A Unified Control Scheme for Current Harmonics Suppression with Ripple Free Power for a Grid Tied SPV System Under Abnormal Grid Voltage Conditions

This paper proposes a unified control scheme for three-phase grid-tied solar photovoltaic (GTSPV) systems to maintain stable operation during grid voltage abnormalities. The proposed scheme incorporates an enhanced proportional multiresonant (EPMR) current controller designed to mitigate harmonic distortion in the injected currents caused by grid voltage harmonics. A coordinated adaptive voltage sag compensator (AVSC), synchronized with a phase-locked loop (PLL), is implemented to maintain seamless grid synchronization and ensure stable injection of ripple-free active and reactive power during unbalanced voltage sags. The synergistic operation of the EPMR controller and AVSC-PLL unit enables simultaneous mitigation of harmonic currents and suppression of power oscillations, ensuring robust performance under grid disturbances. To enhance maximum power extraction under dynamic atmospheric conditions, an optimized step-size incremental conductance (OSINC) algorithm is incorporated into proposed control scheme. The effectiveness of the unified control scheme is validated through real-time digital simulations using the OPAL-RT OP4510 platform, with tests conducted under harmonically distorted and unbalanced grid voltage scenarios. Comparative analyses with conventional proportional multiresonant (PMR) controllers demonstrate the superior harmonic suppression, power quality, and tracking efficiency of the proposed control scheme.