Distributed dynamic secondary control integrated with real-time economic load dispatch for AC microgrids under unknown and varying communication delays

Unknown and time-varying communication delays represent a critical challenge in maintaining reliable control performance in AC microgrids, often degrading dynamic response and potentially threatening system stability. This paper proposes an enhanced distributed adaptive control (DAC) framework for islanded AC microgrids that explicitly accounts for such delays. The methodology is structured in three coordinated layers. First, a real-time delay estimation mechanism based on Global Positioning System (GPS) timestamps is introduced to continuously identify and compensate for unknown communication delays in the control loop. Second, a distributed adaptive secondary control scheme is developed to restore system frequency and voltage under delayed information exchange. Third, the secondary control layer is integrated with an optimal consensus-based economic load dispatch (ELD) algorithm to dynamically allocate active power among distributed generation units while minimizing the incremental cost function. The stability of the proposed delayed system is rigorously analyzed using a Lyapunov–Krasovskii functional approach. Extensive simulation and experimental studies conducted in MATLAB/RT-LAB under various operating scenarios demonstrate that the proposed DAC significantly enhances system performance under large, time-varying communication delays. Quantitatively, the proposed method improves frequency stability by approximately 9.18% and voltage stability by 7.90%, while reducing the incremental cost by about 30.1% compared to conventional control strategies. Additionally, the proposed approach achieves faster convergence and improved robustness in both transient and steady-state conditions.