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

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.

Keywords

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