This article develops a control scheme for automatic generation control (AGC) of a realistic isolated power system comprising of combined cycle gas turbine (CCGT) plant and wind turbine generator (WTG). Robust AGC operation of the hybrid system is done by secondary control action in association with airflow and temperature control. Integral-derivative with filter coefficient (IDF) controller as the secondary, airflow and temperature controlling unit for the test system outperforms other classical controllers for variant perturbations. A novel control strategy has been proposed where IDF in association with integral (I) controller in different combination for the three controlling action has been proposed for the perturbed isolated system. The proposed combination satisfactorily mitigates the frequency and temperature deviation of the test system. The same combination has been simulated for random wind variation in WTG plant against low to high perturbation. Simulation results authenticate the efficacy of the proposed control strategy. © 2018 IEEE.