Browsing by Author "Kibru, Zewdie"

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    Hybrid Active Power Filter Technique to Enhance Power Quality of Electric Railway Traction Substation (Case Study: Minilik Square Traction Substation NS27)
    (Addis Ababa University, 2020-11) Kibru, Zewdie; Mengesha, Mamo (PhD)
    Addis Ababa Light Rail Transit (AALRT) is an electrified railway traction system with large amount of harmonic currents being generated due to the nonlinear characteristics of rectifiers and inverters devices and inject the harmonics back into the grid. This has caused serious impact on the power supply network and resulted in power quality problems within the traction substation that has led to multifunction of some system components. For the overall quality of railway service, there should be reliable, efficient and safe power distribution systems by improving the power quality. The power quality enhancement has been proposed by using hybrid active power filter harmonic current compensation technique. This study presents theoretical and practical aspects in improving the power quality of Minilik Square NS27 railway traction substation network by reducing 11th and 13th harmonic currents using hybrid active power filter (HAPF). Simulation studies of the Minilik Square NS27 railway traction substation network is carried out using MATLAB Simulink in a discrete mode, variable step size with ode45 (Dormand-Prince) solver. The simulation results show that 11th order current harmonics is reduced from 26.99% to 3.75% while 13th order current harmonics is reduced from 11.05% to 4.38% at the point of common coupling (PCC). Consequently, the total harmonic distortion (THD) of currents at PCC is reduced from 88.19% to 80.55%. It is further noted that at primary side of the transformer 11th order current harmonics is reduced from 17.99% to 1.55% while 13th order current harmonics is reduced from 13.43% to 0.89%. Thus, the overall total harmonic distortion (THD) of currents is reduced from 26.46% to 6.88% on the primary side of the transformer. Furthermore, it is observed that the distortion power factor is also improved from 0.955 to 0.995 due to the reduction of 11th and 13th order harmonic currents. Therefore, the effective value of fundamental current has been improved due to the reduction of 11th and 13th order harmonic currents and consequently the corresponding active power in the traction network is also improved. Thus, the simulation results demonstrate the effectiveness of the proposed HAPF technique for selective harmonic currents reduction and thereby power quality enhancement of Minilik Square NS27 railway traction substation network of AALRT.