Optimal design of NL-PIDF and SMES as load frequency controller in a hybrid nonlinear power system using krill herds algorithm

This paper investigates frequency stability in a three area power system including steam and gas turbines by taking into physical nonlinear constraints due to reheat steam turbine, generation rate constraint (GRC), governor dead band (GDB) and boiler dynamics (BD). A new load frequency controller based on nonlinear PID controller with derivative filter (NL-PIDF) is proposed and optimized. In order to improve dynamic stability, superconducting magnetic energy storage (SMES) is considered in first area and parallel HVDC links are used between some interconnected areas. Krill Herds optimization algorithm with hybrid cost function is used to optimally design integral control (AGC), proportional control and inductor current feedback gain of SMES and NL-PIDF controlling parameters. Simulation results in time domain and Eigen values studies demonstrate fast, stable, robust and also desirable performance of proposed control strategies in damping frequency and active power oscillations in the face with random step and sinusoidal load perturbations, variation in nonlinear GRC and GDB constraints and wide uncertainty in dynamic parameters.