  Motivated by the inadequacy of the existing control strategies for power
systems affected by time-varying uncontrolled power injections such as loads
and the increasingly widespread renewable energy sources, this paper proposes
two control schemes based on the well-known output regulation control
methodology. The first one is designed based on the classical output regulation
theory and addresses the so-called Load Frequency Control (LFC) problem in
presence of time-varying uncontrolled power injections. Then, in order to also
minimize the generation costs, we use an approximate output regulation method
that solves numerically only the partial differential equation of the regulator
equation and propose a controller based on this solution, minimizing an
appropriate penalty function. An extensive case study shows excellent
performance of the proposed control schemes in different and critical
scenarios.
