Two-terminal fault combination location method on MMC-HVDC transmission lines based on ensemble empirical mode decomposition

Abstract

In the HVDC transmission system, the main factors that affect the accuracy of traditional two-terminal fault traveling wave distance measurement are the selection of appropriate wave velocity and whether the wave head can be identified. The line dispersion and transition resistance of the DC transmission will make it more difficult to determine the time when the wavehead reaches the two ends of the two sides, and the boundary elements of both terminal of the line will cause distortion of the wave head. Based on fault traveling waves characteristics of the time–frequency domain, we propose a method of Two-Terminal Fault Combination Location (TTFCL) on High Voltage Direct Current based on MMC (MMC-HVDC) transmission line. The method combines the natural frequency fault location method and the traveling wave fault location method. The first step of the walking wave natural frequency method is used for rough ranging, so that the approximate time range of the initial traveling wave of fault to reach the busbar can be obtained, and then can be calculated the rough position range of the fault point. Then the second step of accurate ranging is carried out, using the Ensemble Empirical Mode Decomposition (EEMD) algorithm to decompose the processed signal, extract the traveling wave component of the high-frequency, identify the traveling wave of initial head recognition and calibration, obtain the time parameters required for fault ranging, and calculate the more accurate fault point location by the two-ended fault ranging formula. In PSCAD/EMTDC, we built a simulation model of MMC-HVDC system line fault, and the simulation experiments are compared with different fault types and locations, and the results show that the combined fault ranging method eliminate the wave speed influence on accurate positioning and effectively identifies the wave head, which further improves the ranging accuracy.