DC line soft reclosing sequence for HVDC grid based on hybrid DC breaker

Voltage source converters (VSCs)-based high-voltage direct current grid (HVDC grid) is increasingly being used in high-level and long-distance power transmission. DC breakers could be applied to isolate fault on long overhead DC links, whereas most of these faults would be temporary and can be recovered after some deionisation time. The objective of this article lies in proposing and implementing DC line soft reclosing sequence based on the controllability of hybrid HVDC breaker (HHB). The proposed method has been evaluated in a four-terminal VSC-based HVDC grid with HHBs at each DC lines' end. The analysis and simulations in PSCAD/EMTDC show that the proposed sequential operation of HHB can softly recover the faulty line and identify whether the fault is temporary or permanent, with little impact on the whole DC system.