Maiden application of hybrid pattern search-biogeography based optimisation technique in automatic generation control of a multi-area system incorporating interline power flow controller

This study exhibits the automatic generation control (AGC) of an unequal three-area thermal system having single reheat turbine, generation rate constraint, and governor dead band, in all areas. A three-degree-of-freedom proportional-integral-derivative (3DOF-PID) controller is used as secondary controller in all the areas and its dynamic performance is compared with that of classical PI, ID, and PID controllers. The controller parameters are simultaneously optimised using biogeography-based optimisation (BBO) technique, where 3DOF-PID controller outperforms the other. A hybrid pattern search BBO (hPS-BBO) technique is applied for the first time in AGC, to simultaneously optimise 3DOF-PID controller parameters. Comparison of dynamic responses corresponding to BBO and hPS-BBO optimised 3DOF-PID controller gives better performance of the latter. This is also validated with random disturbance. The considered system is checked for optimal location of interline power flow controller (IPFC) using BBO optimised 3DOF-PID controller. Observations reveal that IPFC placed between Line1 and Line3 is the optimal location. A comparatively better response is observed with hPS-BBO optimised 3DOF-PID controller parameters, having IPFC placed in its optimal location. Sensitivity analysis of the hPS-BBO optimised 3DOF-PID controller parameters is tested and found satisfactory for variations in system loading and inertia constant H.