Research On Short-term Optimal Operation Of Cascade Reservoirs Under Complex Hydraulic Connection

With the rapid development of hydropower development and construction,China has planned to build thirteen hydropower bases including Jinsha River,Yalong River,upper reaches of the Yangtze River,Lancang River,etc.The focus of hydropower energy development and utilization has gradually shifted to the joint optimal operation and management of cascade reservoirs.Through fully excavating the compensation benefits of hydrology and reservoir capacity of cascade reservoirs,the joint optimal operation of cascade reservoirs can improve the comprehensive utilization benefits of flood control,power generation,shipping,water supply and ecology of cascade reservoirs,and realize the efficient utilization of water resources in the basin.Short-term operation of cascade reservoir,as the final execution unit of medium and long-term optimal operation,can be directly used to guide the actual operation of cascade reservoir.However,the traditional short-term operation model of cascade reservoir uses tail-water level curve method to calculate the water level downstream of reservoir,which does not consider the "aftereffect" of water level changes downstream,and is not enough to accurately describe the characteristics of tail-water level of hydropower station.In addition,traditional short-term dispatching models mostly adopt comprehensive output coefficient method or calculate force based on optimal flow distribution of economic operation in the plant.The comprehensive output coefficient method does not consider the differences between different operating conditions of the plant.The calculation method of optimal flow distribution in the plant is biased to be ideal.In practice,it is difficult to achieve the optimal operation mode in the plant due to the requirements of safe and stable operation.The problems mentioned above make it difficult for traditional dispatching model to accurately describe the actual operation process of hydropower station,resulting in deviations in the actual implementation of the proposed dispatching scheme and waste of water resources.Therefore,how to construct a reasonable and accurate short-term optimal dispatching model and formulate an optimal dispatching scheme more in line with actual operation,so as to improve actual power generation efficiency of hydropower station and ensure safe and stable operation of hydropower station are key engineering problems to be solved urgently.In order to solve this problem,based on data mining,hydroelectric energy,operation research and other theories and methods,this paper focuses on the accuracy of short-term dispatching scheme,short-term optimal dispatching model of cascade reservoirs and solving algorithm.The main research contents and innovative achievements include:(1)In order to provide accurate basic data for cascade short-term optimal dispatching modeling and improve the accuracy of short-term dispatching scheme,a forecasting model of downstream water level and water consumption rate based on random forest & gaussian process regression model was established.Construct the set of alternative factors with or without aftereffect,screen the alternative input factors with random forest,then establish the Gauss process regression prediction model.The results show that the forecasting accuracy of the model considering aftereffect is significantly improved and it still maintains good forecast performance in rolling forecast.Integrating downstream water level and flow rate prediction model into cascade reservoir dispatching calculation model significantly improves the accuracy of model calculation and provides reliable support for reservoir dispatching program preparation.(2)Based on the accurate description of the change characteristics of water level and flow rate downstream,and aiming at the reliability requirement of scheduling scheme for cascade reservoir actual production and operation,an optimal short-term power generation dispatching model for cascade reservoir is established considering hydraulic links such as backwater jacking effect,after-effect of downstream water level change and flow propagation delay.A hybrid optimization algorithm(EPOA-GSA)based on extended Progressive optimization algorithm and gravity search algorithm is proposed to solve the model,and EPOA algorithm is used to optimize the outer layer and GSA algorithm is used to optimize the inner layer.The results show that the model can more accurately describe the actual operation process of the power plant,and the proposed algorithm guarantees the quality of the optimization results while having a high solving efficiency.It provides an effective way for accurate and efficient formulation of short-term optimization scheme of cascade reservoir.(3)For different dispatching tasks of cascade reservoir in non-flood season and flood season,the generation-storage coupling model of cascade hydropower station in response to peak regulation demand and the maximum cascade generation capacity model of the Three Gorges Reservoir in response to flood dispatching demand are established respectively.Under the condition that the power generation plan of the Three Gorges Hydropower Station is determined,the energy consumption of the Three Gorges Hydropower Station and the power generation of the Gezhouba hydropower station can be considered equally when the power generation-storage coupling model is optimized for the operation process of the Gezhouba dam,so that the overall benefit of the cascade is optimized.The model of maximum cascade generation in flood season is of great significance to guide the optimal operation of cascade reservoirs under the requirements of flood control dispatching by fully considering the dispatching and application of water release facilities,optimizing the operation mode of cascade hydropower stations and increasing the generation capacity of cascade hydropower stations.