Solid　state　transformer　(SST)　is　able　to　interface　PV　panels　and　distributed　grid,　which　could　serve　as　a　new　structure　for　future　PV　plants.　However,　the　wide　operating　voltage　range　of　PV　system　reduces　the　efficiency　of　DAB　based　modular　cascaded　SST　system.　Thus,　this　paper　analyzes　the　impact　of　DAB　voltage　deviation　between　input　and　output　side　under　frequency　component　analysis.　Besides　adjusting　primary　and　secondary　side　duty　cycles,　which　is　widely　used　in　previous　literature,　this　paper　utilizes　DAB　output　voltage　as　an　extra　control　freedom　in　SST.　Then,　an　adaptive　voltage　control　(AVC)　scheme　is　proposed,　which　changes　DAB　output　voltage　in　accordance　with　input　voltage.　This　paper　presents　the　detailed　implementation　of　AVC　and　thoroughly　compares　SST　cell　efficiency　with　previous　modulation　method.　Finally,　the　proposed　method　is　verified　in　10kV/1MW　SST　system.