Distributed Forced-Boundary-Constrained Secondary Coordination of Islanded Microgrids

This study presents a novel distributed secondary control scheme for microgrids, aiming to accurately suppress the severe and unpredictable disturbances resulting from the increasing integration of renewable energy sources (RESs). The proposed scheme enforces boundary constraints during distributed control to ensure that the voltage and frequency of distributed generators (DGs) always remain within safe limits. By utilizing a symmetric state transformation mapping function, the study transforms the state boundary-constrained control problem into an unconstrained one in a newly defined continuous space. Within this space, a consensus algorithm incorporating a sliding mode surface is designed to address voltage and frequency restorations. The study further explores the stable operation of algorithms in both leader-following and leaderless modes, ensuring microgrid stability and adherence to boundary constraints even during communication interruptions. The theoretical findings are validated using the Lyapunov theory, and the performance of the proposed scheme is demonstrated through simulations and hardware-in-the-loop (HIL) experiments.