In　order　to　further　improve　electromagnetic　transients　of　modular　multilevel　converter　in　simulation,　a　fast　energy　equivalent　model,　simple　and　reliable,　for　converter-arm　and　sub-module　is　proposed.　Specifically,　the　converter-arm　is　equivalent　to　a　controlled　source,　ensuring　that　the　converter　has　the　same　external　characteristics　and　electrically　decoupling　the　sub-module　from　the　arm.　This　model　simplifies　sub-module　switch　and　performs　energy　equivalence,　using　electrical　independence　features　of　the　sub-modules.　The　proposed　method　also　simplifies　simulation　circuit　and　reduces　the　number　of　nonlinear　components　in　the　circuit.　The　proposed　simulation　model　is　verified　on　PSCAD/EMTDC　platform,　showing　that　it　is　1736　times　faster　than　the　detailed　one.　Results　show　effectiveness　of　the　proposed　fast　energy　equivalent　model,　guaranteeing　high　simulation　accuracy　and　greatly　improving　simulation　efficiency.　©　2019,　Power　System　Technology　Press.　All　right　reserved.