A　circuit　configuration　and　circuit　topological　family　of　quasi　single-stage　unidirectional　buck　dc-dc　converter　mode　grid-connected　inverters　with　high　frequency　link　are　proposed　in　this　paper.　Its　circuit　configuration　is　composed　of　the　unidirectional　isolated　buck　dc-dc　converter　and　polarity　reversal　inverting　bridge,　and　its　circuit　topology　includes　single-transistor　forward,　interleaving　single-transistor　forward,　push-pull,　push-pull　forward,　two-transistor　forward,　interleaving　two-transistor　forward,　half-bridge,　and　full-bridge　mode　circuit.　The　circuit　topology,　instantaneous　current　control　strategy,　steady　principle　properties,　and　design　criteria　for　the　key　circuit　parameters　were　deeply　investigated.　Taking　push-pull　forward　mode　topology　as　an　example,　1　kW　48VDC/220V50　HzAC　grid-connected　inverter　prototype　was　developed.　The　research　results　show　that　this　kind　of　inverter　has　the　advantages　such　as　high　frequency　electrical　isolation,　simple　topology,　quasi　single-stage　conversion,　high　conversion　efficiency,　the　polarity　reversal　inverting　bridge＇s　power　switches　having　low　voltage　stress　and　ZVZCS,　high　quality　grid-connected　current　etc.