Due to the complexity and importance of the electricity grid stability, sophisticated control systems and computational approaches are essentially required to solve dynamical system frequency problems in multi-area systems. Participation of wind turbines in power system frequency control in the form of stepwise inertial control in the presence of a proposed adequately tuned fuzzy-PID load-frequency control is investigated in this paper. A two-area power system is studied in which it is linked through tie-line and equipped with fuzzy-PID control systems. To increase the energy transition and flexibility of the entire system against frequency events and parameters uncertainties, the fuzzy-PID controllers are first tuned using lightning flash algorithm (LFA). The tuned controllers are then used in each area to optimally counterbalance the frequency deviations and the tie-line power of the interconnected areas against varying load disturbances, wind power fluctuations, and to keep the renewable integrated system in a stable state. The sensitivity analysis is also conducted with a wide range of system parameter variations, uncertainties, and disturbances. Furthermore, the LFA-tuned fuzzy-PID load-frequency control is also tested in a two-area isolated microgrid, comprising wind turbine, PV panels, fuel cells, micro-turbine, and diesel engine generator. The results obtained using the proposed approach are compared with other state-of-the-arts algorithms and control systems in the literature. The compared results show the efficiency and robustness of the proposed optimization-based controller for better frequency control in multi-area power systems and isolated microgrids. The results also demonstrate that a finely tuned automatic generation controller gives a significant boost to grid frequency control when wind turbines participate in the inertial control, suggesting migration from conventional PID-based automatic generation control to more adaptive control approaches.