A Soft Reclosing Model for Hybrid DC Circuit Breaker in VSC-MTDC System

Abstract

Using hybrid DC circuit breakers (HDCCB) to isolate faults in voltage source converter based multiterminal high voltage direct current (VSC-MTDC) system is a common fault protection solution. Many temporary faults would occur due to the use of long overhead lines, thus it's required to reclose HDCCB at the faulty line after fault is isolated and cleared. Over-current limiting is very important for the security and reliability of DC system during the reclosing process. A soft reclosing model (SRM) for HDCCB to limit the reclosing over-current is proposed in this paper. Operation procedure and detailed mathematical analysis are carried out to design circuit parameter of SRM. The proposed model is evaluated in a 5 terminal VSC-MTDC system. Compared to traditional reclosing method, this proposal can effectively limit the reclosing over-current to reduce the impact when reclosing on fault in DC system, thus the security and reliability of DC system can be improved.