A Staged Current Limiting Scheme of Hybrid DC Circuit Breaker for HVDC Grid

Several half-bridge modular multilevel converter (HB-MMC) HVDC projects have been put into operation in recent years. When the DC side faults, the sharp rise current will easily cause the damage of the converters. This paper proposes a new staged current-limiting HVDC circuit breaker (DCCB) scheme, which is based on the existing hybrid DCCB. The new scheme can not only put into current-limiting quickly after the fault but also maintain current-limiting for a period, which reserves enough time for DC protection judgment. Meanwhile, it can reduce the difficulty of DCCB to cut off the fault line through self-bypass design. The feasibility and validity of the proposed scheme are verified to be applicable for HVDC fault isolation requirements by PSCAD/EMTDC simulation results.