Hybrid DC circuit breaker with fault current suppression capability

Abstract

Due to the rapid development of DC transmission, research on DC side fault protection has also made significant progress. The bipolar short-circuit fault is one of the most severe types of DC side faults. It can cause a current surge, which affects the safe operation of a system. Therefore, this paper proposes a new type of hybrid DC circuit breaker (DCCB) to realize the rapid suppression of bipolar short-circuit current. The new DCCB consists of three parts: a nominal current branch (NCB), an energy absorption branch (EAB), and a freewheeling branch (FB). Different control strategies can be adopted to achieve line protection functions for different types of faults. For transient faults, the absorption and suppression of the fault current are achieved mainly through the EAB and FB. The DCCB ensures that the amplitude of the current delivered by the DC line is maintained in a safe operating area of the transmission line. The EAB is disconnected after a short-term of operation for permanent faults to achieve complete isolation between the converter side and the fault side. The parameter design of the DCCB is carried out to provide a reference for the practical application of this research. Finally, the effectiveness of the proposed DCCB protection strategy is verified by simulations, and the function of the DCCB is further verified by experiments.