  A novel wide-area control design is presented to mitigate inter-area power
frequency oscillations. A large-scale power system is decomposed into a network
of passivity-short subsystems whose nonlinear interconnections have a
state-dependent affine form, and by utilizing the passivity shortage framework
a two-level design procedure is developed. At the lower level, any generator
control can be viewed as one that makes the generator passivity-short and $L_2$
stable, and the stability impact of the lower-level control on the overall
system can be characterized in terms of two parameters. While the system is
nonlinear, the impact parameters can be optimized by solving a data-driven
matrix inequality (DMI), and the high-level wide-area control is then designed
by solving another Lyapunov matrix inequality in terms of the design
parameters. The proposed methodology makes the design modular, and the
resulting control is adaptive with respect to operating conditions of the power
system. A test system is used to illustrate the proposed design, including DMI
and the wide-area control, and simulation results demonstrate effectiveness in
damping out inter-area oscillations.
