An Assembly High Voltage DC Circuit Breaker Based on Pre-charged Capacitors

In order to solve the problems of high cost and poor current limiting effect in most conventional hybrid DC circuit breaker, this paper proposes an assembly DC circuit breaker based on pre-charged capacitors. It mainly includes converter-part and line-part, both of them consist of pre-charged capacitors. Converter-part is installed on DC outlet side of converter station in DC grid, and line-part is installed on each DC transmission line. This hybrid breaker provides the arc-less breaking condition for mechanical breaker branch through the voltage of pre-charged capacitors and can suppress fault current effectively. The hybrid DC breaker topology, working principle, control strategy and comparison results between the proposed scheme and existing schemes are de-scribed in detail. Besides, the feasibility and effectiveness are validated by building a three-terminal DC model in PLECS. The results show that the proposed DC breaker can not only cut off the DC fault line, but also avoid the collapse of bus voltage, which ensures the normal operation of non-faulty lines. Especially in the future multi-terminal DC system, the equipment cost of the shared converter-part will be greatly reduced due to the common part at the converter side.