ΔP — ΔQ area assessment of temporary unintentional islanding with P/f and Q/V droop controlled PV generators in distribution networks

Distributed Generation in Low Voltage grids has raised the concern of unintentional islanding and its probability has increased due to the newly introduced standards for generators, which in particular impose wider frequency and voltage ranges and active and reactive power support capabilities using of P/f and Q/V droop characteristics. Anti-islanding protections that each inverter is equipped with, may fail to detect the grid transition and so uncontrolled islanding operation may appear. This operation may be dangerous especially in presence of automatic reclosing procedure, because of possible out of phase reconnections. In this paper, the temporary unintentional islanding operation (e.g. below 600 ms) is studied considering the effects of P/f and Q/V droop characteristics of generators and their response times. A potential increase of such phenomenon will be shown with simulations and experimental results.