A COMPREHENSIVE REVIEW ON POWER QUALITY IMPROVEMENT IN SOLAR PV SYSTEMS USING ADVANCED TOPOLOGY CONTROLLERS

Abstract- The rapid global proliferation of grid‑connected and stand‑alone photovoltaic (PV) arrays has pushed the renewable‑energy conversation beyond raw kilowatt‑hours toward the subtler but critical issue of power quality (PQ). While sunlight is free, the conversion chain from panel to point of common coupling is anything but benign: high‑frequency switching injects current harmonics, partial shading provokes low‑order voltage distortion, fast irradiance ramps create flicker, and unbalanced islanded operation destabilizes frequency. In weak or meshed grids alike, these disturbances erode energy yield, accelerate equipment aging, and threaten regulatory compliance. This review dissects how advanced topology controllers have become the first line of defense against such PQ degradation in modern PV systems. Drawing on 257 peer‑reviewed papers, industry white books, and field reports issued between January 2010 and March 2025, the study classifies solutions along two intertwined axes: (i) hardware topology—ranging from multilevel inverters (neutral‑point‑clamped, flying‑capacitor, cascaded H‑bridge) and transformer‑less H‑bridge derivatives that suppress common‑mode voltage, to hybrid active filters and DSTATCOM‑integrated converters; and (ii) embedded control—spanning synchronous reference‑frame, hysteresis, finite‑set model‑predictive, space‑vector modulation, and AI‑enhanced schemes such as fuzzy logic, adaptive neuro‑fuzzy inference systems, and reinforcement‑learning regulators.