Pilot Protection for Multi-Terminal Flexible DC Distribution Network Based on Current Mode Component Characteristics

The multi-terminal flexible DC distribution network has drawn a lot of attention due to its major advantages in terms of power delivery dependability. However, the rapid and accurate detection of faults in DC line protection has become one of the key issues that need to be addressed in its rapid development. For that reason, a DC line pilot protection method utilizing the characteristics of current mode components was designed. This method uses the direction of the positive current aerial mode component during a fault to distinguish between internal and external faults, constructs the protection criteria, which distinguish the type of fault, and forms a protection strategy based on the difference in the average value of the positive current zero-mode component at the fault point under different fault conditions. Finally, a multi-terminal flexible DC distribution network model was built on PSCAD/EMTDC4.5, and simulation analysis was conducted on the protection criteria and key influencing factors. The results show that this protection method can selectively, quickly, and reliably identify faults and fault types inside and outside the zone, and has good resistance to transition resistance and noise.