Online Active Impedance Estimation Method in an LCL-Grid-Tied VSI: Analysis of the Multi-Sine Perturbation

Accurate grid impedance estimation is essential for the stability and efficiency of modern power systems, especially with high renewable energy penetration. This paper introduces a signal-based on sum of sine waves (Multi-Sine) approach for broadband impedance estimation, offering superior spectral efficiency and adaptability compared to traditional methods like Pseudo Random Binary Sequence (PRBS) and White Noise. The proposed method ensures precise characterization while minimizing grid disturbances. Validated experimentally on a 60 kW VSI connected to an emulated grid, the approach demonstrates reliable performance under varying conditions, including weak grids and dynamic loads. These findings highlight the practical applicability of Multi-Sine signals, advancing grid management and stability in renewable-dominated systems.