Study on Circulating Current in Parallel Operation of Transformerless UPS

Abstract:
This paper reports on circulating currents in transformer less modular UPSs. There is concern that transformer less modular UPSs decline control performance and exceed component ratings due to circulating currents in the switching frequency component. Circulating currents in a transformer less UPS connected in parallel are even more complex. Therefore, this paper analyzes the circulating current focusing on the switching frequency component. The analysis method of the circulating current was confirmed by the experimental results.