Study on smooth transition between island and grid-connected mode

Microgrid's smooth transition between island mode and grid-connected mode is a hot topic. Academic circles attach great importance to this, but the concept of smooth transition is not clear and the comprehension of it is also different. According to analyse the control process of transition,adjusting the run mode of distributed generations(DG) and storage devices to realize the transition is essential. The run modes of DG and storage devices include PQ,V/f and droop, that is to say, how to choose the run mode is related to run steadily of microgrid. Combined with the control method of voltage outer loop and current inner loop, an improved method of following the control of outer loop to avoid the fluctuation of voltage and frequency is presented to realize the transition smoothly between island mode and grid-connected mode. The effectiveness of this method is confirmed on the platform of simulation.