Sequential auto-reclosing method for hybrid HVDC breaker in VSC HVDC links

Voltage source converters (VSC) are increasingly being used in high voltage direct current (HVDC) systems and with higher power ratings of these converters, the interest for usage with long transmission system is also increasing. With long overhead transmission dc links, many faults would be transient or temporary in nature. Such faults are mainly caused by lightning. The objective of this paper lies in proposing and implementing an auto-reclose feature to the operation of Hybrid HVDC breaker (HHB). The proposed method has been evaluated in a point-to-point HVDC link along with HHB at each end. This study shows that the proposed sequential operation of HHB can quickly and cost-effectively re-close the faulty line with minimal impact on connected ac grid and where the converters can continue to support the ac network with reactive power. Furthermore, the proposed soft start procedure adopted in auto-reclosing operation of HHB assists in reducing the dc current inrush and distribute the energy stress among the non-linear resistors in the main breaker modules of HHB.