Abstract: To address the combined challenges of wind-solar power fluctuations and seasonal hydropower disparities in the Qinghai grid under high renewable energy penetration, this paper presents a bi-level optimization model for energy storage capacity planning. The model explicitly considers the patterns of hydropower output and its complementarity with renewable energy by incorporating time-dependent operational constraints that quantify these characteristics. For a typical year, the optimized storage configuration in the scenario under certain time-segmented hydropower constraints is 526 MW/1578 MWh with a 3-hour duration, achieving a 91% renewable energy utilization rate. This rate is higher than the ones of 84%, 88%, and 86% achieved by the hydropower operations under no constraint, annual wide-constraint, and annual narrow-constraint, respectively. It verifies that our novel method that represents the hydropower features using quantified constraints enhances its rationality and applicability in practical applications of the storage configuration, thereby supporting higher renewable energy integration.

Key words: hydropower characteristics, multi-energy hybrid system, energy storage capacity optimization, bi-level optimization, renewable energy integration