Soft switched ac-link direct-connect photovoltaic inverter

A novel soft switched ac-link buck-boost converter for interfacing grounded solar photovoltaic power sources to the utility grid without transformers or common mode filters in a direct-connected configuration is proposed. Power transfer from input to output is accomplished via a link inductor which is charged from the input phases through AC switches, then discharged to the output phases with a precisely controllable current PWM technique which results in near zero harmonics at all frequencies below twice the link frequency. Capacitance in parallel with the link inductor produces zero-voltage switching for both turn-on and turn-off, with accompanying low switching losses.