A Hybrid H-bridge Fault Current Limiter for HVDC Grid Protection

For half-bridge modular multilevel converter (MMC) based HVDC grids, the fast clearance of DC faults can be achieved by DC circuit breakers (DCCBs). The hybrid fault current limiter (FCL) can be used to assist DCCBs for faster interruption less capacity. Thus, this paper proposes a novel Hbridge hybrid FCL to realize a tradeoff of comprehensive performance. The current commutation branch in the FCL can bidirectionally limit the rate-of-rise of the fault current during the current transfer stage. The working principle and the electrical stress analysis are presented and the impact of the hybrid FCL on the transient energy transfer is analyzed. These approaches are validated by simulations of a ± 500 kV bipolar HVDC grid in PSCAD/EMTDC. Results show that the proposed FCL can reduce the application of IGBTs and the requirement of MOV with the fast speed of fault isolation.