Summary Automatic generation control (AGC) acts as a significant part in alleviating dynamic oscillations and sustaining constancy in frequency and scheduled tie‐line power to establish the reliable, secure, and stable operation of electric energy systems under dynamic conditions. AGC needs energy storage system (ESS) and elevated expert, intelligent, and flexible control strategies to ensure generation‐demand balance in modern complex structured energy systems following inconsistent load demands. Hence, this paper utilizes a new fuzzy fractional order integral derivative (FFOID) controller along with ultra‐capacitor (UC) ESS to solve AGC issue in energy systems effectively. The imperialist competitive algorithm is employed to tune the output scaling factors like integral, derivative, and noninteger order of integrator/derivative of FFOID controller using ISE performance index. Initially, the technique is applied on a one‐area nonreheat thermal system. Then, to demonstrate its competency and scalability, the study is boosted to prevalent two‐area nonreheat thermal, two‐area multisource multi‐unit hydrothermal, and three‐area reheat thermal energy system models. The advantage of the proposed controller is demonstrated by juxtaposing the outcomes with those offered by various best claimed intelligent control approaches expressed in the contemporary literature and fuzzy proportional integral (FPI)/fuzzy FO PI (FFOPI) controller. The UC with the FFOID controller outperforms other methods. The robustness analysis proves that parameters of the utilized controller acquired at nominal situation are healthy enough and necessarily not needed to retune under broad alterations in the system loading/parameters, size/position of load perturbation, and under the appearance of system constraints and random load pattern with/without noise.