Travelling wave fault location approach for hybrid LCC-MMC-MTDC transmission line based on frequency modification algorithm

Line-commutated-converter (LCC) based and modular-multilevel-converter (MMC) based hybrid high-voltage direct-current (HVDC) transmission technology is already applied in actual power grid, which has the ability to avoid commutation failure issue. Besides, aiming to acquire high transmission capacity, the multi-terminal direct-current (MTDC) approach is adopted. Although the travelling wave (TW) fault location approach is widely applied in actual power grid, its adaptability for hybrid MTDC topology and transmission distortion are not well considered. Therefore, a novel TW fault location approach for LCC-MMC-MTDC transmission line based on frequency modification algorithm is proposed in this paper. Firstly, the complete frequency modification algorithm suitable for MTDC transmission system is described. Secondly, the novel TW fault location approach and its implementation scheme are given. Eventually, via PSCAD/EMTDC, a series of case studies are illustrated based on typical +/- 400 kV hybrid LCC-MMC-MTDC simulation model, which implying high robustness against fault location and grounding resistance issues.