Electric Railway Systems Research Articles

Optimal stochastic energy management of electrical railway systems considering renewable energy resources' uncertainties and interactions with utility grid

AbstractSeveral studies have been reported for optimal operation of electrical railway systems (ERSs). However, the stochastic energy management of ERSs, including renewable energy resources (RERs), has received less attention. The RERs’ uncertainties might affect the ERSs. On the other hand, the calculation time of the Monte Carlo simulation (MCS)‐based approaches is an essential challenge, which should be solved, particularly in real‐time decisions and recursive optimization problems. Thus, it is crucial to study the ERSs' stochastic behaviors and uncertainties, including RERs. This paper tries to overcome the discussed concerns and challenges by proposing a novel ERS’s optimal stochastic energy management using clustering algorithms. In this paper, the backward scenario reduction algorithm has been used. In addition, regenerative braking energy (RBE) and energy management systems (ESSs) have been studied. Studying the impacts of changes in the number of passengers on the optimized operation of ERSs and investigating the interaction between the utility grid and the ERS are other contributions of this research. The proposed method is applied to an actual test system of Tehran Urban and Suburban Railway Operation Company (TUSROC). Test results are validated by comparing with available MCS‐based methods. Simulation results illustrate the accuracy and computation time advantages of the proposed method. Simulation results illustrate that <0.6% inaccuracy appears in the proposed method, while it would be 500 times faster than MCS‐based ones. The comparative test results show the advantages of the introduced method.

Droop control operation strategy for advanced DC converter-based electrical railway power supply systems for high-speed lines

Advanced DC converter-based electrical railway power supply systems are very promising power supply configurations for the electrification of high-speed lines. Their full controllable converter-based traction substations along with its continuous catenary, enable the reduction of power quality issues while providing an active power management. However, the power operation performance of these new configurations relies on the development of appropriate control systems. In this sense, this paper introduces a novel operation strategy based on a droop control scheme capable of adapting the power sharing between traction substations without any traffic information. The power operation performance of a simple and complex advanced DC converter-based system following the strategy proposed has been analyzed and compared with the conventional electrification approach. According to the results obtained, the operation strategy presented can adequately control the power flow in the railway grid for both scenarios.

A Review on Power Electronics Technologies for Power Quality Improvement

Nowadays, new challenges arise relating to the compensation of power quality problems, where the introduction of innovative solutions based on power electronics is of paramount importance. The evolution from conventional electrical power grids to smart grids requires the use of a large number of power electronics converters, indispensable for the integration of key technologies, such as renewable energies, electric mobility and energy storage systems, which adds importance to power quality issues. Addressing these topics, this paper presents an extensive review on power electronics technologies applied to power quality improvement, highlighting, and explaining the main phenomena associated with the occurrence of power quality problems in smart grids, their cause and effects for different activity sectors, and the main power electronics topologies for each technological solution. More specifically, the paper presents a review and classification of the main power quality problems and the respective context with the standards, a review of power quality problems related to the power production from renewables, the contextualization with solid-state transformers, electric mobility and electrical railway systems, a review of power electronics solutions to compensate the main power quality problems, as well as power electronics solutions to guarantee high levels of power quality. Relevant experimental results and exemplificative developed power electronics prototypes are also presented throughout the paper.

Sizing Algorithm for a Photovoltaic System along an Urban Railway Network towards Net Zero Emission

