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

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.This work was supported in part by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No. 20154030200730), and in part by the BK21PLUS Program through the National Research Foundation of Korea within the Ministry of Education