Electric Railway Research Articles

An Improved Q-Axis Current Control to Mitigate the Low-Frequency Oscillation in a Single-Phase Grid-Connected Converter System

An electric railway system is a typical single-phase grid-connected converter system, and the low-frequency oscillation (LFO) phenomenon in electric railway systems has been widely reported around the world. Previous research has indicated that the LFO is a small-signal instability issue caused by impedance mismatching between the traction network system and electric trains. Therefore, this paper proposes an improved q-axis current control method to reshape the train’s impedance. The proposed method can be implemented easily by relating a reverse q-axis reactive current directly to the reference of the q-axis current under the dq current decoupled control. Moreover, considering the additional q-axis reactive current control, a small-signal impedance model of a train–network system is built. The impedance-based analysis results indicate that the proposed q-axis reactive current feedback control can increase the magnitude of the train’s impedance, which is beneficial to enhancing the system’s stability. Finally, this paper employs experimental results to verify the effectiveness of the proposed method.

Tuning of controller parameters for suppressing low frequency oscillations in electric railway traction networks using meta‐heuristic algorithms

AbstractDue to the interaction of electric multiple units (EMUs), and the electric traction networks, low frequency oscillations (LFOs) appear leading to traction blockade and overall stability related issues. For suppressing LFOs, coronavirus herd immunity optimiser (CHIO), a recently developed meta‐heuristic, has been applied for tuning controller parameters. Controller parameters are tuned to minimise the integral time absolute error (ITAE) that regulates DC‐link capacitor voltage. Results obtained using CHIO are compared with those found using other well‐established algorithms like symbiotic organisms search (SOS) and particle swarm optimisation (PSO). The supremacy of CHIO over other mentioned algorithms for mitigating LFOs was demonstrated for a diverse range of operating conditions. Results demonstrates that overshoot for the proposed algorithm‐based traction unit is 1.0061% whereas those for SOS and PSO based algorithm are obtained as 6.4542 % and 20.6166%, respectively which are quite high. CHIO is more stable than SOS and PSO and requires settling time of 0.1934 s only to reach steady‐state condition, which is 50.21% faster than SOS and 65.03% faster than PSO. Also, the total harmonic distortion (THD) for line currents of the secondary side of traction transformer (TT) are obtained as 0.88%, 2.17%, and 12.48% for CHIO, SOS, and PSO, respectively.

Fixed (Trackside) Energy Storage System for DC Electric Railways Based on Full-SiC Isolated DC-DC Converters

At present, in several European railway networks using traditional DC electrification systems, it is not possible to increase traffic nor to operate locomotives at their nominal power ratings. Trackside energy storage systems (TESSs) can be an alternative solution for the creation of new substations. A TESS limits contact line voltage drops and smooths the power absorbed during peak traffic. Thus, the efficiency of the power system can be increased while limiting costs and the environmental impact. This paper proposes a new topology of a TESS based on full-SiC isolated DC/DC converters associated with lithium-ion batteries and galvanic isolation, offering major advantages for operational safety. In the event of a fault, the input and output terminals of the converters are electrically separated, and the contact line voltage can never be directly applied to the batteries. In addition, the use of SiC MOSFETs makes it possible to obtain excellent efficiency with a high switching frequency. The first part of this paper presents the main characteristics of an elementary TESS module, while the second part proposes a sizing methodology for the typical case of a 1.5 kV DC line, which shows the limits of using TESSs to reinforce a power supply. Finally, the experimental results of an elementary module prototype are presented.

Assessment of zones prone to sinkhole using ground penetrating radar and soil properties in Central Iran

