Joint Optimal Operation For Cascade Reservoirs System

Reservoir flood resources utilization is one of non-structural measures and soft skills for implementing and accelerating the development of water resources, in order to control flood, reduce calamity, decrease spilled water, and increase water supply, by taking full advantage of water conservancy project, and improving operation schemes as well as rules. Some efficient methods of flood resources utilization, such as uncertainties of optimal operation methods, reservoir operation rules, real time and dynamic control of flood limited water level (FLWL), optimal refill rules for cascade reservoirs and multi-purpose reservoir operation rule curves for adaption to climate change are discussed in this thesis. The Xiluodu reservoir, Xiangjiaba reservoir, Three Gorges Reservoir, Qingjiang River cascade reservoirs and Danjiangkou reservoir are selected as case studies, as well as the main contents and highlights are summarized as follows:1. The purpose and significance of flood resources utilization are stated. The derivation of reservoir operation rules, and various flood resources utilization methods in practice are discussed in detail.2. Long-term power optimal operation is effected by simulating uncertainties of forecasting error, discharge capacity and water level-volume as well as multiple control of FLWL for multi-hydropower stations. The progressive optimal algorithm (POA) is used to solve the optimal operation under various uncertainties. The Three Gorges cascade and Qing River cascade hydropower plants are selected as case study. It is shown that uncertainties of forecasting error and water level-volume as well as multiple control of FLWL have a significant impact on power optimal operation, while uncertainty of discharge capacity has a weak impact. Multiple control of FLWL in pre-flood season or post-flood season is the best opportunity for reservoir flood resources utilization.3. The combination of water (for single reservoir) and energy (for cascade reservoirs) operating rules are established and used to simulate mixed multi-reservoirs operation. The decomposition method is aimed at decomposing total output power of aggregated reservoir and maximizing total initial potential energy in the end of time interval for cascade reservoirs. It is shown that the combination of water and power operating rules can improve not only water resource utilization rate but also the mean hydropower generation when compared with the designed operating rules.4. A joint operation and dynamic control of FLWLs for Three Gorges cascade and Qingjiang cascade reservoirs is proposed. Three schemes, the design rules, FLWLs for cascade reservoirs, as well as FLWLs for mixed multi-reservoirs are applied to simulate various reservoirs flood resources utilization. The proposed model can be adopted to obtain more economic benefits without increasing flood control risk. Moreover, a model for real time dynamic control of FLWLs is proposed according to coupling long-term and short-term operating rules, in order to maximize benefits of comprehensive utilization. The results show that real time dynamic control coupling long-term operating rules can improve not only water resource utilization rate, but also the mean hydropower generation, when compared with the designed operating rules as well as real time dynamic control without coupling long-term operating rules.5. A joint refill operation model of cascade reservoir including flood control risk module, utilization benefits analysis module, and multi-purpose evaluation module is developed to derive the optimal refill rule. The Xiluodu reservoir, Xiangjiaba reservoir, and Three Gorges Reservoir are selected as case study. It is shown that both of optimal synchronous and asynchronous refill operation schemes can improve benefits of comprehensive utilization without reducing originally designed flood prevention standards. The former has better power generation benefit, but the latter has better water storage efficiency. The propose model can effectively resolve the conflict among of flood control, power generation, and refill operation, as well as provide multi-purpose decision-making schemes by optimization of time and space of refill operation.6. In order to investigate the potential impact of climate change on the hydrological process, ecological system, and water resources in the region, this study incorporates ecological requirement into reservoir operating rule curves employing a framework of the integrated adaptive optimization model (IAOM) that consists of three modules:(1) global climate model (GCM) weather generator module,(2) variable infiltration capability (VIC) model as the hydrological simulation module,(3) multipurpose reservoir optimization module. Danjiangkou reservoir in Han River basin is selected for a case study. The results demonstrate that the IAOM provides optimal multipurpose reservoir operating rule curves that reflect the hydrologic characteristics of future climate change. Ecological supply water operation will alleviate negative effect of dam on river ecosystem without reducing conservation benefits and flood control standard, compared to the designed operating rules.