DC protection for a multi‐terminal HVDC network including offshore wind power, featuring a reduced DC circuit breaker count

Abstract

Large offshore wind farms located far from shore, as are being planned or built in the North Sea, will require high‐voltage DC (HVDC) transmission to shore, and multi‐terminal HVDC could offer further benefits. Currently proposed methods to protect against faults in the DC network are based on extremely fast‐acting DC circuit breakers located on all cable ends, leading to high cost. A method is proposed based around discharging the DC network to isolate the fault, which drastically reduces the circuit breaker requirement, while making use of the inherent current‐limiting behaviour of the wind turbines. The validity of this approach is demonstrated in simulation.