Design Theory of Nonlinear Reduced-order Observers for Power Systems

In this paper, a general design theory of nonlinear reduced-order observers for the forced nonlinear plants is proposed. Applying this method to reconstruct the power angle δ(t) of a synchronous generator-infinite bus power system, the nonlinear first-order δ^-observer with very simple structure and good performances can be found. The inherent stability region of which is | δ|= 90°. The simulation results of the DFL-LQ optimal exciter (Gao, 1992) with the δ^-oberver show that fast response, good trace ability, wide dynamical stability region, and ideal closed-loop response are all achieved.