A reliable transportation system is essential for the development of a community. Especially in urban transportation, rail transportation is a faster, more comfortable way to travel for the commuters. These benefits can be valued further when the rail transportation system is with zero emissions. Electric trains can be considered a zero-emission transportation method. However, a rail transportation system operates with net-zero emissions when electricity is generated from zero-emission-based sources. Photovoltaic systems have already been integrated into railway stations and spare land owned by railways to achieve net-zero emissions. Furthermore, medium-voltage DC network and microgrid concepts have been proposed to incorporate more renewable energy sources into railway electrification systems. However, the energy generated from those systems is not enough to realise net-zero emissions, as the power requirements of an urban railway electrification system are high. Accordingly, this article investigates the possibility of implementing a photovoltaic system along the railway tracks to meet the energy demands of an urban railway electrification system so that net-zero emissions can be achieved. Other significant advantages of the proposed photovoltaic system are lower feeder losses due to distributed photovoltaic systems integrated into the railway electrification system, lower conversion losses due to the direct integration of the photovoltaic system into the railway electrification system, and the nonrequirement of additional space to install the photovoltaic system. In this paper, a photovoltaic system capacity sizing algorithm is proposed and presented by considering a railway electrification system, the daily schedule of trains, and historical photovoltaic weather data. This proposed photovoltaic system capacity sizing algorithm was evaluated considering a section of the urban railway network of Sri Lanka and a three-year, 2017-2020, photovoltaic weather data. The results indicated that the potential for photovoltaic generation by installing photovoltaic systems along a railway track is much higher than the requirement, and it is possible to meet the required train scheduling options with proper sizing. Furthermore, in the three-year analysis, it is possible to achieve 90% of the energy required for the railway electrification system with effective train scheduling methods.

Optimal operation and simultaneous analysis of the electric transport systems and distributed energy resources in the smart city

Today due to population growth as well as air pollution and lack of energy many countries are motivated to use technology to provide services and solve city problems. The idea of a smart city allows to interact directly with urban infrastructure and monitoring whatever that happens and is in progress. A smart city is a city, based on information and communication technology. In this paper, optimal operation of electrical transportation system and energy distribution resources has been studied. The major energy consumption systems in a smart city are electrical transportation systems such as Electric Vehicles in power systems and Electric Railway systems. Analyses the interaction of an interconnected systems using a linear model for co-optimization planning and operation of subway system. For optimal operation of the smart city, an optimization problem that minimizes the total cost of all the energy systems and maximizes the Regenerative Braking energy to recover subway is solved. In this paper, considering the electric vehicles such as vehicle to Grid and Subway technology located in the special depot, the traffic and length of the routes are modeled. Based on degradation model has been presented to rise battery life of Electric vehicles. Also, a machine learning technique based on the long short-term memory (LSTM) is used to forecast the hourly solar radiation and wind speed. To depict the uncertain behavior of electric vehicles, electric transportation system and loads in smart city, Point Estimate Method, as a stochastic framework is suggested. All in all, using uncertainty and deterministic method the proposed model is analyzed.

Impacts of Quadrature Signal Generation-Based PLLs on Low-Frequency Oscillation in an Electric Railway System

The low-frequency oscillation (LFO) issue has occurred frequently in single-phase electric train and traction network interactive systems (hereinafter train-network systems). On a single-phase electric train, the quadrature signal generation-based phase-locked loop (QSG-PLL) has been widely used to achieve unit power factor operation. The bandwidth of the single-phase PLL is close to the frequency of the LFO, but its impacts on the LFO are not considered fully in previous works. In this article, three typical QSG-PLLs are studied in depth, and their unified model is derived in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> frame. Furthermore, the impacts of the QSG-PLL structure and parameters on the LFO are revealed. The analysis results indicate that the QSG part plays an important role in the LFO analysis, but the parameters of the PLL part have slight impacts on the train’s impedance under the low-power operation mode. Three different QSGs can all be regarded as providing a second-order low-pass filter (LPF) to generate the virtual <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> component in the single-phase system. The higher damping ratio of the second-order LPF can increase the magnitude of the train’s impedance, which is beneficial to enhance the stability of the train-network system. Finally, experimental results via hardware in loop (HIL) are employed to verify the correctness of the theoretical analysis results.

P213 - RF-EMF exposure levels in municipal waste collection service and ELF-EMF exposure levels at the electric railway system of Greece

P213 - RF-EMF exposure levels in municipal waste collection service and ELF-EMF exposure levels at the electric railway system of Greece

전류 위상각 차이를 이용한 교류 전기철도 급전계통의 급전선 지락 고장 유형 판별법

When a fault generates on AT feeding line of AC electrical railway system, train operation service would be stopped on about 10km feeding line section at both ends of Auto-transformer. When a fault generates on AT feeding line of AC electrical railway system, train operation service would be stopped on about 10km feeding line section at both ends of Auto-transformer. To obtain varied information is important to take a action for a rapid restoration of AT feeding line. In this paper, it presents how to distinct type of ground fault using measured fault current based that angle of TF and AF current are almost in-phase in case of TF-R ground fault and almost antiphase in case of AF-R ground fault. The distinction method is verified on PSCAD/EMTDC simulation and real field of AT feeding line.

