The controller 550 may control a primary side voltage of the transformer 536 to be greater than a secondary side voltage of the transformer in a partial section before a first reference point in time Trf1 in the second period Pbm. Accordingly, the converter 530 in the power converting apparatus 500 including the unfolding inverter 540 may operate as a bidirectional converter 530. Therefore, it is possible to control a power factor.

Here, the first reference point in time Trf1 may be a point in time corresponding to one quarter of the control cycle.

Meanwhile, a width of the section where a primary side voltage of the transformer 536 is greater than a secondary side voltage of the transformer 536 may increase as the second period Pbm increases.

FIGS. 9A and 9B are diagrams showing an example of an output current waveform of an inverter in accordance with operation of the controller 550 when a grid voltage leads in phase.

For example, as shown in FIG. 9B, in the case where the grid voltage Vacr crosses zero at T0, T1, and T2 and a current Vac1 output from the unfolding inverter 540 crosses zero at Tk1 and Tk2, the phase of the grid voltage is faster and thus the grid voltage may be regarded as leading in phase.