  In order to deal with issues caused by the increasing penetration of
renewable resources in power systems, this paper proposes a novel distributed
frequency control algorithm for each generating unit and controllable load in a
transmission network to replace the conventional automatic generation control
(AGC). The targets of the proposed control algorithm are twofold. First, it is
to restore the nominal frequency and scheduled net inter-area power exchanges
after an active power mismatch between generation and demand. Second, it is to
optimally coordinate the active powers of all controllable units in a
distributed manner. The designed controller only relies on local information,
computation, and peer-to-peer communication between cyber-connected buses, and
it is also robust against uncertain system parameters. Asymptotic stability of
the closed-loop system under the designed algorithm is analysed by using a
nonlinear structure-preserving model including the first-order turbine-governor
dynamics. Finally, case studies validate the effectiveness of the proposed
method.
