A control plan for the stable operation of microgrids during grid-connected and islanded modes

This paper presents a control technique that enhances microgrids stability during the grid-connected and islanded modes. The proposed technique is compared with several existing control strategies in the context of microgrids integration into smart grids. The Lyapunov control theory is utilized in this paper to investigate the operation stability of DG units operating along with the utility grid. As the main contribution, the proposed technique compensates for the instantaneous variations of the reference current components of DG units in the ac-side of the converters. The presented method also considers and properly addresses the dc-voltage variations in the dc-side of the interfacing system. Under the proposed control strategy, DG units are able to deliver active and reactive power to the local loads and/or the main grid in fundamental and harmonic frequencies, with a fast dynamic response and without any interruption. Several simulation scenarios are carried out to demonstrate effectiveness of the proposed control strategy in microgrids during the transient and steady-state operation.