Electronics
2021, 10, 115
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made virtually. Although control schemes have been developed to control their active and
reactive power; firstly, they cannot be controlled over a wide range that was the case for
SGs, and secondly, they have an intermittent power output, which is almost continuously
varying and is not exactly predictable. According to the report by the IEEE PES Task Force
on Microgrid Stability Analysis and Modeling [
2
], though having a generating unit close
to the load in an MG helps in the reduction of voltage drop, the limitation on the output
current of IBRs is a crucial factor for voltage instability of MGs. A Microgrid generates
dynamics that impact the direction of the current flow and its magnitude [
3
]. Furthermore,
the short-circuit capacity of an IBG compared to an SG is very low, which may cause a
considerable drop in the MG fault level [
4
,
5
]. The low short-circuit capacity also limits its
ability in providing the inrush current for induction motors [
2
,
6
], and creates a bus with
lower strength compared with a similar bus connected to an SG.
These characteristics of IBGs cause some significant changes in the system character-
istics concerning the power system stability and in particular the voltage stability [
7
]. To
address these changes, various operation and control schemes have been proposed for
power IBGs, for example [
8
–
12
].
The stability concepts and practices used for the conventional power systems are
not sufficient for the stability analysis of MGs and power systems with a high level of
connected DGs. The research has been conducted to develop new approaches for the
stability analysis of systems with MGs. In the literature, two main approaches can be
observed [
13
]: (a) small-signal stability assessments, and (b) investigating dynamics of the
inverters.
