Bidirectional deduction four-terminal flexible direct current transmission line fault location method and system

The invention relates to a bidirectional deduction four-terminal flexible DC power transmission line fault location method and system, and belongs to the technical field of power system relay protection. According to the method, a ring shift left matrix and a ring shift right matrix are constructed by using a fault voltage traveling wave sequence, the product of the two matrixes is calculated, each row of the product matrix is summed, and the distance corresponding to the row with the minimum sum value is the fault distance. Compared with time domain traveling wave single-end distance measurement, the distance measurement method has the advantages that the bottleneck of calibrating the traveling wave arrival time in the time domain is broken through, the automatic single-end traveling wave distance measurement of the grounding electrode line is easy to realize, and the fault distance measurement accuracy is improved. Errors caused by unreliable wave head identification and inaccurate wave arrival time calibra