| Abstract: | Considering the advantages and limitations of traditional identification method, combined with the strategy of
active detection, the principle of DC grid pilot protection based on active detection is proposed to improve the
sensitivity and reliability of hybrid MMC DC grid protection, and to ensure the accurate identification of fault areas
in DC grid. By using the DC fault ride-through control strategy of the hybrid sub-module MMC, the fault current at
the converter station DC terminal is limited. Based on the high controllability of hybrid MMC, sinusoidal fault
detection signals with the same frequency are injected into the line at each converter station. Based on model
recognition, the capacitance model condition is satisfied by the detected signals at both ends during external faults
whereas not satisfied during internal faults. The Spearman correlation coefficients is then introduced, and the
correlation discriminant of capacitance model is constructed to realize fault area discrimination of DC grid. The
simulation results show that the active detection protection scheme proposed in this paper can accurately identify
the fault area of DC grid, and is not affected by fault impedance and has low sampling rate requirement. |
