Harmonic injection technique-based grid impedance estimation for an LCL-filtered grid connected inverter - an investigation

摘要

Harmonic injection technique for grid impedance estimation involves active perturbation of the system through LCL -filtered grid connected inverter (GCI) and processing the measured voltage and current responses at the point of common coupling (PCC). The relative effect of the perturbation on the power quality is kept low by injecting harmonic signal intermittently. This paper presents an analysis of harmonic injection-based grid impedance estimation for an LCL -filtered GCI and investigates the several factors which should be considered for fast and accurate estimation. The estimation includes post-processing of the signal responses captured at PCC in a digital platform. This paper brings out the effect of the computational time on the choice of the number of harmonic cycles to be injected. Based on the analysis it also suggests how to reduce estimation time. The analysis is aided by necessary simulation results.