  Inverter-based microgrids are an important technology for sustainable
electrical power systems and typically use droop-controlled grid-forming
inverters to interface distributed energy resources to the network and control
the voltage and frequency. Ensuring stability of such microgrids is a key
issue, which requires the use of appropriate models for analysis and control
system design. Full-order detailed models can be more difficult to analyze and
increase computational complexity, hence a number of reduced-order models have
been proposed in the literature which present various trade-offs between
accuracy and complexity. However, these simplifications present the risk of
failing to adequately capture important dynamics of the microgrid. Therefore,
there is a need for a comprehensive review and assessment of their relative
quality, which is something that has not been systematically carried out thus
far in the literature and we aim to address in this paper. In particular, we
review various inverter-based microgrid reduced-order models and investigate
the accuracy of their predictions for stability via a comparison with a
corresponding detailed average model. Our study shows that the simplifications
reduced order models rely upon can affect their accuracy in various regimes of
the line R/X ratios, and that inappropriate model choices can result in
substantially inaccurate stability results. Finally, we present recommendations
on the use of reduced order models for the stability analysis of microgrids.
