Fault Segment Detection Method of Multi-Terminal Hybrid Overhead-Submarine MMC-HVDC Transmission Lines Based on Waveform Similarity

With the development of offshore wind power, the emerging multi-terminal hybrid overhead-submarine MMCHVDC transmission lines system has become one of the important directions for the development of DC transmission technology today. Fault segment detection is essential for ensuring the protection of multi-terminal hybrid overhead-submarine MMCHVDC transmission lines to complete fault isolation and recovery. Consequently, studying the fault segment detection method of these lines is of great significance. Therefore, this article firstly analyzes the transient propagation mechanism of faults in the multi-terminal hybrid overhead-submarine MMC-HVDC transmission lines system of offshore wind farms. Then the differences in transient traveling wave propagation of different lines at faults occur are explored and the waveform characteristics of fault transient voltage at the measurement end of onshore converter station under different line section faults are qualitatively analyzed. Furthermore, the highly similar characteristics of transient voltage waveforms under faults in the same section have been revealed. Based on the similarity characteristics of fault traveling wave waveforms, the fault segment of multi-terminal hybrid overhead-submarine transmission lines can be detected by establishing a sample dataset of fault transient voltage waveform and using the waveform matching technology. Finally, the offshore wind power multiterminal hybrid overhead-submarine MMC-HVDC transmission lines system model, which is built using PSCAD/EMTDC electromagnetic transient simulation software, was simulated for various fault situations to verify the proposed fault section localization method based on waveform similarity. The results showed that the proposed method was feasible.