Flexible solution for grid-connected operation of microgrids, based on a leading inverter with supercapacitor energy storage

This paper proposes a control solution for connecting microgrids (MGs) to the utility grid. An MG-leading inverter (MGLI) incorporating a supercapacitor energy storage system (SC-ESS) coordinates the MG, in both grid-connected and autonomous mode. Focusing on the grid-connected operation, this paper shows that, by the proposed control mechanism, a precise control of the power exchange with the grid can be obtained. An advantage of the proposed control method is that, regardless of the MG operation status, the units supplying the MG (e.g. MG-supporting inverters) operate without changes in their operating mode. Moreover, the proposed control approach ensures the MGLI to take over only transitory loads, which are then distributed among the MG sources capable of sharing the permanent load, this way an increased power reserve is always available to be deployed in case of contingencies that can jeopardize the MG stability. In order to validate the grid-connected operation of the proposed MG, experimental results obtained in laboratory are included in the paper.