Virtual Node Control Strategy Based on FBD Detection for Harmonic Suppression

With the continuous development of the renewable energy industry, modern power systems exhibit "double-high" characteristics, leading to reduced grid strength, increased background harmonic interference, and prominent power quality issues. To enhance the weak-grid adaptability of inverter systems, the virtual node voltage feedback control is proposed. While this method effectively improves inverter stability under weak-grid conditions, it results in higher output current harmonic distortion in strong grids. To simultaneously address harmonic suppression capability and weak-grid stability, a virtual node control strategy based on Fryze-Buchholz-Depenbrock (FBD) detection is proposed. The method employs FBD-based detection to extract grid-connected current harmonic components and utilizes the virtual node control strategy for harmonic suppression. The control model built in Matlab/Simulink demonstrate stable operation across short-circuit ratio (SCR) range from 2 to 20. Results show that under strong-grid conditions with SCR=20, the proposed strategy reduces output current total harmonic distortion (THD) by up to 30%; under weak-grid conditions with SCR=2, it achieves up to 24% THD reduction.