An Adaptive Stabilization Strategy for Harmonic Oscillation of SAPF Interacted With Nonlinear Load and Grid Impedance

A shunt active power filter (SAPF) can interact with the nonlinear load and grid impedance, which may lead to unexpected harmonic oscillation. To describe the interaction, this article builds the interaction model including the source-current-detected SAPF, nonlinear load, and grid impedance. The interaction model reveals that the harmonic oscillation is prone to occur when the passive resonant frequency from grid impedance and nonlinear loads gets close to the harmonic frequency compensated by SAPF. This kind of harmonic oscillation is normally unpredictable because grid impedance and state of the nonlinear load continuously change. To cope with it, this article proposes a harmonic oscillation observation and adaptive stabilization strategy, which is implemented by monitoring and controlling the phase trajectory of the grid harmonic current through adjusting the phase and emergency damping factor of the harmonic resonant controllers in SAPF. This strategy has low requirement on real-time calculation and does not affect the dynamic response of the SAPF. In the end, the effectiveness of the stabilization strategy is verified by experiment results.