Sequential auto-reclosing strategy for hybrid HVDC breakers in VSC-based DC grids

The use of overhead lines for power transmission in the future high-voltage and large-capacity voltage-source converter (VSC)-based direct current (DC) grid will significantly increase the probability of temporary faults. To eliminate potential adverse impacts such as erroneous protection, line-insulation failure, and even damage to power electronic devices resulting from a DC breaker reclosing operation with the traditional sequential auto-reclosing strategy, a novel sequential auto-reclosing strategy for hybrid HVDC breakers (HHBs) in VSC-based DC grids is proposed. This strategy is based on the step-by-step operation of the transfer branch in the HHB. As a result,
$\mathrm{d}u/\mathrm{d}t$
resulting from the HHB reclosing operation is greatly reduced, and therefore those potential negative impacts can be eliminated. Several other advantages are also presented. The feasibility and validity of the proposed strategy are verified in a four-terminal annular VSC-based DC grid electromagnetic transient model.