Transient fault studies in a multi-terminal VSC-HVDC grid utilizing protection means through DC circuit breakers

Multi-terminal DC grids is a promising solution for integrating distant renewable energy sources and offshore wind farms into onshore AC networks. Protection of such networks is one of key factors ensuring their reliability and continuity of service. This paper addresses the dynamic behavior and sensitivity of a typical multi-terminal DC grid under faulty conditions, observing the severe impacts these could have on the entire hybrid AC-DC system. Protection measures will be introduced in the form of DC circuit breakers (CBs) to isolate the faults and recover system´s normal operation. The study concludes the feasibility in using DC-CBs in a multi-terminal VSC-HVDC network serving as fault protection and stability recovery tool when the DC-CBs are located in an optimally distributed way. The simulation work depicting the various scenarios has been performed under DigSILENT PowerFactory environment.