ADVANCED POWER QUALITY ENHANCEMENT IN GRID-INTEGRATED PVG– UAPF SYSTEMS USING A MODIFIED SOGI–NOTCH FILTER CONTROL STRATEGY

Abstract

modern electrical distribution networks has significantly increased the need for maintaining high power quality under varying operating conditions. However, grid-connected PV systems are often affected by current harmonics, voltage distortions, reactive power fluctuations, and synchronization issues caused by nonlinear loads and grid disturbances. Conventional control strategies based on the Second Order Generalized Integrator (SOGI) exhibit limited performance under frequency deviations, DC offsets, and harmonic-rich environments, resulting in degraded harmonic compensation and slower dynamic response. This paper proposes an enhanced power quality control strategy for Grid-Tied Photovoltaic Generation–Unified Active Power Filter (PVG-UAPF) systems using a Modified Second Order Generalized Integrator (MSOGI) integrated with a Notch Filter. The proposed controller accurately extracts the fundamental grid voltage component while effectively suppressing low-order harmonics, DC offsets, and frequency variations. The extracted signals are utilized for precise reference current generation, enabling efficient harmonic mitigation, reactive power compensation, and improved synchronization between the PV inverter and the utility grid. The UAPF simultaneously injects active power from the photovoltaic source and compensates power quality disturbances, ensuring compliance with IEEE-519 harmonic standards. Simulation studies conducted under various operating conditions demonstrate that the proposed MSOGI-Notch Filter controller achieves lower Total Harmonic Distortion (THD), faster transient response, reduced current tracking error, improved power factor, and enhanced DC-link voltage stability compared with conventional SOGI-based methods. The proposed approach provides a robust and reliable solution for improving the performance of grid-connected renewable energy systems and contributes to the development of intelligent, efficient, and resilient smart grids.