In　this　paper,　an　improved　power　flow　model　for　dual　active　bridge　(DAB)　converters　with　phase-shift　modulation　is　introduced.　Based　on　the　analysis　and　the　accordingly　derived　equations,　a　power　plateau　phenomenon,　in　which　the　phase　shift　loses　its　power-regulating　capability,　is　investigated.　Moreover,　it　is　found　that　this　power　plateau　phenomenon　leads　to　an　inversed　power　flow　characteristic　in　some　specific　regions　compared　to　the　models　reported　in　previous　literature.　The　characteristics　of　the　power　plateau　and　its　occurring　conditions　are　derived　and　analyzed　in　depth.　The　calculations,　simulations　and　analyses　have　been　verified　by　experiments.　©　2018　IEEE.