Decentralized Robust Voltage Control of Islanded AC Microgrids: An LMI-Based $H_{\infty}$ Approach

In this paper, a decentralized control method is presented for the islanded inverter-interfaced microgrids with robust performance approach. The system is consisted of two Distributed Generations (DG) linked to their loads by inverter, RL filter and a step up transformer. The objective here is to guarantee the stability of the system and its desired performance under large load perturbation and Plug-and-Play (PnP) of the DGs. To achieve that aim, a Linear Matrix Inequality (LMI) state-feedback control technique with $H_{\infty}$ guaranteed cost is used for each DG. Contributions of the designed control system are: 1) the control design is entirely decentralized; 2) the stability and the desired performance of the overall system is guaranteed; 3) the control system is completely robust against PnP functionality of the DGs; 4) the controller provides robustness against large load perturbation. The ability of the presented control system with regard to voltage tracking, load changes and topology changes is evaluated on several case studies based on simulation in SimPowerSystems Toolbox in MATLAB.