Analysis of Circulating current in Two Parallel-Connected AC/DC/AC Converter

Parallel-connected ac/dc/ac converters are used to increase power capability and have redundancy in high power applications. However, due to parallel connection, there exists a circulating current which does not contribute to the ac side load or source currents and causes extra losses. This paper analyses the circulating current for two parallel-connected ac/dc/ac converter system. The ac/dc/ac converter system may have separate dc-links for each ac/dc/ac converter or a common dc-link. In both cases, the circulating currents are analyzed in this paper. The system with and without common dc-links are simulated, and the comparison of the circulating current and total ac side source and load currents in both cases are presented.