Power conversion device and program

This power conversion device comprises a conversion unit, a grid forming control unit, a grid following control unit, a modulation unit, a switching unit, and a synchronization adjustment unit. The grid forming control unit generates a first modulation command. The grid following control unit generates a second modulation command. The modulation unit changes the amplitude and phase of an output voltage on the basis of the first modulation command or the second modulation command. The switching unit switches an input to the modulation unit so that either the first modulation command or the second modulation command is input to the modulation unit. Before the input to the modulation unit is switched from the second modulation command to the first modulation command, the synchronization adjustment unit corrects the first modulation command so that the difference between the target amplitude of the first modulation command and the amplitude of a grid voltage becomes less than or equal to a threshold value, the difference between the target frequency of the first modulation command and the frequency of the grid voltage becomes less than or equal to a threshold value, and the difference between the target phase of the first modulation command and the phase of the grid voltage becomes less than or equal to a threshold value.