The　novel　single-stage　three-phase　voltage-fed　quasi-Z-source　photovoltaic　(PV)　grid-connected　inverter　with　strong　boost　ability　is　proposed　in　this　paper.　The　circuit　topology,　the　modified　space　vector　pulse　width　modulation　(SVPWM)　control　strategy　and　steady　principle　characteristic　were　deeply　investigated.　The　steady　principle　characteristics　include　the　low　frequency　operation　mode,　high　frequency　switching　process　and　external　characteristics.　And　the　important　conclusions　as　well　as　the　expression　of　the　voltage　transfer　ratio　were　abstained.　The　circuit　topology　is　composed　of　a　large　boost　ratio　quasi-Z-source　impedance　network,　a　three　phase　inverter　bridge　and　a　three　phase　LCL　filter.　The　modified　SVPWM　control　strategy　includes　the　control　for　the　energy　storage　capacitor　voltage　of　the　large　boost　ratio　impedance　network　as　well　as　the　outer　loop　control　for　the　maximum　power　point　tracking　(MPPT)　with　the　inner　loop　control　for　the　grid-connected　current.　The　real　characteristics　of　the　quasi-Z-source　inverter　adopting　the　modified　SVPWM　control　strategy　are　verified　by　the　experimental　results.　So　the　proposed　quasi-Z-source　inverter　provides　an　effective　method　for　the　new　energy　grid-connected　power　generation　systems　with　low　input　voltages　or　wide　range　input　voltages.　©　2017　Chin.　Soc.　for　Elec.　Eng.