With　the　conventional　single-phase-shift　(SPS)　control,　part　of　switches　of　dual　active　bridge　(DAB)　dc-dc　converter　lose　zero-voltage　switching　(ZVS)　operation　at　low　loads　when　the　voltage　conversion　ratio　is　different　from　unity.　Consequently,　the　switching　losses　increase.　Triple-phase-shift　(TPS)　control　which　introduces　additional　inner　phase-shift　ratios　has　two　more　degrees　of　freedom　than　SPS　control.　Thus,　TPS　control　is　more　flexible.　This　paper　proposed　an　optimized　modulation　scheme　based　on　TPS　control　to　improve　the　DAB　performances.　With　the　proposed　modulation　scheme,　all　active　switches　were　operated　under　soft　switching　in　the　whole　load　range.　Simultaneously,　the　current　stress　and　conduction　losses　decreased　at　low　loads.　The　efficiency　of　the　converter　increased　accordingly.　Moreover,　the　proposed　algorithm　to　calculate　the　optimal　control　parameters　had　great　universality,　and　could　be　used　for　other　optimizations　of　DAB.　The　experimental　results　verify　the　effectiveness　of　the　proposed　modulation　scheme.　©　2016　Chin.　Soc.　for　Elec.　Eng.