Abstract: An inverter device, including: a booster circuit that includes a switch element and a booster coil, the booster circuit boosting a voltage of direct-current power by the switch element being driven using a first on-off signal; an inverter circuit that includes switch elements, the inverter circuit converting the direct-current power, which is outputted from the booster circuit, into alternating-current power by the switch elements being driven using a second on-off signal; a coil for filter through which the alternating-current power passes; and a control unit configured to drive (i) the switch element using the first on-off signal for which a duty cycle is changed according to a first frequency, and (ii) the switch elements using the second on-off signal generated based on a carrier wave having a second frequency higher than a first frequency and a modulation wave having a frequency which synchronizes to a frequency of a power grid.

Abstract: An inverter device converts a DC power into a three-phase AC power and superimposes the AC power on a power grid. A method for controlling the inverter device includes: obtaining, when the three-phase AC power is formed to contain a reactive power having a same amount in each of phases of the three-phase AC power, frequencies of respective phases of the power grid as present frequencies; controlling the reactive power to be contained in each of the phases to have a same amount such that the frequencies further increase when the present frequencies are higher than previous frequencies which have been obtained before the present frequencies are obtained, and such that the frequencies further decrease when the present frequencies are lower than the previous frequencies; and detecting a power outage state of the power grid based on the present frequencies of the respective phases and the previous frequencies.