Requirements for Fault Protection in HVDC Grids

Abstract

Conventional Voltage Source Converters (VSC) cannot interrupt DC fault currents and DC circuit breakers are not yet commercially available for HVDC power ratings. Thus, the protection of VSC-HVDC systems is still an obstacle for the development of this technology. The features of VSC-HVDC systems make them suitable for implementing HVDC grids. Nevertheless, HVDC grids are more complex than point-to-point links. Accordingly, the fault protection of these HVDC grids is a bigger challenge due to the specific requirements of DC grids. Nowadays there is no real HVDC grid operating, but it is expected that in the near future HVDC grids will be widespread, reinforcing the predominant AC systems. In this paper, the protection required by HVDC grids is thoroughly analyzed.