  Distributed generation resources have become significantly more prevalent in
the electric power system over the past few years. This warrants
reconsideration on how the coordination of generation resources is achieved. In
this paper, we particularly focus on secondary frequency control and how to
enhance it by exploiting peer-to-peer communication among the resources. We
design a control framework based on a consensus-plus-global-innovation
approach, which guarantees bringing the frequency back to its nominal value.
The control signals of the distributed resources are updated in response to a
global innovation corresponding to the ACE signal, and additional information
exchanged via communication among neighboring resources. We show that such a
distributed control scheme can be very well approximated by a PI controller and
can stabilize the system. Moreover, since our control scheme takes advantage of
both the ACE signal and peer-to-peer communication, simulation results
demonstrate that our control scheme can stabilize the system significantly
faster than the AGC framework. Also, an important feature of our scheme is that
it performs $c\epsilon$-close to the centralized optimal economic dispatch,
where $c$ is a positive constant depending only on the cost parameters and the
communication topology and $\epsilon$ denotes the maximum rate of change of
overall system.
