Optimal Sizing of High-Altitude Wind–Solar–Hydrogen Storage Systems Considering Hybrid Electricity–Hydrogen Dispatch

High-altitude regions provide abundant wind and solar resources but impose severe environmental constraints on energy storage systems. To address these challenges, this study proposes a bi-level optimal sizing method for wind–solar–hydrogen storage systems considering altitude-induced impacts. A system model integrating electrochemical storage and hydrogen storage is established, and a hybrid electricity–hydrogen storage dispatch strategy is designed to exploit their complementary characteristics. The upper-level optimization minimizes lifecycle cost using the Golden Sine Algorithm-Subtraction Average Based Optimizer (GSABO), while the lower level conducts 8760 h simulations to optimize the loss of power supply probability (LPSP) and excess energy rate (EER). A case study in western Sichuan, China, at an altitude of approximately 3500 m, demonstrates the method achieves 0% EER and 0.8% LPSP, reducing total costs by 50.65% compared to single electrochemical storage.