Evaluating the performance of seasonal pumped hydro storage coordinated operation with cascade hydropower station integrating variable renewable energy

Seasonal pumped hydro storage (SPHS) presents a promising solution for China's evolving power systems dominated by variable renewable energy (VRE) sources with pronounced seasonal variations. Unlike conventional pumped storage addressing short-term fluctuations, SPHS integrates new upstream reservoirs with existing cascade hydropower through reversible units and pipelines to mitigate seasonal generation disparities in river-based hydropower systems. This study develops a refined nested long-short term production simulation model to evaluate SPHS's potential in facilitating VRE integration. The model examines three operational modes (non-regulation, short-term regulation, seasonal regulation) across different hydrological conditions and seasonal periods. Case results demonstrate that SPHS implementation enhances system VRE accommodation capacity by 20 % despite having only 8.6 % (1:11.6 ratio) of the downstream reservoir's storage capacity. Annual generation increases by 1.60 %, 1.02 %, and 0.84 % in wet, normal, and dry years respectively, while maintaining stable power supply. The analysis reveals significant sensitivity of system performance to SPHS's water storage redistribution strategies, suggesting seasonal flexibility optimization could yield additional benefits. The findings demonstrate SPHS's capacity to address seasonal hydropower variability while establishing a scalable framework for advancing pumped hydro storage's operational flexibility and evaluation methodologies in long-term renewable energy integration scenarios.