This paper presents a nonlinear excitation controller design technique for interconnected power systems. A zero dynamic design approach is used to design the controller which is useful when the system is partially linearizable and the obtained control law, using this approach is simpler as compared to that of a fully or exactly linearizable system. The performance of this controller is tested on a single machine infinite bus (SMIB) system over a wide variation of operating region and compared to the nonlinear excitation controller which is designed using the concept of exact linearization. Simulation results show that the proposed control scheme can improve the stability of power systems, regardless of operating points and the performance is very similar to that of exactly linearized controller.