Distributed Control Strategies for Microgrids: An Overview
There is an increasing interest and research effort focused on the analysis, design and implementation of distributed control systems for AC, DC and hybrid AC/DC microgrids. It is claimed that distributed controllers have several advantages over centralised control schemes, e.g., improved reliability, flexibility, controllability, black start operation, robustness to failure in the communication links, etc. In this work, an overview of the state-of-the-art of distributed cooperative control
... ems for isolated microgrids is presented. Protocols for cooperative control such as linear consensus, heterogeneous consensus and finitetime consensus are discussed and reviewed in this paper. Distributed cooperative algorithms for primary and secondary control systems, including (among others issues) virtual impedance, synthetic inertia, droopfree control, stability analysis, imbalance sharing, total harmonic distortion regulation, are also reviewed and discussed in this survey. Tertiary control systems, e.g., for economic dispatch of electric energy, based on cooperative control approaches, are also addressed in this work. This review also highlights existing issues, research challenges and future trends in distributed cooperative control of microgrids and their future applications. FIGURE 3. General topology of a hybrid-MG. FIGURE 4. Control layers typically utilised for hierarchical control of MGs. systems. However, some approaches, as the utilisation of high-pass "wash-out" filters have been proposed in the literature , . Espina et al.: Distributed Control Strategies for Microgrids: An Overview FIGURE 8. Droop deviations over AC MG. FIGURE 9. Implementation of virtual impedances for the purpose of sharing imbalances and providing active damping in a four-leg MG. a) Topology of the DER including the output power filter filter. b) Control loops where G V i (s) is the transfer function of the voltage control loop; G Ci (s) is the controller of the current (i Li ); Mi(s) is the plant for the current control system and Ni(s) is the plant for the loop regulating the voltage.