A highly accurate double-ended traveling wave fault location method using GWO-VMD and the Hilbert transform for offshore MMC-MTDC grids

Accurate and reliable DC fault location methods can significantly enhance the resilience and reliability of offshore MMC-based multi-terminal direct current (MTDC) grids. This research proposes a novel double-ended DC fault location method using the GWO-VMD and the Hilbert transform. First, the propagation of traveling waves (TWs) in the faulty line-mode network is described, leading to the theoretical expressions for the Backward Line-mode Voltage TWs (BLVTWs). Next, the Gray Wolf Optimizer-Variational Mode Decomposition (GWO-VMD) algorithm is employed to extract the high-frequency components contained in the measured BLVTWs, and the Hilbert transform is used to obtain the Instantaneous Energy Spectrum (IES) of the specific IMFs, allowing for the determination of the arrival times of the TWs. Numerous simulations in the PSCAD/EMTDC and RTDS environments confirm that the fault location method is accurate under various sampling frequencies and for close-in faults. Comparison studies also demonstrate that the proposed method is more accurate than existing classical TW-based methods. Additionally, the RTDS tests show that the method can withstand noise disturbances of at least 30 dB and has the potential to be applied in real projects.