This paper highlights an effort of incorporating several renewabIes like geothermal power plant (GTP), solar thermal and wind in automatic generation control and analyse its impact along with FACT devices on conventional thermal system. Suitable generation rate constraint for thermal units is considered. Fractional order (FO) Proportional Integral - FO Proportional Derivative (FOPI-FOPD) is used as secondary controller implementing the innovative concept of FO cascade controller. The dynamic performance of FOPI-FOPD controller is compared with the normally used traditional controllers and the controller parameters are optimized by means of the Sine Cosine Algorithm. Superiority of FOPI-FOPD is clearly revealed in the analysis over others. Effect of integrating GTP and other renewables is also highlighted on the thermal system. The performance of interline power flow controller (IPFC) is also evaluated on system dynamics. Observations reflect IPFC in between Linel and Line3 is the optimal location and inclusion of the same improves the system dynamics. System dynamic behavior is studied under 1 % step load perturbation in areal. © 2018 IEEE.