Uninterruptible power supply system and method for supplying backup power

摘要

A UPS system includes UPS devices and a common bus. The UPS devices are configured to output respective backup voltages. The common bus electrically interconnects the UPS devices for receiving the backup voltages, and is configured to output to the UPS devices a greatest one of the backup voltages as a dominant voltage. Each UPS device is operable to detect the backup voltage outputted thereby, to compare the backup voltage with the dominant voltage, to determine whether a power recovery signal is received from the power supply equipment, and to vary the backup voltage with a descending trend, where the varying of the backup voltage is conducted at least based on the dominant voltage and the backup voltage.