We propose a decentralized control synthesis procedure for stabilizing voltage and frequency in AC Islanded microGrids (ImGs) composed of Distributed Generation Units (DGUs) and loads interconnected through power lines. The presented approach enables Plug-and-Play (PnP) operations, meaning that DGUs can be added or removed without compromising the overall ImG stability. The main feature of our design algorithm is that it does not depend on line parameters. This implies that (i) the synthesis of each local controller requires only the model of the corresponding DGU, and (ii) whenever a new DGU is plugged in, neighboring DGUs do not have to retune their regulators because of the new power line connected to them. Moreover, we formally prove that stabilizing local controllers can be always computed, independently of the electrical parameters. Theoretical results are validated by simulating in PSCAD the behavior of a 10-DGUs ImG. (C) 2019 Elsevier Ltd. All rights reserved.