Multiobjective optimal robust damping controller for unified power flow controller using evolutionary algorithms

Abstract

Modern power system has been connected by means of weak tie lines. Low frequency electromechanical oscillations are experienced among the group of interconnected generators. These oscillations create severe hazard to the normal operation of the power system. The oscillations residing within a plant are called local mode of oscillations. The range of frequency is in between 0.7 2.0 Hz. The oscillations available in the interconnected power system are called inter-area mode oscillations. The range of frequency is in between 0.1 0.8 Hz. Power system stabilizers are also used to damp out oscillations. It causes large voltage variations with leading power factor operation and losing stability under severe disturbances. newlineFast development in the field of power electronics had opened new opportunities for the exercise of the Flexible AC Transmission system (FACTS) devices. Modulation of bus voltage, phase shift between the buses and transmission line reactance are used to improve power system operation controllability and power transfer limits. These can be achieved by FACTS devices. FACTS improves power system damping and also improves the system voltage profile. Unified Power Flow Controller (UPFC) is one of the important FACTS devices, which is used for damp out electromechanical oscillations in the power system and also enhances small signal stability of the power system. UPFC is a combination of Static synchronous compensator (STATCOM) and a Static Synchronous Series Compensator (SSSC), which are joined through common DC link, to allow bi-directional flow of real newlinepower between the series converter SSSC and the shunt converter STATCOM. newline newline