Fault Current Limiting in VSC-HVDC Systems with MMC Converters

High Voltage Direct Current (HVDC) transmission systems are playing an important role due to their economical and technical benefits in the countries where the electric grid is expanding fast. However, fault current interruption is still an unsolved challenge in these HVDC grids. In order to interrupt undesirable currents, DC circuit breakers can be used, but their capability is limited. With that scenario, Fault Current Limiters (FCL) arise as a good approach in order to reduce fault currents to a more manageable level allowing to increase the transmission ratings of an electrical system, without changing the equipment. Thus, the existing equipment would be able to handle the new currents and protect properly the system. In this paper, the general characteristics and classification of FCLs are explained. After that, a Solid State FCL is applied on a VSC-HVDC system with MMC converters. A simulation case of its optimal behavior is presented.