A bi-directional current-limiting hybrid DC circuit breaker with fast-breaking capability

The use of a DC circuit breaker to open and isolate DC faults in a flexible DC grid is one of the simplest and most reliable methods for handling DC faults. However, current limiting capacity and opening time generally contradict each other in most DC circuit breakers during the DC opening process. Furthermore, current limiting is generally not possible during mechanical switching, which results in higher requirements for the quick-acting nature of protection. To address these issues, a bi-directional current-limited hybrid DCCB topology with fast DC fault opening is proposed. Bi-directional power electronic switches enable a rapid and flexible conversion between low reactance in non-current-limited mode and high reactance in current-limited mode, suppressing the development of DC faults while achieving current limitation during mechanical switch opening, in addition, the time for the arrester to release energy is shortened. The simulation testing system is built on PSCAD/EMTDC, using the Zhangbei Flexible DC Grid project as the engineering background. Comparative analysis of numerous test results demonstrates that the proposed DCCB topology has low DC breaking voltage and current stress, short breaking time, and certain economic benefits.