Due to the variability of renewable energy, early-phase dynamic simulation of green energy plant is required to understand the entire process, analyse dynamic solution, and improve design/ opimization. Samsung C&T and AVEVA Korea have closely worked on building a standard dynamic model of large scale green hydrogen and ammonia production using APS. This model, created during the Pre-FEED stage, will be updated throughout the project lifecycle for detailed design, operator training (OTS), and real-time operational monitoring. It helps manage the variable power from renewables, ensuring stable and cost-effective ammonia production. The simulation aids in optimizing processes, validating control strategies, and enhancing overall project efficiency from start to finish.