This　paper　presents　a　comprehensive　analysis　of　the　current-stress　optimization　and　soft-switching　operation　of　the　isolated　bidirectional　dual　active　bridge　(DAB)　dc-dc　converter　with　the　unified　triple-phase-shift　(UTPS)　control.　On　this　basis,　the　current-stress-optimized　modulation　scheme　is　proposed　for　DAB,　which　leads　to　the　minimum　current　stress　with　the　required　transmission　power　and　voltage　conversion　ratio　in　the　whole　load　range.　Moreover,　the　full　soft-switching　operation　is　achieved　for　the　converter　simultaneously.　Distinct　from　the　previous　modulation　schemes,　the　proposed　optimized　modulation　scheme　is　deduced　from　a　unified　analysis　of　TPS　where　all　effective　switching　modes　are　investigated.　A　novel　algorithm　based　on　the　Karush-Kuhn-Tucker　(KKT)　conditions　is　originally　proposed　to　derive　closed-form　solutions　for　the　global　optimal　control　parameters.　This　paper　also　presents　a　typical　closed-loop　control　strategy　for　DAB　with　TPS　control　and　detailed　descriptions　about　the　closed-loop　operation.　A　laboratory　prototype　is　applied,　and　the　experimental　results　validate　that　the　current-stress　optimization　and　efficiency　improvement　are　realized　by　applying　the　optimized　modulation　scheme.　The　experimental　results　also　verify　the　effectiveness　of　the　closed-loop　control　strategy　for　DAB　with　TPS　control.