Research on Improved Method for Connecting Water Level of Cascade Hydropower Stations Based on Peak Regulation Operation

The minimum discharge flow is one of the most critical indicators for coordinating the comprehensive utilization of water resources in cascade hydropower stations within basin water resource management.Generally, the implementation conditions of the minimum discharge for cascade hydropower stations are determined by the connecting water level. Existing research on factors influencing connecting water level determination has primarily focused on cascade reservoir operating water level overlap, river channel water depth between cascade reservoirs, and ecological protection, while insufficiently considering the impact of power station peak - shaving operations under the background of frequent extreme high temperatures and the "Double Carbon" goal.This study takes the TJZ - SW cascade hydropower stations in the lower reaches of the A River as the research object. Aiming at the collaborative problem of surging grid peak - shaving demand and river ecological flow protection, an improved method for determining connecting water levels in cascade hydropower stations based on peak - shaving operations is proposed through comparative analysis with traditional cascade water level overlap methods and downstream river channel water depth methods. The research reveals:1)The optimal connecting water level of the TJZ - SW cascade determined by the improved cascade water level connection method based on peak - shaving operations is 430.57 m. The comprehensive peak - shaving amplitude of the TJZ and SW power stations is increased by 0.2% and 8.8% respectively compared with the cascade water level overlap method and the downstream river channel water depth method. 2)The peak - shaving - oriented connecting water level mechanism maintains the water depth in the cascade power station reach to meet the ecological and environmental needs during low - valley periods. The TJZ and SW power stations improve power generation revenue through "pulse - type" energy storage and water head - flow optimization strategies respectively, increasing the total cascade revenue by 6.5% and achieving a phased reconciliation of the contradiction between "ecological protection" and "benefit pursuit". 3)The improved cascade water level connection method based on peak - shaving operations effectively coordinates multiple objectives such as power generation benefits of cascade power stations, safe grid operation, and river ecological flow protection. The coordination of negative discharge energy storage in TJZ during low - valley periods and early water storage in SW ensures 100% compliance with ecological flow throughout the entire period while achieving collaborative optimization of peak - shaving and economic benefits, with remarkable ecological, peak - shaving, and power generation benefits.The method proposed in this study provides a new path for resolving the contradiction between "ecological protection" and "peak - shaving emphasis" in the A River Basin and can also serve as a reference for the collaborative optimal dispatching of cascade hydropower stations in the Yangtze River Basin.