In this paper, a consistent pattern with the optimal coordinated design of PSS and SSSC controller to improve the damping of low frequency oscillations is shown. In this design, sensing and signal transmission time delays are considered as effectiveness parameters. The design problem has been considered an optimization problem and biogeography-based optimization (BBO) algorithm is used for searching the optimal controller parameters. The proposed controller is employed for a single machine and two-machine power systems. The results are displayed in different load conditions to present the efficiency of the proposed method. The proposed controller provides sufficient damping for power system oscillations, in different operating conditions and disturbances. Results analysis shows that the use of biogeography-based optimization algorithm has a higher efficiency in damping oscillations of the power system, compared with the PSO algorithm, and increases the dynamic stability more. Manuscript profile