Novel fault area identification scheme for VSC-HVDC grids based on traveling-wave dispersion coefficient

Compared with the distributed configuration of current-limiting reactors at both line terminals, centralized installation of reactors at converter station outlets in VSC-based DC grids allows not only reduced construction costs but also enhanced economic efficiency. To address the incompatibility of boundary-based single-ended protection schemes with this topology, this paper derives analytical expressions for line-mode voltage traveling-wave during internal and external faults based on traveling-wave dispersion phenomena. The results demonstrate that both fault types exhibit double-exponential decay characteristics, with the dispersion coefficient-related exponential term for internal faults exceeding that of external faults. A protection scheme is subsequently developed by extracting this coefficient through the Levenberg-Marquardt (LM) algorithm. PSCAD/EMTDC simulations confirm that the proposed scheme covers the majority of line sections and exhibits robust tolerance to transition al resistances.