Stability framework for off-grid hydrogen production systems: Coordinated control of steady-state source-load balancing and transient frequency response
Yongxin Lu, Guotian Yang, Jianguo Liu, Xinli Li, Wei Xu
Abstract
Disturbances within renewable energy hydrogen production systems can significantly impact the source-load balance. Off-grid hydrogen production microgrids , lacking support from the main grid, face critical frequency stability issues. Currently, research into the steady-state balance and transient stability of off-grid hydrogen production systems is isolated, and a comprehensive stability framework is still lacking. Additionally, the interplay between steady-state source-load balance and transient stability, along with related risks, remains unexplored. This paper proposes a novel architecture for an off-grid hybrid hydrogen production system, and a multi-time scale control strategy that integrates steady-state source-load balance optimization with transient frequency response control. We analyze the frequency regulation resource characteristics of off-grid hydrogen production systems and establish a transient coordination response mechanism based on these characteristics. To achieve direct and efficient coupling between renewable energy sources and hydrogen production loads, an optimized Variational Mode Decomposition (VMD) method is employed. This method improves the hybrid electrolyzer system's responsiveness to renewable energy fluctuations by decomposing, reconstructing, and precisely distributing that power. Furthermore, this method optimizes the grid-forming energy storage system's capacity reserve and transient frequency support. Results show that the proposed strategy achieves good steady-state balance and significant transient stability improvement. Specifically, it enhances the system's transient frequency regulation by over 25 %, reduces risk areas related to disturbance resistance by 75 %, and cuts energy storage costs to 17.6 % for maintaining steady-state source-load balance. This study provides valuable insights for refining the stability framework of off-grid hydrogen production systems and optimizing their coordinated control mechanisms.