When the pole-to-pole fault occurs at the line of a flexible DC distribution grid

the fault current will rise quickly to a high peak value

which will seriously threat to the fragile power electronic components in the system

leading to MMC blocks. However

the existing protections have the problem of weak ability to identify the high resistance fault

resulting in reduced reliability and selectivity. In order to solve the above problems

a protection based on the line-mode fault component current (LFCC) integration is proposed. Firstly

the expression of LFCC under the internal and external faults is theoretically analyzed. It can be analyzed that the amplitude of the LFCC increases rapidly after the fault

and the polarity is related to the fault direction. Thus

the fault identification criterion is constructed by the LFCC. Only by applying the local information can the metallic fault be quickly identified

and the internal high resistance fault can be identified by integrating the fault direction information on the other line end. Finally

the PSCAD is applied to verify the proposed protection. Extensive simulation results prove that the protection has fast speed and high sensitivity

and is robust to high resistance fault.