Design theory and application of nonlinear reduced-order observer

General design theory for nonlinear reduced-order observers (NRO) for forced nonlinear multivariable plants was proposed, with the Luenberger linear reduced-order observer as just a special form of the general model. The method was used to reconstruct the power angle δ(t) of a synchronous generator infinite bus power system to develop a nonlinear first-order δ-observer with very simple structure and good performances. The digital simulation results show that fast response, good traceability, wide dynamic stability region and ideal closed-loop responses can be achieved.