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1. A power conversion device which comprises: a first power converter and a second power converter each having switching devices, and each capable of an inverter operation for performing bidirectional DC/AC conversion by on/off driving the switching devices and a rectifier operation for converting an alternating current to a direct current by turning off the switching devices; an insulation transformer that connects an AC-side terminal of the first power converter with an AC-side terminal of the second power converter; and a control circuit that controls the first and second power converters; and
which performs bidirectional DC-power conversion between a first DC-voltage source to which a DC-side terminal of the first power converter is connected and a second DC-voltage source to which a DC-side terminal of the second power converter is connected; wherein the control circuit includes four control modes of a first rectifier-control mode, a first inverter-control mode, a second rectifier-control mode, and a second inverter-control mode; wherein, at the time of supplying power from the first DC-voltage source to the second DC-voltage source, the control circuit utilizes the first rectifier-control mode in which the first power converter is placed under an output variable control according to the inverter operation while the second power converter is controlled to be according to the rectifier operation, and when a command value for controlling the first power converter becomes a first setup value or more, the control circuit switches the mode to the first inverter-control mode in which the first power converter is placed under an output fixed control according to the inverter operation while the second power converter is placed under an output variable control according to the inverter operation; and wherein, at the time of supplying power from the second DC-voltage source to the first DC-voltage source, the control circuit utilizes the second rectifier-control mode in which the second power converter is placed under an output variable control according to the inverter operation while the first power converter is controlled to be according to the rectifier operation, and when a command value for controlling the second power converter becomes a second setup value or more, the control circuit switches the mode to the second inverter-control mode in which the second power converter is placed under an output fixed control according to the inverter operation while the first power converter is placed under an output variable control according to the inverter operation. |
