Multi-objective Optimal Operation Scheme Decision And Risk Analysis Of Cascade Reservoirs

Water is the origins of life and an indispensable resource for human survival and develop:ment.Under the impact of global climate change and human activities,available water resources are getting increasingly scarce.How to use water resources effciently and reasonably has become a world-wide common concern.Therefore,considering the influence of various uncertain factors,it is of great practical significance for efficient utilization of water resources towards disaster prevention and reduction to carry out study on decision-making and risk analysis of multi-objective optimal operation schemes of cascade reservoirs and seek multi-objective optimal operation schemes in changing environment,while meeting the requirements of flood control,power generation,water supply,shipping and other comprehensive utilization objectives.To tackle this interdisciplinary and complicated system-engineering problem,in this paper,a framework coupled cascade reservoirs' optimal operation algorithms,multi-objective optimal operation scheme decision-making,inflow uncertainty and risk analysis was conducted based on hydrology,hydraulics,economics,mathematics and computer science.The major findings are as follows.(1)Improved harmony search algorithm and its application in optimal operation of cascade reservoirs.In order to solve the problems of uneven distribution of initial harmony memory and easily falling into local optimum in harmony search algorithm,the uniform design method is used to generate initial harmony memory to increase its diversity and effectiveness.The chaotic sequence is introduced to improve the global search ability of the algorithm Thereby,an improved harmony search algorithm is proposed and applied to solve the optimal power generation operation model of cascade reservoirs.By comparison with harmony search algorithm and dynamic programming algorithm,the advantages of the improved harmony search algorithm are verified,which provides a feasible way of solving the optimal power generation operation model of cascade reservoirs.(2)Study on multi-objective optimal reservoir operation scheme decision-making based on the marginal conversion rate.In order to obtain the multi-objective optimal reservoir operation scheme under the condition of uncertain inflow,the Three Gorges Reservoir with combined storage capacity of flood control and power generation was selected as the case study.Based on quantifying the inflow forecast errors and the microeconomics principle of coupling the product conversion curve with the equal income line to obtain the maximum benefit,the marginal conversion rate is applied to the decision-making of multi-objective optimal reservoir operation schemes to seek the best equilibrium point between flood control and power generation.The calculation and analysis results show that the method can obtain not only the optimal equilibrium point between flood control and power generation benefits under the condition of deterministic inflow,but also the dynamic control area of the maximum water level for power generation considering inflow forecast errors.The dynamic control area can provide theoretical reference for determining the starting water level in medium/small floods and flood resources utilization.(3)Study on multi-objective optimal reservoir operation scheme decision-making with uncertain inflow based on an improved VIKOR model To overcome the shortage of traditional multi-objective optimal operation scheme decision-making which often ignores the impact of inflow uncertainty,on the one hand,the evaluation index is represented by an interval number whose upper,and lower limits are respectively the maximum and minimum values obtained by optimal calculation with the simulated inflow considering forecast errors as the input.On the other hand,the game theory set model is used to combine the subjective weight based on order relation analysis and the objective weight based on the Critic method,and thereby the VIKOR model is improved to enhance the reliability and rationality of evaluation index weight.The soundness and practicability of the model and method are verified by the case study which provides a powerful approach for multi-objective reservoir operation scheme decision-making under inflow uncertainty.(4)Risk analysis of short-term power generation operation of cascade reservoirs considering multivariate inflow forecast errors.In the risk analysis of short-term power generation operation of cascade reservoirs,the downstream reservoir inflow is related to not only upstream but also interval reservoir inflow forecast errors.Besides,there lies correlation among inflow forecast errors in different forecast periods.To study this multivariate correlation issue,the distribution characteristics of inflow forecast errors in different forecast periods are analyzed,and the t-Copula method is used to fit the multivariate inflow forecast error function.On this basis,a stochastic model is established to randomly simulate forecast inflow with errors in multiple forecast periods.And then risk analysis is conducted on short-term power generation operation of cascade reservoirs.The feasibility and effectiveness of the proposed method are proved by the case study.This research provides new visual insights on short-term power generation operation of cascade reservoirs.