  An islanded inverter-based microgrid is a collection of heterogeneous DC
energy resources, e.g., photovoltaic arrays, fuel cells, and energy-storage
devices, interfaced to an AC distribution network and operated independently
from the bulk power system. Energy conversion is typically managed by power
electronics in voltage source inverters. Drawing from the control of
synchronous machines in bulk power systems, different control schemes have been
recently adopted in order to achieve a stable network operation. The vast
majority of academic and industrial efforts opt for these strategies during
real-time operation.
  Starting with a dynamical averaged DC/AC converter model, we review different
controllers by presenting their main scope analytically and through
simulations. Next, we explore a new alternative of controlling DC/AC converters
in bulk power systems by matching traditional synchronous machines with
emphasis on the role that DC-circuit can play in control architecture, usually
neglected in conventional strategies. Compared to standard emulation methods,
our controller relies solely on readily available DC-side measurements and
takes into account the natural DC and AC storage elements. As a result, our
controller is generally faster and less vulnerable to delays and measurement
inaccuracies. We additionally provide insightful interpretations of the
suggested control, various plug-and-play properties of the closed-loop, such as
steady-state power flow analysis, passivity with respect to the DC and AC
ports, stability proof as well as high-level control architectures contributing
to enhancing the controller performance and attaining further control goals,
which we illustrate in both analysis and simulation.
