  The increasing number of inverter based resources (IBRs) connected to modern
power systems necessitate accurate modeling of IBRs in stability studies.
Measurement-based modeling approaches can create an impedance/admittance model
of IBRs to be subsequently used in small signal stability studies. Such
measurement-based approaches have previously been successfully used for dc-dc
converters but present unique challenges for three-phase IBRs. This paper
discusses the choices and challenges that can lead to an incorrect model from
measurement-based approaches as well as mitigation mechanisms of the adverse
impacts using an illustrative example. A discussion of small signal stability
assessment involving such admittance models is also provided. It is seen
through the illustrative example shown that the injection signal and the model
fitting procedure, the phase locked loop used for the measurement device, and
the grid impedance may impact the accuracy of the measurement-based admittance
model of the IBRs.
