A power supply apparatus includes converters connected in parallel to a three-phase alternating-current power supply, input current detectors that detect current flowing through the respective three phases of the three-phase alternating-current power supply, and load current detectors that detect load current of the converters. Each of the converters includes AC-DC converters inputs of connected to two of the three phases. The AC-DC converters are connected in parallel to each other using a common output. The AC-DC converters that are driven maintain balance of output current. A controller determines whether switching between a driven state and a stopped state of the respective AC-DC converters is performed based on detection results from the load current detectors and switches between the driven state and the stopped state of the respective multiple AC-DC converters based on detection results by the input current detectors.

A power supply apparatus includes converters connected in parallel to a three-phase alternating-current power supply, input current detectors that detect current flowing through the respective three phases of the three-phase alternating-current power supply, and load current detectors that detect load current of the converters. Each of the converters includes AC-DC converters inputs of connected to two of the three phases. The AC-DC converters are connected in parallel to each other using a common output. The AC-DC converters that are driven maintain balance of output current. A controller determines whether switching between a driven state and a stopped state of the respective AC-DC converters is performed based on detection results from the load current detectors and switches between the driven state and the stopped state of the respective multiple AC-DC converters based on detection results by the input current detectors.

A power converter. The power converter comprising: two or more multi-phase AC sources; an AC-DC converter circuit for each of the multi-phase AC sources, each AC-DC converter circuit being connected to a respective multi-phase AC source via a multi-phase input and configured to rectify a received multi-phase current into a DC current; a transformer, which is connected between the multi-phase AC inputs; a DC-link, shared between each of the AC-DC converter circuits; a load, connected to the DC-link and able to receive DC current therefrom; and a common mode filter, located within the DC-link, and configured to reduce a circulatory current which, when the power converter is in use, flows from the transformer through one of the AC-DC converter circuits, through the DC-link and through a further of the

AC-DC converter circuits back to the transformer.

A power converter. The power converter comprising: two or more multi-phase AC sources; an AC-DC converter circuit for each of the multi-phase AC sources, each AC-DC converter circuit being connected to a respective multi-phase AC source via a multi-phase input and configured to rectify a received multi-phase current into a DC current; a transformer, which is connected between the multi-phase AC inputs; a DC-link, shared between each of the AC-DC converter circuits; a load, connected to the DC-link and able to receive DC current therefrom; and a common mode filter, located within the DC-link, and configured to reduce a circulatory current which, when the power converter is in use, flows from the transformer through one of the AC-DC converter circuits, through the DC-link and through a further of the

AC-DC converter circuits back to the transformer.

A power conversion device is configured with a plurality of power conversion units multiplexed in parallel each having a power converter for converting a power between a power source and a common load. At least one of the power conversion units is provided with an operation manager for managing the operation of the power converter. The operation manager changes the proportional gain of a voltage adjuster that performs a proportional control by inputting the steady-state offset between a target voltage and a voltage to the load, to determine, by comparing a change in the steady-state offset with a change in the proportional gain, whether the at least one power conversion unit is in a single operation in which the other power conversion units are in no operation.

A power conversion device is configured with a plurality of power conversion units multiplexed in parallel each having a power converter for converting a power between a power source and a common load. At least one of the power conversion units is provided with an operation manager for managing the operation of the power converter. The operation manager changes the proportional gain of a voltage adjuster that performs a proportional control by inputting the steady-state offset between a target voltage and a voltage to the load, to determine, by comparing a change in the steady-state offset with a change in the proportional gain, whether the at least one power conversion unit is in a single operation in which the other power conversion units are in no operation.

The power supply device includes a first winding, a second winding, a third winding, a fourth winding, a first AC-DC conversion unit, a second AC-DC conversion unit, a first power supply terminal and a second power supply terminal. The first and second windings are disposed on a secondary side of a multi-pulse transformer, and coupled to an input of the first AC-DC conversion unit. The first power supply terminal is coupled to an output of the first AC-DC conversion unit. The third and fourth windings are disposed on the secondary side of the multi-pulse transformer, and coupled to an input of the second AC-DC conversion unit. The second power supply terminal is coupled to an output of the second AC-DC conversion unit. Phases of output voltages of the first winding, the third winding, the second winding and the fourth winding are successively shifted left or successively shifted right for 15.

A high voltage rectifier includes: a power divider (2) dividing power of high-frequency wave RF to be rectified; a capacitor (3) cutting-off direct current flowing between the power divider (2) and a first rectifier (10): and a capacitor (4) cutting-off direct current flowing between the power divider (2) and a second rectifier (20). The first rectifier (10) generates a direct-current voltage DC.sub.1 by rectifying a high-frequency wave RF.sub.1 output from the power divider (2), and outputs the direct-current voltage DC.sub.1 to one end of a load (7). The second rectifier (20) generates a direct-current voltage DC.sub.2 having a different polarity from that of the direct-current voltage DC.sub.1 by rectifying high-frequency wave RF.sub.2 output from the power divider (2), and outputs the direct-current voltage DC.sub.2 to the other end of the load (7).

A high voltage rectifier includes: a power divider (2) dividing power of high-frequency wave RF to be rectified; a capacitor (3) cutting-off direct current flowing between the power divider (2) and a first rectifier (10): and a capacitor (4) cutting-off direct current flowing between the power divider (2) and a second rectifier (20). The first rectifier (10) generates a direct-current voltage DC.sub.1 by rectifying a high-frequency wave RF.sub.1 output from the power divider (2), and outputs the direct-current voltage DC.sub.1 to one end of a load (7). The second rectifier (20) generates a direct-current voltage DC.sub.2 having a different polarity from that of the direct-current voltage DC.sub.1 by rectifying high-frequency wave RF.sub.2 output from the power divider (2), and outputs the direct-current voltage DC.sub.2 to the other end of the load (7).

A plurality of uninterruptible power supplies of an uninterruptible power supply system controls start or stop of shared current supply from power converters to a load based on shared current commands, which indicate command values for determining a value of shared current to be supplied from the power converters of the plurality of uninterruptible power supplies to the load.