The　modular　multilevel　converter　(MMC)　based　dc　grid　has　attracted　much　attention.　The　protection　for　dc　fault　is　a　critical　issue　in　MMC　based　dc　grid.　In　this　paper,　an　integrated　thyristor　submodule　(ITSM)　for　dc　fault　current　interruption　is　proposed　with　the　advantages　of　reduced　semiconductor　costs　and　less　conduction　losses.　The　protection　scheme　for　ITSM　based　MMC　under　the　dc　fault　is　presented　and　the　working　principle　of　fault　interrupting　in　each　period　is　analyzed.　A　two-terminal　dc　grid　with　proposed　ITSM　based　MMC　is　simulated　with　PSCAD/EMTDC　to　verify　the　effectiveness　of　the　proposed　protection　scheme.　The　simulation　results　show　that　the　dc　fault　current　can　be　interrupted　within　a　fundamental　period.　©　2021　IEEE.