Abstract:
Transmission systems are critical in the transmission of electricity from power plants to
distribution stations. However, as the load demand and generation units grow without
transmission network expansion, the transmission line is exposed to power losses. Moreover,
the result of increased power losses over the transmission network decreases the bus voltage
profile. Therefore, the thesis aims to reduce transmission line loss and increase the voltage
profile of the southeastern region part of Ethiopia's transmission network by using the FACTS
device. Hence, this thesis used the FACTS family called unified power flow controller (UPFC)
which is the most versatile and flexible FACTS device that controls power in the transmission
systems by controlling the impedance, voltage magnitude, and phase angle between two buses
either simultaneously or selectively and it contains two voltage source converters. The first
converter is connected in parallel to the transmission line through a shunt transformer and the
second is connected in series with the transmission line through a series-connected transformer.
The necessary data was collected from the Ethiopian Electric Power (EEP) and the data was
analyzed under peak load to find a solution to the problem. The UPFC modeling and simulation
and coding studies have been carried out using MATLAB R2017b software. Ant Colony
Optimization (ACO) algorithm was used to get the optimal place and rating of UPFC. The
result showed that UPFC was installed at bus 7 with a rating of 52.773 MVar. Depending on
this rating, the incorporated UPFC to the southeastern region part of Ethiopia has an annual
financial saving of 125.092 million ETB and it improves the voltage profile of buses in the
acceptable limits of 0.95 and 1.05. Generally, the existing transmission network has total
183.72 MW real power demand and 79.38 MVar reactive power demand. Incorporating of
UPFC to the network reduces total power loss from 28.1662 MW to 16.6705 MW and 16.6236 to 13.6012 MVar real and reactive power loss respectively.
