Quantitative analysis and operation strategies for daily-regulation hydropower plants impacted by upstream plant

In recent years, hydropower has rapidly developed as an efficient and clean peak-shaving energy source to accommodate the large-scale integration of wind and solar power. However, the operations of upstream hydropower plants significantly alter inflow processes for downstream plants. For daily regulation hydropower plants, the limited regulation capacity amplifies the impact of inflow variability on power generation efficiency. Thus, adjustments to the operational scheduling of such plants are urgently required. This study proposes a research framework to quantify the influence of upstream hydropower plants on downstream daily regulation plants and to establish operational scheduling rules in response. Firstly, a flow routing model is developed to simulate both dynamic and diffusion waves in river flow propagation. Secondly, a two-stage short-term peak-shaving scheduling model is constructed by integrating the flow routing model with the daily peak-shaving operations of hydropower plants. A dynamic control strategy for the initial and final water levels is innovatively incorporated into the scheduling model. Finally, the Alpha shapes algorithm is used to derive operational scheduling rules for daily regulation hydropower plants. Taking the upstream cascade hydropower stations of the Han River as an example, the study concludes that newly constructed hydropower plants shorten the flow routing time between existing cascade plants. Coordinating peaking times reduces water level fluctuations and boosts downstream plants’ power generation. When the full generation discharge of upstream plants exceeds that of downstream plants, the multi-year average power generation of downstream plants decreases. Additionally, specific scheduling rules are established for downstream daily regulation hydropower plants to mitigate the impacts of upstream operations. These results provide scientific decision support for operators of downstream hydropower plants affected by upstream reservoir construction and can be extended to similar hydropower systems worldwide.