Land subsidence and sinkhole, natural and anthropogenic events, occur globally especially in arid and semi-arid regions. The major problem of this phenomenon is over exploitation of ground water. Identification of important factors in the soils as soil properties were prone to sinkholes detection of subsurface holes as soil texture essentially. For detecting subsurface layers were used Ground Penetrating Radar (GPR) in the study area. The study area is Abarkooh alluvial plain of about 250 km2 is part of the Eghlid-Abarkooh watershed. For assessment potential zones prone to sinkhole, eight routs were determined in two different regions for the measurement of GPR and soil chemical, physical and mechanical properties. In GPR sections around the sinkholes, there were some breaks in subsoil layers and found subsurface cavities and on the side of the mountain slopes, the subsoil layers were uniform and there was no sign of breaks in subsoil layers and cavities. Regarding soil characteristics, soil texture near sinkholes was silt loam, sandy loam and loamy sand and on the side of mountain slope was Skeletal sandy loam, Skeletal loamy sand and Skeletal sand because of the existence of gravel on the slopes of the mountain. For evaluating soil parameters in two selected regions, some differences were observed such as Ca2+/Mg2+ in lime, COLE and Atterberg limits. Mg2+ in lime is more than to Ca2+ near sinkholes and the limes of the soils were dolomitic type and unstable. The amount of COLE and Atterberg limits as divergence index were high near sinkholes but on the side of mountain slopes were low. An increase in Mg2+ in lime, COLE and Atterberg limits near sinkholes proved the activity of clays and their movement underground and the GPR results confirmed the clay activity as breaks in stratigraphy traces to depth of 5 m and these soils are prone to sinkhole phenomenon. It has been concluded that GPR and Soil properties is the best way to determine areas that prone to sinkhole and also to detect the safe area for construction and contracting works. It is suggested that land conservation be introduced as the best alternative near sinkholes and redrawing the plan of urban development, construction of electric tower and railway from lowlands to the piedmonts as detected the safe area.

Railway Emission Trends in China Based on Fuel Life Cycle Analysis

Railway transportation is one of the main modes of modern transportation. Under the dual constraints of air quality improvement and carbon neutrality achievement, clarifying the emission trend of CO2 and pollutants in railway transportation is of great significance for pollution and carbon reduction in the transport sector. In this study, the CO2 and pollutant emission characteristics of Chinese railways from 2001 to 2018 were analyzed based on the fuel life cycle method. Then, railway emission trends from 2019-2030 were assessed combined with scenario analysis. The results showed that with the advancement of railway electrification, the use of new diesel locomotives, and the continuous upgrading of fuel standards, the total CO2 and pollutant emissions in the fuel life cycle of railway transportation showed an upward and downward trend, respectively. In 2018, the total emissions of CO2, NOx, CO, BC, and SOx from railway transportation were 3780.29×104t, 11.98×104t, 3.94×104t, 0.20×104t, and 3.08×104t, respectively. Accelerating the improvement of power structure and reducing unit energy consumption were the best single control strategies to reduce railway emissions of CO2, SOx, NOx, BC, and CO, respectively. Under the comprehensive scenario of actively responding to railway pollution and carbon reduction, the emission reduction rates of CO2, NOx, CO, BC, and SOx could reach 35%, 37%, 39%, 32%, and 45%, respectively. The stagnation of power structure reform or the railway electrification process will lead to a significant increase in total emissions of railway transportation. Therefore, the pollution and carbon reduction of railway transportation requires continuous attention.

Robust Optimization of Energy-Saving Train Trajectories Under Passenger Load Uncertainty Based on p-NSGA-II

Railway electrification has attracted substantial interest in recent years as a key part of the global effort to achieve transport decarbonization. To improve the energy efficiency of train operations, of particular interest is the optimization of train speed trajectories. However, most studies formulate the problem as a single-objective optimization model and do not take into account train mass uncertainty associated with the passenger load variations. This article formulates a biobjective robust optimization model to minimize both the energy consumption and journey time, in which the robustness against the uncertain train mass is considered and viewed as a decision-maker preference. A novel multiobjective optimization algorithm, namely, p-nondominated sorting genetic algorithm-II (NSGA-II), is proposed, incorporating the original NSGA-II and a proposed preference dominance criterion to handle the DM preference. With the proposed p-NSGA-II, not only all solutions will converge to the optimal Pareto front but also solutions with better robustness in the Pareto front will be automatically selected and retained; meanwhile, the spread of the selected solutions is maintained. The effectiveness of the p-NSGA-II to generate a set of performance-robust driving schemes is verified by numerical case studies. The results show that the p-NSGA-II can achieve up to 40.59% robustness improvement compared to the original NSGA-II.

