A Multifunctional Frequency Adaptive Control Strategy of Grid Connected SPV System for Simultaneous Mitigation of Current Harmonics and Power Oscillations

This paper proposes a multifunctional frequency adaptive control approach for a three-phase single-stage grid connected solar photovoltaic (GCSPV) system. The proposed control strategy integrates a frequency-adaptive proportional multi-resonant (FAPMR) current controller, which effectively suppresses grid current harmonics in the presence of harmonically distorted grid voltage conditions caused by nonlinear loads. To enhance synchronization with the grid and simultaneously eliminate frequency oscillations, an improved second-order generalized integrator-based frequency locked loop (ISOGI-FLL) is incorporated with the proposed FAPMR controller. This strategy also mitigates oscillations in active and reactive power during unbalanced grid faults and improves the frequency adaptability of the GCSPV system during grid frequency variations. The proposed control strategy is implemented in the αβ reference frame, avoiding Park’s transformation, thereby significantly reducing computational complexity. Real-time digital simulations are executed with OPAL-RT OP4510 in a software-in-the-loop (SIL) environment to validate the efficacy of the proposed control strategy. Various adverse grid voltage conditions, including harmonically distorted voltages, unbalanced grid faults, and grid frequency variations are encompassed within these simulations.