Patent ID: 7638899

Claim:
An uninterruptible power supply (UPS) system, comprising: at least three UPSs configured to be connected in parallel to a common load: and control circuitry configured to support at least two redundant groups among the UPSs and to support at least two redundant subgroups among at least one of the redundant groups of UPSs, wherein the control circuitry is configured to determine a loading of a first redundant group when concurrently providing power to the load with a second redundant group, to allow selective enabling and disabling of the UPSs within the first redundant group when the determined loading of the first redundant group is less than a predetermined level, to collectively disable the UPSs in the first redundant group when the determined loading of the first redundant group is greater than the predetermined level, and to allow the second redundant group to continue providing power to the load after collectively disabling the UPSs in the first redundant group.