This paper introduces a novel method for synchronizing two energized AC grids through a fast synchronization machine, which integrates a battery energy storage system (BESS) with a grid-imposed frequency voltage source power converter. The grid-imposed power converter is used to automatically provide the desired amount of power to the synchronous generators, and the BESS is connected to the DC side of the power converter, which exchanges energy with the grids. This method can achieve fast synchronization of grid frequencies and phases through active and automatic power exchanges between the battery based power converter and the grids. The effectiveness of the proposed method has been demonstrated by simulating interconnection of two synchronous generator based systems in the Matlab/Simulink environment. The simulation results show that compared with traditional methods the synchronization time can be reduced by an order of magnitude by using the proposed method.