Research On Control Method Of Spillage For Xijin Cascade Reservoirs In Yujiang River Basin

Spilled water is the main problem of reservoir operation in hydropower enrichment areas.The research of spilled water control method is very important to reservoir operation and is directly related to the social and economic benefits of hydropower station operation.Firstly,this paper analyzes the rules of water abandonment in non-flood season and flood season of power stations in Yujiang River Basin,and analyzes the risk of spillage by constructing Copula joint distribution.In flood season,appropriate hedging rules are made to reduce spilled water and increase power generation.In non-flood season,time-varying penalty coefficient is introduced to control the spilled water of downstream power stations and increase cascade power generation.The main research contents and results are as follows:(1)The spillage rules of power stations in Yujiang River Basin are analyzed in flood season and non-flood season,and the relationship among spilled water discharge,inflow and upstream water level is analyzed concretely.To analyse the most possible value and confidence interval of spilled water discharge,the multivariate joint distribution of spilled water discharge and other factors is constructed by using Copula function,and the uncertainty of spillage in Yujiang River Basin in abundant,flat and dry years is analyzed.The results show that when the actual spilled water discharge is zero,the most likely spilled water discharge is also zero,and the upper confidence interval is too large.When the actual spilled water discharge is greater than zero,there is little difference between the most likely spilled water discharge and the actual spilled water discharge,mostly in the confidence interval.(2)For the flood season,to consider the advantages and disadvantages of reducing the risk of spilled water and increasing the benefit of water storage,three time-varying parameter water storage hedging rules for linear hedging with and without hedging lower bound and curve hedging are proposed and a multi-objective optimal dispatching model considering spilled water and power generation is constructed to solve the hedging rule parameters in each period.The spilled water rules of Yujiang power station in abundant,flat and dry years are analyzed to determine the optimal rules considering spilled water and power generation simultaneously in flood season.The results show that both hedging rule 1and hedging rule 3 are effective in increasing power generation and reducing spilled water in abundant year,while hedging rule 2 is the worst.If you prefer to reduce spilled water,hedging rule 3 can be chosen.If you prefer to increase power generation,hedging rule 1can be chosen.Hedging rule 1 has the best effect in increasing power generation and reducing spilled water in flat year,while hedging rule 2 is the worst,so hedging rule 1should be chosen as the flat year hedging rule.In dry year,hedging rule 1 is the best in increasing power generation and reducing spilled water,while hedging rule 2 is the worst,so hedging rule 1 should be chosen.(3)For the non-flood season,a method of using variable penalty coefficient to control the spilled water before flood is proposed.It uses the double-layer optimal dispatching model.The upper layer aims at the maximum cascade power generation and the minimum cascade spilled water.The lower layer aims at the maximum power generation of the upstream power station,and increases the constraint conditions for the downstream power station by imposing penalty on the Xijin power station.The penalty coefficient of different periods can be determined by solving the model to better achieve the effect of spillage control.And the scheme of no penalty,penalty coefficient remaining unchanged and variable penalty coefficient is set for comparison.The results show that by punishing the outflow of the upstream power station,the spilled water of the downstream power station can be effectively reduced and the power generation of the downstream power station can be increased,while the generation capacity of the upstream power station will be sacrificed and a small amount of spilled water will be increased meanwhile.When the inflow is large,the cascade power generation of the time-varying penalty coefficient will be smaller than that of the penalty coefficient remaining unchanged.When the inflow is not too large,the cascade power generation of the time-varying penalty coefficient will be larger.And the method of time-varying penalty coefficient can effectively reduce the cascade spilled water no matter in the abundant year,the flat year or the dry year.