Fast Detection Method of DC Short Circuit Fault of MMC-HVDC Grid

This paper presents a fast detection method of DC short-circuit faults of high voltage direct current based on modular multilevel converter (MMC-HVDC) grid, which is characterized by fault identification according to the voltage change rate of the arm inductance of MMC converter station. When the internal fault occurs, the voltage change rate of the arm inductance is positive and not less than the set value; when the external fault occurs, the voltage change rate of the arm inductance is positive and not more than the set value. Then according to the change of transient current at the outlet of each DC line in MMC converter station, the DC line with faults in the area can be judged. Taking the outlet of any DC line in the converter station as the detection point, if the change of transient current at the detection point is positive, the fault occurs on the positive direction of the original current; if the change of transient current at the detection point is negative, the fault occurs on the reverse direction of the original current. The invention can detect the fault within 1ms or even shorter time after the fault occurs, and determine the location of the fault line.