Online Impedance Estimation in AC Grids Considering Parallel-Connected Converters

This paper addresses the estimation of the grid impedance under unbalanced conditions in AC Grids with power converter operating in parallel. A Pulsed Signal Injection (PSI) approach is employed for online estimating the grid impedance using an Recursive Least Square (RLS) algorithm. The method proposes here extends previous works focused on the impedance measurement and identification for pure passive grids. The most important contribution of the proposal can thus be summarized as the presentation of an online impedance technique suitable to be used in distribution grids having other power converters connected near the Point of Common Coupling (PCC). The proposal is valid both for balanced and unbalanced conditions.