Flexible DC bridge arm reactor protection method and device

The invention relates to a flexible direct-current bridge arm reactor protection method and device, and belongs to the technical field of flexible direct-current power transmission. A threshold value is set to be the maximum value of a differential protection current constant value and a protection braking current constant value, and the protection braking current constant value is the product of the root mean square of the sum of three-phase current instantaneous values of an upper bridge arm or a lower bridge arm, the maximum value of positive or negative current absolute values and a protection braking proportionality coefficient. Calculating the difference between the absolute value of the sum of the three-phase current instantaneous values of the upper or lower bridge arm of the converter at N continuous acquisition moments and the absolute value of the positive or negative direct current, comparing the difference with a threshold value, if the absolute value is greater than the threshold value, performi