Electrified Railway Systems Research Articles

Power quality solutions for rail transport using AI-based unified power quality conditioners

This paper proposes an artificial intelligence-based Unified Power Quality Conditioner (AI-UPQC) and a unique Dynamic K-factor PI (DKPI) algorithm for PI-UPQC to address power quality issues in electrified railway systems. The widespread use of power electronic converters in modern traction drives has exacerbated problems such as harmonics, voltage fluctuations, and resonance phenomena. The proposed AI-UPQC utilizes artificial neural networks (ANNs) to generate optimal reference signals for controlling series and shunt active power filters. A detailed 25 kV, 50 Hz traction power supply system model is developed in MATLAB/Simulink to evaluate the AI-UPQC's performance. Simulation results demonstrate that the AI-UPQC significantly outperforms conventional PI-controlled UPQCs in reducing voltage and current total harmonic distortion (THD), improving power factor, and providing faster response times under varying load conditions. The AI-UPQC reduced source current THD from 25.16 to 1.12% and load voltage THD from 6.62 to 2.07%. Sensitivity analysis further validates the robustness of the proposed system across different operating parameters. The AI-UPQC shows promise as an effective solution for enhancing power quality in modern electrified railway networks.

Research on Improved GPC of Pantograph Considering Actuator Time Delay and External Disturbance.

Active control of pantograph is an effective method to improve the current received quality in electrified railway systems. To alleviate the negative impact of time delay in pantograph actuator, a Controlled Auto-Regressive Integrated Moving Average (CARIMA) model was designed for pantograph active control. In conjunction with the Euler-Bernoulli catenary model, an improved generalized predictive control (IGPC) algorithm was proposed, and its stability was analyzed. Then, the control performance was verified and discussed through testing. Subsequently, the effects of external disturbances and time delay on control performance were discussed. The results indicate that the proposed controller with a larger control gain, exhibits better performance in reducing fluctuation in contact force between pantograph and catenary, despite being affected by external disturbance and actuator time delay, it still shows significant control performance.

A Review on Single Phase AC System of Railway Electrification

The widespread adoption of 25 kV, 50 Hz single-phase AC supply in long-distance electrified railway systems poses significant challenges to power quality in transmission networks. This paper presents an in-depth investigation into the influence of electric railway systems on a 110 kV transmission system, with a specific focus on locomotives equipped with diode rectifiers. Harmonic currents generated by these locomotives and unbalanced voltages introduced by single-phase traction loads are known to adversely affect power system components, leading to issues such as overheating, additional losses, and interference with communication systems. The focus of this paper is not only to understand the fundamental principles but to conduct a deep exploration of the functioning of various components such as locomotives, contact lines, and substations. High voltage This voltage is supplied from the substation or directly from the generating station. This high AC voltage (25KV) is first transformed into low AC voltage (415V). Three-phase induction motors are used because they provide high torque, are reliable, and are more efficient. The AC voltage in the second phase is rectified to DC and then converted into a phase AC using VFD. The VFD provides variable frequency and voltage to run the induction motor at different speeds.

A Novel Power Electronic Autotransformer-Based Bipolar MVDC Electrified Railway System

A Novel Power Electronic Autotransformer-Based Bipolar MVDC Electrified Railway System

Stability Enhancement Method Based on Adaptive Virtual Impedance Control for a PV-integrated Electrified Railway System

Stability Enhancement Method Based on Adaptive Virtual Impedance Control for a PV-integrated Electrified Railway System

