DC Traction Power Supply System Research Articles

Train-earth-grid coupling DC magnetic bias model for stray current diffusion

The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation.

Fault Analysis and Protection in Flexible DC Traction Power Supply System

Fault Analysis and Protection in Flexible DC Traction Power Supply System

Dynamic Diffusion Model of Stray Current in DC Traction Power Supply System

The dynamic fluctuation of stray current is the main characteristic of the metro causing harm to surrounding buried metal structures. While establishing the equivalent circuit model of the return system, not only mainline but also metro depot should be considered. The diffusion models of the dynamic stray current of the DC traction power supply system (DTS) in multi-layer soil medium and massive texture soil medium are established. They are co-simulated with the DC traction power supply return system. The massive texture model (MTSM) is verified by an on-site experiment of ground potential distribution. In the case study, the direct grounding of the rail in the depot will deteriorate the ground potential gradient and stray current. When considering the impact of the river or lake, the stray current easily flows to the low resistivity texture soil, the maximum ground potential gradient increases.

МОДЕЛИРОВАНИЕ СИСТЕМЫ ТЯГОВОГО ЭЛЕКТРОСНАБЖЕНИЯ ПОСТОЯННОГО ТОКА С 6-ТИ ПУЛЬСНЫМИ ПРЕОБРАЗОВАТЕЛЯМИ

The technique of computer modeling of DC traction power supply system’s modes in phase coordinates implemented in Fazonord software package is considered. The developed computer models can be used to determine the parameters of the DC and AC current subsystems mode and also to determine the mode at higher harmonics

Refined Model of a DC Traction Power-Supply System to Determine the Parameters of Systems of Electric-Energy Storage

Refined Model of a DC Traction Power-Supply System to Determine the Parameters of Systems of Electric-Energy Storage

Train Control and Schedule Integrated Optimization With Reversible Substations

The Carbon Neutralization is a grand strategy to deal with global climate change. As a major energy consumer, urban rail transit (URT) system should contribute corresponding solutions. This paper proposes an energy-efficient train control and schedule integrated optimization method under DC traction power supply system (TPSS) with reversible substation (RSS). The dynamic coupling mechanism between the train movement process and the RSS working mode is analyzed and modeled. Aiming to minimize the total RSS energy consumption for the train traveling over multi-interstation with a given total trip time, the train trajectory and schedule optimization problem is integrated in the same level, and is formulated as a multi-phase optimal control problem (MOCP) to be solved by a pseudo-spectral method (PSM). As a supplement, a customized dynamic programming (DP) method for the problem is introduced to verify the validity of the proposed solution framework. Simulation results under the models of the RSS energy together with conventional rectifier substation energy and vehicle mechanical energy are presented and compared, indicating that the proposed methodology has great energy saving performance for the new-type DC railway system.

Bi-level optimal design for DC traction power supply system with reversible substations

Bi-level optimal design for DC traction power supply system with reversible substations

Simulation models and application options of electric power storage systems in traction power supply

Background: the determination of the energy indicators of the traction power supply system based on the train schedule in the conditions of operation of storage devices is based on the solution of a number of instantaneous schemes, each of which corresponds to the established operating mode. These methods require adaptation to account for non-linear characteristics or indicators, the value of which is associated with the retrospective of the change. In this regard, it is necessary to use calculation methods based on the solution of differential equations to solve problems related to the assessment of performance in transient or emergency modes, taking into account dynamic characteristics. Modeling the operation of storage devices in the traction power supply system allows you to evaluate the change in indicators depending on the parameters of the devices, traction load and circuit solutions for various topologies.
 Aim: to determine the structure of models of electric power storage devices in DC and AC traction power supply systems, to consider the results of calculating the main energy indicators, to determine ways to improve circuit solutions based on the identified features, to determine the technical requirements for electric power storage devices in traction power supply.
 Materials and Methods: to obtain the results, methods for solving differential equations corresponding to various variants of the topology of storage devices in traction power supply, implemented in the Matlab software package, are used.
 Results: the results obtained allow us to determine the structure of storage devices for traction power supply, evaluate models of devices for traction power supply of direct and alternating current, outline the prospects for further research in the field of circuit solutions and required device parameters.
 Conclusion: the results of the study allow models of electricity storage devices and technical solutions for their implementation aimed at introducing DC and AC traction power supply into the system.

