In this paper, considerable efforts have been made to enhance the dynamical stability of the interconnected power system (IPS) in perturbing situations. In this regard, a three-degree-of-freedom proportional–integral–derivative (3DOFPID) controller is presented based on the optimization technique of the fruit fly algorithm (FFA) for the load frequency control (LFC) problem. The LFC analysis is performed on the multi-area non-linear diverse source (MANLDS) power system subjected to area 1 with 10% step load disturbance (SLD). However, the sovereignty of the 3DOFPID controller is demonstrated with other control approaches reported in the literature. Moreover, the non-linearity effects on the LFC of the MANLDS power system are presented in this work. To further improve the MANLDS power system's dynamic behavior, the battery energy storage (BES) and a Thyristor-controlled series compensator (TCSC) is implemented as additional regulatory mechanism. The simulation analysis confirmed the dynamic stability enhancement with the employment of the BES-TCSC strategy with regards to the responses settling time and peak undershoots.