A review of decentralized and distributed control approaches for islanded microgrids: Novel designs, current trends, and emerging challenges

Distributed energy resources (DER) on the demand side have been fast growing, which could boost energy resilience by uninterruptedly supplying the commercial and residential sectors in the form of islanded microgrids when the utility electricity grid is out of service. Nevertheless, simply applying the centralized hierarchical control strategies, traditionally used for utility electricity grids, onto the islanded microgrids would encounter several critical issues. For instance, the control goals in secondary and tertiary control could be activated tardily, the single-point fault could cause critical system failure, and the properties of dynamic plug and play would be hard to achieve. To this end, decentralized and distributed control approaches have been explored to cope with the issues. Specifically, compared to the centralized hierarchical control, decentralized and distributed control strategies can (i) respond to disturbances more promptly, enhancing the performance of islanded microgrids with limited resources; (ii) guarantee system stability especially when a fault occurs and certain DERs are disconnected from the network; and (iii) facilitate deeper penetration of DERs in the microgrid, owning to the low computational complexity and sparse communication network. In this article, the common approaches for decentralized and distributed control are reviewed, and the current design trends and critical technical challenges are discussed to offer a comprehensive understanding of decentralized and distributed controlled microgrids.