Performance evaluation for grid impedance based islanding detection method

This paper develops an approach for islanding detection based on measurements of the frequency dependent impedance at the point of common coupling (PCC) that exploits the presence of harmonics introduced by the electric power system (EPS) and harmonics introduced by the distributed generator (DG). The approach is new: i) an analytic model for the frequency dependent impedance is derived from the interconnection topology and this may be used as a basis for selecting features of the impedance that change when islanding occurs, and ii) the variation of a frequency dependent feature is used to characterize a non detection zone (NDZ) and iii) the load parameter space is used to compare the NDZ of the grid impedance based scheme with under/over frequency schemes. Although the focus is passive islanding detection, it also encompasses active schemes where certain harmonics are intentionally injected rather than inherent.