Load Frequency Control of Multi-area Hybrid Power System Using Symbiotic Organisms Search Optimized Two Degree of Freedom Controller

This paper presents the load frequency control of three area interconnected system. Area1 comprises of thermal and distributed generation (DG) resources. Area2 and area3 are having thermal generations. The DG combination with conventional thermal generation makes the system hybrid. The DG resources comprises of wind turbine generator, diesel engine generator, fuel cell, aqua-electrolyzer and battery energy storage system. The single degree of freedom integral (I), proportional-integral (PI), proportional-integral-derivative (PID) and two degree of freedom-PID (2-DOF-PID) controllers are applied as secondary controllers in the system. These controller gains and other parameters are optimized simultaneously using a new robust and powerful metaheuristic algorithm called symbiotic organisms search (SOS) technique. Studies reveal the better performance of 2-DOF-PID controller over I, PI and PID controllers in terms of reduced peak overshoots, minimum settling time and lesser value of cost function. Comparative performances of various algorithms proves superiority of SOS over others. Sensitivity analysis reveals the robustness of optimum gains and other parameters of 2-DOF-PID controller attained at nominal conditions for wide changes in system loading, inertia constant and size, position of step load perturbation. System dynamics are obtained by considering 1% SLP in area1. The 2-DOF-PID controller also performs satisfactorily in the event of random load perturbation and random wind generator input.