Investigation on Fuzzy Logic and Optimal Fuzzy Logic Controllers Using GA for Multi Area Load Frequency Control with Frequency Controllable HVDC Links

The load–frequency control (LFC) problem has been one of the major subjects in a power system. In practice, LFC systems use proportional–integral (PI) controllers. However since these controllers are designed using a linear model, the non-linearities of the system are not accounted for and they are incapable of gaining good dynamical performance for a wide range of operating conditions in a multi-area power system. This paper focuses on a new optimization technique of a fuzzy logic controller based load frequency controller (LFC) tuned by genetic algorithm (GA) in co-ordination with frequency controllable HVDC links. Conventionally, the membership functions and control rules of fuzzy logic control are obtained by trial and error method are experience of designers. To overcome this problem, the GA tuned FLC is proposed to simultaneously tune the membership functions and control rules of a FLC load frequency controller in order to minimize the frequency deviations of the inter connected power system against load disturbances. The GA introduces additional techniques for improvement of the search process initialization, adaptive search, multiple searches, and crossover and restart process. Simulation results explicitly a show that the performance of the proposed GA tuned FLC is superior to FLC in terms of overshoot and settling time. Furthermore, the robustness of the proposed controller under variations of system parameters and load changes are higher than that of conventional FLC.