This work focuses on incorporation of distribution generation (DG) units in unequal three area interconnected automatic generation control (AGC) system with diversified sources. The particular system is associated with appropriate value of generation rate constraint for realistic approach. A cascade combination of integer order proportional-integral-derivative with filter and fractional order integral derivative (PIDN-FOID) is utilized for study. The controller gains plus parameters are obtained using whale optimization algorithm. The performance of PIDN-FOID controller is evaluated against classical controllers. Analyses show that inclusion of DG units provides noticeable improvement on system dynamics. In AGC various energy storage devices are used in order to mitigate interarea oscillations. Here, energy storage device redox flow battery (RFB) is incorporated in all areas. Observation reflects that inclusion of RFB improves system dynamics. Sensitivity analysis is performed for increased value of step load perturbation in presence of DG units as well as RFB. © 2018 IEEE.