Power supply device

1. A power supply device comprising:

an input terminal connected to an AC power supply;

an output terminal connected to a load;

a DC terminal connected to a power storage device;

a switch connected between the input terminal and the output terminal;

a plurality of power converters, each of the plurality of power converters performing bidirectional power conversion between the DC terminal and the output terminal; and

a controller that controls the switch and the plurality of power converters, wherein

the plurality of power converters include at least one first power converter,

the at least one first power converter has a charging mode and a standby mode, the charging mode being a mode of converting AC power supplied from the AC power supply through the switch into DC power and storing the DC power in a corresponding power storage device, the standby mode being a mode of generating a control signal for the power conversion and awaiting the power conversion,

when an AC voltage supplied from the AC power supply is normal, the controller turns on the switch and alternately switches the at least one first power converter between the charging mode and the standby mode, and

when the AC voltage is not normal, the controller turns off the switch and controls the plurality of power converters such that each of the plurality of power converters converts DC power of the power storage device into AC power and supplies the AC power to the load.

2. The power supply device according to claim 1 , wherein

the plurality of power converters further include at least one second power converter, and

when the AC voltage is normal, the controller controls the at least one second power converter to supply a compensation current to the load, the compensation current having a polarity opposite to that of a harmonic current flowing out to the load.

3. The power supply device according to claim 1 , wherein

the controller includes a timer that measures an execution time of the charging mode and an execution time of the standby mode, and based on the times measured by the timer, the controller alternately switches the at least one first power converter between the charging mode and the standby mode at predetermined time intervals.

4. The power supply device according to claim 1 , further comprising

a plurality of mechanical switches provided to correspond to the plurality of power converters, respectively, each of the plurality of mechanical switches being connected between a corresponding one of the plurality of power converters and the output terminal, wherein

during normal operation of the power supply device, the controller turns on the plurality of mechanical switches.

5. The power supply device according to claim 1 , wherein

in the standby mode, the controller generates a first control signal and a second control signal, the first control signal being a signal for bringing a difference between a DC voltage of the DC terminal and a reference DC voltage to zero, the second control signal being a signal for bringing a difference between an AC voltage of the output terminal and a reference AC voltage to zero.

6. The power supply device according to claim 1 , wherein

the power supply device is an instantaneous voltage drop compensation device.