  This paper proposes a novel wide-area control strategy for modulating the
active power injections to damp the critical frequency oscillations in power
systems, this includes the inter-area oscillations and the transient frequency
swing. The proposed method pursues an efficient utilization of the limited
power reserve of existing distributed energy resources (DERs) to mitigate these
oscillations. This is accomplished by decoupling the damping control actions at
different sites using the oscillation signals of the concerned mode as the
power commands. A theoretical basis for this decoupled modulating control is
provided. Technically, the desired sole modal oscillation signals are filtered
out by linearly combining the system-wide frequencies, which is determined by
the linear quadratic regulator based sparsity-promoting (LQRSP) technique. With
the proposed strategy, the modulation of each active power injection can be
effectively engineered considering the response limit and steady-state output
capability of the supporting device. The method is validated based on a
two-area test system and is further demonstrated based on the New England
39-bus test system.
