Diode　neutral-point-clamped　(NPC)　three-level　dual-active　bridge　(DAB)　converters　can　extend　the　input　or　output　voltage　range　and　adapt　to　higher　voltage　level　conversion.　An　optimal　modulation　to　minimize　the　current　stress　for　three-level　extended　phase　shift　control　is　proposed　in　this　paper.　The　three-level　diode　clamp　structure　is　applied　to　the　primary　full　bridge.　The　output　voltage　of　the　primary　full-bridge　is　a　symmetrical　five-level　voltage,　and　the　output　voltage　of　the　secondary　full-bridge　is　a　symmetrical　two-level　voltage,　which　constitutes　a　three-level　extended　phase　shift　control.　The　mathematical　model　of　the　converter　in　four　working　modes　was　established,　and　the　shift　constraint　and　power　range　were　obtained.　Taking　the　inductor　current　stress　as　an　optimization　goal,　the　Karush-Kuhn-Tucker　(KKT)　method　is　applied　to　get　the　optimal　solutions.　Different　optimal　solutions　can　achieve　different　power　ranges.　In　the　power　overlapping　interval,　the　optimal　solutions　with　the　lowest　inductor　current　stress　is　identified　as　the　final　optimal　solutions.　Finally,　the　proposed　modulation　scheme　is　experimentally　verified,　and　the　three-level　extended　phase-shift　optimal　modulation　is　compared　with　two-level　EPS　control　with　minimum　current　stress　and　SPS　control　and　the　experimental　results　verify　that　the　proposed　three-level　extended　phase-shifting　optimization　modulation　strategy　can　further　reduce　current　stress　and　improve　conversion　efficiency　in　a　wide　voltage　range.　©　2025　Power　System　Technology　Press.　All　rights　reserved.