Multi-line Hybrid DC Circuit Breaker with Low Conduction Loss and Reduced Semiconductor Breaker

We propose a new multi-line hybrid dc circuit breaker (DCCB) for high-voltage dc (HVDC) grids. The proposed hybrid DCCB includes mechanical switches, a semiconductor breaker (SB), and a commutation circuit. In an interruption process, the commutation circuit commutates the fault current from the mechanical switches to the SB, and the SB interrupts the fault current lastly. The conduction loss in a normal power transmission is considerably low, because the current flows through only the mechanical switches. Moreover, the proposed multi-line hybrid DCCB is configured at a dc bus in the HVDC grid and shares the SB with multiple transmission lines. SBs are bulky, because it must withstand a transient interruption voltage (TIV) in the transmission line. Therefore, the proposed topology, sharing the SB with multiple transmission lines, allows for a significant reduction in the number of components of the DCCB. This paper presents the configuration of the proposed hybrid multi-line DCCB and its interruption process. The commutation process is analyzed, and the design method of the commutation circuit is provided. Lastly, a circuit simulation verifies the interruption process of the proposed DCCB.