Fault Identification Algorithm for Transmission Line Integrated with MMC-HVDC Converter Station

Introduction: Currently, modular multilevel converter (MMC)-based HVDC technology is utilized in the power grid. As known, the transmission line, integrated with MMC-based station, adopts travelling wave (TW) algorithm to identify partial discharge, which is highly dependent on the calculation of the initial TW velocity that correlates with the precise acquisition of the TW spectrum. Methods: Firstly, in this work, the frequency-dependent feature of underground cables was analysed. Secondly, the correction algorithm for TW attenuation was obtained. Thirdly, a detailed partial discharge location algorithm was derived. Results and Discussion: Using PSCAD/EMTDC, a ±400kV MMC-based power grid simulation model has been constructed, followed by performing a typical case study to verify the robustness of the proposed algorithm. To overcome these shortcomings, a novel partial discharge location principle for transmission line integrated with MMC-based station has been illustrated. However, it should be noted that the proposed method has only achieved frequency domain corrections, rather than the time-frequency domain, which still requires further research. Furthermore, the calculation has contained too many iterations, causing significant computational pressure. Conclusion: The comprehensive frequency correction algorithm has exhibited the ability to recover the initial frequency spectrum information from highly attenuated TW signal, and the proposed fault location principle has been found suitable for transmission line integrated with MMC-based station.