Abstract
The integration of Distributed Generation (DG) units, especially from renewable sources, is transforming low-voltage grids from passive to active systems. Accurate grid impedance information is vital for the reliable operation of grid-connected inverters, enabling stability analysis, fault detection, short-circuit current calculation, and islanding detection. This paper proposes a passive grid impedance estimation method leveraging on the harmonics introduced by variations in the operating conditions. The method records voltages and currents and uses these data when a current variation is detected. Moreover, it performs the parametric estimation using two approaches in parallel to achieve redundancy and it validates the impedance estimates to ensure a Desired Reliability Rate (DRR). Simulation parameters and validation results show a very small error in estimating resistive and inductive components. Hardware-In-the-Loop (HIL) emulation using a real-time FPGA-based platform confirms the algorithm's effectiveness in a controlled environment.