DC Traction Research Articles

PWM 정류기를 적용한 직류급전시스템의 조류계산에 대한 연구

In general, Diode rectifier has been applied to DC traction power supply system. Diode has some characteristics which is voltage drop in inverse proportion of load because of non-controlled switch, and cannot flow a current in reverse bias. So, voltage drop occurs frequently, and regenerated power cannot use in substation. The PWM rectifier is able to control output voltage constantly to reduce voltage drop and to use regeneration power without additional inverter. This paper proposes analysis algorithm for DC traction power supply system with PWM rectifier

CONSTRUCTIVE MODELLING FOR ZONE OF RECOVERY ENERGY DISTRIBUTION OF DC TRACTION

Purpose.The article is aimed to develop the means and methods of forming a plurality of real and potential structural diagrams for zones of energy recovery and different locations of trains for further training neuro-fuzzy networks on the basis of expert solutions and also for the formation of good control. Methodology. Methodology of mathematical and algorithmic constructivism for modeling the structural diagrams of the electric supply system and modes of traction power consumption and the train’s locations in zones of energy recovery was applied. This approach involves the development of constructive-synthesizing structures (CSS) with transformation by specialization, interpretation, specification and implementation. Development CSS provides an extensible definition media, relations and the signature of operations and constructive axiomatic. The most complex and essential part of the axioms is the set formed by the substitution rules defining the process of withdrawal of the corresponding structures. Findings. A specialized and specified CSS, which allows considering all the possibilities and features, that supply power traction systems with modern equipment, stations and trains location was designed. Its feature: the semantic content of the terminal alphabet images of electrical traction network and power consumers with relevant attributes. A special case of the formation of the structural diagram shows the possibilities CSS in relation to this problem. Originality. A new approach to solving the problem of rational use of energy recovery, which consists in application of the methods and means of artificial neural networks, expert systems, fuzzy logic and mathematical and algorithmic constructivism. This paper presents the methods of constructive simulation of a production-distribution of energy recovery zone structure in the system of the DC traction. Practical value. The tasks decision of the rational use of energy recovery can significantly save energy, contribute to the technical re-equipment of a railway transportation of Ukraine through the introduction of modern means and capabilities. The developed model can be used to solve other energy-saving tasks in different systems of electric transport.

Evaluation of Rail Potential Based on Power Distribution in DC Traction Power Systems

Running rails used as a return conductor and ungrounded scheme have been widely adopted in DC traction power systems. Due to the longitudinal resistance of running rails and insulation resistance of rail-to-ground, there will be a potential rise between running rails and the ground when return current flows through the running rails, which is known as rail potential. At present, abnormal rise of rail potential exists widely in DC traction power systems. The present rail potential model still cannot simulate and explain the abnormal rail potential in the system. Based on the analysis of power distribution with multiple trains running in multiple sections, a dynamic simulation model of rail potential in the whole line is proposed. The dynamic distribution of rail potential and stray current in DC traction power systems when multiple trains run in multiple sections is analyzed, and the impact of traction current distribution on rail potential is evaluated. Simulation results show that the abnormal rise of rail potential during the dynamic operation of the system can be evaluated effectively.

Energy Is On Board: Energy Storage and Other Alternatives in Modern Light Railways

