| During the next National Twelfth Five-Year Plan period, massive small and medium hydropower will be developed by Yunnan power grid in its'northwest. These small and medium hydropower are widely distributed and most of which are far from the load center. There is usually a long electric distance between Hydropower Stations and main grid, which easily results in stability problems. As one kind of HVDC power transmission projects, the DC back to back project for network link will be able to realize the economic dispatch between interconnection power grid and improve the safety and stability of the power grid operationBased on the control principle and mode of DC back-to-back system, the paper researches the following the aspects by using PSD-BPA:oscillation mode of Yunnan power grid, northwest power grid stability under N-1 fault, main section transmission limit and foreign send limit of Yunnan power grid under the plentiful large way in 2015, which provides the foundation for further analysis. Aiming at the problems of the northwest Yunnan power grid, two DC back to back projects for network link schemes are carried out which are JianChuan DC back-to-back project and HuangPing DC back-to-back project. After DC back-to-back project accessing system, the oscillation mode of Yunnan power grid, northwest power grid stability, main transmission section limit and foreign send limit of Yunnan power grid are researched. The influence of DC back-to-back fault on the power grid stability is also analyzed. The analysis results show that the DC back-to-back project could improve the stability and main transmission section limit of northwest Yunnan power grid. After comparing the above two DC back-to-back projects in investment, dynamic stability level, transmission limit and investment recovery period, the results show that the HuangPing DC back-to-back is advantaged to the other. So this scheme is suggested to be used in back-to-back project. |
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