Modified VMD Algorithm-Based Fault Location Method for Overhead-Cable Hybrid Transmission Line in MTDC System
Dachuan Yu, Niancheng Zhou, Jianquan Liao, Qianggang Wang, Yuanzheng Lyu
Abstract
The precise identification of fault locations in multi-terminal DC (MTDC) transmission systems using traveling waves (TW) is imperative for ensuring the secure and stable operation of power systems. The presence of the wave impedance discontinuity in overhead-cable hybrid transmission lines (OCHTL) causes significant changes in TW velocity. Traditional TW-based fault location methods struggle to adapt to these changes. This paper 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 voltage TW 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.