Research On Reservoir Flood Control Optimal Dispatching Model And Solution Method Considering Random Runoff

China has abundant water resources,but the spatial and temporal distribution is very uneven.Rainfall is concentrated in the flood season,which leads to frequent floods.At the same time,China has a wide range of floods and heavy losses once the disaster occurs.With the vigorous development of the major river basins in recent years,the number of water conservancy facilities built on the major rivers has increased dramatically,and the space for further construction is small.At the same time,construction projects not only need a lot of investment,but also change the hydrological runoff characteristics of the river basin,which is contrary to the natural law,and may have adverse effects on the ecological environment of the river basin.At the same time,there is a long-term disconnection between the design and operation of water resources and Hydropower projects.Conventional dispatching regulations emphasize too much on the safety of the project and neglect the scientific application of the project.Therefore,it is of great practical significance to study non-engineering measures for flood control.Flood control optimal operation of reservoir group is an important non-engineering measure for flood control.This paper focuses on the optimal operation of reservoir flood control from two aspects: the optimal operation of joint flood control of reservoir group and the optimal operation of reservoir flood control considering the uncertainty of incoming water.Firstly,the optimal operation method of joint flood control of reservoirs in river basin is studied in order to give full play to the benefits of hydrological compensation and reservoir capacity compensation between reservoirs and explore the potential of joint flood control of reservoirs in river basin.Then,considering the uncertainty of reservoir inflow runoff,the stochastic runoff description model is applied to describe the inflow runoff scientifically,and the apparent stochastic optimal dispatching model of reservoir flood control is established.The stochastic optimal dispatching method of reservoir flood control based on stochastic dynamic programming algorithm is studied,and the optimal dispatching rules of reservoir flood control are solved.The main research contents and innovative achievements of this paper are as follows:(1)In view of the uncertainty of reservoir inflow runoff,Markov chain is used to describe the inflow runoff of reservoirs in a river basin.The probability transfer matrix of runoff state is derived by hydrological stochastic simulation method and Copula function method,respectively.For the inflow runoff satisfying the normal transformation condition in the hydrological simulation model,a multi-variable seasonal first-order autoregressive model is established to simulate a large number of runoff series which accord with the statistical characteristics of historical runoff.Taking the simulated runoff series as samples,the probability matrix of runoff state transition is obtained by statistical analysis.For the inflow runoff which does not satisfy the normal transformation condition in MSAR model,the joint distribution of runoff between reservoir periods is established by using Copula function.The the condition distribution function of runoff in different time is derived from the edge distribution function of runoff in each time and joint distribution function of runoffs in different time,thus the probability transfer matrix of runoff state is obtained.(2)For the basin flood control system consisting of reservoirs and interval rivers,according to the spatial distribution of reservoirs and flood control points and actual flood control requirements in the study of joint flood control dispatching of reservoirs,the structural characteristics of the basin general flood control system are abstracted,and a general model for joint flood control operation of reservoir groups in river basins is established,which aims at ensuring the safety of downstream areas while satisfing the reservoir safety constraints and the water level constraints at the beginning and end of reservoir dispatching period.Considering the phenomena of uncontrollable incoming water at control points and controllable reservoir discharge,and the response of reservoir discharge at flood control control point increases with the increase of reservoir discharge,a reservoirs' joint flood control optimal dispatching algorithm based on DP-POA algorithm algorithm is designed to solve the model.On the basis of using DP algorithm to cut peak efficiently for single reservoir discharge,POA algorithm is applied to realize the compensatory dispatch of reservoir discharge to the incoming water at the control point interval through the reservoirs' joint optimal dispatch in the basin.Taking the mixed reservoir group in the upper reaches of the Yangtze River as an example,the results show that the general model of joint flood control optimal dispatch of reservoir group in the basin is applicable,the DP-POA nested algorithm is feasible and effective in solving the reservoirs' joint flood control optimal dispatch in the basin.(3)In view of the stochastic characteristics of runoff,the explicit stochastic optimal dispatching method is applied to the flood control of reservoirs.The stochastic optimal dispatching model of reservoir flood control is established with applying the probability transfer matrix of runoff state.The model guarantees the reservoir's own flood control safety,respects the reservoir's discharge capacity,and retains sufficient reservoir capacity at the end of the dispatching period to withstand possible flood in the future.The stochastic optimal dispatching method of reservoir flood control based on SDP algorithm is designed to reduce the spillway peak of reservoir.Taking the reservoir group in the upper reaches of the Yangtze River as an example,the flood control optimal dispatching rules of each reservoir are optimized according to the proposed method,and two typical floods are selected as runoff input to simulate the dispatching.The results of reservoir simulation operation show that,according to the optimized rules,each reservoir can play a better role in regulating reservoir inflow runoff,and basically control the water level at the end of reservoir dispatching period as the flood limit water level which can fully reserve reservoir capacity for the later possible inflow.However,the process of reservoir discharge evolving to the control point is not taken into account in the model,which makes the flood control for the downstream area less effective than the existing dispatching rules when running according to the dispatching rules in this paper.