Power quality phenomena in electrified railways: Conventional and new trends in power quality improvement toward public power systems

Abstract

Nowadays, railway electrification is the most efficient way to power the trains. However, power quality (PQ) phenomena toward public power systems (PPSs) have always a main concern to the railway operators, especially when the single-phase traction power system is interconnected to the three-phase PPS. The last decades have witnessed an on-going evolution of PQ improvement and traction power supply systems, contributing to diminish the negative impacts of AC railway networks on PQ of the three-phase PPS. In this context, this paper presents a global overview of the PQ phenomena in AC railway electrification, as well as the impacts of the potential hazards on the safe operation of electrified railways. The paper also reviews PQ improvement methods from the early use of AC railway electrification until the emergence of the new power electronics devices in railways industry.

Power Quality Disturbances of Electrified Railway

“…A low power factor value indicates a high amount of reactive power, which is an amount of the exchanged energy between the power supply substation and the reactive part of traction power substation. The reactive power is necessary for the traction system operation, but it should be reduced as much as possible to reduce the operation costs of the electrified railway [5]. This may lead to increase the power losses and heating the wires of the contact network which leads to a loss of their mechanical strength.…”

“…These phenomena occurs because of the interaction between the pantograph and the overhead line or between the brushes and the third/fourth rail. The main reason of the voltage arcing in the electrified railway is the varied airgaps due to the train mechanical oscillations [5].…”

Topologies and Operation Modes of Rail Power Conditioners in AC Traction Grids: Review and Comprehensive Comparison

“…The power quality deterioration not only affects the single-phase traction power grid, but it also threatens the stability and the safe operation of the three-phase power grid. Therefore, power quality improvement is a significant factor to guarantee the safety and the economical operation of the electric trains [2][3][4].…”

Deadbeat Predictive Current Control for Circulating Currents Reduction in a Modular Multilevel Converter Based Rail Power Conditioner

“…Railway operators have an absolute interest to run the electrified trains with the lowest possible costs. In this context, various solutions were proposed to overcome the power quality deterioration in the electrified railway, e.g., the flexible AC transmission systems (FACTS) presented in [1][2][3][4][5]. On the other side, the modular multilevel converter (MMC) is an attractive solution for medium-voltage applications due to the lower harmonics, lower switching losses, MMC flexibility, and scalability [6,7] since other multilevel converters, such as the neutral point clamp and the flying capacitor multilevel converters, are quite hard to extend to higher levels [8].…”