The recent grid integration of Distributed Energy Resources (DER) possibility the formation ofintentional islands in the case of a grid fault conditions. For such island formation is required an activeagent capable of governing the micro-grid connection state in a safe mode, especially in connectionand disconnection transients. This paper focuses on the design of a method oriented to carry out astable intentional disconnection, and later re-connection, of local grids from the main distribution gridin an intentional way; also under unbalance load condition. Seamless transfer between grid-connectedand isolated mode has been achieved in an alpha-beta stationary reference frame with a frequencybased synchronization control loop. Simulation and experimental results are provided to verify theproper performance of the proposed solution.