Multi-objective optimization and mechanism analysis of integrated hydro-wind-solar-storage system: Based on medium-long-term complementary dispatching model coupled with short-term power balance

The integration of multi-source renewable energy systems necessitates advanced operational frameworks to resolve temporal coupling challenges across different dispatching horizons. While existing studies have developed isolated short-term and medium-long-term dispatch models for multi-energy systems, critical knowledge gaps persist in establishing a multi-timescale coupling framework and elucidating how multi-energy interactions govern synergistic and competitive mechanisms in large-scale renewable energy bases (REB). To address this, we develop a medium-long-term complementary dispatch model incorporating short-term power balance for an integrated hydro-wind-solar-storage system. This model is applied to a REB containing 21.78 GW of combined wind power (WP) and photovoltaic (PV) capacity. Through controlled experiments with multi-objective optimization, we analyze complementarity effects on power generation and grid absorption, revealing the synergistic and competitive dynamics among hydropower, WP, PV, and pumped hydro storage systems. Simulation results demonstrate that optimized dispatch strategies increase annual power generation by 1.43 %–4.42 % while enhancing annual utilization hours of ±800 kV ultra-high voltage direct current transmission lines from 4,699 to 5,095 h. Notably, the interaction between hydropower potential and renewable energy utilization follows nonlinear relationships, contradicting the simplistic positive correlation assumptions prevalent in conventional studies. These findings advance theoretical frameworks for REB optimization while providing operational guidelines for balancing infrastructure synergies and resource competition.