GSOANR-based multi-objective train trajectory optimization

ABSTRACT Railway transport is an important mode of transportation in China, UK, and worldwide. It is expected to play an even more important role in transportation decarbonization in shifting more passenger trips and freight transportations to railway. It is strategically important to reduce the energy consumption and improve the overall energy efficiency of the railway systems. The introduction of automatic train operation (ATO) systems in electrified railway systems makes it possible to achieve energy consumption reduction while satisfying other railway operation criteria such as the need for passenger comfort, train punctuality, and safety. Although energy saving of railway systems has attracted substantial interest in recent years, ATO systems are not environmentally friendly as expected and there is a lack of a set of energy saving performance measures for railway system planning and operation. In this paper, the features of ATO systems are incorporated into the problem formulation, and a modified GSO algorithm with adaptive neighbourhood range (namely the GSOANR algorithm) is proposed as the solver of the problem. The proposed method is applied to the trajectory planning of a 58-km-long route between Heishan North Station and Fuxin Station of the Beijing-Shenzhen Line in China, and the results confirm that the train operation trajectory generated by the GSOANR algorithm-based optimization method can reduce the electrical energy consumption by about 5.6% compared with the results generated by the standard GSO algorithms, confirming the efficacy of the proposed energy-saving measures and the effectiveness of the novel optimization method, and the referential significance for the study of the train trajectory optimization.

EMI and IEMI Impacts on the Radio Communication Network of Electrified Railway Systems: A Critical Review

The electrified railway system has been rapidly rolled out in many countries and regions in the past decades, along with the transportation decarbonization agenda. The latest development in power electronics and electrical railway systems has increased the risks of electromagnetic interference (EMI) and intentional EMI (IEMI) emissions, introducing new challenges to the railway radio communications network. It is vital to have a robust and reliable railway communication network that can be resistant and immune to these interferences for the safe and efficient operation of modern railway systems. Yet, the source and new features of EMI and IEMI emerging along with the latest technological development have not been thoroughly investigated and understood. This review paper aims to fill the research gap. First, railway communications systems are introduced. The EMI and IEMI are discussed at the whole system level, and the corresponding impacts on the signaling and communication systems are reviewed comprehensively. Current electromagnetic compatibility (EMC) methods are surveyed, and challenges of tackling the impacts of EMI and IEMI on the signaling and communication systems are discussed. Finally, future research directions are outlined.

Flashover characteristics and altitude correction of railway insulators at high altitude and polluted areas

The reduction of electrical performance of railway insulators at high altitude and polluted areas affects the safe operation of the railway. A lot of studies have been carried out on transmission line insulators at home and abroad, but whether the results can guide the design of railway insulators has not yet been determined. This paper takes the railway insulator QBG-25/16 as the research object, experimentally studied the lightning impulse and AC pollution flashover characteristics of the railway insulator under low air pressure, analyzed its insulation configuration under high altitude and pollution environment, and finally proposed its altitude correction method. The results show that the flashover voltages of the insulator decrease in a power function as the air pressure decreases, and decrease in a power function as the salt deposit density increases, and the air pressure influence characteristic index and pollution influence characteristic index are related to voltage type, air pressure and salt deposit density. The tested insulators do not satisfy the requirements for insulation strength at certain high altitude and polluted areas. Finally, the altitude correction method for railway insulators is given. The results of the study provide guidance for the selection of external insulation for electrified railway systems at high altitude.

A Comprehensive Review of Power Converters for E-Mobility

The penetration of electric vehicles is becoming more and more widespread and recently electric buses and trains are fetching the attention of researchers and developers. In this review, we examine the charging systems applied to the fast charging of electric vehicles and buses as well as the charging strategies, mainly applied to electric buses. We also briefly delve into power topologies for a more electrified railway system where we discuss their different supply systems as well as their motor drive systems. Problems and charge challenges for electric buses and trains are discussed too.

On-Line Detection of Railway Power Frequency Current Based on Tunnel Magnetoresistance

In an electrified railway system, electrical energy is provided to the train through the traction network for its normal operation. Starting from the traction substation, the traction current flows through the catenary, the train, and finally returns to the traction substation via the steel rail. Due to the absence of the on-line detection technology for rail current, it has been a long time that the magnitude of the current flowing on the rail is unclear. Therefore, how to effectively detect rail current has become an industrial and academic focus recently. This article uses a new type of tunnel magnetoresistance (TMR) sensor, focusing on the rail power frequency current online detection technology based on the TMR gradient method. First, this article analyzes the current and the magnetic field distribution characteristics near the rail, then considers the actual installation situation on the spot, and selects the appropriate sensor installation location. Finally, through simulation and actual measurement, it is verified that the scheme has a flexible structure, easy installation, strong anti-interference ability, and good detection accuracy.

