A Research On Ecology And Shipping Based Multi-objective Generation Scheduling Of Cascaded Hydropower Stations

With the continued growth of population and the rapid development of economy in China, the problem of energy shortage and environmental pollution is becoming increasingly serious. How to achieve energy saving and emission reduction to promote energy saving and environment friendly society construction is a major challenge in our country. Hydropower as a kind of clean, renewable and cheaply energy source with highly effective to peak load regulation, is widely favored by countries around the world. China is rich in hydropower resources, which has now playing an important role in national economy. The large hydropower hubs been built have a great degree of improvement over flood control, power generation, shipping, water supply, ecological restoration and so on. The operation of hydropower stations, however, influenced by meteorological, hydrological, electricity demand, water demand, and many other factors, which makes the coordination of different benefits one of the hot research fields of engineering and academic circles. The integrated water resources management for cascade hydropower stations is the main purpose of this thesis. Considering the actual operation conditions and rules of cascade hydropower stations, the modeling theory and calculating method of water resources optimization is studied. Efficient utilization of water resources among the multiple benefits is achieved and provides a theoretical basis and technological means of optimal operation of hydropower station, as well as the integrated river basin management. Some of the achievements in this thesis are programmed into business software which has now been applied at the control centers of The Three Gorges Cascade and the Jinsha River Cascade. The main content of the innovation and contribution in this thesis are listed as follows.(1) Focused on the water head connection between the upstream and downstream reservoirs of cascade, the basic data of reservoir operation is collected and stored. Then the responses mode between the water head connection and the cascade overall efficiency is studied. A complete set of water level control methods is proposed on the basis of one-dimensional hydrodynamic model, data fitting, units refinement simulation and the Vague sets. The case study of The Three Gorges Cascade shows that the method has good practicability. Because of the adjustment tardiness of the Xiangjiaba’s water level, a strict constraint is added to gain the water level optimization control mode in the case study of the Jinsha River Cascade. The conclusion can provide good decision support on daily plan and Real-time output adjustment for cascade hydropower stations.(2) In view of the characteristics of the operation for multi-objective reservoirs, the DE (the Differential Evolution) framework is improved and perfected, and the Dual-population Multi-objective Differential Evolution Algorithm (DPMODE) is presented. The variation operator is improved and a local search technique is applied in DPMODE, which boost the algorithm convergence while avoiding the lack of the population diversity. In the meantime, the water level optimization control mode, proposed in this thesis, is applied to improve the population initialization and the Constraint handling, which makes DPMODE more suitable for hydropower optimal operation. Through a series of function test, it verify the high efficiency of the proposed method when handling multi-problems with high-dimensional, non-linear and discontinuous features.(3) In order to meet the requirement of river ecological restoration, the ecological operation practice of the Three Gorges Reservoir and the hydrology statistical methods are used to determine the feasible range of the suitable ecological flow. According to the analysis of several typical ecological objects in the middle and lower reaches of the Yangtze River, the suitable ecological flow sequence of the Three Gorges Reservoir is obtained, which is to establish the ecological-generation optimal model. The DPMODE is applied to solve the model and a set of non-dominated dispatch schemes is obtained rapidly, which reveals the mutually contradictory between ecology and power generation. Meanwhile, because of the signs of water supply problem in the upper Yangtze River, the guarantee rate of water supply is proposed to establish the optimal model of ecology, water supply and generation. The results of the model verifies the possible water scarcity in the upper Yangtze River in future, and provide feasible scheduling plan for the water resource management.(4) The actual situation of shipping is considered in this thesis. The way to calculate the shipping benefit is presented by the operation process of the ship lock. Then the optimal model of shipping and flood control is established for the flood season, and the optimal model of shipping, ecology and generation is proposed for the impoundment period. The DPMODE is used to solve the models. Through the analysis of the results, the operation mode of shipping schedule faced with flood is obtained:the discharge should be decreased at the periods with low inflow, and the over stored flood volume should be dispatched to other periods. The research work contributes to the comprehensive utilization of shipping and other benefits of the Three Gorges Reservoir.