Study On Short-Term Refined Calculation Methods About Water Volume And Dispatching Modeling For The Three Gorges Hydropower Station

As the centralized development for hydroelectric power has entered the final stage in China,many giant hydropower stations epuipped with large capacity and strong peak load regulation capacity are placed on big rivers,and are playing pivotal roles in flood control,power generation,ecology and other aspects.At present,the developments of wind power,photovoltaic and other new energy sources are strong,resulting in a growing demand in peak load regulation by hydropower,which puts forward higher requirements for the refinement dispatching of hydropower stations;how to accurately calculate tail water level and outflow of hydropower stations under given output and explore the corresponding characterization method for the water volume connection are the key problems to be solved.Besides,under new situations,it is a general trend to consider substation constraints when formulating daily plans and conducting actual dispatching of hydropower stations,and how to formulate start-stop and load distribution strategies for units restricted by substation constraints is another key problem.For the above problems,the Three Gorges hydropower station was taken as the main research object,and a series of studies were conducted by multi-disciplinary theories and methods,such as hydroelectric enelgy and artificial intelligence.Some valuable results were obtained,which could provide model and method supports for ultimately short-term refined dispatching of cascade hydropower stations.The main research contents and creative achievements of this paper were as follows:(1)For the calculation accuracy problem of tail water level,the nonlinear characteristics and aftereffects for tail water level of Three Gorges were analyzed,and the artificial neural network(ANN)models based on monitoring data for tail water level were established.The accuracy differences among the empirical formula,the jacking curve and ANN models for tail water level were compared in single period and rolling calculation.Results showed that the empirical formula and the jacking curve owned similar calculation accuracy,and showed poor practicability caused by their unknown input parameters in the dispatching mode under given output.In comparison,the ANN model for tail water level,whose parameters were the forebay and tail water level of Three Gorges during the last three periods,and output of Three Gorges from the last three periods to the current period,could combine the calculation accuracy with practicability to a certain extent;it could provide model supports for accurate calculation of tail water level of Three Gorges.(2)For the calculation accuracy problem of outflow,a method was proposed herein for formulating the optimal load allocation table with gross head as parameters.According to the current processes for formulating daily plans,seven kinds of methods for outflow were proposed from aspects of optimizing power generation streamflow,water-energy conversion characteristics and data mining respectively,and their accuracy differences in single period and rolling calculation were compared.Results showed that compared with the empirical formula,the ANN model for tail water level could slightly improve the calculation accuracy of outflow,and showed strong robustness to the calculation deviation for outflow.Besides,the ANN model for outflow,which owned the same input features as the ANN model for tail water level,could overcome the difficulty in summarizing the load distribution strategy of giant hydropower stations to a certain extent,and was the first choice to calculate outflow of Three Gorges.(3)For the problem of characterizing the the water volume connection between outflow of Three Gorges and inflow of Gezhouba,the corresponding rules in historical operation data between outflow and inflow were analyzed,and the ANN models for inflow were established.Then,sensitivity analysis experiments about rolling calculation for inflow of Gezhouba were designed,and the matching effects between the ANN model for outflow and different water volume connection characterization methods were checked.Results showed that during the flood and non-flood season,the water volume connection characterization method and model matching with the ANN model for outflow were the current convert coefficient method and ANN model for inflow respectively,whose parameters the outflow of Three Gorges from the last one periods to the current period.(4)For the problem of modeling and solving for the internal economic operation restricted by substation constraints,the internal economic operation model considering substation constraints was established on the basis of analyzing unit operation characteristics,and a set of solving method was proposed.Results showed that the proposed model and method could flexibly handle the bus connection problem,and effectively coordinate output of substations to meet the constraint of substation stable operation zones;simultaneously,the model and method could ensure that units were in a stable and efficient operation state,and owned a good applicability.Besides,the internal economic operation model and the ANN model for outflow complemented each other,and owned a high degree of matching with the ANN model for tail water level and inflow.