
Cyber-Physical System Security—Smart Grid Example ◾ 131
after the Kron-reduced model (Equation 10.5) and let K be a k-dimensional attack set. Permit
VQ
K
T
K
T
∈
×
R
to be an orthonormal matrix so that
KK
BasisIm( BasisIm(
)]
⊥
and let
BBVD BBIDD
ZKKK KK
−
()
Identify the subspace
to be the smallest
ABVD VCKerQ C
−
†
-condi-
tioned invariant subspace containing Im
and allow J
K
to be an output injection matrix so that
()
†
ABVD VC JQCS S
KKKK KK
⊆
Permit P
K
to be an orthonormal projection matrix onto the quotient space
2n
, and let
APAB VC JQCPVD
T
=− +((
.
†
Last, allow H