  In power system analysis, the Equal Area Criterion is of great importance on
revealing the condition for a grid-connected synchronous generator to maintain
its transient rotor angle stability with the grid under a large disturbance. At
present, the increasing renewable distributed energy resources (DERs) are
introducing a variety of new nonlinear characteristics that are different from
those of conventional generation although these DERs can still be operated and
modeled as grid-connected oscillators with synthetic inertias. To study
stability and synchronism of a grid-connected DER operated as a more general
nonlinear oscillator, this paper proposes a Generalized Equal Area Criterion
for estimation of transient stability margin subject to a large disturbance.
