An active grounding fault line selection method for DC distribution network based on waveform correlation

Abstract

The fault characteristics of direct current (DC) distribution network with small current grounding mode are inconspicuous when single-pole grounding fault occurs. In order to accurately and reliably select the fault line, a grounding fault selection method based on the injected signal waveform correlation is proposed. Firstly, a predesigned additional control strategy is applied to the modular multilevel converter (MMC) of the DC distribution network to achieve the detection signal injection. Then, in combination with the zero-mode network, the fault characteristics are as follows. The specific frequency zero-mode current flow at the beginning of each sound feeder are same, which are opposite to zero-mode current flow at the beginning of the faulty feeder. Finally, based on this fault characteristic, the fault selection criterion is designed, and the Pearson correlation coefficient is introduced to compare the correlation between the normalized zero-mode current of each feeder and the total normalized zero-mode current. The fault selection is completed based on the characteristics that the correlation coefficient of the sound feeder is close to 1 and the correlation coefficient of the faulty feeder is close to -1. The simulation results show that the proposed method can reliably identify single-pole grounding fault occurring at any location on the bus or each feeder under high-resistance grounding fault.

Keywords

• direct current (dc) distribution network
• modular multilevel converte (mmc)
• line selection of small current grounding fault
• injected signal
• zero-mode network
• normalized current
• pearson correlation coefficient