Voltage Profile Improvement of a Disturbed Electric Power System using UPFC Compensation

Abstract

The major objective of using flexible alternating current transmission systems (FACTS) devices in an interconnected electric power transmission network is to improve the parameters of the transmission line. This study presents the voltage profile improvement and power loss reduction of the Nigeria 330 kV transmission network using the unified power flow controller (UPFC) as an optimal FACTS device. The study utilized the power systems analysis toolbox (PSAT) 2.1.10 that is embedded in MATLAB 2017a to model the Nigeria 330 kV transmission network that consists of 9 generating stations, 31 buses and 42 transmission lines. The Newton Raphson load flow algorithm was used to carry out the load flow study using data obtained from the transmission company of Nigeria. Voltages less than 0.95pu (313.5kV) were assumed to be low voltage while those greater than 1.05pu (346.5kV) were assumed to be high voltage. A base case load flow study was carried out without the use of UPFC to determine weak buses. The outcome of the base case simulation without the use of the UPFC showed that seven buses were operating outside the lower operating limit. After compensation using the UPFC, the operating voltages at each of the buses were found to be within the stated limit. Findings from the study show that the weak buses occurred as a result of the long distances between the transmission lines and the generating stations. The transmission line losses were found to have been reduced from 71.66MW to 32.95MW and from 76.7MVAR to 41.89MVAR respectively.