Analysis of Current Fluctuation Caused by Series Active Power Filter Based on Magnetic Flux Compensation

The series active power filter based on magnetic flux compensation (MFC-APF) may lead to low-frequency oscillation of the amplitude of power grid current in the transient process. In the previous research, it has been found that the equivalent impedance of MFC-APF will show obvious negative damping characteristic in the low frequency range higher than the fundamental frequency. This paper analyzes that it may act together with the load impedance to make the system resonate. After simplifying the system reasonably, the transfer function model of system equivalent admittance including MFC-APF and the load is established. The analysis results of the model show that the amplitude of the equivalent admittance has a resonant peak near the fundamental frequency, resulting in the corresponding harmonic component of the current in the dynamic process, which is manifested as the low-frequency oscillation of the current amplitude. Finally, according to the impedance characteristics of MFC-APF, an improvement method is proposed, and effectiveness of the proposed model and method are verified by simulation in Matlab/Simulink.