Robust Distributed Secondary Control for AC Microgrids With Time-Varying Delay

Non-smooth, nonuniform, and even unbounded communication time delays, which are called irregular time delays, are unavoidable in many practical systems. Currently, there is no available approach that can solve the secondary voltage and frequency restoration control problem for an ac microgrid (MG) in the presence of such unknown irregular time delays. In this brief, we propose a resilient secondary control scheme to solve the problem. To ensure system stability and achieve asymptotic voltage and frequency restoration, sufficient conditions are established in the form of algebraic gains using a multidimensional small gain approach. Simulation and experimental case studies validate that the proposed control scheme can effectively solve this problem in a tested ac MG.