In multi-interconnected power system, keeping the changes in frequencies and tie-line powers at their specied values is vital process especially during operation under load disturbance. This target can be achieved by installing load frequency control (LFC), the main object of LFC is damping the deviations of frequencies and tie-line powers to zero. This paper proposes a new approach incorporated recent optimizer of movable damped wave algorithm (MDVA) to identify the unknown parameters of LFC represented by fractional-order proportional integral derivative (FOPID). FOPID controller is selected as it has better and robust performance, the controller is installed in multi-interconnected system with multi-sources considering renewable energy-based plants. Minimizing the integral time absolute error (ITAE) of the change in frequencies and tie-line powers is the main target. Two power systems are considered in this work, the rst one comprises photovoltaic (PV) and thermal generating units while the second system includes four plants of PV, wind turbine (WT), and two thermal based plants. Moreover, the generation rate constraints and governor dead-band of thermal plant are considered. Different load disturbances in both studied systems are investigated and the obtained results via the proposed DMVA are compared to coronavirus herd immunity optimizer (CHIO), antlion optimizer (ALO), sooty tern optimization algorithm (STOA), manta ray foraging optimizer (MRFO), and sin-cos algorithm (SCA). Regarding the two-interconnected system, the proposed DMVA succeeded in achieving the best ITAE of 6.3911 during 10% disturbance applied on PV plant. Regarding to the multi-interconnected system, the best (minimum) tness function is 0.015029 achieved via the proposed DMVA at 1% load disturbance on the rst area. The results conrmed the robustness of the proposed algorithm in solving the LFC parameter estimation.