-content/uploads/2025/03/GridLab-Report-Large-LoadsInterim-Report.pdf

[4] J. Sun, "Impedance-Based Stability Criterion for Grid-Connected Inverters," in IEEE Transactions on Power Electronics, vol. 26, no. 11, pp. 3075-3078, Nov. 2011, doi: 10.1109/TPEL.2011.2136439.