High Voltage DC Auto-Transformer Traction Power Supply for Braking Energy Utilization, Rail Potential, and Stray Current Mitigation

For urban rail transit, high-voltage ac power is generally transmitted from the main substation to the traction substation (TS), which employs isolated diode–rectifiers to feed the dc traction power supply system. The train current feeds back to the negative cubicle of TS through the running rail, which is not totally isolated from the Earth. However, the traditional traction power supply (TTPS) shows limitations on braking energy-wasting, high rail potential, stray current, and so on. Thus, a high-voltage dc autotransformer (DCAT) traction power supply (HDATPS) is proposed in this article. Both configurations and principles of three typical HDATPSs are analyzed, which mainly consists of the dc main substation, the dc TS, and the DCAT substation. Then, through modeling of HDATPS and TTPS, the comparisons on braking energy utilization, rail potential, and stray current mitigation are discussed in detail. Finally, the simulation model and experimental platform of HDATPS are built, respectively, and the theoretical analysis is verified with the simulation and experimental results.

Comparison of energy parameters of electric storage systems for DC and AC traction power supply systems

Introduction. The article discusses the energy parameters of electric power storage systems for DC and AC traction power supply systems. The purpose of the research is to evaluate the energy parameters of electric power storage systems located within the inter-substation zone boundaries of the AC traction power supply system at the 25 kV voltage.Materials and methods. The author used the methods of modeling, statistics and the experimental results processing. Moreover, the paper presented the parameter estimation of the energy accumulation system on the basis of the traction calculations for the AC rolling stock. In addition, the author made two variants of calculations — in the presence and the absence of the electric storage system. The researcher also made the simulation of the electric storage system for the voltage source connected to the sectioning post busbars.Results. Using the simulation modeling, the author presents active and reactive power graphs of the inter-substation zone boundaries in the active sectioning post operation conditions. Therefore, the article demonstrates the graph of the expected charge, the discharge depth calculations for the nominal energy capacity and the required charging features, which guarantee the charge restoration of the accumulation system to the initial level.Discussion and conclusion. The author offers the comparative assessment of the electric storage systems for the traction power supply with the DС voltage of 3 kV and the AC voltage of 25 kV. The research demonstrates the reducing potential of the nominal accumulation parameters.

Analysis of 3 kV DC Contact Line High-Speed Circuit Breaker Unit Protection Scheme Limitations

The High-Speed Circuit Breaker (HSCB) is a de-facto electro-mechanical contact line protection device employed in the 3 kV DC traction power supply system. The breakers installed at the terminal ends of the contact line make a unit protection scheme configuration. While the HSCBs seem to trip under fault conditions, there is an unknown source that keeps on supplying residual current into the faults. This necessitates some explanation of the source of energy of the continual flow of residual energy. This paper makes an analysis of the limitations in the HSCB unit protection scheme using MATLAB simulation and how the scheme can be optimized with digital protection devices augmented with a peer-to-peer transfer trip as an end-to-end protection solution.

Study on Distribution Characteristics of Metro Stray Current and Evaluation of Cumulative Corrosion Effect

Stray current directly affects the regular operation of electrical equipment and facilities in the subway DC traction power supply system. Therefore, it is worthwhile to study the stray current distribution characteristics during train operation and the quantitative corrosion of buried pipelines. This paper introduces the traction characteristics of power carriages and power wheelsets of subway vehicles into the DC traction process. A finite element model considering the dynamic distribution of stray current under the actual operation of subway vehicles is established. The interference characteristics of stray current and the contribution of power sources under the multiparticle model are analyzed. The rail insulation damage caused by long service time and the quantitative calculation of rail and buried pipeline corrosion is considered. The model results show that the stray current in the buried pipeline under the multiparticle model is more accurate and more suitable for the protection in the actual subway. The quantitative corrosion of the buried pipeline is stronger than the partial insulation damage environment when the rail is not insulated. The rail and buried pipeline corrosion at both ends of the insulation damage position is relatively severe. The stray current distribution model established in this paper gives full play to the solution advantages of the finite element method and provides a new idea for the quantitative calculation of buried pipeline corrosion.

