Enhancement of UPFC performance using Fuzzy Logic based intelligent controller

In today's highly complex and interconnected power systems, sometimes made of thousands of buses and hundreds of generators, there is a great need to improve electric power utilization while still maintaining reliability and security. In order to meet the ever-growing power demand, utilities prefer to rely on already existing generation instead of building new transmission lines that are subject to environmental and regulatory policies. On the other hand, power flows in some of the transmission lines are well below their thermal limits, while certain lines are overloaded, which has as an overall effect of deteriorating voltage profiles and decreasing system stability and security. In addition, existing traditional transmission facilities in most cases are not designed to handle the control requirements of complex highly interconnected power systems. This overall situation requires the review of traditional transmission methods and practices, and the creation of new concepts which would allow the use of existing generation and transmission lines up to their full capabilities without reduction in system stability and security. If the oscillatory response of a power system during the transient period following a disturbance is damped and the system settles in a finite time to a new steady operating condition, we say the system is stable. If the system is not stable, it is considered unstable. This primitive definition of stability requires that the system oscillations should be damped. Keywords—UPFC, Fuzzy logic controller and Proportional-Integral (PI) Controller