Control system design of a low‐frequency‐switchingsingle‐phase four‐quadrant PWMconverter

This work is focused on the control of low-frequency-switching single-phase four-quadrant pulse width modulation (PWM) converters used in grid-connected modern power electronics applications. The switching frequency is chosen to be lower than that used in industrial applications in order to use the designed control system in high-power applications such as railway electrical traction systems. The control system is designed under three main headings: grid synchronization, input current control, and voltage control, where grid synchronization is achieved by a single-phase phase-locked loop (PLL). The current loop is designed by using a proportional-resonant (PR) controller, and the classical proportional-integral (PI) controller is employed in the voltage control loop. The parameters of the PI controller are determined by using the coefficient diagram method (CDM). The control system is modelled as a discrete-time system to get the response closest to the actual system and to be easily implemented on the TMS320F28335 DSP platform. The performance of designed control system is tested on a 30-kW single-phase PWM converter test set-up, and experimental results show that bidirectional power flow, sinusoidal input current, power factor correction, and constant output voltage are achieved. This study is aimed to be a guide for the designers, from the selection of converter passive elements to controller design and experimental verification.

Corrosion mechanism and damage characteristic of steel fiber concrete under the effect of stray current and salt solution

Steel fiber reinforced concrete (SFRC) has been widely used in construction and transportation due to its superior mechanical properties. From the perspective of structure, SFRC is a potential solution to the problem of stray current induced corrosion in electrical railway systems. However, the corrosion mechanism of SFRC under the coupling effect of stray current and salt solution is not clear, and the change of mechanical properties in the process still lacks a quantitative description, so it is difficult to predict the structural life. In this paper, different corrosive media were selected for the stray current induced corrosion test of SFRC, in which the chloride concentration was adjusted to study its influence on the corrosion rate. Ultrasonic and electric current were combined to monitor the corrosion process. The colorimetric and titration method were used to measure the chloride depth and concentration in the specimen after corrosion, mercury intrusion porosimetry was employed to determine the pore structure. It is found that chloride is the most destructive to SFRC and dominates the corrosion process, while sulfate and caustic alkali contribute secondary effect. Chloride destroyed the passive film on the surface of the steel fiber and corroded it to form a local rust expansion area, causing concrete damage and reducing mechanical properties. In addition, if the damage degree reaches 0.3 ∼ 0.4, the structure will be destroyed. When the environmental chloride concentration reaches the threshold 0.6 mol/L, the higher the concentration, the faster the SFRC corrosion. The quantitative relationship between the main influencing factors (concentration of chloride, corrosion time and chloride penetration depth) and damage degree is proposed based on the experimental data. The research may provide reference for the application of SFRC in electric railway projects.

Equivalent load estimation method for determining railway power requirements under extended feeding conditions using a simplex algorithm

Electric railway system substations (S/Ss) extend the power supply distances under extended feeding conditions to maintain continued service in the event of a failure in an adjacent S/S. Accurate load modeling is thus required to design realistically the capacity of a subway S/S in consideration of the extended feeding conditions. However, it is difficult to measure accurately or predict the amounts of active and reactive power consumed by the load and the location of the load owing to the nature of the moving train load. Therefore, in this paper, we propose an algorithm to estimate the net supplied power accurately from the viewpoint of the S/S over a specific time interval. The algorithm first estimates the power consumed by the load and the location of the load based on actual measured data under normal power supply conditions. Then, the electric train load state estimated in the power-supplying section of each S/S can be used to simulate the system with extended feeding conditions—which is challenging to evaluate and verify in the field—through software-in-loop simulations.

