Decision-making For Cascade-Reservoir Operation With Game-Theoretical Methodology

As many large-scale reservoirs have been constructed in China,the number of stakeholders with local interests is increasing,resulting in an intensification of competition for the limited water resources.Because this phenomenon seriously hampered the healthy development of rivers,it is critical to coordinate the conflicting interests of stakeholders for sustainable water resources management.In this paper,the Xiluodu-Xiangjiaba-Three Gorges reservoir-Gezhouba was selected as case study.The main contents are summarized as follows:(1)To avoid premature convergence,a modified water cycle algorithm based on the diversity evaluation and chaos theory(DC-WCA)is provided.DC-WCA can check the capability of the population in getting rid of the local optima and enrich the diversity of the population based on chaos theory if necessary.Based on the validation by the six benchmark problems,DC-WCA shows excellent performance in exploring the global optimum for highdimensional non-linear problems.The Xiluodu-Xiangjiaba-Three Gorges reservoirGezhouba is used as a case study.After sensitivity analyses of the parameters,DC-WCA is used for the long-term cascade-reservoir optimization for hydropower generation.The optimization results show that compared to ICGA,CPSO and WCA,the application of DCWCA for cascade-reservoir optimization is more effective and stable.(2)A game-theoretical model for cascade-reservoir hydropower operation is provided,which is included two sub-models: a strategy-equlibrium model based on Stackelberg theory and a benefits compensation model based on Nash-Harsanyi bargaining theory.The strategyequlibrium model is used to simulate the competition among reservoirs,and the benefits compensation model is used to guarantee individual rationality for sustainable competition.In the case study of Xiluodu-Xiangjiaba-Three Gorges reservoir-Gezhouba,the noncooperative model,centralized model and integrated game-theoretical model are compared and analyzed.The results indicate that through the proposed integrated game-theoretical model,the cascade-reservoir operation will result in a “win-win” situation for the individual and system’s hydropower generation,which are practical and stable when reservoir operators are not in full cooperation in the real-world operation.(3)A game-theoretical model for cascade-reservoir flood control operation is proposed.The Xiluodu-Xiangjiaba-Three Gorges reservoir is used as a case study.Based on Copula function,the joint flood volume probability distribution function is constructed.When the basin encounters a 1000-year flood,different interval inflow schemes are set up,and the inflow process of typical years is enlarged according to these inflow schemes,which results in several designed flood schemes.For each designed flood schemes,POA is used to solve the proposed model.The results indicate that the proposed model can compensate and adjust the flood control storage between the upstream and downstream reservoirs which have competitive flood control objectives,and strive for more flood control storage to prevent the next flood.In addition,when the whole basin flood is happened,the competition between upstream and downstream reservoir can impel the reservoir with relatively weak flood regulation capacity provide more flood volume to reduce more flood volume used by the downstream reservoirs.Moreover,when the local flood is happened,as the local flood increasing,the upstream reservoir would reduce the compensation for the downstream reservoir,because of its security.(4)A multi-objective decision-making method based on game theory is proposed.Based on the combination of subjective weight and objective weight,a combination weight based game theory is proposed.The Xiluodu-Xiangjiaba-Three Gorges reservoir is used as a case study.Several asynchronous refill operation strategies are proposed and evaluated based on multi-objective evaluation model,which results in non-dominated strategies.To coupled the subjective and objective weight,a combination weight is provided and used to select the optimal strategy from the non-dominated strategies.The results indicate that the selected strategy can improve hydropower benefits and reduce spilled water without reducing the originally designed flood prevention standards.(5)Analyzing the impacts of climate change on the strategy-selection of multi-objective decision-making methods.The Three Gorges reservoir is used as a case study.The climate model and hydrological model are used to predict the future climate change and streamflow process.Definition the water-conflict years based on different environmental flow pattern.For each water-conflict year,a multi-objective reservoir operation model is built and solved by NSGA-II.The fuzzy social choice methods(FSCMs)and four game-theoretical bargaining methods(GTBMs)are used to select the socio-optimal strategy from nondominated strategies.The results show that the strategy selection of GTBMs is more stable and results in a better balance between hydropower and environmental objectives,compared to that of FSCMs.Moreover,considering climate change,under the appropriate environmental flow pattern,the stabilities of the strategy selections of FSCMs and GTBMs are slightly influenced,and the average satisfied degrees of both objectives obtained by FSCMs and GTBMs in the future period are lower than those in the base period.