Uninterruptible power supply apparatus and method

An uninterruptible power supply method comprising:

• changing an output of a first generator based on a sum of a power consumption amount of a first load and a power consumption amount of a second load;
• setting an output of a second power converter to zero;
• transferring voltage information of a power grid to the second power converter;
• supplying, by the second power converter, constant-voltage power corresponding to the voltage information;
• and
• turning off a third switch connected to the power grid, the second power converter, the first load and the second load.

An uninterruptible power supply method comprising:

• when a power grid, a first generator and a second power converter do not operate due to a power failure,
• changing a state of a first power converter to a constant voltage state;
• supplying constant-voltage power corresponding to voltage information of the power grid;
• and
• turning off a first switch, a second switch and a third switch,
• wherein:
• the first switch is configured to open or close a connection between the power grid, the first generator and a first load,
• the second switch is configured to open or close a connection between a second load, the second power converter and the first generator, and
• the third switch is configured to open or close a connection between the power grid, the second power converter, the first load and the second load.