Adaptive Parameter Tuning and Virtual Impedance Injection Control for Coupled Harmonic Mitigation of Photovoltaic Converter

Suppressing current harmonics is an essential issue for photovoltaics (PVs). The equivalent impedance or admittance expresses the interaction between the PV converter (PVC) and the background harmonics from the grid, where the control strategies and parameters play a crucial role in the process. Currently, multifrequency coupling characteristics have become more vital in harmonic analysis, and traditional selective harmonic suppression methods show imperfect performance. The key to solving this issue is constructing an adaptive controller for coupled harmonic mitigation according to grid conditions. Therefore, this article first constructs a harmonic coupling matrix model (HCMM) of the PVC to describe the harmonic coupling characteristics, which can represent the influence of topology and control parameters simultaneously. Second, the effect of the critical controller parameters and virtual impedance method on the coupled harmonic admittance of the HCMM is analyzed. Finally, coordinated control of adaptive parameter tuning and virtual impedance injection method is proposed to reduce coupled harmonics efficiently and to avoid the instability caused by the modulation voltage saturation. Comparative experiments are provided by a three-phase PVC with a digital signal processing (DSP) controller, and the results verify the validity of the coupled harmonic analysis and the effectiveness of the proposed method.