科研之友
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摘要
When the current limiting reactor in the multi-terminal DC grid is designed for centralized confi-guration,the lack of boundary elements between the DC lines will make it difficult to distinguish internal and external faults. Aiming at the above-mentioned VSC-MTDC grid,a blocking pilot protection scheme based on the ratio of superimposed energy is proposed. The superimposed energy in the protection installation site is used as the start-up criterion to detect the fault in the DC grid,and the protection action criterion is constructed by using the difference between the ratio of superimposed energies of forward and backward traveling waves at two sides of the converter station. A logical exchange can be made to determine whether to perform a trip or not after the judgment of two-terminal protection is completed. The effectiveness of the proposed protection scheme is verified on the PSCAD/EMTDC platform. The simulative results show that the proposed protection scheme can effectively distinguish internal and external faults with better resistant capability to transition resistance and noise.
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