Modified VMD Algorithm-Based Fault Location Method for Overhead-Cable Hybrid Transmission Line in MTDC System

The precise identification of fault locations in multiterminal dc (MTDC) transmission systems using traveling waves (TWs) is imperative for ensuring the secure and stable operation of power systems. The presence of wave impedance discontinuity in overhead-cable hybrid transmission lines (OCHTLs) causes significant changes in TW velocity. Traditional TW-based fault location methods struggle to adapt to these changes. This article introduces an innovative fault location approach tailored for OCHTL, with the primary aim of enhancing fault-ranging accuracy. Initially, a typical OCHTL equivalent model is established, and the propagation characteristics of the OCHTLs’ fault voltage TW (VTW) are analyzed. The variational mode decomposition-Teager energy operator (VMD-TEO) algorithm is then employed to determine the arrival time of the VTW wavefront. To optimize VMD parameters, the Kullback–Leibler (K–L) divergence method is applied, addressing modal aliasing. Additionally, we explore TW velocity attenuation characteristics across segments and introduce a frequency-modified algorithm for faulty segment identification. A high-precision fault location algorithm is then proposed based on two-terminal information, and its robustness and accuracy are validated through simulations using a PSCAD-built MTDC system with OCHTLs.