Islanding Detection of Distributed Generation Based on Parallel Inductive Impedance Switching

This paper deals with a new islanding detection method based on parallel inductive impedance (PII) switching at distributed generation (DG) connection point, and monitoring the rate of change of voltage
$(dv\!/\!dt)$
at DG output. In the proposed approach, switching the PII causes variation in the
$dv\!/\!dt$
. This variation is very small in the case that DG operates in parallel with the main grid, whereas the changes will be very large during the occurrence of islanding. Therefore, the
$dv\!/\!dt$
is employed to identify both the islanding and nonislanding situations; however, to better analyze the
$dv\!/\!dt$
changes, a fast Fourier transform (FFT) is employed to process the variation of the
$dv\!/\!dt$
. To select the type of inserted impedance, the effect of switching various impedance types on the
$\text{FFT}$
$(dv\!/\!dt)$
is thoroughly analyzed. It is demonstrated that the purely inductive impedance has better performance than other impedance types. The performance of the proposed method is examined through comprehensive simulation studies in MATLAB. The simulation results indicate that the proposed method retains its efficiency for both inverters- and synchronous-based DGs. Moreover, the proposed method not only has a substantial influence on the reduction of disturbances due to the small amount of PII but also eliminates the nondetection zone entirely in comparison with other available methods.