Cooperative Eco-Driving of Multi-Train Under dc Traction Network

Cooperative eco-driving of multi-train combined with dc railway system can achieve energy saving at the substation level for the metro system. This article presents an integrated optimization method for eco-driving by combining energy-efficient train control and dc traction power supply system (TPSS) model, to minimize the substation energy consumption. The coupled time-varying TPSS models for single train and multi-train are established, and a novel power flow calculation (PFC) method is proposed, to directly obtain the precise power flow distribution without iterations. Then, customized dynamic programming (DP) algorithms for specific TPSS models are developed, and optimal speed profiles of the tracking train and the preceding train can be respectively obtained by the multi-phase DP method. The former maximizes the utilization of a distributed regenerative braking energy (RBE), and the latter actively generates RBE to be fully utilized. Finally, the performance of the proposed method is analyzed by implementing the numerical experiments with field data from Guangzhou Metro Line 8, and the effectiveness is verified by comparing it with a previous study-based heuristic algorithm (HA). The simulation result indicates that the proposed method can also effectively reduce the lost energy on the catenary, suppress catenary voltage fluctuations, and precise match power during the RBE transmission phase.

Multi-VSM based fuzzy adaptive cooperative control strategy for MVDC traction power supply system

This paper studies the control of a medium-voltage DC (MVDC) traction power supply system for rail transit (RT). In order to optimize the ability of DC voltage fluctuation and frequency regulation of rail trains, a fuzzy adaptive cooperative secondary control strategy based on improved virtual synchronous machine (VSM) is proposed. Firstly, the improved VSM control strategy is adopted in the traction substations (TSSs), which makes the RT trains have the external characteristics of synchronous generator and have certain inertia and damping support capacity, so as to improve the ability of the RT traction system to cope with traction network transient changes. Secondly, the virtual inertia and virtual damping can be dynamically adjusted by the system frequency deviating from the nominal steady-state frequency, and the dynamic fuzzy adjustment can be carried out by the fuzzy logic system to slow down the frequency fluctuation. Then, due to the different power supply distances and parameter settings between multiple TSSs, cooperative control is used to coordinate local TSS perceptions of information between adjacent TSS to achieve consistency of frequency response of multiple TSSs under different parameters. Besides, a time-varying switching topology handoff method is considered to select the optimal communication topology between adjacent base stations. Finally, simulation results verify the effectiveness of the proposed control strategy.

Evaluation of the Effect of Stray Current Collection System in DC-Electrified Railway System

Stray current corrosion damage is significant in DC traction power supply system (DTS). Stray current collection system including stray current collection network (SCCN) and stray current drainage device (SCDD) is designed to control the stray current. A comprehensive system integrated calculation model is established to evaluate the stray current. And the iterative power flow algorithm with simplification of DTS is proposed. The stray current distribution is calculated by multi sections rail reflux system model. The model is verified with CDEGS simulation. The influence of stray current collection system on stray current is evaluated. The result shows that the primary stray current is mainly affected by rail to SCCN resistance and the length of the line. The efficiency of collecting stray current of SCCN is mainly affected by the resistance of SCCN and the SCCN to earth resistance. While the use of SCDD deteriorates the efficiency of collecting stray current of SCCN. A site test was carried out in Chengdu Metro Line 1 to evaluate the effect of stray current collection system.

Energy Characteristics of the DC Distributed Power Supply Systems

Currently the circuit technology of the DC traction power supply system cannot provide the necessary requirements for introduction of high-speed traffic. Numbers of measures and tools have been developed to improve the traction lines that no longer meet current requirements. One of the most promising means for strengthening the traction DC lines is transition to the distributed power supply of the rolling stock. In this article, a comparative analysis was carried out of energy indicators of the classic centralized power system and distributed power systems with use of one aggregate traction substation and with use of the solar generators. That comparative analysis of these systems was performed on a simulation model with the same parameters of the traction line and rolling stock.

