The integration of large-scale electrolyzers into modern power systems offers a promising solution to stability challenges from high renewable penetration. This paper presents a scalable modeling and control framework for grid-connected electrolyzers, linking electrochemical dynamics with system-level behavior. Detailed models of alkaline and proton exchange membrane electrolyzers are developed and scaled in DIgSILENT PowerFactory, featuring nested converter controls for droop-based active and reactive power support. Validation includes cell benchmarking, infinite-bus tests, and one of the first real-world grid simulations for electrolyzers using the Faroese bulk grid, demonstrating that electrolyzers can enhance frequency response and voltage support, acting as proactive stability assets in low inertia systems.