Adaptive nonlinear excitation control of large-scale power systems is considered in this paper. The approach used is an adaptive feedback linearizing control to enhance the robustness to unknown or varying interconnection parameters like equivalent reactances of the transmission lines. Adaptation in estimated parameters is utilized to achieve an asymptotically exact cancellation of terms. Simulation results for a two generator-infinite bus power system are presented to validate the robustness of the adaptive feedback linearizing scheme to unknown interconnections arising due to faults and subsequent line switchings. The performance using the nonadaptive feedback linearizing control is shown to degrade for network configuration variations arising due to transmission line faults. The studies validate the fact that connective stability and robust performance is maintained for unknown interconnection topology using the adaptive feedback linearizing scheme.