Grid integration impacts and control strategies for renewable based microgrid

Microgrids are electricity distribution systems containing renewable or non-renewable-based distributed energy resources (DERs), storage devices, and loads, which operate either in grid-connected mode or islanded mode. Their integration with the distribution network requires hierarchical control structure for maintaining stable operation and control, which is otherwise challenging due to several technical challenges related to the large-scale integration of inverter-based resources (IBR). Hence, this paper first identifies these major challenges and then presents a comprehensive review of state-of-the-art hierarchical control structure for meeting expected functionalities. Emergence of advanced control trends, such as rise of cooperative distributed control method-ologies and unification of the traditional three layers of the hierarchical control into fewer (two or one) layers considering applications and operation, are also described.