  This paper presents an aggregate reduced-order model for a wind farm composed
of identical parallel-connected Type-3 wind turbines. The model for individual
turbines includes mechanical dynamics (arising from the turbine and doubly fed
induction generator) and electrical dynamics (arising from the rotor-side and
grid-side converters and associated filters). The proposed aggregate wind-farm
model is structure preserving, in the sense that the parameters of the model
are derived by scaling corresponding ones from the individual turbines. The
aggregate model hence maps to an equivalent--albeit fictitious--wind turbine
that captures the dynamics corresponding to the entire wind farm. The
reduced-order model has obvious computational advantages, but more importantly,
the presented analysis rigorously formalizes parametric scalings for aggregate
wind-turbine models that have been applied with limited justification in prior
works. Exhaustive numerical simulations validate the accuracy and computational
benefits of the proposed reduced-order model.
