As　an　effective　carrier　of　a　new　energy　collection,　the　DC　power　grid　has　low　inertia　and　weak　damping　characteristics,　making　it　essential　to　limit　fault　current　and　isolate　the　DC　system.　To　quickly　and　effectively　suppress　fault　current,　a　flexible　current-limiting　device　(FCLD)　is　proposed,　which　can　realize　transient　fault　self-recovery　without　circuit　breaker　action　and　permanent　and　quick　isolation　of　a　fault.　It　improves　the　operational　ability　of　the　DC　system　under　an　asymmetric　condition.　First,　a　rectifier　provides　a　set-slope　current　to　each　cascade　inductor,　so　the　voltage　of　the　inductor　can　be　clamped.　Second,　a　controlled　current　source　(CCS)　is　applied　to　generate　inverse　flux　to　prevent　the　inductor　from　magnetic　saturation.　The　protection　action　time　of　the　DC　circuit　breaker　is　reformulated.　Finally,　by　considering　the　synergistic　action　of　the　current-limiting　device,　the　circuit　breaker,　and　the　transient　characteristics　of　the　DC　grid　fault,　the　protection　scheme　of　the　multi-terminal　flexible　DC　system　can　be　formulated.　To　verify　the　validity　of　the　proposed　flexible　current-limiting　device,　a　multi-terminal　flexible　DC　simulation　platform　is　established,　and　the　faults　of　DC　lines　are　simulated　and　analyzed.