A power conversion device comprising: - a main circuit unit including - a plurality of arms to which outputs of a plurality of converters are connected in series, each of the plurality of converters being adapted to include a plurality of semiconductor switching elements and a capacitor and being configured to receive a DC voltage of the capacitor and to control an output voltage by on/off driving of the semiconductor switching elements, and the main circuit unit including an AC side connectable to a target to be controlled; - a driving unit configured to receive a voltage command, to generate a driving signal for driving the plurality of semiconductor switching elements in the main circuit unit according to the voltage command, and to output the driving signal to the plurality of semiconductor switching elements; - an AC control unit configured to generate AC voltage commands (Vacur, Vacvr, Vacwr) for the number of phases on the AC side for controlling AC power of the target to be controlled; and - a DC control unit configured to generate a DC voltage command (Vdcr) for setting an average value of the DC voltages (Vcjk) of the capacitors of each of the plurality of converters in the main circuit unit to a predetermined value, based at least on detected capacitor DC voltages (Vcjk) of each of the plurality of converters and a DC voltage rated value (VdcO) of a DC line to which the arms are connected; - an adder configured to add the DC voltage command (Vdcr) generated by the DC control unit to the AC voltage commands (Vacur, Vacvr, Vacwr) generated by the AC control unit, to generate a voltage command comprising a modulation wave, and to provide the voltage command to the driving unit. - a main circuit unit including - a plurality of arms to which outputs of a plurality of converters are connected in series, each of the plurality of converters being adapted to include a plurality of semiconductor switching elements and a capacitor and being configured to receive a DC voltage of the capacitor and to control an output voltage by on/off driving of the semiconductor switching elements, and the main circuit unit including an AC side connectable to a target to be controlled; - a driving unit configured to receive a voltage command, to generate a driving signal for driving the plurality of semiconductor switching elements in the main circuit unit according to the voltage command, and to output the driving signal to the plurality of semiconductor switching elements; - an AC control unit configured to generate AC voltage commands (Vacur, Vacvr, Vacwr) for the number of phases on the AC side for controlling AC power of the target to be controlled; and - a DC control unit configured to generate a DC voltage command (Vdcr) for setting an average value of the DC voltages (Vcjk) of the capacitors of each of the plurality of converters in the main circuit unit to a predetermined value, based at least on detected capacitor DC voltages (Vcjk) of each of the plurality of converters and a DC voltage rated value (VdcO) of a DC line to which the arms are connected; - an adder configured to add the DC voltage command (Vdcr) generated by the DC control unit to the AC voltage commands (Vacur, Vacvr, Vacwr) generated by the AC control unit, to generate a voltage command comprising a modulation wave, and to provide the voltage command to the driving unit. - a driving unit configured to receive a voltage command, to generate a driving signal for driving the plurality of semiconductor switching elements in the main circuit unit according to the voltage command, and to output the driving signal to the plurality of semiconductor switching elements; - an AC control unit configured to generate AC voltage commands (Vacur, Vacvr, Vacwr) for the number of phases on the AC side for controlling AC power of the target to be controlled; and - a DC control unit configured to generate a DC voltage command (Vdcr) for setting an average value of the DC voltages (Vcjk) of the capacitors of each of the plurality of converters in the main circuit unit to a predetermined value, based at least on detected capacitor DC voltages (Vcjk) of each of the plurality of converters and a DC voltage rated value (VdcO) of a DC line to which the arms are connected; - an adder configured to add the DC voltage command (Vdcr) generated by the DC control unit to the AC voltage commands (Vacur, Vacvr, Vacwr) generated by the AC control unit, to generate a voltage command comprising a modulation wave, and to provide the voltage command to the driving unit.