Abstract—In order to improve the ability of the modular
multi-level converter to quickly clear and isolate faults in the
multi-terminal flexible DC grid, this paper analyzes the characteristics
of current faults in the multi-terminal flexible direct current grid,
introduces the comprehensive distance of current fault waveform, and
proposes a line protection method based on the similarity of current
fault waveform. This protection method firstly uses Euclid DTW (Dynamic
Time Warping) distance and entropy weight method to process electrical
quantity signals, calculates the comprehensive distance of current fault
waveform of two converter stations, and builds the protection criterion
based on the similarity of current fault waveform. Then, the fault
identification is realized by using the calculated comprehensive
distance, and the fault pole identification is realized by using the
ratio of comprehensive distance between positive and negative poles.
Finally, PSCAD was used to build a simulation model to output the fault
data under different fault conditions, and MATLAB was used to process
the fault data to verify the protection algorithm. The simulation
results show that the proposed method has good resistance to high
resistance, and its rapidity and adaptability are further improved. The
research results will provide a theoretical basis for the safe and
reliable operation of flexible DC power grid.