Harmonic Oscillation and Stabilization Strategy of Source-Current-Detected Shunt APF Considering Interaction With Nonlinear Load and Grid Impedance

The shunt active power filter (APF) can effectively compensate for the harmonics caused by nonlinear loads and improve the power quality. Compared with load current detection, the shunt APF with source current detection is considered to have better harmonic filtering performance. However, the harmonic oscillation caused by APF may occur when interacting with nonlinear loads and grid impedance but the dynamics of the nonlinear loads are generally ignored in the existing research works. Therefore, this article built the interaction model of APF, nonlinear loads, and grid impedance to investigate the reason and characteristics of the harmonic oscillation. It is found that the harmonics oscillation is prone to happen when the passive resonant frequency of grid impedance and nonlinear loads gets close to the harmonic frequency compensated by APF, besides, the frequency coupling effect caused by the nonlinear loads will lead to symmetric harmonics oscillation. Then a stabilization strategy based on the phase adjustment of vector resonant controller for harmonics detection is proposed. Without affecting the system dynamics, the proposed method can effectively cope with the harmonic oscillation. Finally, simulation and experiment validate the precision of the built models and effectiveness of the proposed method.