Method for Identifying Symmetrical Inrush Current of UHV Converter Transformer Based on Matrix Pencil

摘要

UHV converters are equipped with large-difference protection and small-difference protection. When transformer is switched on under no load condition. The differential current of the large-difference protection is symmetrical magnetizing inrush current, and the second harmonic content of this inrush current is low, which makes the large-difference protection easy to malfunction. Because the symmetrical inrush current is not easy to identify from the waveform, but the matrix pencil can identify the amplitude and decay time constant of each harmonic component of the signal, this feature of the matrix pencil can distinguish fault current, inrush current and symmetric inrush current. In this paper, the formation mechanism of symmetrical inrush current is analyzed, and a UHV converter station model is established. The simulation test results verify the effectiveness of the matrix pencil method.