This paper proposes a nonlinear control strategy for enhancement of dynamic stability of a power system. The zero dynamic design theory of feedback linearization is employed to design the Nonlinear Excitation Controller (NEC). The performance of this nonlinear controller has been compared with the performance of robust H∞ excitation controller for different operating scenarios of a Single Machine Infinite Bus (SMIB) power system. The mixed-sensitivity based Linear Matrix Inequality (LMI) approach with pole placement constraint has been adopted to design the H∞ controller. Simulation studies interpret that the proposed nonlinear controller and the H∞ are both effective in power system stability improvements, regardless of the operating points. It has been further observed that the performance of the nonlinear excitation controller is significantly better than the robust H∞.