The traditional concept of dc traction systems for light rail applications was based in a simple dc system that was fed by ac/dc noncontrolled diode rectifier substations connected to the ac distribution network. Low-energy efficiency and controllability were not a problem. However, with the massive implementation of regenerative braking technologies in light trains and trams, the development of an effective way to manage the recovered energy became an important issue. The regenerated power injected in the system by a train in braking mode could be used only in the case where another nearby train was in traction mode. Otherwise, the regenerated power was dissipated in the dc traction system or in the rheostatic braking equipment, decreasing the overall system energy efficiency. The need for more solutions that would allow more use of the regenerated energy and increased energy efficiency in the system was the driving force for new technological developments. First, proposals were for the use of reversible substations able to give back the dc energy surplus to the ac distribution system. Then, due to energy storage cost reductions, a combination of technologies such as insulated-gate bipolar transistor (IGBT)-based reversible substations with on-board and off-board accumulation systems evolved into a reality. The use of substation-level off-board accumulation systems can also avoid the installation of reversible infrastructure, providing a high degree of controllability over the dc traction system voltage. However, higher efficiency rates are achieved when the energy storage is installed on board. In such a case, the regenerated power is used in-situ, minimizing the transmission losses. One of the main benefits of the offboard accumulation approach is the fact that many trains equipped with regenerative braking systems can take advantage of a single device. On the other hand, the use of on-board accumulation leads us toward more flexible, efficient, and dependable systems. Therefore, some manufacturers are using these kinds of on-board accumulation systems to avoid the use of overhead line equipment and to reduce the visual impact, offering catenary-free solutions.

What the IEC Tells Us About Stray Currents: Guidance for a Practical Approach

It is well known that in dc-electrified rail lines, the running rails are used to return the traction current to the rectifier substations. However, we cannot avoid some part of this current leaving the rails and instead passing through the earth to rejoin the return circuit at a point that is closer to the rectifier substation, and so the current reaching the negative busbar of the rectifier substation. These leakages, called stray currents, seek the least-resistant paths and, in particular, piping and cable systems of any kind placed in the neighborhood of tracks. Thus, a stray current is the part of a current caused by a dc traction system that follows paths other than the return circuit. The major effects of stray currents can be the corrosion and subsequent damage of metallic structures at the points where stray currents exit. The metallic mass dissipated onto the soil can be estimated through the Faraday's laws of electrolysis. For example, considering 1 A of stray current flowing continuously through a steel structure, the metallic mass of corroded steel dissipated onto the soil is equivalent to 9.13 kg per year. There is also the risk of overheating, arcing, fire, and subsequent danger to people and equipment both inside and outside the dc traction system.

Improvement of basic requirements for the system and devices of traction dc power supply

Abstract—“The Technical Maintenance Regulations of Russian Federation Railways” and “The Arrangement Regulations of the Russian Federation Railways Traction Power Supply System (TsE-462)” set out clear requirements to ensure minimum voltage in the aerial contact wire for freight and high-speed passenger train movement. These requirements are confirmed by the Norms of the European Electrotechnical Standard EN 50163 (1995). However, the voltage norms at traction substations (TsE-462) are in contradiction to the maximum continuous voltage in the aerial contact wire demanded by Railway Research Institute (VNIIZhT) and accepted by EN 50163 Standard. This paper proposes using continuous voltage at traction substations in the normal operating mode in the range of from 3600 (the minimum value) to 3700 V. The maximum voltage (3700 V) was obtained as a result of electrical calculation of the traction power supply system at the track sections with hard mountainous track profile while running trains with an increased weight of 6300–9000 t or two combined trains with a combined weight of 12000 t with powerful electric locomotives of 2ES6, 2ES10, and 3ES10 series. This voltage value was confirmed by long-term operation on a Tyumen–Yekaterinburg–Perm–Balezino track section of 923-km length with voltage stabilization at the level of 3650 V at the traction substations. The voltage levels at the traction substation buses are provided by a contactless automatic control system (CACS) with ±0.6% inaccuracy. The maximum voltage in the traction substation buses is acceptable and equal to maximum aerial contact wire voltage (4000 V) under the recuperation mode.

A METHOD FOR TRAIN WEIGHT ESTIMATION

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT There are difficulties and deficiencies in procedures of weighing of railway cars and trains, as well as there is a persisting need to know cargo loads on the rail track. The article offers a simple way to estimate weight of a train as it moves along a control track section. It is based on measurement of intensity of magnetic field generated by locomotive DC traction motors. The role of weighing devices is performed by ferroprobes having as recording devices milliammeters with a calibrated scale for measuring train weight. The results achieved by the authors confirm method’s effectiveness. Keywords: train weight, locomotive, DC traction motors, constant magnetic field, magnetic field intensity, ferroprobes, train weighing method.

