Research On Optimal Scheduling Of Dynamic Control Of Flood Limit Water Level For Cascade Reservoirs

Reservoirs play a significant role in water resources management and water resource allocation.Traditional flood limited water level(FLWL)of reservoirs is set as a fixed value which over-considers the reservoir flood control and limits the benefits of reservoirs to a certain extent.However,the dynamic control of the reservoir FLWL is an effective solution.It is a method to temporarily increase the water level of the reservoir during the flood season by using forecast information and discharge capacity,and it can both consider flood control and power generation during the flood season.Firstly,this paper analyzes the shortcomings of the pre-release capacity constraint method and proposes an adaptive grading pre-release method to determine the dynamic control bound of water level during the flood season.Secondly,an optimal scheduling model of dynamic control of FLWL for cascade reservoirs with the goal of maximizing the combined power generation of the cascade reservoirs and minimizing the extreme risk rate is constructed and applied to the cascade reservoirs in the middle and upper reaches of Hanjiang Basin.Finally,a multi-objective evolutionary algorithm is used to solve the model,and a series of solutions of dynamic control of FLWL are compared and analyzed to explain the applicable scope and rationality of the model in detail.The main work and research results of this article include the following aspects:(1)Aiming at the capacity-constrained pre-release method without considering the current reservoir water level status,neglecting operability in the actual operation of the reservoir,and excessive pre-release flow,etc.,an adaptive grading pre-release method was proposed to improve the pre-release operation of reservoir.The adaptive grading pre-release method includes two steps.The first step is to determine the dynamic control bound;the second step is the adaptive grading pre-release.This method classifies the pre-release flow into several ranks under the premise of considering the current water level status of the reservoir,which improves the problems of excessive pre-discharge flow and poor operability,and provides a new method for dynamically controlling the pre-release operation of the reservoir during the flood season.(2)A new dynamic control method of dynamic control of FLWL is proposed.The method includes four phases,namely the normal operation phase,the pre-release phase,the flood control operation phase,and the flood retention and refill phase.And it is applied to the optimal scheduling model of dynamic control of FLWL for cascade reservoirs in the middle and upper reaches of Hanjiang Basin.This method provides a new idea for the development of reservoir water level dynamic control scheme in flood season.(3)An optimal scheduling model of dynamic control of FLWL for cascade reservoirs with the goal of maximizing the combined power generation of the cascade reservoirs and minimizing the extreme risk rate is constructed,and it is used for the cascade reservoirs in the middle and upper reaches of Hanjiang Basin.The purpose of this research is to study the effect of the upper limit combination of the cascade reservoir dynamic control domain on the combined power generation and the extreme risk rate of the cascade reservoir.The model was solved by a multi-objective evolutionary algorithm,and obtain a set of dynamic control schemes.The results were compared and analyzed in detail to explain the applicable scope and rationality of the model.It provides a reference for the dynamic control of FLWL for the cascade reservoirs in the middle and upper reaches of Hanjiang Basin.