A Novel Active Mechanical HVDC Breaker With Consecutive Interruption Capability for Fault Clearances in MMC-HVDC Systems

The lack of dc fault clearance capability is a major obstacle that restricts the development of high-voltage direct current (HVdc) systems. Employing an active mechanical dc circuit breaker (M-DCCB) is an effective method to handle the dc fault. However, the existing active M-DCCBs can interrupt the fault current once but have problems in making the second interruption instantly in case of reclosing a permanent dc fault. In this paper, a novel topology of the active M-DCCB is proposed by inserting a precharged capacitor into a bridge formed by four spark gap switches. The operating strategy for the proposed M-DCCB is discussed to handle the dc faults. Its parameters, including the oscillation inductor and the oscillation capacitor, are determined by inequations derived from the requirements of dc fault interruption. The selection standard for the spark gap switch is set based on its breakdown characteristics. Finally, simulations are conducted to investigate the performance of the proposed M-DCCB. Results show that the capacitor can accumulate a sufficiently large reverse charge voltage automatically charged by the fault current. The proposed active M-DCCB topology and the dc fault handling strategy can interrupt the dc fault in HVdc power systems consecutively.