Design of type- II fuzzy logic load frequency controller for two area thermal reheat power systems

Nowadays due to increase in size, increasing demand and complexity in interconnected power system, load frequency control has become more significant. In general Proportional Integral [PI] controllers are used for Load frequency Control, which is generally tuned on the basis of classical approaches. Because of that they are incapable of obtaining good dynamic performance. Hence it is much more needed to have controllers which are capable of self-tuning in nature according to situations. For power system stabilization control fuzzy logic controllers can be used because of their ability to utilize expert knowledge and being adaptive in nature. Fuzzy Logic controller [Type-I] is a sophisticated technique that is easy to design and implement, nevertheless the determination of Membership Functions and control rules is an essential part of design. To achieve satisfactory Membership Functions and control rules, designer experience is necessary. In other hand, type-I fuzzy controller is further modified into Type-II Fuzzy controller by giving grading to Membership Functions which are themselves fuzzy which leads to provide new design degrees of freedom for handling uncertainties. In this paper, simulations are carried out for a two area thermal reheat power system.