Industrial frequency single-phase AC traction power supply system for urban rail transit and its key technologies

To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation (MSS) and cable traction network (CTN). The MSS includes a single-phase main traction transformer and a negative-sequence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as (1) the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; (2) the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; (3) a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

Power quality analysis in electric traction system with three-phase induction motors

Three-phase induction motors are widely used in electric traction systems. The impacts of the traction vehicles equipped with three-phase induction motors on power quality are much different from the impacts of vehicles with DC traction motors. In this paper, the effects of the traction vehicle operation with three-phase induction motors on power quality in a 110kV transmission network are investigated.The electric traction system 25kV, 50Hz and the traction vehicle with three-phase induction motors were modeled including AC/DC rectifier and DC/AC inverter based on IGBT technology. The parameters of those power electronic elements directly determine the current and voltage waveforms, and consequently power quality parameters.Measurements and calculations of power quality parameters were presented. Three operation modes of traction vehicle were considered including acceleration, constant drive and regenerative breaking. During the test drives, the values of total harmonic distortion, unbalance, flicker and power factor were obtained.

BFS Algorithm for Voltage-Constrained Meshed DC Traction Networks With Nonsmooth Voltage-Dependent Loads and Generators

In this paper, a new procedure based on a backward/forward sweep (BFS) algorithm for solving power flows in weakly meshed dc traction networks is presented. The proposed technique is able to consider the trains as nonlinear and nonsmooth (nondifferentiable) voltage-dependent loads or generators. This feature permits the inclusion of the trains’ overcurrent protection and the squeeze control. With the use of the mentioned controls, the conventional power flow problem becomes a voltage constrained power flow problem, and the interaction between the trains and the network can be accurately modeled. However, the train control induces a highly nonsmooth voltage-dependent load characteristic, causing convergence problems in most of the derivative-based algorithms. The proposed algorithm is faster, more robust, and more stable than the derivative-based ones. In addition, the authors present all of the formulation in a compact matrix-based form by means of the graph theory application and the node incidence matrix.

Modeling of traction electric drive with dc series motors

Analysis of existing models of the Weber-ampere characteristic of the DC motor is performed. It showed that the use of the universal magnetization curve is not always correct, since traction DC motors have local features of design and magnetic system. It is proposed to define the value of the flux КФ as a function of the magnetomotive force of the currents of the series field winding I SFW and the anchor winding I A . The model of the Weber-ampere characteristic of the DC motor is developed. It takes into account the actual values of the currents of the anchor winding and series field winding, which enhances the computation accuracy in the field reduction modes. The structure of the automatic control system of the traction electric drive using the functional converter to determine the field reduction factor based on the above model is proposed.

Measurements of armature current in the brush collector unit of a direct current motor during the commutation period

The operating conditions of locomotives determine the special technical state requirements of individual units and aggregates. Traction dc motors are the most heavily loaded and vulnerable objects as far as the work of commutators and their influence on the commutation processes in a motor are concerned. Analysis of the effects of a brush collector unit shows that the split-type-brush-based method for finding the technical state of a dc machine is not sufficiently informative about the commutation process. The current measurement of a short-circuited section of the armature winding during the commutation period was made using two parts of a split-type brush and a proper measurement scheme was proposed. A test bench for the research of the commutation processes in a dc motor was designed, which provided the description of the transition processes in a commutator of a dc machine at the use of a brush consisting of two parts. The current distribution in a short circuited coil and separate parts of a brush was obtained. The measurement scheme of the armature current at a commutator is presented and the experimental results are provided in the form of oscillograms of the characteristics of a real motor.

Modernised DC traction substation recuperating energy of braking

The traction substation composed of the 3-phase transformer and the output diode rectifier is still the fundamental device for DC traction supply. In this paper two technical solutions (power electronic converters) allowing for braking energy recuperation to the AC mains are discussed. This has been thought as the modernisation of the existing traction substations allowing for high speed trains regenerative braking and braking of heavy train hollers. Such a solution brings some profits: energy recuperation, mechanical brakes saving and enhanced quality of traction vehicle control. For the proposed converters technical and economical advantages and drawbacks are indicated.

