Power Quality Enhancement in Grid-Connected and Islanded Microgrids Using Fuzzy Logic-Based UPQC with Intelligent Islanding and Reconnection

Abstract This paper presents a novel methodology for the strategic placement, control, and integration of a Unified Power Quality Conditioner (UPQC) within grid-connected and islanded microgrid (µG) systems that integrate Distributed Generation (DG). The system is modeled and studied using MATLAB/Simulink. The Point of Common Coupling (PCC) hosts both the DG converters equipped with the battery and the shunt active power filter (APFsh) component of the UPQC. Positioned in series between the grid and the PCC is the UPQC’s series active power filter (APFse). A DC link facilitates the integration of the energy storage system. A key innovation in this approach is the implementation of a fuzzy logic (FLC) based islanding detection and reconnection mechanism, referred to as UPQCIDR, which functions as a secondary control layer. This control strategy enhances the system’s ability to manage voltage interruptions during grid-connected operation, while also addressing reactive power compensation, harmonic distortion, and voltage sags/swells. During both islanded and interconnected modes, the DG converter is responsible for supplying active power, whereas the shunt component of UPQC compensates for harmonic power and reactive demands. Furthermore, the suggested configuration ensures continuous operation of the DG converter during voltage disturbances, including phase jumps, thereby improving overall system resilience and power quality.