Optimal short-term scheduling of a hybrid pumped storage system coupled with photovoltaic under reservoir-plan guidance

Hybrid pumped storage (HPS) plants can leverage existing cascade reservoirs to provide pumped-storage operation, thereby reducing the need for new reservoirs and lowering capital costs; consequently, they are increasingly viewed as a promising alternative to conventional pumped storage. However, while this configuration improves PV integration and enhances system flexibility, it also poses new challenges for coordinating multi-energy dispatch and managing cascade-reservoir regulation. This study selects the first two reservoirs/plants in the middle reaches of the Yalong River as the case system and develops a short-term multi-energy optimal scheduling model that integrates hybrid pumped storage and photovoltaic generation (HPS–PV). The annual water level regulation plan for the upstream reservoir is introduced as the primary driver of system operation innovatively. Five representative hydrological operation scenarios are then designed, covering water storage, steady operation, and drawdown phases under different water head conditions. Finally, from an energy-storage perspective, this study characterizes how cascade water-level management shapes the storage-state boundaries and the feasible operating region of the hybrid pumped storage system, and quantitatively evaluates its contribution to renewable energy integration and system flexibility.