Control scheme for seamless operating mode transfer of AC microgrid

On-site small-scale electricity generation through a cluster of micro-sources with their local loads known as, microgrid has attracted significant attention as an alternative to traditional centralized power generation plants. The advantage of microgrid lies in its capability to work in stand-alone (island) and grid-connected mode. During the transition from grid-connected mode to island mode, there is a possibility of large voltage and frequency deviations, which is undesirable for the local loads connected to the system. These variations also build up stress on the power converter components associated with the circuitry of each of the micro-source. During the transition from stand-alone mode to grid, connected mode there is large probability of voltage and current transients. To avoid such situations, seamless mode transfer between the two working modes, an appropriate control scheme should be devised. This paper presents a control scheme wherein the micro-source inverter works in voltage control mode amid stand-alone operation and in current control mode amid grid-connected operation and switches over easily between these modes during the transition phase. The exhibited control scheme is simulated with MATLAB/Simulink and the obtained results are confirmed with hardware implementation utilizing Texas Instruments digital signal processor TMS320F28069. Simulation and hardware results establish the accomplishment of the proposed control strategy for seamless mode transfer in the microgrid.