DC microgrids often present a hierarchical
control architecture, requiring integration of communication
layers. This leads to the possibility of malicious attackers
disrupting the overall system. Motivated by this application,
in this article, we present a distributed monitoring
scheme to provide attack-detection capabilities for linear
large-scale systems. The proposed architecture relies on
a Luenberger observer together with a bank of unknowninput
observers at each subsystem, providing attack detection
capabilities. We describe the architecture and analyze
conditions under which attacks are guaranteed to be detected,
and, conversely, when they are stealthy. Our analysis
shows that some classes of attacks cannot be detected
using either module independently; rather, by exploiting
both modules simultaneously, we are able to improve the
detection properties of the diagnostic tool as a whole. Theoretical
results are backed up by simulations, where our
method is applied to a realistic model of a low-voltage DC
microgrid under attack.
