load frequency control in power systems using improved particle swarm optimization algorithm

the purpose of load frequency control is to reduce transient oscillation frequencies than its nominal valueand achieve zero steady-state error for it.a common technique used in real applications is to use theproportional integral controller (pi). but this controller has a longer settling time and a lot of extramutation in output response of system so it required that the parameters be adjusted as appropriate . in thispaper, we aim to design a system based on pi controllers using improved particle swarm optimizationalgorithm for load frequency control .multi-population approach and local search to improve theoptimization algorithms is used and displayed. that this approach will lead to accelerating the achievementof results, preventing entrapment in a local minimum, and get better system output compared with similarmethods.