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One of the well-known methods to share active and reactive power in microgrids, is droop control. A disadvantage of this method is that in steady state the frequency of the microgrid deviates from the nominal value, and has to be restored using a Secondary Control System (SCS). The signal obtained at the output of the SCS is transmitted using a communication channel to the generation sources in the microgrid, correcting the frequency. However, communication channels are prone to time delays which should be considered in the design of the SCS; otherwise, the operation of the microgrid could be compromised. In this paper, two new SCSs control schemes are discussed to deal with this issue: a Model Predictive Controller (MPC) and a Smith predictor based controller. The performance of both control methodologies are compared to that obtained using a conventional PI-based SCS using simulation work. Stability analysis based on small signal models and participation factors is also realised. It is concluded that in terms of robustness, the MPC has better performance. Index Terms -Droop Control, Microgrid Control, ModelPredictive Control, Smith Predictors.

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Artículo de publicación ISIMillennium Institute Complex Engineering Systems ICM: P-05-004-F CONICYT: FBO16 National Fund for Science and Technology 1140775 CONICYT/FONDAP/15110019Millennium Institute Complex Engineering Systems, National Fund for Science and Technolog

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 systems 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.