A system is provided. The system includes a plurality of uninterruptible power supplies (UPSs), a ring bus, and at least one controller communicatively coupled to the plurality of UPSs, the at least one controller configured to calculate an output voltage frequency for each UPS of the plurality of UPSs, wherein the output voltage frequency for a UPS of the plurality of UPSs is calculated based at least on a derivative of an average active output power of the UPS, and control operation of each UPS based on the respective calculated output voltage frequencies.