The control strategy of grid-connected converters in microgrids with unbalanced load

A multi-loop controller for grid-connected voltage source converters with LCL filter is proposed in this paper. The controller consists of three segments - inner predictive current controller, outer voltage vector controller, and the command voltage modifier. The whole controller is applied to converters based DRs in microgrids, and regulate the load terminal voltage with zero steady-state error even under unbalanced conditions. Selected results from simulation studies conducted on the performance of the controller under balanced and unbalanced conditions both in island and grid-connected mode are presented.