In　this　paper,　a　three-stage　space　vector　pulse　width　modulation　(SVPWM)　along　with　soft　switching　is　proposed　for　a　high-voltage　transfer　ratio　single-stage　three-phase　current-source　inverter　(HVTR-CSI)　to　reduce　switching　losses　and　improve　inverter　efficiency.　The　proposed　SVPWM　strategy　utilizes　the　conduction　state　of　the　energy　storage　switch　as　the　zero　vector　and　assigning　effective　vectors　action　modes.　The　zero-voltage-switching　(ZVS)　of　the　energy　storage　switch　is　achieved　by　resonant　parameters　and　controlling　the　turn-on　time　of　the　active　clamp　circuit.　The　circuit　topology,　operation　principle,　high-frequency　switching　process　of　the　studied　CSI　are　thoroughly　analyzed,　and　detailed　calculations　of　the　circuit　parameters　and　soft-switching　design　are　performed.　Experimental　results　on　a　1　kW　24　VDC/84　VAC　3-phase　AC　prototype　show　that　the　modulation　improves　the　CSI　peak　efficiency　by　1.15%　compared　to　sinusoidal　pulse　width　modulation　(SPWM).　This　study　provides　an　effective　design　approach　for　the　HVTR-CSI　in　terms　of　reducing　switching　losses.　©　2024.　The　Author(s).