Effect of Over Zone Feeding on Rail Potential and Stray Current in DC Mass Transit System

DC traction power system with running rails as reflux conductor has been adopted in Guangzhou Metro Line 8. During the operation of the Guangzhou Metro Line, a high rail potential has been observed, and the leakage of stray current increases significantly. Because of the electrical connectivity of the catenary, over zone feeding of traction current may exist when multiple trains run in multiple traction substations. Guangzhou Metro Line 8 suspects that over zone feeding of traction current is the major cause of the high rail potential. In this paper, a unified chain model of DC traction power system is proposed to simulate the distribution of rail potential and stray current. Field tests and simulations have been carried out to study whether over zone feeding has an impact on rail potential and stray current. Results show that over zone feeding widely exists in DC traction power system and that the rail potential and stray current can be reduced effectively by preventing the over zone feeding of traction current.

Introduction and Practical Use of Energy Storage System with Lithium-ion Battery for DC Traction Power Supply System

In this paper, concerned with an energy storage system (ESS) with Li-ion battery for DC traction power system, a study about planning of introducing ESS and the performances of two examples in actual operation are described. Through this study, a suitable condition for introducing ESS with respect to headway of trains was obtained and confirmed by analysis measurements. Further, the effects of adjusting threshold voltages of charge and discharge on the practical use of ESS are also described.

Оценка пропускной способности участка с учетом режима напряжения в тяговой сети постоянного тока

Оценка пропускной способности участка с учетом режима напряжения в тяговой сети постоянного тока

Учет потерь электрической мощности в трансформаторах тяговых подс танций по стоянного тока

Учет потерь электрической мощности в трансформаторах тяговых подс танций по стоянного тока

Ground Fault Detection and Location for Ungrounded DC Traction Power Systems

A fault protection and location method for ungrounded dc traction power systems is presented in this paper. Many dc traction power systems have an ungrounded power circuit to increase the leakage path resistance. Although ungrounded systems can continue operating with a single ground contact, unlike solid- or low-resistance grounded systems, because of the very low fault current, a second ground fault in another pole will result in a line-to-line fault that could cause significant system damage. However, it is difficult to detect the first ground contact due to the low ground current and even harder to locate because it can be seen by many detectors in the network. The proposed scheme in this paper uses a probe unit to detect and locate the first single ground fault in ungrounded traction power systems. The probe unit applies probe voltage to detect the fault and, once the fault is detected, analyzes the response to dc or swept-frequency ac probe voltage to locate the fault. The proposed concepts have been verified with computer simulations and hardware experiments and demonstrated a successful performance.

The prospects for development of renewable power engineering and providing electrical safety and electromagnetic compatibility

The prospects of the development of renewable power and the creation and implementation of fundamentally new technologies of electric and electronic equipment in order to improve the power supply, to improve energy conservation and efficiency, and to provide electrical safety and the electromagnetic compatibility are discussed. According to research results, the efficiency of the traction power supply system can be improved by increasing the rated voltage in a dc traction network up to 24 kV. The increased voltage results in higher railroad traffic and carrying capacities and allows energy losses throughout the whole system to be reduced. It is shown by analysis and simulation of electromagnetic processes and by comparison of technical and economic characteristics of converters that 24-pulse rectifier circuits with a series connection of threephase bridges are the most effective for the aforementioned system. Such rectifiers improve the power quality both in the primary power-supply system and in the traction network. They also allow one to use simpler and more efficient active-passive smoothing filters, which provide electromagnetic compatibility of the new dc traction power supply system with communication devices and railroad automatic machinery.

Simulink Library for Reference Current Generation in Active DC Traction Substations

Simulink Library for Reference Current Generation in Active DC Traction Substations