An electric power conversion device comprising: - a power conversion unit connected to a three-phase AC circuit; and - a converter control unit for controlling the power conversion unit, wherein the power conversion unit includes three arms connected to the AC circuit and connected in a delta-connection manner, each arm has one or a plurality of unit cells connected in cascade, to which a reactor is connected in series, each unit cell includes a series unit of a plurality of semiconductor switches connected in series to each other, and a DC capacitor connected in parallel to the series unit, wherein the converter control unit includes: - a phase DC voltage control unit for calculating phase arm current command values on the basis of DC capacitor voltages of the cells; - a negative sequence current command value calculation unit for calculating a negative sequence current command value on the basis of the phase arm current command values; - an output current control unit for, on the basis of the negative sequence current command value and a predetermined positive sequence current command value, calculating a voltage command value including both a positive sequence component and a negative sequence component, for controlling output current of the power conversion unit; - a circulating current control unit for, on the basis of the phase arm current command values, calculating a zero sequence voltage command value for controlling circulating current; - a voltage command value calculation unit for calculating an output voltage command value for each unit cell on the basis of the voltage command value including both the positive sequence component and the negative sequence component, the zero sequence voltage command value, the cell DC capacitor voltages, and the phase arm currents; and - a gate signal generation unit for calculating a gate signal for controlling each semiconductor switch in the unit cell on the basis of the output voltage command value, and imbalance of the cell DC capacitor voltages among phases due to grid imbalance is controlled by the circulating current and the negative sequence current. - a power conversion unit connected to a three-phase AC circuit; and - a converter control unit for controlling the power conversion unit, - a phase DC voltage control unit for calculating phase arm current command values on the basis of DC capacitor voltages of the cells; - a negative sequence current command value calculation unit for calculating a negative sequence current command value on the basis of the phase arm current command values; - an output current control unit for, on the basis of the negative sequence current command value and a predetermined positive sequence current command value, calculating a voltage command value including both a positive sequence component and a negative sequence component, for controlling output current of the power conversion unit; - a circulating current control unit for, on the basis of the phase arm current command values, calculating a zero sequence voltage command value for controlling circulating current; - a voltage command value calculation unit for calculating an output voltage command value for each unit cell on the basis of the voltage command value including both the positive sequence component and the negative sequence component, the zero sequence voltage command value, the cell DC capacitor voltages, and the phase arm currents; and - a gate signal generation unit for calculating a gate signal for controlling each semiconductor switch in the unit cell on the basis of the output voltage command value, and