Analytical and Experimental Evaluation of the Joints in Bi-Based Superconducting Tape for the Feeder Cable

Electric railways have several problems due to the electrical resistance of feeder lines, such as transmission loss and voltage drop. In order to solve these problems, we have been developing a superconducting feeder cable, which enables zero-resistance power transmission. Due to restrictions during transportation, the length of one superconducting cable is at most 500 m, although the average distance between substations is about several kilometers. Hence, to introduce superconducting feeder cables between substations, it is required to join superconducting feeder cables to each other at a railway site. This article reports analytical and experimental results of joining tests of the superconducting tape, assuming the joining of superconducting feeder cables at railway sites, and gives standards for the joining of superconducting feeder cables.

Transactive Control of Electric Railways Using Dynamic Market Mechanisms

Electricity demand of electric railways is a relatively unexplored source of flexibility in demand response applications in power systems. In this article, we propose a transactive control-based optimization framework for coordinating the power grid network and the train network. This is accomplished by coordinating dispatchable distributed energy resources (DERs) and demand profiles of trains using a two-step optimization. A railway-based dynamic market mechanism (rDMM) is proposed for the dispatch of DERs in the power network along the electric railway using an iterative negotiation process, generates the profiles of electricity prices, and constitutes the first step. The train dispatch attempts to minimize the operational costs of trains that ply along the railway, while subject to constraints on their acceleration profiles, route schedules, and the train dynamics, and generate demand profiles of trains and constitute the second step. The rDMM seeks to optimize the operational costs of the underlying DERs while ensuring power balance. Together, they form an overall framework that yields the desired transactions between the railway and power grid infrastructures. This overall optimization approach is validated using simulation studies of the Southbound Amtrak service along the Northeast Corridor (NEC) in USA, which shows a 25% reduction in energy costs when compared to standard trip optimization based on minimum work and a 75% reduction in energy costs when compared to the train cost calculated using a field dataset.

Distribution of Currents in 2 × 25 kV Electric Railway Systems under Normal Conditions

This article shows a detailed analysis of the distribution of currents in 2 × 25 kV electric railway systems under normal conditions. The network equations are clearly formulated in a way that enables the presentation of a novel simplified analytical solution as well as the traditional numerical solution of the equation set. The simplified analytical solution is obtained when the transformer impedances are neglected, and under these conditions: (a) the distributions of currents are analytically deduced for cases with only one train; (b) the distribution of currents among autotransformers and between catenary and feeder can be easily understood, as well as the effect of the train position on the distribution of currents; and (c) the superposition method is applied for cases with multiple trains in order to clearly explain the distribution of currents from the results with only one train. On the other hand, the network equations are also numerically solved, including autotransformer impedances, and it is shown that their effect is very low, especially because these impedances are typically small. Therefore, the proposed analytical method is a good tool to obtain an easy and approximate solution for the distribution of currents in these systems, as well as an excellent tool to facilitate the understanding of that distribution.

Distributed consensus-based secondary control of multi-terminal DC railway systems

Electrification of the transportation sector is one of the main pillars of the future decarbonized society. In this context, high-speed railway corridors are expected to reduce as much as possible their environmental impact while maintaining the safety and quality of service with minimum investments. In pursuing those objectives, the multi-terminal DC railway system may become the preferred paradigm. In contrast to conventional AC railway electrification schemes, the multi-terminal DC railway system requires the adoption of a control algorithm to establish suitable references for the power converters. This paper elaborates on a new consensus-based secondary control strategy, which can be implemented in a distributed fashion. In this approach, each power converter controller receives information from its nearest neighbors to adjust its operating point. A 600-km railway system, subject to realistic train traffic, is used to compare the performance of the proposed control strategy with that of purely local controllers. Numerical simulations evidence that the proposed distributed control scheme provides a compromise solution in terms of voltage drops and equalization of power converter loading, surpassing the performance of conventional state-of-the art controllers.

