Abstract: With the rapid increase in the share of wind and solar renewable energy in power systems, enhancing the system’s regulatory flexibility and clean energy accommodation through multi-energy complementarity has become a critical challenge. Addressing the long-overlooked issue of hydropower generation costs in long-term time-series production simulations of multi-energy complementary systems, this paper proposes a "storage variation representation method" to quantify the energy consumption of hydropower station reservoirs. Based on this, we establish a time-series production simulation model for multi-energy complementarity that minimizes total system cost while considering hydropower generation energy consumption. Furthermore, a multi-timescale solution method is introduced. Case study results demonstrate that the proposed model reduces hydropower storage consumption by 37.42%, significantly enhancing long-term hydropower output sustainability while decreasing the Loss of Load Probability by 34.31% and thermal power operating costs by 14.11%, thereby reducing the dependency on thermal power for regulation. This work provides a reference for ensuring reliable, economical, and low-carbon coordinated operation in emerging power systems.