Converter valve-level fault location method based on the temporal differences among horizontal and longitudinal valve states

Abstract

AC fault or converter fault could lead to LCC-HVDC converter protection operation, and converter protection outlet involves a random bypass pair scheme, which would expand the fault. To address this issue, a converter valve-level fault location method based on temporal differences among horizontal and longitudinal valve states is proposed. The research focuses on the inverter as the object, and analyzes the circuit state characteristics at the different fault locations within converter. In the horizontal direction of converter structure, conduction widths of AC current are constructed based on the location of commutation groups. In the converter longitudinal direction, temporal features of conduction widths are constructed based on single bridge or two bridges. Firstly, fault area is identified based on the amplitude characteristics of converter terminal currents and the abnormal characteristics of valve states. Secondly, converter internal fault is located by using the difference in the horizontal conduction width and the longitudinal temporal features between two bridges. Thirdly, the faulty phase or faulty valve is located as the valve that has the greatest virtual conduction width within the time window interval. Finally, simulations and field record data verify the validity of the proposed fault location method, and show that the proposed method has strong adaptability.