Painstaking Start of Railway Electrification in China: The Baocheng Electrified Railway(1952—1975)

Painstaking Start of Railway Electrification in China: The Baocheng Electrified Railway(1952—1975)

Modal Choice Analysis of Electric Railway Train and Private Vehicle for Travelers in Mangga Dua With Stated Preference Method

Transportation activity is a vital need for urban economic development. Mangga Dua, as a shopping center area and many other commercial points, has been supported by various modes of public transportation, one of which is the Electric Rail Train (KRL). The Bekasi area and its surroundings are a supporter of the transportation and agglomeration of Jakarta. Every day, many Bekasi people use the KRL for mobility activities to various areas covered by the KRL, including Mangga Dua. Even so, many private vehicle users still depend on road infrastructure which causes traffic congestion problems for Jakarta – Bekasi mobility. However, the fact that the Cikarang - Kampung Bandan KRL route is always busy indicates that KRL is still a solution for Bekasi - Jakarta transportation problem that many people choose. This research is intended to determine what factors influence the choice of KRL mode and what factors influence the choice of that mode. The method used is stated preference by collecting primary data using questionnaires from respondents who commute using Cikarang – Kampung Bandan Line. Data processing and analysis were carried out with the help of SPSS software version 16.0. The data processing and analysis results show that the factors influencing the choice of KRL mode are cost-effectiveness, safety, and convenience. Congestion and ease of access are the most influential factors afterward, and the effectiveness of travel time is the last order factor out of 5 factors in the most influential hypothesis. With the result that 71% of respondents chose KRL over motorbikes, it was concluded that KRL as a rail-based mode is a solution to the Jakarta - Bekasi transportation problem.

Improvement of the Electrical Performance of Outdoor Porcelain Insulators by Utilization of a Novel Nano-TiO2 Coating for Application in Railway Electrification Systems

The present study aimed to develop the electrical performance of outdoor insulators using a nano-TiO2 coating for railway electrification systems. The prototype design of porcelain insulators with normal coatings and using a nano-TiO2 coating is based on IEC 60815-1. The first test was performed to measure the low-frequency flashover AC voltage under both dry and wet conditions. In addition, the other test was conducted to measure the lightning impulse critical-flashover voltage at positive and negative polarity under dry-normal and wet-contaminated conditions. X-ray diffraction (X-RD) and Scanning electron microscopy (SEM) were used to examine the micro surface and show that the nano-TiO2 coating was adhered to the surface of the outdoor porcelain insulator and exists in an amorphous state. Additionally, it was observed and discovered that scattered nano-TiO2 strengthens the glassy matrix and creates a sturdy barrier that causes flashover voltage to be reduced under conditions of high dielectric strength. Nanostructured ceramic formulations outperform ordinary porcelain in terms of breakdown voltage strength, particularly for the insulators’ low-frequency flashover performances under dry and wet test conditions. However, a significant change in the lightning impulse critical-flashover voltage characteristics is observed and is not much better when adding the nano-TiO2 coating to the porcelain insulators.

A Comprehensive Perspective of Different Compensators of Railway Traction System

Due to their non-linear load characteristics, train locomotives play a significant part in the installation of railway electrification in India and around the world. Numerous techniques have been researched and used with both AC and DC locomotives to enhance power quality. The development of train locomotives is used in this research to provide a viewpoint on various power quality issues as well as to explore the demand for power quality problems and system requirements for acceptable power quality. The many sorts of compensation schemes are contrasted with one another. this would help academics and engineers working on railway electrification.

An Analysis of DC Electric Field Generated by Electric Railway Considering Constructions

An Analysis of DC Electric Field Generated by Electric Railway Considering Constructions

Investigating the impacts of high voltage powerlines on ground current fields

Stray currents are a typical problem of areas crossed by electric railways. This well-known phenomenon can cause significant damage to all underground metallic installations, especially in case of DC stray currents. In areas close to the railway, the presence of stray currents is expected, and protective measures are applied to all sensitive installations like pipelines. However, field measurements have shown that the presence of high voltage power lines can significantly affect the ground current field due to the well-grounded ground wire representing an excellent alternative path for ground currents. This way, stray currents can appear in areas where the presence of ground current field from DC traction is normally not expected. Preliminary simulations have confirmed that high voltage power lines are a significant element affecting the spreading of ground current and the presence of high voltage power lines must be considered when investigating the ground current field of an area. However, these simulations were performed only for a limited area with a very simplified geometry of railway truck and a single power line. This paper presents results of a more complex simulation involving a large area crossed by a DC railway traction system and a complex high voltage network. The simulation is based on real topology representing an area around the town of Zilina, an industrial area with a complex high voltage network and an important railway hub.

