Hierarchical operation optimization of reserve storage capacity in pumped-storage power stations for enhanced high-penetration renewable energy accommodation

Pumped-storage power (PSP) stations play a vital role in promoting renewable energy accommodation, yet the operational potential of their reserve storage capacity (RSC) remains insufficiently exploited. This study proposes a hierarchical control framework for RSC in PSP peak-shaving and valley-filling operation, coordinating hydropower benefit and mitigating residual load fluctuation (RLF) while contributing to carbon emission reduction. The framework is implemented through a multi-objective operation model and applied to the Heimifeng PSP station in Hunan, China, under diverse equivalent load scenarios. Results reveal distinct allocation characteristics between the two reservoirs: preferred lower-reservoir RSC allocations are concentrated within 1–4%, whereas upper-reservoir RSC varies over a broader 1–7% range under different operating conditions. The coordinated operation scheme therefore achieves a compromise between hydropower benefit enhancement and residual load fluctuation mitigation. Under Scenario S3 in spring, the hydropower benefit reaches USD 22.92 million, while RLF is reduced by approximately 8% compared with fixed RSC control. Carbon emission reductions are achieved under all 12 load season conditions, with the maximum improvement reaching approximately 24% under Scenario S2 in winter. The proposed hierarchical RSC control framework enables scenario-adaptive RSC allocation and provides a practical approach for improving peak-shaving performance and hydropower benefits under high renewable energy penetration.