  In this paper we propose a co-design of the secondary frequency regulation in
systems of AC microgrids and its cyber securty solutions. We term the secondary
frequency regulator a Micro-Automatic Generation Control (Micro-AGC) for
highlighting its same functionality as the AGC in bulk power systems. We
identify sensory challenges and cyber threats facing the Micro-AGC. To address
the sensory challenges, we introduce a new microgrid model by exploiting the
rank-one deficiency property of microgrid dynamics. This model is used to pose
an optimal Micro-AGC control problem that is easily implemented, because it
does not require fast frequency measurements. An end-to-end cyber security
solution to the False Data Injection (FDI) attack detection and mitigation is
developed for the proposed Micro-AGC. The front-end barrier of applying
off-the-shelf algorithms for cyber attack detection is removed by introducing a
data-driven modeling approach. Finally, we propose an observer-based corrective
control for an islanded microgrid and a collaborative mitigation schemes in
systems of AC microgrids. We demonstrate a collaborative role of systems of
microgrids during cyber attacks. The performance of the proposed
cyber-resilient Micro-AGC is tested in a system of two networked microgrids.
