Abstract: Two redundant configuration schemes of UPS were compared. Combining with the example of unit tripping caused by UPS fault in power plant and the successful reformation of UPS system, an optimal design scheme of UPS was proposed, in which the output of two UPS directly parallel connected into load, and each of them can be put in automatically. The scheme can ensure the reliability of power supply, and provides a reference for UPS system design and reformation in thermal power plant.

Key words: uninterruptible power supply (UPS), redundant configuration, directly parallel connection, automatic mutual throw