Currently,　regarding　the　active　neutral-point-clamped　multilevel　inverters　(ANPC),　the　unified　theory　between　the　triangular　carrier-based　sinusoidal　pulse　width　modulation　(SPWM)　and　space　vector　pulse　width　modulation　(SVPWM)　hasn＇t　been　systematically　analyzed.　This　paper　firstly　focuses　on　the　topology　and　switching　sequence　of　ANPC,　and　then　proposes　a　novel　method　of　decomposing　modulation　wave　based　on　the　redundancies　of　phase　voltages.　This　method　avoids　the　disadvantages　of　the　conventional　method　that　cannot　decide　the　redundant　states　of　phase　voltages　and　the　switching　sequences.　Meanwhile,　the　proposed　method　has　definite　physical　meaning.　It　can　be　used　in　the　topology,　which　has　many　phase　voltage　redundant　states　such　as　cascaded　H-bridge　multilevel　inverters.　By　injecting　zero-sequence　voltage　into　the　SPWM　modulated　wave　and　decomposing　the　new　modulation　wave　according　to　the　number　of　free　switches,　the　signal　of　SPWM　is　used　to　control　the　switches　directly,　then　the　same　sequence　of　SVPWM　modulation　can　be　uniquely　determined.　At　last,　the　unified　theory　of　the　SVPWM　and　SPWM　in　N　level　with　arbitrary　number　of　segments　sequence　is　deduced.　Experimental　results　have　verified　the　unified　theory.　©　2017,　The　editorial　office　of　Transaction　of　China　Electrotechnical　Society.　All　right　reserved.