DC fault protection strategy considering DC network partition

This paper investigates DC network partition and alternative DC fault protection strategy for Multi-terminal HVDC (MTDC) system. Fast acting DC Circuit Breakers (DCCBs) or fault blocking DC-DC converters can be configured at strategic locations to allow the entire MTDC system to be operated interconnected but partitioned into islanded DC network zones following faults. In case of any DC fault event, the DCCBs or DC-DC converters at the strategic cable connections that link the different DC network partitions are opened or blocked such that the faulty DC network zone is quickly isolated from the remaining of the MTDC system. Thus, the healthy DC network zone can remain operational or recover quickly to restore power transmission. Each DC network zone can be protected using AC circuit breakers and DC switches for cost reduction. The validity of the proposed protection strategy is confirmed using MATLAB/SIMULINK simulations.