Interlink hybrid DC circuit breaker

—To protect HVDC grids from DC faults, the concept of a hybrid DC circuit breaker is widely accepted due to its low conduction losses and fast interruption speed. For a well-built DC grid, a massive number of hybrid DC circuit breakers have to be installed. This will lead to high capital costs. An interlink DC circuit breaker based on an idea of sharing main breaker branch between two circuit breakers is proposed to reduce the overall costs of circuit breakers in a DC grid. Comparing with existing hybrid DC circuit breakers, the interlink hybrid DC circuit breaker can achieve the same DC fault interruption capability with fewer components. Novel structures of main breaker branches are designed and their parameters are determined to make the interlink hybrid DC circuit breakers be capable for both unidirectional and bidirectional interruption on demand. For a unidirectional interlink hybrid DC circuit breaker, the size of MOVs is reduced by 50%. For a bidirectional interlink hybrid HVDC circuit breaker, the number of IGBTs and MOVs are reduced by 25%. The interlink hybrid DC breakers are verified and compared to the hybrid DC circuit breaker via a three-terminal HVDC grid in PSCAD/EMTDC