This　article　presents　a　novel　nonisolated　high　step-up　dc-dc　converter　for　renewable　energy　generation　systems.　The　converter　combines　a　three-winding　coupled　inductor　(CI),　voltage　multiplier　cells　(VMCs),　and　two　power　switches　with　simultaneous　operation.　Compared　with　existing　high　step-up　converters,　the　proposed　converter　can　achieve　high　voltage　gain　under　a　low　number　of　turns　ratio　while　avoiding　a　large　duty　cycle.　Moreover,　the　passive　clamp　circuit　recycles　leakage　inductor　energy　and　reduces　the　voltage　spike　of　switches.　The　continuity　of　input　current　and　existence　of　common　ground　between　the　input　energy　source　and　load　make　the　converter　suitable　for　renewable　energy　applications.　Also,　the　proposed　converter　shares　high　voltage　gain　with　low　voltage　stress　on　semiconductors　(switches/diodes),　improved　compactness,　and　high　efficiency.　The　operating　principles　and　steady-state　analysis　of　the　proposed　converter　are　illustrated.　Then　the　theoretical　efficiency　analysis　and　performance　comparison　with　other　converters　are　discussed.　Finally,　a　200　W　prototype　with　380　V　output　voltage　is　established　based　on　the　design　guidelines,　and　experimental　results　verify　the　accuracy　of　the　theoretical　analysis.　©　2021　IEEE.