Enhanced Power Quality Control in Grid Tied PVG-UAPF Systems Using a Modified Second Order Generalized Integrator and Notch Filter

Modern electrical distribution networks encounter significant challenges due to DC offsets, harmonics from nonlinear loads, and distorted grid voltages. These issues lead to increased total harmonic distortion (THD), reduced power factor, degraded power quality, and potential instability. Conventional controllers, such as second order generalized integrator (SOGI) and enhanced SOGI (ESOGI), are able to mitigate these issues but involve a trade off between harmonic filtering performance and dynamic response. Moreover, the gain magnitudes achieved for rejecting DC offsets, lower order harmonics, and higher order harmonics are relatively low. To address these limitations, this work introduces a modified second order generalized integrator with a notch filter (MSOGI) in a photovoltaic generator fed unified active power filter (PVG-UAPF) framework. By combining SOGI with a notch filter, the proposed approach leverages their complementary characteristics, achieving both superior harmonic filtering and a fast dynamic response. Furthermore, the proposed control structure effectively suppresses DC offsets and compensates for grid side and load side abnormalities while maintaining a unity power factor in the grid. The effectiveness of the proposed controller in a grid synchronized PVG-UAPF system is evaluated through MATLAB simulations under diverse operating conditions and further validated via real time simulation using the OPAL-RT 5700 platform. Compared to SOGI and ESOGI, the proposed method enhances harmonic filtering accuracy and dynamic response, achieving lower THD values of 1.85% for grid currents and 2.04% for load voltages, ensuring compliance with IEEE-519 standards.