Study On Multi-Objective Refined Operation Of Cascade Reservoir Based On Surrogate Model

With the large-scale development and utilization of hydropower energy in China,thirteen hydropower bases have been formed.The optimal operation of cascade reservoirs is not only limited by many factors such as load,runoff and differences in water demand,but also needs to coordinate the balanced optimization of multiple dispatching objectives,which is a hot issue in the field of scientific research and engineering application research in the field of water resources management.Centering on the operation requirements of the three Gorges cascade reservoirs,with the goal of optimizing the comprehensive benefits of hydropower energy development and utilization,this paper studies the quantitati ve methods of reservoir ecological operation objectives and shipping objectives by using hydraulic model and habitat model.furthermore,the multi-objective fine operation problem of cascade reservoirs is solved efficiently by using surrogate model and multi-objective optimization algorithm,and the set of non-inferior dispatching schemes for each objective is obtained.It provides some technical support for multi-objective operation of reservoirs.The main research contents and innovations of this paper are as follows:(1)According to the ecological and shipping requirements of the three Gorges and Gezhouba cascade reservoirs in the Yangtze River basin,a two-dimensional hydrodynamic model is established to simulate the temporal and spatial distribution of hydraulic elements such as velocity and water depth of fish spawning ground.at the same time,the habitat model and suitability curve method are introduced to calculate the mapping relationship between hydraulic elements and suitable habitat area,so as to realize the quantification of ecological dispatching objectives.Through the statistics of the number and types of ships passing through the lock,combined with the shipping dispatching rules,the approximate relation curve between the discharge of the three Gorges and the guarantee rate of cascade navigation is established to realize the quantification of shipping dispatching objectives.furthermore,a multi-objective scheduling model considering ecological,shipping and power generation demand is established.(2)In order to solve the time-consuming problem of frequently calling the hydrodynamic model in the quantitative calculation of ecological dispatching objectives,a surrogate model based on Gaussian process regression is introduced to describe the response relationship between hydraulic elements and hydrodynamic processes.At the same time,in order to effectively solve the optimization model,an improved NSGAⅡ algorithm(INSGAⅡ)based on adaptive strategy is proposed.The algorithm adds the Gaussian distribution crossover operator and a new crowding distance formula to improve its search ability and the distribution of the solution set.The function test results show that th e INSGAⅡ algorithm can effectively deal with the multi-objective optimization problems with complex non-inferior frontier characteristics,and has good convergence and distribution.On this basis,an efficient multi-objective model solving algorithm INSGAⅡGPR,coupled with surrogate model and multi-objective algorithm is proposed to provide technical support for solving the multi-objective fine operation model of cascade reservoirs.(3)Taking the cascade of the three Gorges as the research object,the pr oposed INSGAⅡ-GPR algorithm is used to realize the efficient solution of the multi-objective dispatching model,obtain the non-inferior dispatching scheme set about power generation,ecology and shipping,and quantitatively analyze the competition and cooperation among different dispatching objectives.Furthermore,the grey relational analysis method based on combinatorial entropy method is used to evaluate the dispatching scheme set of runoff representative inflow years,and the comprehensive optimal scheduling scheme is given.The multi-objective fine operation decision of cascade reservoirs provides theoretical basis and technical support for the cascade optimal operation of the three Gorges.