Simulating Study Of Three Gorges HVDC System Harmonics For Three Gorges Power Station And Its AC & DC Hybrid Transmission System

As the largest power system in China and one of the largest in the world, Three Gorges power system has the features of great unit, AC & DC hybrid transmission and flexible operation modes. Wide attention in the whole world is attracted to the operation characteristics and possible problems of Three Gorges power system, such as power harmonic and system stability. As the object of study, the models construction and simulation of Three Gorges power station and its AC & DC hybrid transmission system is researched, and the result of research is valuable for theory and engineering. The key of simulation and analysis is the construction of accurate mathematic and simulation models. Because of the AC & DC hybrid transmission, great unit, large number of unit and the complexity of Huazhong grid structure, the construction and solution of the model of system is very difficult. Therefore, a large-scale commercial software Saber is chosen as software platform, which lays the foundation for the analysis of steady and transient characteristics of Three Gorges power system.In this paper, the mathematic models of system components are analyzed. The mathematic models of generator and transformer are proposed considering the influence of saturation of main magnetic circuit. The Saber general simulation template of generator unit, transformer, and converter are constructed. Based on the mathematic models and simulation templates of system components, the systematic simulation model including Three Gorges power station and its AC & DC transmission hybrid system is established for the first time. The rationality of established simulation models is verified according to the theory or experiments. Some steady state operation modes and transient processes are simulated using established systematic simulation model. At the same time, a direct method for calculation of interharmonics in an HVDC system is proposed theoretically. Its rationality is verified by simulation also. According to the result of steady state, transient processes simulation and power harmonic calculation, the influence of power harmonic and transient processes on generators, transformers, communication lines and power system stability is analyzed. And the possible problem and corresponding technique means is analyzed. The result of simulation and analysis has important reference value for the steady and safe operation of Three Gorges power system. As one part of this paper, the frequency characteristics, parameter sensibility and power characteristics of AC & DC filters equipped in Three Gorges power system are analyzed. Some useful conclusion for design, manufacture and operation of filters are drawn. On the other hand, the constructed simulation models of Three Gorges power system lays foundation for father analysis of operation modes and possible problems of future Three Gorges power system.