An Effective Solution for Regeneration Protection in Uninterruptible Power Supply

In this paper, a regeneration protection solution is proposed to address the dc-link overvoltage issue and the unequal power sharing in the parallel uninterruptible power supply (UPS) systems. First, a dc-link voltage protection control strategy is proposed to protect the inverter against the excessive dc-link voltage that may trigger the protection mechanism of the UPS system. In addition, an active power-sharing control strategy by regulating the virtual resistance is proposed to solve the circulating current caused by UPS regeneration issue. Finally, the feasibility of the proposed regeneration protection solution is verified by experimental results from the parallel UPS system prototype.