The emergence of smart grids has introduced new challenges to traditional power system control due to the increasing number of risk factors. This paper presents a parameter tuning strategy using an optimisation algorithm to optimise the weights of the objective function. This enhances the adaptive control capabilities of online supplementary control to address the complexities of power system control in smart grids and offers a promising solution for improving overall system performance. The proposed online control, based on approximate dynamic programming, operates in conjunction with an existing power system controller. The results demonstrate the effectiveness of the proposed approach in maintaining frequency within acceptable limits. Comparative studies are performed against conventional frequency control strategies to highlight the advantages of the proposed method. The findings of this study contribute to the development of efficient and adaptive frequency control strategies for power systems with high renewable energy penetration.