Abstract: The calculation method of closed loop surge current in the parallel conversion of automatic transfer switch equipment(ATSE) was introduced.Two kinds of closed loop selection combination with the latest research results both in China and abroad were compared and analyzed.By the practical caladation,the references for the conditional parameter setting of parallel conversion were provided.It can be used for reference significance in the development of parallel conversion products.

Key words: automatic transfer switch equipment(ATSE), parallel conversion, closed loop, closed loop surge current, closed loop selection