Study of Performance of RZhFA‑6500 Smoothing Reactors

DC traction power supply systems have become widespread in several countries. Electricity consumption by traction power supply systems has pronounced seasonal and daily peaks. The peak nature of consumption leads to additional heating of live parts since time constants of transient thermal and electrophysical processes differ by several orders of magnitude, therefore, reducing ohmic resistance of electrical equipment, other things being equal, is an extremely important task.Within the framework of solving the problem of increasing energy efficiency of equipment of DC traction substations, smoothing reactor filter devices with an armoured radial-cylindrical magnetic core with low ohmic resistance, named RZhFA‑6500, were developed and manufactured.In 2018, two blocks of RZhFA‑6500 smoothing reactors were put into pilot operation at one of the most heavily loaded sections of DC electrified railways, providing traffic of trains weighing up to 9000 tons and traffic volume of about a hundred pairs of trains per day.To determine comparative indicators of energy efficiency, data on consumption of electric power for traction of trains for the compared periods before and after introduction of smoothing reactors of a new type were requested. The data received from JSC Russian Railways contained information on the traffic volume, type of rolling stock, and weight of the transported goods in accordance with the executed traffic schedule through section under consideration. The resulting set of data served as the basis for development of a multivariate methodology for assessing energy efficiency of reactors of a new type, as well as their contribution to efficiency of train operation over the considered comparative time interval. Since efficiency of power equipment also depends on the ambient temperature, the average integral parameter of average daily temperature was introduced into the calculation methodology, which, as it turned out, during processing initial data and construction of characteristic graphical dependencies, has a comparative difference of less than one percent for the same monitored periods.Accurate quantitative accounting of the data on consumption of electrical energy provided for traction of trains, exchange of reactive energy with the supply network, volume of transportation allowed to obtain an objective comparison of contribution of smoothing reactors of a new type to increasing efficiency of train operation and reducing consumption of electrical energy for traction of trains.

Operation Mode of DC Traction Power Supply System and its Feeder Protection

At this stage, DC traction power supply systems are widely used in the development of China’s rail transit. In order to ensure the safety of rail transit, we need to strengthen the research work of DC traction power supply system. We can study and explore from the operation mode of the power supply system and feeder protection measures. Among them, we must pay special attention to feeder protection measures, as far as possible to ensure the safe operation of the DC traction power supply system, so as to ensure the stable operation of rail transit.

Методика выбора мест установки систем автоматического резервирования мощности тяговых подстанций постоянного тока

The paper presents a method for selecting the installation locations of power reservation systems of traction substations to reduce electricity losses in the system of traction power supply of DC railways. The analysis of the main criteria affecting the efficiency and reliability of the DC traction power supply system is carried out. The algorithm for selecting the installation locations of power reservation systems has been developed, which allows selecting traction substations that provide the greatest energy effect during the installation of systems

Algorithm for calculating the rail-ground potential in heavy load conditions

Increased freight turnover on railway transport inevitably leads to increased traction current in DC and AC traction power supply systems. The increase in traction current is already causing problems related to the normal operation of the 25 kV AC traction power supply systems. One of the adverse consequences of the increased traction currents is the increased rail-to-ground potential. This has already caused a number of accidents and related traffic interruptions on the Far Eastern Railway of Russia and other railway sections powered with alternating current. The study considers the problem of increased rail-to-ground potentials and provides basic formulae for calculating the wave parameters of the rail network and rail-to-ground potentials. Various methods are given for calculating rail-to-ground potentials for a 25 kV AC traction power supply system. Since in an alternating current system, expressions for calculating the potential are functions of a complex variable, the calculation of such expressions requires the use of special programs. Adaptation of existing methods to modern software and computing systems allows you to optimize and significantly speed up the process of calculating the “rail-to-ground” potentials, either considering the use of certain potential-reducing measures or not. A calculation method includes an algorithm developed for calculating the rail-to-ground potentials in the 25 kV AC traction power supply system for an inter-substation zone of any length with any number of electric locomotives within the zone.