Uninterruptible power supply system

An uninterruptible power supply system, comprising:

• a plurality of uninterruptible power supply devices which are connected in parallel with respect to a load, and switch between power supplies supplying power to said load depending on states of said power supplies;
• a control unit controlling an operation of switching between said power supplies by said uninterruptible power supply devices;
• and
• a storage battery connected to the plurality of said uninterruptible power supply devices in common,
• said uninterruptible power supply device having
• a conversion unit converting AC power of an AC power supply into DC power,
• a switching unit switching between the DC power converted by said conversion unit and DC power input from said storage battery, and
• an inversion unit inverting the DC power converted by said conversion unit or the DC power input from said storage battery into AC power and supplying the power to said load,
• said control unit deactivating said inversion unit which does not contribute to supplying a power amount required for said load, of a plurality of said inversion units.