Non-detection zone (NDZ)
The effectiveness of the Islanding Detection Methods (IDM) is usually
depends on the NDZ which relies mainly on the amount of local loads
connected to the DG [10]. The closer the active power consumed by
these loads is to the active power supplied by the DG, the higher the
probability to form an islanding.
In the same way, as the resonant frequency of the local load approaches
the local grid nominal frequency the potential formation of the
islanding also increases. There are two kinds of representation methods
up to now as follows: Power Mismatch Space Representation (PMSR), Load
Parameter Space Representation (LPSR) [11].
PMSR uses the amount of active power flow (DP) and reactive power flow
(DQ) to the grid. After islanding occurs, the islanding voltage and
islanding frequency goes to the new operating point for the power
balance between PV generation and local load consumption [12]. Under
the local passive AIMs, the quantitative NDZ of PMSR can be analyzed as
Eqs. (1) and (2) and this NDZ zone is described in figure 2.
\begin{equation}
{\text{\ \ \ }\left(\frac{V}{V_{\max}}\right)}^{2}-1\leq\ \frac{\text{ΔP}}{P}\ \leq\left(\frac{V}{V_{\min}}\right)^{2}-1\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (1)\nonumber \\
\end{equation}\begin{equation}
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1-\left(\frac{f}{f_{\min}}\right)^{2}\ \leq\ \frac{\Delta Q}{P}\ \leq 1-\left(\frac{f}{f_{\max}}\right)^{2}\ \ \ \ \ \ \ \ \ \ \ \ \ \ (2)\nonumber \\
\end{equation}