Abstract This paper proposes a modified optimal control strategy for enhancing the frequency stability of a power grid. The considered grid includes different generation sources and renewable energy distributed in two interconnected areas. This strategy is based on applying a modified control configuration based on two‐degree of freedom for an improved tilt‐integral‐derivative controller entitled () for load frequency control (LFC). This study considers the effect of the automatic voltage regulator (AVR) and its effect on the frequency stability. The modified 2DOF‐T controller is based on utilizing the merits of the two degree of freedom (2‐DOF) structure, and applying the fractional order. Also, an improved gradient‐based optimizer (GBO) is proposed to optimally adjust the gains of the developed control technique. For robust design of the proposed control strategy, the system constraints are considered besides the high renewable power penetration. The effectiveness of the proposed controller in LFC has been confirmed by comparing its efficiency with other control strategies' efficiency in previous studies such as modified TID (IT n D), and FO‐PID () controllers. Furthermore, in cases of high renewable penetration, the AVR with LFC is superior to conventional LFC in terms of decreasing the value of fluctuations while maintaining voltage and frequency stability.