The　independent　decoupling　control　of　two　motors　in　the　six-phase　series　three-phase　PMSM　system　can　be　realized　by　controlling　the　voltage　vectors　of　different　planes　in　the　static　coordinate　system.　Based　on　this,　the　rotating　high　frequency　voltage　is　injected　into　the　six-phase　plane　and　the　three-phase　plane　at　the　same　time　in　the　static　coordinate　system.　By　demodulation　of　the　negative　sequence　component　of　the　corresponding　plane　high　frequency　current,　the　preliminary　observed　rotor　position　angles　of　the　two　motors　are　obtained　by　decoupling.　To　compensate　the　error　caused　by　stator　resistance,　speed　and　filter,　the　rotor　position　angle　is　compensated　by　combining　the　error　angle　information　in　the　positive　sequence　component　of　high　frequency　current　with　the　speed　feedforward.　The　experimental　results　show　that　the　average　absolute　value　of　the　steady-state　rotor　position　angle　observation　error　values　of　six-phase　and　three-phase　motors　are　0.　146　and　0.　106　rad,　and　the　maximum　error　values　under　dynamic　conditions　is　0.　2　rad.　The　sensorless　direct　torque　control　system　based　on　the　observed　rotor　position　angle　has　excellent　performance　in　various　operating　conditions　at　low　speed.　©　2023　Science　Press.　All　rights　reserved.