Nested redundant uninterruptible power supply apparatus and methods

Abstract

An uninterruptible power supply (UPS) system includes at least three UPSs configured to be connected in parallel to a common load. The system further includes 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. In this manner, a nested redundancy may be provided.

1 . A UPS assembly, comprising:
 a frame;   a plurality of UPS modules mounted in and/or on the frame and configured to be coupled in parallel to serve a load;   an first digital communications bus coupled to each of the UPS modules; and   a control circuit mounted in and/or on the frame, coupled to the first digital communications bus and configured to determine a magnitude of the load and to selectively enable or disable the UPS modules based on the determined magnitude of the load to maintain service to the load.   
   
   
       2 . The system of  claim 1 , wherein the control circuit is configured to selectively enable and disable the UPS modules to maintain service to the load when the determined magnitude of the load meets a predetermined criterion and to collectively disable the UPS modules when the determined magnitude of the load fails to meet the predetermined criterion.