| 摘要 |
The purpose of the present invention is to provide a power conversion device that exhibits high efficiency through selective use of power converters for balance control of series capacitors and to reduce common-mode circulating current. Multiple power conversion units are connected in parallel between a three-phase alternating-current power supply (200) and a load (300), each of the power conversion units comprising a converter (102) and an inverter (105) each being a three-level circuit, a direct-current intermediate circuit (104) including capacitors (103a, 103b), and a chopper (111). When the alternating-current power supply is normal and a zero-phase current flowing in the converter (102) or inverter (105) is smaller than a predetermined value, a control circuit changes the zero-phase voltage of the converter (102) on the basis of a voltage deviation between the capacitors (103a, 103b) in order to achieve balance control. When the alternating-current power supply is abnormal, or when the zero-phase current is larger than or equal to the predetermined value, the control circuit controls operation of the chopper (111) in order to achieve balance control. |
