Uninterruptible power supply

An uninterruptible power supply comprising:

• a first switch that has one terminal receiving AC power supplied from an AC power source and has the other terminal connected to an AC node;
• a second switch that has one terminal connected to the AC node and has the other terminal connected to a load;
• a first power converter that exchanges power between the AC node and a power storage device;
• a second power converter that exchanges power between the power storage device and the other terminal of the second switch;
• and
• a controller that selects any power supply mode from a first power supply mode, a second power supply mode and a third power supply mode, and executes power supply operations in accordance with the selected power supply mode, wherein
• when the first power supply mode is selected, the controller turns on the first switch and the second switch so as to supply AC power from the AC power source to the load via the first switch and the second switch, and controls the first power converter so as to convert the AC power supplied from the AC power source via the first switch into DC power and store the DC power in the power storage device,
• when the second power supply mode is selected, the controller turns off the first switch, and controls the second power converter so as to convert the DC power of the power storage device into AC power and supply the AC power to the load, and
• when the third power supply mode is selected, the controller turns off the first switch and turns on the second switch, and controls the first power converter so as to convert the DC power of the power storage device into AC power and supply the AC power to the load via the second switch.