AUTHOR=Zhao Tao , Cao Yunkai , Zhang Mingzhou , Wang Chunlin , Sun Quan 

TITLE=Research on the Resonance Suppression Method for Parallel Grid-Connected Inverters Based on Active Impedance

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 9 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2021.823746

DOI=10.3389/fenrg.2021.823746

ISSN=2296-598X

ABSTRACT=Under the condition of weak grid, the coupling between parallel inverters and grid impedance is easy to cause harmonic resonance, which seriously affects the grid-connected power quality. Firstly, the equivalent circuit model of multi-inverter parallel system is established, and the mechanism of harmonic resonance is analyzed from the perspective of impedance; Through the resonance detection method based on self-tuning filter, the voltage resonance component of parallel node is extracted; On that basis, an active impedance is designed to suppress the resonance of multi-inverter parallel system, which can equivalent construct a virtual impedance branch to improve the grid impedance characteristics at the resonance frequency, and its effectiveness is verified by using the impedance stability criterion; Finally, simulation experiments are carried out. The results show that this method can effectively suppress the resonance of multi-inverter parallel system, and can significantly improve the adaptability of inverters to weak grid.