A three-phase off-line UPS system for transformer coupled loads

Abstract

A number of critical load applications depend on a UPS system to uphold the normal operation. As soon as any disruption happens on the utility, an off-line UPS system starts supplying the power to the load to prevent blackout. Nonetheless, during this process, a substantial inrush current can be observed for the transformer-coupled loads. To avoid this inrush current, we propose an off-line UPS system based on a current regulated voltage source inverter. The inverter of the proposed UPS system uses a current control scheme executed in a stationary frame to regulate the load current and eliminates the likelihood of the inrush current. To endorse the performance of the proposed UPS system, we constructed a small prototype to obtain the experimental results.