As　one　promising　topology　for　high-voltage　and　high-power　application,　IGBT-based　modular　multilevel　converters　(MMC)　have　gained　extensive　attentions　recently　due　to　modular　design　and　easy　scalability.　This　paper　presents　an　open-circuit　fault　diagnosis　and　tolerant　control　based　on　the　capacitor　voltage　balance　principle　for　the　MMC　applications.　Taking　eight　IGBT-based　submodules　as　an　example,　the　capacitor　balance　algorithm　with　the　carrier　phase-shift　control　is　implemented　and　three　fault-tolerant-control　strategies　are　compared.　Main　simulation　evaluation　results　are　provided　in　order　to　validate　the　effectiveness　of　the　proposed　strategy.　©　2020　IEEE.