Research On Practical Method Of Short-term Scheduling Of Tianshengqiao Cascaded Hydropower Plants

Driven by the reverse distribution of resources and demand in China,a number of huge cascade hydropower systems in southwest China have been built and put into operation.The project of "West-to-East Power Transmission" further promotes the construction of interconnected large power grid platform,and the operation mode of hydropower scheduling in China has changed accordingly.Scheduling from single reservoir to "one-reservoir with multiple cascade hydropower stations",receiving power grid from single to multiple,and absorption from local to trans-provincial,trans-regional,has produced a lot of unique problems that cannot be used for reference in China,such as cascade scheduling under complex hydraulic links,multi-grid peak shaving,etc.,which greatly affects the generation efficiency and planning arrangement.In this paper,aiming at the short-term optimal scheduling problem of "one-reservoir with multiple cascade hydropower stations",Tianshengqiao cascaded hydropower plants are taken as application examples to carry out the research on the formulation of short-term generation plan of cascade and the load distribution method among multiple power grids.The results are as follows:(1)Aiming at the short-term optimal operation problem of "one-reservoir with multiple cascade hydropower stations",with the unit as the basic dispatching unit,this paper put forward a short-term optimal scheduling model of cascaded hydropower stations with one reservoir,which takes the effect of backwater into consideration.Through the interval division of the downstream reservoir water level,the three-dimensional curve of tail water level ~ discharge ~ reservoir water level is described as three typical scenarios,and the linear description is realized by piecewise linear method.The developed model converts into a mixed integer linear programming model,which can be solved by commercial software Lingo.Based on a case study,the study shows that the proposed model considering backwater effect can realize the refined calculation and improve the economic benefits of scheduling.(2)Aiming at the problem of load distribution among multiple power grids,a multi-grid peak shaving method based on load sectional evaluation is proposed.Based on the load characteristics of the grid,the peak and valley segments of the daily grid load are divided,so that the weight of the peak and valley segments of each power grid is consistent with the agreed proportion.A quadratic programming model is constructed by taking the weighted average minimum of subsection standard deviation of the remaining load as the objective function of a single power grid and introducing the objective weight to transform the multi-objective problem into a single objective.The commercial software Lingo is used to solve the problem.The case study shows that the proposed model not only guarantees peak shaving effect,but also takes into account the requirements of timeliness.It provides a reliable solution for load distribution among multi-grid networks with different characteristics.