Electrical and Computer Engineering for Railway System Analysis of Power Quality Issues in Ethiopia Railway Traction System: The Case of Awash-Woldia Project
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Date
2016-08
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Addis Ababa University
Abstract
The economic growth of any country depends on the utilization of energy resources. This paper
presents the traction system power quality issues and methods of improvement about harmonics
current, voltage unbalance, and power factor problems. Power quality issues in power systems
have been increased due to nonlinear loads. To compensate these problems direct power
compensator (DPC) will be proposed in this paper, in which a capacitive coupled hybrid LLC
structure is added. The proposed DPC contains back to back converter by giving out the same dc
link power and also connected with the secondary side of 132/27.5kV v/v transformer to provide
a voltage balance in transmission line. A dual converter with a compensator is employed together
with co-phase traction transformers to reduce the current harmonics, telecommunication
disturbance, voltage unbalance and power factor problems.
Reduction in direct power compensator (DPC) operation voltage can lead to a decrease in the
compensation device capacity, power consumptions, and installation cost. The parameter design
procedures for minimum dc voltage operation of direct power compensator (DPC) are being
explored. To inject the same compensating currents to the traction power supply system, the DC
bus voltage of the direct power compensator (DPC) could be much lower than that of a
conventional railway power conditioner (RPC). As a result, the cost of the power quality
conditioner is reduced.
Simulation models are built with a direct power compensator (DPC) connected to the secondary
side of a 132 kV/27.5 kV V/V transformer. Simulation results shows the direct power
compensator (DPC) could compensate reactive power, unbalance voltage and current harmonics
simultaneously.
According to this research the system voltage and current harmonic distortion without direct
power compensator was 6.71% and 26.46% respectively with power factor value of 0.81. But
when DPC is used voltage and current harmonic distortion is changed to 0.82% and 1.28% with
power factor value of 0.99. Co-phase traction power supply with proposed direct power
compensator (DPC) is therefore, suitable for high-speed traction applications.
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Keywords
Co phase traction power supply system, direct power compensator, V/V transformer, minimum dc operation voltage, voltage unbalance, power factor and current harmonics