Decoupled scheduling of water-energy nexus system in coastal regions: A desalination-driven flexibility approach

With the high-proportion grid integration of renewable energy sources (RES), coastal and island regions are confronted with challenges such as insufficient conventional power supply, significant fluctuations in RES output, and severe flexibility shortages, which severely restrict system security and RES accommodation. Focusing on a regional water-energy nexus (WENS), this paper explores the flexible regulation potential of seawater desalination plants (SWDP) and proposes a day-ahead and intraday two-stage optimal scheduling framework. First, the operational characteristics of reverse osmosis (RO) desalination loads are analyzed, and an operational model covering water intake devices, high-pressure pumps, and water storage facilities is constructed to realize decoupled regulation of electricity consumption and water supply demand. Second, a two-stage scheduling model is established: in the day-ahead stage, the operating schedules of thermal power units (TPUs), desalination loads, and energy storage systems are optimized with the goal of minimizing total system operating costs; in the intraday stage, variational mode decomposition (VMD) is introduced to decompose the net load into high-frequency and low-frequency components. With the objectives of mitigating high-frequency fluctuations and reducing costs, the day-ahead plan is revised and the charging and discharging strategy of supercapacitors within the SWDP is optimized. Simulation results show that the proposed method can significantly reduce the day-ahead and intraday wind curtailment rates, effectively mitigate net load fluctuations, and simultaneously lower the total system operating cost, providing a feasible pathway for water-energy collaborative optimization in coastal regions.