In the global pursuit of decarbonization electrofuels have emerged as the key protagonist, offering a multifaceted solution across various sectors. At the forefront of this energy revolution is hydrogen, showing immense promise as a clean, sustainable and versatile energy carrier, capable of accelerating the transition to a carbon-neutral future. Since most demand for hydrogen production is in areas with scarce grid and good wind resource, the simplest most cost-effective approach to guarantee its "green-ness" is an islanded setup. This paper presents such a concept for large-scale green-hydrogen production from water electrolysis via electricity produced directly from a co-located onshore wind power plant. Special off-grid wind turbines and electrolyzer are used with a battery energy storage system and optimized plant controller. EMT simulations have been performed in PSCAD® using source code models to accurately assess plant stability and robustness. A load-flow study has also been conducted to verify the operational limits without additional network compensation. The results show that optimized control tuning can ensure operation of the off-grid green-hydrogen plant with a reduced battery unit size without additional stabilizing elements, thus achieving a minimum cost solution and attractive return of investment. The plant design solution is modular and scalable.