Design of an Energy Hub for Stable Large-Scale Green Hydrogen

The study aims to validate the feasibility of an off-grid architecture dominated by converterbased resources (CBRs) and to define principles for frequency and voltage control. The work focuses on electrical architecture screening, stability assessment, and dynamic simulations to ensure robustness against severe disturbances and operational uncertainties.

The approach combines conceptual screening with detailed dynamic studies. Multiple architectures were evaluated, including centralized and decentralized configurations and AC versus hybrid AC/DC coupling. Screening criteria encompassed technical performance, operability, resilience, and cost. Dynamic simulations were performed using OEM wind turbine models and real wind data to capture fast transients. SCR-based stability indices guided the sizing of dynamic compensators. Frequency and voltage control strategies were tested under worst-case scenarios, including rapid wind ramps and busbar faults.

A decentralized AC configuration was identified as the most robust and cost-effective. It couples renewable generation and electrolyzers (ELYs) at 33 kV within hubs, interconnected by a 150 kV AC ring supplying critical process loads. This design minimizes power flows on the ring, reduces cascading failure risks, and leverages hydrogen pipelines for buffering.

In the absence of synchronous generators, system inertia is extremely low, making active power balancing critical. ELYs provide primary flexibility with ramp rates up to 2%/s, sufficient to manage wind transients without additional battery storage. A hierarchical control scheme—local hub coordinators supported by a Power Management Unit—optimizes load dispatch and emergency shedding. Simulations confirmed stability showing that a coordinated control if the ELYs improves the performances of the system.

Reactive power support and voltage control relies mainly on synchronous condensers

(SynCons). With proper dimensioning of the SynCons, the system can survive critical faults.

The sizing is very dependent on the robustness of the converters control tuning.

The study demonstrates that decentralized architectures, robust converter controls for weak grid conditions, and integrated stability strategies enable the deployment of gigawatt-scale off-grid Power-to-X systems. These findings provide a replicable framework for similar projects worldwide, supporting the transition to green fuels and resilient energy infrastructures.