A power conversion device configured to convert power between a DC unit (2, 2x) and a three-phase AC system, the power conversion device comprising: a first-phase conversion device configured to convert power between the DC unit (2, 2x) and a first phase of the three-phase AC system, via a filter circuit including a first reactor; a second-phase conversion device configured to convert power between the DC unit (2, 2x) and a second phase of the three-phase AC system, via a filter circuit including a second reactor; a third-phase conversion device configured to convert power between the DC unit (2, 2x) and a third phase of the three-phase AC system, via a filter circuit including a third reactor; and a control unit configured to control the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device, wherein the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device each include a DC/DC conversion circuit and a single-phase inverter circuit, wherein the first-phase conversion device, the second-phase conversion device and the third-phase conversion device are configured to perform systeminterconnection with the three-phase AC system via three or four electric lines to be taken out from respective phases of the three-phase AC system, and for each of the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device, when an absolute value of a voltage target value for the AC exceeds DC voltage of each DC unit (2, 2x), the control unit is configured to control the DC/DC conversion circuit to operate to achieve the absolute value of the voltage target value and configured to control the single-phase inverter circuit to only perform necessary polarity inversion, and when the absolute value of the voltage target value is smaller than the DC voltage, the control unit is configured to stop operation of the DC/DC conversion circuit and is configured to control the single-phase inverter circuit to operate to achieve the voltage target value, wherein the voltage target value is a voltage that is outputted for the single-phase inverter circuit at a circuit connection point between the single-phase inverter circuit and the filter circuit. a first-phase conversion device configured to convert power between the DC unit (2, 2x) and a first phase of the three-phase AC system, via a filter circuit including a first reactor; a second-phase conversion device configured to convert power between the DC unit (2, 2x) and a second phase of the three-phase AC system, via a filter circuit including a second reactor; a third-phase conversion device configured to convert power between the DC unit (2, 2x) and a third phase of the three-phase AC system, via a filter circuit including a third reactor; and a control unit configured to control the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device, wherein the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device each include a DC/DC conversion circuit and a single-phase inverter circuit, wherein the first-phase conversion device, the second-phase conversion device and the third-phase conversion device are configured to perform systeminterconnection with the three-phase AC system via three or four electric lines to be taken out from respective phases of the three-phase AC system, and for each of the first-phase conversion device, the second-phase conversion device, and the third-phase conversion device, when an absolute value of a voltage target value for the AC exceeds DC voltage of each DC unit (2, 2x), the control unit is configured to control the DC/DC conversion circuit to operate to achieve the absolute value of the voltage target value and configured to control the single-phase inverter circuit to only perform necessary polarity inversion, and when the absolute value of the voltage target value is smaller than the DC voltage, the control unit is configured to stop operation of the DC/DC conversion circuit and is configured to control the single-phase inverter circuit to operate to achieve the voltage target value, wherein the voltage target value is a voltage that is outputted for the single-phase inverter circuit at a circuit connection point between the single-phase inverter circuit and the filter circuit.