As　an　effective　carrier　of　new　energy　collection,　DC　power　grid　has　characteristics　of　low　inertia　and　weak　damping,　which　makes　DC　fault　propagate　extremely　fast.　However,　the　existing　protection　and　DC　circuit　breaker　(DCCB)　technique　still　could　not　match　its　fault　propagation　speed.　Therefore,　to　solve　this　problem,　a　novel　of　flexible　fault　current　limiter　(NFFCL)　is　presented　in　this　paper.　Under　normal　operation　condition,　NFFCL　is　connected　to　DC　line　in　series　without　negative　influence.　When　a　fault　occurs　to　DC　line,　NFFCL＇s　rectifier　circuit,　according　to　the　protection　criterion,　provides　cascade　inductor,　which　is　connected　to　DC　line　in　series,　with　a　set-slope　linear　current.　In　this　case,　the　voltage　drop　between　both　ends　of　inductor　can　be　clamped　flexibly,　which　can　even　completely　isolate　the　fault　area.　A　controlled　voltage　source　(CCVS)　is　applied　to　generate　inverse　flux　to　prevent　the　cascading　inductor　from　magnetic　saturation.　When　the　fault　disappears,　the　energy　of　current-limit　inductor　can　be　released　and　transferred　to　AC　power　grid　through　NFFCL＇s　converter.　Finally,　simulation　cases　are　carried　out　to　verify　the　working　principles　and　practicability　of　proposed　NFFCL.　©　2010-2012　IEEE.