Summary: In the fast developing electric power system network, ancillary services like automatic generation control (AGC) plays a vital and significant role to ensure good quality of power supply in the system. To distribute good quality of power, a hybrid AGC system along with an efficient and intelligent controller is compelled. So, in this article, a cascaded proportional‐integral (PI)‐proportional‐derivative (PD) controller with filter (PI‐PDF) is proposed as secondary controller for AGC system. A nature inspired optimization algorithm named as moth flame optimization (MFO) algorithm is employed for simultaneous optimization of controller gains. Initially, a two‐area interconnected nonreheat thermal power system is investigated. Analysis revealed that MFO‐tuned PI controller performs better than the different optimization techniques tuned PI controller for the same system and PI‐PDF controller performs better than PI controller does. Then, the study is extended to a three‐area interconnected hybrid system with proper generation rate constraint. Area‐1 consists of solar thermal‐thermal unit; area‐2 consists of thermal‐hydro unit and area‐3 thermal‐gas unit as generating sources. Performance of PI‐PDF controller is compared with classical controllers such as PI, PID, PIDF, and PI‐PD controller without filter. Result analysis divulges that MFO‐tuned PI‐PDF controller performs better than all other controllers considered in this article. Robustness of the PI‐PDF controller is evaluated using parameter variations and random load variation. [ABSTRACT FROM AUTHOR]