| The Xiluodu-Xianjiaba cascade reservoirs as an important cascade reservoirs in the lower reaches of the main stream of the Jinsha River,which is of great significance for the operation of the Three Gorges Reservoir and flood control in the middle and lower reaches of the Yangtze River.The reasonable operation of the reservoir is an effective way to exert the comprehensive benefits of the cascade reservoirs.However,the uncertainty of the inflow and suspended sediment transport concentrations(SSCs)will not only affect the comprehensive benefits of the cascade reservoirs,but also bring certain risks to the operation of the cascade reservoirs;In the past research on the risk of reservoir operation,there is little research on the risk of water and sediment operation.This paper mainly studies from three aspects:random simulation of the process of flow and SSCs,risk regulation of operation of water and sediment discharge of the reservoir and multi-objective decision-making methods.Firstly,a stochastic simulation method based on multi-dimensional Copula function was proposed,which can consider the correlation between inflow and SSCs,and the method was applied to the random simulation of daily inflow and SSCs at Pingshan Station.Secondly,in order to more effectively describe the risk of water and sediment operation under the uncertainty of inflow and SSCs,this paper introduces the value-at-risk method to describe the probability and severity of the maximum possible loss of power generation targets and sediment targets in future water and sediment operation.Then,the value-at-risk was introduced into the objective function of the water and sediment joint scheduling model,and a combined water and sediment operation model for cascaded reservoirs that considers risk losses was established,this model achieves the purpose of combining risk loss,sediment and power generation goals in the process of water and sediment operation.The multilayer nested multi-objective dynamic programming successive approximation iterative algorithm was used to solve the model,and an improved grey correlation evaluation method based on the Topsis was used to evaluate non-inferior schemes.Finally,the method and model proposed in this paper were applied to the risk study of water and sediment operation in Xiluodu-Xianjiaba cascade reservoirs.The results reveal that the stochastic simulation method based on multi-dimensional Copula function can well simulate daily flow and SSCs in this paper;the water and sediment operation model considering the risk loss can reduce the risk of water and sediment operation,and effectively regulate the risk of water and sediment operation due to the uncertainty of inflow and SSCs;The best solutions change as confidence levels and risk attitudes change,and the best solutions corresponding to some considerations of risk control and no consideration of risk control were 9th option and 7th option,respectively.When the risk control is fully considered,the best solutions corresponding to the 95%and 90%confidence levels were 9th option and 8th option,respectively.The research results can provide technical support for the risk management of water and sediment operation in the Xiluodu-Xiangjiaba cascade reservoirs. |
