  In a power grid with growing penetrations of renewable energy sources,
inverters play a larger role in the dynamic interactions among network
components. However, much is yet to be studied regarding inverter-dominated
grid stability. This has initiated a re-examination of long-established
assumptions made when conducting power systems studies. In this work we study
the small-signal stability characteristics of a power system comprised of
inverter and synchronous machine sources, and consider the effect of inverter
control gains, transmission line dynamics, and network operating conditions. We
utilize PowerSimulationsDynamics.jl to perform this study on the IEEE WSCC 9
Bus test system. We vary inverter parameters across reported ranges in the
literature, we consider three transmission line models of varying fidelity, and
compare results across different operating conditions. We find that line
dynamics are generally important for correctly assessing small-signal stability
in networks with large penetrations of grid-following converters, and that gain
tuning in these networks should utilize high fidelity line models.
