Anti-islanding, islanding detection algorithm for inverters connected to the utility grid. Any inverter connected to the grid must be able to detect disconnection quickly and reliably under any circumstance. Most inverters designed to feed energy at the utility grid are current controlled voltage source converters (CC-VSC), only able to work if the grid or a voltage controlled voltage source converter (VC-VSC) is connected. CC-VSCs are unable to generate controlled voltages as an island by themselves. This project aims to study and design an anti-islanding algorithm for voltage controlled voltage source converters (VC-VSC), able to work connected to the grid and as an island. During the first chapter the main parts of the simulated plant model are explained focusing on converters working principles and the pulse width modulation method. Also some simplifications regarding simulation limitations are introduced, such as implementing an averaged model over a commutated one. In the second chapter the control loops for both CC-VSC and VC-VSC are explained, this aims to give the lector an idea about cascaded control loops design and control of alternating variables with resonant controllers. This chapter also covers the main differences in design and nature of both kinds of converters. The third chapter analyses the most important anti islanding algorithms for both CC-VSC and VC VSC. It also explains the resonant load situation and the need to develop active methods to cover this particular situation. It focuses on impedance measurement and harmonic injection the main method studied during this project. Fourth and final chapter studies and analyses the harmonic injection method based on impedance measurement. First, it aims to give the lector a general idea of the working principles to later on conduct a study to determine its optimal values and extract some conclusions.