Non-unit full selective protection algorithm for MTDC grids

In a near future in Europe, reliable MTDC grids will emerge and be complementary to the AC transmission systems. An important stage to achieve before the deployment of such MTDC grids is the development of efficient protection strategies. In this paper, a non-unit full selective protection algorithm is introduced. Applied into protection relays located at each link end, this algorithm is capable of identifying the faulty link by only using local measurements. The algorithm is implemented and tested into a meshed 7-link DC grid modelled in the EMTP software. VSC-MMC converters with half-bridge submodules working under a symmetrical monopolar configuration are considered. Both pole-to-ground and pole-to-pole faults are covered.