In this paper, an improved Takagi-Sugeno fuzzy logic PSS is proposed with a novel automatic design method called CDCARLA. As an optimal control system, the proposed PSS can be designed for optimizing any reasonable objective function based on any desired technical requirements. As another advantage of the proposed method, it needs no information about the dynamical model of the power system. And as a consequence, the method is able to consider all nonlinear features of the power system including hard limiters in the excitation system in the PSS design scenario. The proposed system is implemented for both single machine-infinite bus (SMIB) system and multi machine system, and the results are compared with those obtained from two IEEE standard PSS systems. Also, the controller can easily be retuned for any changes in the power system. Simulation results prove the superiority of the designed PSS in terms of both performance and robustness over the conventional PSSs.