Compared　to　the　conventional　dual-active-bridge　(DAB)　converter,　three-level　DAB　(TL-DAB)　can　reduce　the　voltage　stress　on　the　devices　and　improve　the　operating　performance.　However,　as　the　voltage　level　of　the　converter　increases,　the　complexity　of　power　modeling　increases.　In　addition,　the　effect　of　the　conventional　current　stress　optimization　(CSO)　strategies　for　TL-DAB　is　limited　over　wide　voltage　ranges.　Thus,　this　article　first　proposes　a　direct　equivalent　modeling　method,　which　equates　the　power　models　of　multilevel　DAB　to　the　combination　of　several　simple　single-phase-shift　modulations,　thereby　reducing　the　complexity　of　modeling.　Based　on　the　obtained　model,　a　hybrid　CSO　(HCSO)　strategy　adapted　to　wide　voltage　ranges　is　proposed.　The　Karush-Kuhn-Tucker　(KKT)　condition　is　utilized　to　solve　the　optimization　table　with　three　degree-of-freedoms　(DOFs)　at　low　voltage　ratios.　For　high　voltage　ratios,　the　optimized　current　stress　of　the　KKT　condition　and　conventional　CSO　is　consistent　with　that　of　two-level　DAB.　Thus,　a　novel　blocking　capacitor　(BC)　modulation　is　employed　to　halve　the　voltage　ratio.　Then,　the　current　stress　is　reduced　further　under　light　load　by　utilizing　the　optimization　table　of　lower　voltage　ratios.　The　hybrid　modulation　of　multiple　DOFs　and　BC　realized　lower　current　stress　and　higher　efficiency　than　the　conventional　CSO　strategies　across　full　power　and　over　wide　voltage　ranges.　Finally,　the　improvement　caused　by　the　proposed　HCSO　was　verified　by　experimental　results.