In　this　article,　a　modified　quasi-Z-source　high　step-up　dc-dc　converter　is　suggested　for　renewable　energy　applications,　which　features　lower　voltage　stress　of　switch　and　wider　region　of　duty　cycle　control.　In　addition,　the　superiority　of　the　novel　converter　embodies　ultrahigh　voltage　gain　with　a　small　turns　ratio　of　coupled　inductor,　continuous　input　current,　and　an　adjustable　wide　range　of　voltage　gain.　From　coupled　inductor,　a　step-down　type　winding　(turn　ratio　less　than　1)　and　a　step-up　type　winding　(turn　ratio　more　than　1)　not　only　enhance　the　voltage　gain,　but　also　provide　more　flexible　voltage　regulation.　The　low　pulsating　input　current　can　decrease　the　volume　and　capacity　of　the　input　filter.　Moreover,　the　switched-capacitor　contains　an　internal　passive　clamp　circuit　for　the　power　switch,　which　can　alleviate　the　voltage　spike　during　turn-off　operation　and　restore　the　leakage　inductor　energy.　The　operating　principle　and　theoretical　analysis　of　the　converter　are　given　in　detail.　A　200-W　prototype　was　fabricated　in　the　laboratory　according　to　the　design　guideline,　and　the　experimental　results　verify　the　validity　of　analysis.　©　1986-2012　IEEE.