Power Quality Problem Investigation and Mitigation for Lebu - Adama AC Electrified Railway Line
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Date
2019-08
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Addis Ababa University
Abstract
Power quality is the main concern in electric traction system due to the involvement of power electronic converters, transformers, and variable loads. It always requires an efficient, reliable and cost-effective power supply system. The Ethio-Djibouti railway line is a 752.6 km line runs from Addis Ababa, Ethiopia to Nagad, Djibouti, which is supplied by 25 kV, 50Hz AC overhead power supply. Power factor and reactive power problem have been recorded in the line from Lebu to Adama. The average power factor in August, 2018 was found to be 0.85 as well as the live record while the train was passing showed the power factor variation from 0.67 to 0.98. This thesis presents modeling, power quality assessment and improvement of traction power supply system for the case of Lebu to Adama railway line. Relevant data and parameters of traction power supply system’s components have been collected to model the system and analyzed. Mathematical analysis and modeling of all major traction power supply system components; both constant and variable power models are done. The variable power model emulates the real phenomena of traction power fluctuation of running train. Train dynamics analysis is also undergone.
A STATCOM, that works with the algorism based on instantaneous active and non-active currents theory has been analyzed, modeled as a controller and applied to return good reactive power compensation, and enhancement of poor power factor while keeping line voltage in the prescribed range. It incorporates reference current generator, hysteresis band current controller as well as voltage source converter. Finally, the overall system, considering a static and dynamic power model, is simulated in MATLAB/Simulink environment and compared with the model of the existing system, without the introduction of the controller. As a result, 98.5 % of reactive power is compensated and power factor of 0.99 has been achieved throughout the course of motion after the inclusion of this technique.
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Keywords
Ethio-Djibouti Railway line, Power quality, Dynamic power model, STATCOM, non-active current, MATLAB/Simulink