An embodiment of the present application discloses a photovoltaic power generation inverter system, which is used for increasing an input voltage and a grid-connected voltage of an inverter under thesame power conversion conditions, and reducing an energy loss in the photovoltaic power generation inverter system. A method for apply that invention comprises the follow steps: a photovoltaic array,a DC conversion unit, a bus unit and an inverter unit; Wherein the photovoltaic array is one or more pairs of photovoltaic arrays, and each pair of photovoltaic arrays comprises two photovoltaic arrays, wherein the DC conversion unit comprises a first stage DC-DC converting DC sub-unit, a second stage DC-DC converting DC sub-unit and a cascade sub-unit, and the number of the DC conversion units isat least one; When the inverter works normally, the bus voltage and the grid-connected voltage in the photovoltaic inverter system are increased, so that the current is reduced, and the energy loss of the system is reduced by the coupling connection or decoupling function of the cascaded sub-units.