Comprehensive Effects of Operation of Pumped-Storage Hydropower Plants on Downstream Conventional Hydropower Plants

[Objective] Following the construction of pumped-storage hydropower plant upstream of conventional hydropower plant, its operation alters the original natural inflow process, causing increased frequency of water level fluctuations and intraday flow reversal regulation, thereby affecting the scheduling processes of the downstream conventional hydropower plants. Such effects are reflected not only in the water level regulation of the downstream conventional hydropower plants, but also in power generation output, operation stability, and economic benefits. A comprehensive analysis of the systematic effect of the operation of the pumped-storage hydropower plants on the downstream conventional hydropower plants holds significant practical value for scientifically developing scheduling strategies for regional power stations and improving overall operational efficiency.[Methods] To systematically and quantitatively analyze this effect, this study proposed a water consumption rate-head curve fitting method based on a multi-layer perceptron (MLP). By integrating this method with the local grid’s time-of-use electricity pricing policy, a power generation scheduling model for conventional hydropower plants was established. Subsequently, the variations in different economic operation indicators of conventional hydropower plants were analyzed under different scheduling modes of pumped-storage hydropower plants.[Results] When the existing scheduling modes of conventional hydropower plants remained unchanged, different scheduling modes of pumped-storage hydropower plants (“dual pumping and dual generation” and “single pumping and dual generation”) resulted in a decline of approximately 0.2 m in the operating water level of downstream conventional hydropower plants. Additionally, the water level regulation process was significantly altered, thereby affecting the generation heads during different periods. Under the “dual-pumping and dual-generation” scheduling mode, the annual power generation decreased by an average of about 6.667 million kW·h, accounting for 0.65% of the multi-year average. The annual power generation benefit decreased by approximately 9.667 million yuan, representing 2.02% of its multi-year average benefit. This was because the pumped-storage hydropower plant occupied part of the conventional hydropower plant’s reservoir storage capacity, lowering the conventional plant’s total generation head, increasing the unit water consumption rate, and reducing the composite output coefficient. Ultimately, the total power generation was decreased. Statistical results indicated that, under the “single-pumping and dual-generation” scheduling mode, the annual power generation of conventional hydropower plants reduced by an average of about 5 million kW·h (0.49% of its multi-year average), and the annual generation benefit declined by about 10.667 million yuan (2.23% of its multi-year average).[Conclusion] Further analysis shows that the operation of the pumped-storage hydropower plants has a pronounced “peak-valley mismatch” effect on downstream conventional hydropower plants: the operation of upstream pumped-storage hydropower plants reduces the maximum operating water level at downstream conventional hydropower plants, decreases the generation head during peak periods, increases available water flow during off-peak periods, and reduces overall water utilization efficiency. Consequently, conventional plants experience reduced power generation during peak periods, increased generation during off-peak periods, and an overall decline in total power generation. Although power generation during off-peak periods increases, the significant differences in electricity prices between the two periods result in insufficient off-peak revenue gains to compensate the losses during peak periods, leading to reduced total annual generation benefit. In summary, this study provides valuable insights for investigating the effects of pumped-storage hydropower plants on downstream conventional hydropower plants and for their planning and construction.