This article presents robust design of conventional power system stabiliser (CPSS) by using metaheuristic cuckoo search algorithm (CSA). The free coefficients of the CPSS are optimised using CSA connected with a single-machine infinite-bus (SMIB) power system at nominal operating condition. The performance of such optimised controller (CSA-CPSS) is compared with the performance of well established H∞-based power system stabiliser (H∞-PSS) over a wide range of operating conditions of the SMIB power system. The superiority of the proposed CSA-CPSS is validated with least value of settling time and the performance indices as ITAE, IAE and ISE of speed response over the H∞-PSS. Moreover, the superiority is proved by eigenvalue plot for considered 209 plants as a fan-shaped structure in left side of s-plane with damping factor as more than 0.1. The performance of CSA-CPSS is also considered for the multimachine power system. The CSA-CPSS outperforms the CDCARLA-CPSS, BFOA-CPSS and SPEA-CPSS in terms of reduced settling time, overshoot and performance indices.