Laser-Induced Ultrasonic Guided Waves Based Corrosion Diagnosis of Rail Foot

Rail foot corrosion is an important issue for electrified railway system. It usually initiates at the bottom of rail foot edges covered by a rail clip and is hardly accessible to conventional online inspection systems. To address this problem, this study combines air-coupled ultrasonic transducer (AUT) and laser-induced ultrasonic guided wave to detect rail foot corrosion. The corrosion sensitivity of the guided wave below 500 kHz is examined considering the impact of rail clip. The results have shown that A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> are the dominant wave modes near the edge of rail foot. The preferred A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> wave is insensitive to allowable rail foot corrosion below 100 kHz. It is neither sensitive above 270 kHz due to wave mode conversion and reduced wave penetration. The optimal frequency is about 200 kHz where the attenuation of A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> wave can reflect the impact of all levels of corrosion even in the presence of a rail clip. Accordingly, an end-to-end deep learning model is employed for corrosion detection based on 200-kHz air-coupled ultrasonic signals. It can automatically extract signal features for corrosion diagnosis as well as differentiate unknown anomalous signals by environmental interference. It is tested with 8122 labeled signal samples collected from field trial and achieves a detection accuracy of 99.5%. All the anomalous signals are also correctly identified.

A Method for the Automatic Extraction of Support Devices in an Overhead Catenary System Based on MLS Point Clouds

A mobile laser scanning (MLS) system can acquire railway scene information quickly and provide a data foundation for regular railway inspections. The location of the catenary support device in an electrified railway system has a direct impact on the regular operation of the power supply system. However, multi-type support device data accounts for a tiny proportion of the whole railway scene, resulting in its poor characteristic expression in the scene. Therefore, using traditional point cloud filtering or point cloud segmentation methods alone makes it difficult to achieve an effective segmentation and extraction of the support device. As a result, this paper proposes an automatic extraction algorithm for complex railway support devices based on MLS point clouds. First, the algorithm obtains hierarchies of the pillar point clouds and the support device point clouds in the railway scene through high stratification and then realizes the noise that was point-cloud-filtered in the scene. Then, the center point of the pillar device is retrieved from the pillar corridor by a neighborhood search, and then the locating and initial extracting of the support device are realized based on the relatively stable spatial topological relationship between the pillar and the support device. Finally, a post-processing optimization method integrating the pillar filter and the voxelized projection filter is designed to achieve the accurate and efficient extraction of the support device based on the feature differences between the support device and other devices in the initial extraction results. Furthermore, in the experimental part, we evaluate the treatment effect of the algorithm in six types of support devices, three types of support device distribution scenes, and two types of railway units. The experimental results show that the average extraction IoU of the multi-type support device, support device distribution scenes, and railway unit were 97.20%, 94.29%, and 96.11%, respectively. In general, the proposed algorithm can achieve the accurate and efficient extraction of various support devices in different scenes, and the influence of the algorithm parameters on the extraction accuracy and efficiency is elaborated in the discussion section.

A novel measurement approach based on wideband excitation for frequency-coupling admittances of train converter

ABSTRACT In order to assess the high-frequency resonance and stability issue in the electrified railway system, a novel wideband measurement approach based on multi-tone signal is developed for extracting the sampling frequency-coupling admittances (SFCAs) of train converter. By injecting a series of linearly independent wideband excitation signals, the SFCAs of train are obtained simultaneously without affecting the network impedance. Considering the frequency distribution of wideband signal, an alternating injection method based on multi-tone signal is proposed. It aims at eliminating the overlapping effects of various frequency relationships on the target coupling harmonics in the 4QC control system. With unknown network impedance, the SFCAs of train covering all the desired frequencies, even several times sampling frequency, can be captured by the proposed wideband measurement approach. Comprehensive experiments are conducted on a hardware-in-the-loop (HIL) system for validating the measurement results.

