Design of the Electrical Interface of Hydrogen Electrolyzers Limiting the Power Ramp-Rate While Providing Instantaneous Reserves

A massive capacity of Hydrogen electrolyzers (HE) is foreseen to be integrated into electrical power systems. Simultaneously, power systems worldwide are facing an increased need for instantaneous reserves (IR) to secure frequency stability. Therefore, provision of IR by HE may highly improve the reliability of future power systems. However, IR provision requires rapid power changes, which pose risks to the operation, and durability of large-scale HE. Consequently, power changes at the HE stack should be limited to practically confirmed ramprates. Thus, this paper proposes a novel design method to provide IR while limiting power gradients at the electrolysis stack to fixed ramp-rates. The developed method analytically designs the intermediate DC-link capacity to decouple the grid-side IR power gradients from the HE stack. The resulting designs are verified through EMT-simulations. The analytical analysis reveals that the required energy buffer highly depends on grid code requirements, particularly in case of slower power ramp-rates at the HE stack ($\leq {0.4}{\frac{pu}{s}}$). Moreover, the results show that the presented design effectively limits rapid power changes at the HE stack for worstcase frequency and phase jump scenarios.