Fuzzy logic (FL) controlled HVDC system-influence of shape, width & distribution of membership functions (MFs)

A Membership Function (MF) is a key parameter in the design of a fuzzy logic (FL) controller. Earlier work on FL controller for a HVDC system using triangular MFs was reported but the focus was not on the choice of a MF. This paper aims at selection of a MF which minimizes the total control error. This is done by studying the effect of various MF shapes, widths and distribution on the performance of a FL controlled HVDC system under different system conditions. Simulated results show that the shape, width and distribution of a MF influence the performance of the HVDC system. This work concludes that nonlinear MFs (i.e. Gaussian) are better choice than linear (i.e. Triangular) MFs as the former provides a smoother transition at the switching points and thus offers a better controller.