A Comprehensive Review on Modular Multilevel Converters, Submodule Topologies, and Modulation Techniques

The concept of the modular multilevel converter (MLC) has been raising interest in research in order to improve their performance and applicability. The potential of an MLC is enormous, with a great focus on medium- and high-voltage applications, such as solar photovoltaic and wind farms, electrified railway systems, or power distribution systems. This concept makes it possible to overcome the limitation of the semiconductors blocking voltages, presenting advantageous characteristics. However, the complexity of implementation and control presents added challenges. Thus, this paper aims to contribute with a critical and comparative analysis of the state-of-the-art aspects of this concept in order to maximize its potential. In this paper, different power electronics converter topologies that can be integrated into the MLC concept are presented, highlighting the advantages and disadvantages of each topology. Nevertheless, different modulation techniques used in an MLC are also presented and analyzed. Computational simulations of all the modulation techniques under analysis were developed, based on four cascaded full-bridge topologies. Considering the simulation results, a comparative analysis was possible to make regarding the symmetry of the synthesized waveforms, the harmonic content, and the power distribution in each submodule constituting the MLC.

A Stable Extended FDTD Thin-Wire Model for Lossy Wire Structures With Irregular Cross Sections

A stable extended FDTD thin-wire model for lossy wire structures with irregular cross sections is presented for lightning transient analysis. In this model, the electro-magnetic field in the vicinity of a conductor with an irregular cross section is taken into account by adopting a single constant correction factor, and the conductor loss is represented with an internal impedance. These two parameters are calculated with a charge simulation method and an equivalent circuit method, respectively. The proposed model is validated in terms of the characteristic impedance, conductor loss and time-domain waveform with analytical and numerical methods. Good agreements are observed. Considering the rigid conductor-size/cell-size requirement and eight tedious convolutional processes in the existing non-circular thin-wire model, the implementation complexity of this proposed model is significantly simplified, and the computational stability is remarkably enhanced. Without reducing the time step, the simulation can maintain its stability when the conductor size varies from 0.01 to 1 of the FDTD cell size. It is also revealed that using a single intrinsic model for conductors with different cross sections could lead to significant calculation errors. Finally, this proposed model is applied for the lightning transient analysis in an electrified railway system.

Stress Analysis and Fatigue Life Prediction of Contact Wire Located at Steady Arms in High-Speed Railway Catenary System

In an electrified railway system, the pantograph on the train roof is used to collect the electric current through a sliding contact with the contact wire (CW) of the catenary. The CW is mounted laterally in a zigzag relative to the track centerline with the help of a steady arm to ensure symmetrical wear on the pantograph&#x2019;s strip, which is beneficial to slow the wear process and extend the service life. Under the pantograph&#x2019;s impact, the CW around the steady arm forms a stress concentration and has been recognized as a vulnerable point in the catenary system. This article performed a uniaxial tensile test and high-cycle fatigue test to measure the mechanical properties and fatigue characteristics of Cu&#x2013;Mg alloy that is used for manufacturing high-speed CW. A stress analysis method is proposed based on the combination of the pantograph&#x2013;catenary interaction model and the solid CW specimen model. In the pantograph&#x2013;catenary interaction simulation, the catenary is modeled using the Euler&#x2013;Bernoulli beam element. The 3-D solid element is used to model the CW segment. The nodal displacements of the CW segment obtained from the pantograph&#x2013;catenary interaction simulation are transferred to the CW specimen model. The stress distribution on the CW section and the entire multiaxial transient stress field are analyzed. Based on fatigue test results and stress time history data obtained by simulation, using the nominal stress method, the uniaxial fatigue and multiaxial fatigue analyses are performed to reveal the fatigue characteristics with different speed classes. The results indicate that the weakest points appear at both the wing point and the top point on a CW section. The CW&#x2019;s fatigue life reduces by over 50&#x0025; when the speed class is upgraded from 350 to 400 km/h.

