Robust Fractional PI Controller Design for StandAlone Microgrid under Load Variation: An Optimization-Based Approach

The primary goal of power control in an autonomous Microgrid (MG) is to reduce power fluctuations caused by undesirable operational conditions. This paper presents a reliable control method for standalone-based Microgrids with a single power source, specifically focusing on output voltage control. The proposed approach is based on a robust Fractional-Order Proportional Integral (FO-PI) controller. To achieve accurate control of current and voltage, a comprehensive Voltage Source Converter (VSC) model is developed, and the controller is meticulously tuned. The fractional voltage controller ensures a specified phase margin and enhances system robustness. Controller parameters are obtained using the constrained optimization algorithm. The robustness of the proposed controller is assessed under various conditions including voltage reference changes, high resistive load variations, filter parameter adjustments, and nonlinear load perturbations. Simulation results are conducted using MATLAB/Simulink and they highlight the advantages of the FO-PI controller over the conventional PI controller, including reduced peak overshoot, improved response time, enhanced output voltage quality, and reduced total harmonic distortion. Furthermore, the fractional characteristics of the FO-PI controller enhance the robustness of the Voltage Source Converter system compared to the PI controller.