Analysis of $\Delta P -\Delta Q$ Area of Uncontrolled Islanding in Low-Voltage Grids With PV Generators

The large penetration of distributed energy resources (DERs), especially photovoltaic (PV), in low-voltage (LV) distribution grids has raised the concern of unintentional islanding operations. The probability of unintentional islanding is increased mainly due to the newly introduced standards with extended frequency and voltage thresholds and the additional grid support functions, such as active and reactive power regulation using P/f and Q/V droop characteristics. Moreover, islanding operation due to faulty events at the medium-voltage (MV) distribution level may be dangerous in the presence of automatic reclosing procedure leading to out-of-phase reconnections. In this paper, an analysis of this phenomena is provided using simplified generator and load models. Simulation results based on MATLAB and DIgSILENT tools on a simplified LV distribution network are reported together with experimental results on a lab-scale prototype.