Zero-sequence voltage injection-based grid impedance estimation method for three-phase four-wire DC/AC grid-connected inverterZero-sequence voltage injection-based grid impedance estimation method for three-phase four-wire DC/AC grid-connected inverter Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2025-09-122024enIn this article, a novel method based on zero-sequence voltage injection to estimate grid impedance is proposed. The target of the proposed method is to inject a third harmonic before space vector pulse width modulation in order to generate zero-sequence voltage on the output side of the inverter. Then, the voltage response of the point of common coupling is measured to estimate the grid impedance. The main advantage of this method is that it minimizes the impact on the operation of the grid-connected inverter, without complex signal processing calculations. A three-phase four-wire dc–ac inverter configuration interconnected with the electric grid has been used to verify the effectiveness of the proposed method experimentally.This work was supported in part by “Bilateral and Multilateral Research and Technology Co-o. between Greece and China” under Grant 2017YFE0134300 and Grant eSOLAR/T7ΔKI-00066.http://creativecommons.org/licenses/by/4.0/IEEE Transactions on Industrial Electronics7177273-7279 Cheng Yanqi Wu Weimin Yang Yong Koutroulis Eftychios Κουτρουλης Ευτυχιος Chung Henry Liserre Marco Blaabjerg, Frede, 1963- Institute of Electrical and Electronics Engineers Grid impedance estimation Kalman filter Three-phase four-wire Zero-sequence voltage