For a complex running microgrid

a method of microgrid connecting and off-grid smooth control is proposed based on self-identification for running mode. Collecting the real-time characteristics of microgrid

this method can identify the current running mode and switch the microgrid smoothly between the connecting and off-grid mode by using the extensible markup language (XML) file

the logical expressions of microgrid for its running mode

and can quickly control the exchanged power of tie-lines by generic object oriented substation event (GOOSE). The method can adjust its control strategy automatically

increase its reliability

and decrease its impact on microgrid. So far

the method has successfully been used in the Luxi Island microgrid project supported by National “863 Program”. It has a certain practical value. This works is supported by National Key Technologies R&D Program (No. 2012BAA15G00).