Uninterruptible power supply device

An uninterruptible power supply device connected between an alternate-current (AC) power supply and a load, the uninterruptible power supply device comprising:

• a converter that converts AC power supplied from the AC power supply into direct-current (DC) power;
• an inverter that converts the DC power into AC power and supplies the AC power to the load;
• a DC link connected between the converter and the inverter for inputting the DC power to the inverter;
• and
• a bidirectional chopper that performs DC voltage conversion between the DC link and a power storage device, wherein
• the bidirectional chopper is configured to perform a charging operation of storing the DC power of the DC link in the power storage device during normal operation of the AC power supply, and
• when a charge termination voltage of the power storage device is higher than a DC link voltage of the DC link and a discharge termination voltage of the power storage device is lower than the DC link voltage, the bidirectional chopper performs, when performing the charging operation, a first step-down operation of stepping down the DC link voltage and a first step-up operation of stepping up the DC link voltage while switching therebetween in accordance with a voltage of the power storage device.