In　order　to　improve　boost　capability　of　quasi-Z-source　inverter　and　grid-connected　current　quality,　a　single-stage　three-phase　voltage-fed　quasi-Z-source　photovoltaic　grid-connected　inverter　system　with　strong　boost　capability　with　repetitive　control　is　proposed.　Circuit　topology,　control　strategy　of　modified　space　vector　pulse　width　modulation　(SVPWM),　system　stability　and　modulator　design　under　discrete　control　system　were　researched.　The　circuit　topology　is　composed　of　a　high　boost　ratio　quasi-Z-source　impedance　network,　a　three-phase　inverter　bridge　and　a　three-phase　LCL　filter.　The　modified　SVPWM　control　strategy　includes　control　for　maximum　power　point　tracking(MPPT)　of　photovoltaic　array　and　outer　loop　control　for　energy　storage　capacitor　voltage　with　inner　loop　control　for　grid-connected　current.　Inverter-side　current　feedback　control　strategy　is　used　in　grid-connected　currentinner　loop　with　grid　voltage　proportional　feedforward,　repetitive　control　and　PI　series　embedded　composite　control　to　improve　grid-connected　currentquality.　Experiment　results　show　validity　of　the　inverter　system　topology,　control　strategy　and　system　design.　©　2017,　Power　System　Technology　Press.　All　right　reserved.