向家坝电站调峰能力及其影响因素分析

Analysis on peak shaving capacity and its influencing factors of Xiangjiaba Hydropower Station

摘要

【目的】向家坝电站是“西电东送”的重要调峰电源，为充分挖掘向家坝电站调峰能力、明确各因素对调峰的影响，【方法】首先构建电站发电调度模拟模型和坝下游非恒定流水动力模型分别模拟电站调度过程和调峰出流情景下坝下游河道断面水位过程，接着通过尾水位和河道断面水位时段变幅最大值的映射关系求解尾水位时段变幅的阈值，然后根据电站调度约束条件和尾水位时段变幅阈值构建电站调峰能力计算模型，求解枯水期和汛期典型负荷曲线、不同量级来水和库水位组合条件下电站的调峰能力。【结果】结果显示：电站发电调度模拟模型可以较好地模拟电站出力，非恒定流水动力模型可以较好地反映向家坝坝下游水位实际变化过程；下游水位最大小时变幅与尾水位最大小时变幅显著线性正相关，根据两者的关系，尾水位最大小时变幅阈值取为1.3 m/h;通过增加尾水位变幅阈值建立的电站调峰能力计算模型可以求解兼顾坝下游航运需求的电站的调峰能力。【结论】向家坝枯水期和汛期最大调峰幅度分别为140~150万kW和240万kW,电站最大调峰幅度与单峰或双峰调峰模式无关，取决于基荷的大小。电站调峰影响因素表明，水库初始水位较低时，入库流量较小和入库流量较大将会分别使库水位和库水位日升幅超过限值，库水位日降幅和枯水期时库水位上限对调峰没有影响，汛期库水位上限≤378 m、入库流量较大、水库初始水位较接近上限水位时将限制电站调峰运行；电站可以调峰运行时，相同入库流量下，电站调峰能力随着水库初始水位的增高而增强，当达到电站最大调峰能力后保持不变；坝下游航运在枯水期时对电站调峰影响较大，但在汛期时无影响。研究成果对水电站调峰能力量化方法和向家坝电站调峰运行具有指导与借鉴意义。

Abstract

[Objective] Xiangjiaba hydropower station is an important peak-shaving power source for China's west-east power transmission. In order to fully tap the peak shaving capacity of Xiangjiaba hydropower Station and clarify the influence of various factors, [Methods] firstly, a hydropower operation model and a unsteady flow hydrodynamic model are constructed to simulate the reservoir regulation process and the water level process of the downstream river section of the dam under XiangjiaBa peak shaving scenarios, respectively. Then, the mapping relationship of maximum hourly variation amplitude of water level between downstream sections and tail water is used to calculate the amplitude threshold of the tail water level. Finally, according to the operation constraints and amplitude threshold of the tail water level, the peak shaving capacity calculation model is constructed to evaluate the peaking shaving capacity of Xiangjiaba hydropower station under different combinations of typical load curve during dry season and flood season, different levels of inflow and reservoir water level. [Results] The results show that the hydropower operation model can simulate the hydropower station output well, and the unsteady flow hydrodynamic model can simulate the change process of water level downstream of Xiangjiaba dam well. There is a significant linear positive correlation for maximum hourly variation amplitude of water level between downstream sections and tail water. According to the relationship between the two, the threshold of maximum hourly variation of the tail water level is set as 1.3 m/h. The peak shaving capacity of hydropower stations that take into account the downstream navigation demand can be solved by the peak shaving capacity calculation model established by additionally considering the threshold of maximum hourly variation of the tail water level. [Conclusion] The maximum peak shaving amplitude of Xiangjiaba hydropower station in dry season and flood season is 1.4~1.5 million kW and 2.4 million kW, respectively. The maximum peak amplitude is dependent on base load and independent on peak regulation modes of single and double peaks. Study of influencing factors of peak shaving capacity indicates that when the initial reservoir water level is low, a small inflow and a large inflow will respectively cause the reservoir water level and the daily increase in reservoir water level to exceed the limit. The limit daily decrease in reservoir water level and the upper limit of reservoir water level during the dry season have no effect on peak shaving. But the upper limit of reservoir water level will restrict the peak shaving operation of hydropower station during flood season when the upper limit of reservoir water level is ≤ 378 m, the inflow is large, and the reservoir water level is close to the upper limit.When the hydropower station can operate with peak regulation, the peak regulation capacity of increases with the initial water level of the reservoir under the same inflow, and remains unchanged after reaching the maximum value. The downstream navigation severely restricts the peak shaving capacity of Xiangjiaba hydropower stations during the dry season, but has no effect during the flood season. The research result can provide guiding and reference significance for the quantification method of peak shaving capacity of hydropower stations and peak shaving operation of Xiangjiaba hydropower station.

关键词

向家坝电站 / 调峰能力 / 影响因素 / 水位变幅 / 水电站 / 径流 / 数值模拟

Key words

Xiangjiaba hydropower station / peak shaving capacity / influencing factors / water level variation amplitude / hydropower station / runoff / numerical simulation

基金资助

中国长江三峡集团有限公司科研项目(0704201)

国家重点研发计划项目(2021YFC3200305)