Pantograph Arc Location Estimation Using Resonant Frequencies in DC Railway Power Systems

Pantograph arcing in electrified railway systems not only reduces the power collection quality of a locomotive but can also damage pantograph strips and overhead lines (OHLs). Most research detects pantograph-to-OHL arcs based on onboard voltage/current measurements, pantograph cameras, and so on. The use of onboard voltage/current data, though being cost-effective, rarely reflects arc locations along OHLs. This article develops an arc positioning method, which matches the position-dependent resonant frequency (RF) of an OHL with the RF extracted from voltage measurements in a pantograph arc event. A particular 20-km DC railway line supplied by two substations is first modelled in MATLAB/Simulink, with the model effectiveness being assessed based on voltage measurements in an arc event. Then, the OHL-related RFs estimated by the model are validated by the Tableau formula and discussed alongside impacts on RFs based on line models, locomotive locations, and line lengths. These evaluations permit the generation of an RF curve that links OHL-related RFs with arc locations. The arc positioning method is tested based on the pantograph arc events presumed at various positions along the 20-km line, showing errors within 0.2 km at certain locations. The ability to determine arc locations will permit periodic inspections to be performed on the determined line sections.

Using C‐type filter with partial compensation method for capacity reduction of hybrid power quality conditioner in co‐phase traction power system

Hybrid power quality conditioner (HPQC) has been utilised in a co-phase electrified railway system with the aim of improving power quality indices. A C-type filter is designed as an auxiliary device alongside the HPQC for high-order harmonics mitigation in this paper. Alternatively, the C-type filter compensates a selected portion of load reactive power, while the HPQC compensates for the left required power. Furthermore, the HPQC mitigates grid side unbalance and other harmonics in a co-phase supplied system simultaneously. In addition, a design procedure of LCL filters is proposed to suppress high-order harmonic contents induced by the HPQC converters to achieve lower grid-side total harmonic distortion (THD). Moreover, a flexible partial compensation (PC) method considering the C-type filter effect on the HPQC performance is adapted to maintain the grid-side power quality indices in an acceptable range. The C-type filter and PC method provide VA rating reduction of the HPQC without applying any complication to the compensation control system. Finally, simulation and experimental results are presented to validate the feasibility and functionality of the proposed configuration.

Evaluation of Static Synchronous Compensator and Rail Power Conditioner in Electrified Railway Systems Using V/V and Scott Power Transformers

In this paper a comprehensive review of electrified railway systems is carried out, identifying the electric power quality deterioration which may appear due to nonlinear dynamic traction loads. Following this topic, a computational simulation of Static Synchronous Compensator

The Detailed Representation and Computation of the Traction Network and its Application to the Transient Analysis in Electrified Railways

This paper intends to derive a detailed representation and attain a suitable computation method for the traction network. The transient analysis of the lossy multiconductor transmission lines (MTLs) is performed considering the electromagnetic characteristics of the rail track, which accounts for the frequency‐dependent and distributed nature of the line parameters over the entire frequency range for the traction network. Due to the practical difficulty in wideband parameter determination and the complex layout for the traction power supply system, the model implemented has been validated by comparison to several field tests that are carried out on a real high speed railway line for the purpose of identifying possible power quality problem. The good high representation of the frequency‐dependent parameter and the numerical solution will provide a reliable method for the transient analysis of the electrified railway. Afterwards, the transient calculation using vector fitting and modal decomposition is presented to evaluate how the emission is propagating along the MTLs of the electrified railways. Performing detailed and suitable analysis is necessary to determine the overvoltage conditions during the transients. The outcome of the analysis could be beneficial for the transient protection study in the electrified railway system. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.