First-Order-Delay-Controlled Slip-Angular Frequency for the Dynamic Performance of an Indirect-Field-Orientation-Controlled Induction Motor-Driving Inertial Load

Sophisticated torque-current control is required in inertial load-drive applications, such as in electric vehicles and electric railway vehicles, over a wide speed range. However, the conventional indirect-field-orientation control (FOC) lacks the current response during the transient response because the conventional feedforward slip-angular-frequency control causes secondary flux fluctuation. Therefore, this article proposes FOC with first-order-delay slip-angular-frequency control, which reduces the secondary flux fluctuation and realizes high-performance torque-current control during transient response. The proposed method was verified through numerical simulation and small-scale model experiments with a 750 W induction motor and an inertial load.

Real Property

This Article covers Real Property cases from Southwestern Reporter (Third) volumes 633 through 652 and federal cases during the Survey period that the authors believe are noteworthy to the jurisprudence on the applicable subject. A number of significant cases, mostly from the Texas Supreme Court, have been handed down during this survey period. The due process requirements for the scope of inquiry for substituted service have been promulgated in MAP Resources. Additional procedural issues for service on financial institutions, which were decided differently by various state and federal courts, were resolved in Moss. The Texas Supreme Court provided helpful guidance on the measurement of consequential damages in Signature, and offered a cautionary tale to practitioners about the drafting of consequential damage waivers in James. In another cautionary tale to practitioners, the Tyler Court of Appeals in Tiner addressed the enforceability of a fixed price 100-year option contract. Likewise, in Rancho Viejo, following guidance from the Texas Supreme Court, the San Antonio Court of Appeals narrowly interpreted a restrictive covenant to allow construction of a solid waste facility. The narrow interpretation of restrictive covenants was again reiterated by the Texas Supreme Court in JBrice. The supreme court has also addressed, in a case of first impression, the issue of implied revocation of an outstanding offer in Tauch. In premises liability cases, it also discussed the “dual capacity” for successor liability in Eagleridge, and the “necessary use” doctrine in Sandridge. The Texas Attorney General issued guidance on the meaning of “person” for purposes of nonjudicial foreclosures. Unfortunately, the limitations period for equitably subrogated lien claims, under Howard I and its prodigy, continued in Howard III. From a governance perspective, the Texas Supreme Court refined the fiduciary duties of directors in the Poe decision. Regulatory takings were addressed in Schrock, but with significant possible changes in jurisprudence raised in the concurring opinions. Additionally, the Texas Supreme Court jumped on the Dallas to Houston highspeed train project in defining an interurban electric railway.

A Train Scheduling for Energy Optimization: Tehran Metro System as a Case Study

Energy efficiency is one of the main issues in designing and operating different electrical systems. Energy-saving in electrical railway systems is an important concern due to the high amount of used energy. In order to find optimum energy consumption, different methodologies shall be examined. In addition, various affecting factors should be determined, and suitable solutions should be adopted. This paper illustrates that proper train scheduling is one of the effective approaches to optimize the system energy. Accordingly, comprehensive modeling is proposed considering different affecting factors such as the slope of different lines, the speed limits in each section, the time limit between the arrivals of trains to each station, and different modes of operation such as motoring and braking. Using the proposed model, an optimization problem with the objective function of energy-saving is solved. To evaluate the effectiveness of the proposed method, the proposed scheduling scheme is applied to Line 2 of Tehran Urban & Suburban Railway Operation Company. Based on the results, using the proposed scheme causes a 3.2% energy-saving compared to the existing train movement schedule in the same line. The proposed train movement scheduling program is proceeding to the last verification steps and will be used as a part of Tehran Metro navigation system in the near future.

에너지 전환에 따른 전기철도의 태양광발전 적용 방안에 관한 연구

The increasing interest of the Nationally determined contributions (NDC) to reduce national emissions has given rise to the need for turning our attention to new renewable energy sources, especially photovoltaic (PV) generation. To evaluate the impact of interconnecting PV and railway systems in Korea Railroad (Korail), this study analyzes the power system configurations and the load characteristics of railway system in Korail. In addition, the impact of System Marginal Price (SMP) variations and renewable energy policies on the introduction of renewable energy in electric railways was analyzed. Also, the PV power generation types applicable to electric railways is presented. Through a case study applied to Korail Line 1 station between Guro and Suwon, economic benefits from the introduction of vertical photovoltaic power generation are analyzed.