AT급전방식 통합접지시스템의 주파수별 접지임피던스 특성 분석

This paper, when lightning current flows into the AT electric railway power feeding system, the ground impedance characteristics according to the length of the buried earth wire and the earth resistivity are analyzed and presented. Due to the increase in accidents caused by lightning and surges in the electric railway operation section, the need to review the grounding impedance of the electric railway integrated earthing system is increasing. The grounding system currently applied to the electric railway operation section has been considered in terms of preventing electric shock to the human body and protecting facilities in the event of a ground fault or short circuit in a commercial power supply of 60[Hz] band. Recently, electronicization of signal and communication facilities installed around railway tracks, high-quality power supply is required. Therefore, the need for technical analysis on ground impedance and transients in high-frequency bands is increasing. The ground impedance is an important factor that distinguishes the characteristics of the AT electric railway integrated earthing system.

Integration of Distributed Energy Resources and EV Fast-Charging Infrastructure in High-Speed Railway Systems

Low carbon emission transportation is attracting global attention where electric railway power systems (ERPS) and electric vehicles (EVs) act as a load. Besides the main utility grid, renewable energy sources (RES) including photovoltaic (PV) panels and wind turbines are implemented to supply the loads fully or partially. In this paper, a novel smart DC catenary system is proposed in which renewable sources, storage systems, and DC fast-charging stations are connected to the overhead DC catenary line of the high-speed railway power system. The generated power from renewable sources and consumed power by charging stations are processed by their dedicated DC-DC power electronics converters. Furthermore, a storage system is used as a backup system not only for the case of blackouts but also because of the intermittent nature of renewable energy sources to supply the loads continuously. The paper presents an optimal power control for various parts and a power management system (PMS) that manages the power flow from wind-PV-storage system to EV-ERPS system. The proposed system has been investigated using a real Italian Rome-Florence 3 kV high-speed line as a case study with real data of ERPS load. The EV fast-charging station power demand, wind speed, solar irradiance, and temperature were recorded for 24 h in order to provide us with realistic output data. The simulation results obtained by MATLAB/Simulink are presented to validate the effectiveness of the proposed system.

Vehicle-to-Grid (V2G) as line-side energy storage for support of DC-powered electric railway systems

Two predominant areas of ongoing transport electrification are the uptake of electric vehicles (EVs) in personal transportation and electrically powered trains for mass transportation - both significantly increase demand stresses on the electric power grid. In this research, a novel V2G application to support electrically powered rail transport is proposed. A local V2G network can reduce peak demand stresses on the power grid arising from electrified rail traffic and enable brake energy recovery from DC-powered electric trains. A case study examining an existing third-rail DC-powered rail system in England supported by a simulated population of aggregated parked EVs is presented. Simulation results for 24 h of V2G supported rail traffic from the view of a single train station with nearby V2G enabled car park are discussed. Therein the EV population size, charging rate limits per EV and the overall power made available from the power grid are variables. The V2G network's ability to absorb power from regenerative braking on the rail system was found to be more sensitive to changes in EV charging rates than its ability to provide traction power. In particular, careful power management is required to avoid charging EVs ‘too quickly’ during periods without rail traffic.

Analysis of rail potential and stray current in MVDC railway electrification system

In contrast to the conventional direct current railway electrification system (DC-RES), the medium voltage direct current (MVDC)-RES is considered promising for long-distance high-speed corridors. In the MVDC-RES, traction substations (TSSs) are placed much farther and train loads are much heavier than in the conventional DC-RES. Hence, the MVDC-RES brings a drastic change in catenary voltage, TSS spacing, and train loading, which affects rail potential and stray current. In this connection, this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment. An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario. According to the simulation and analysis, the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.

Development of Scott Transformer Model in Electromagnetic Transients Programs for Real-Time Simulations

This paper presents a Scott transformer model to be applied in electromagnetic transients (EMT) programs, particularly in the absence of a detailed Scott transformer model for performing real-time simulations (RTS). Regarding a Scott transformer, a common topology for converting a three-phase network into two single-phase networks, the transformer model in EMT programs is essential to simulate large-scale electric railway systems. A code-based model has been developed to simulate the transformer in RTS directly and contain the transformer’s actual impedance characteristics. By establishing a mathematical foundation with the current injection method, we presented a matrix representation in conjunction with a network solution of EMT programs. The proposed model can handle more practical parameters of Scott transformers with a relatively low computational load. Thus, it supports the flexible computation of real-time simulators with a finite number of processor units. The accuracy of the model is verified by simulating it and comparing the simulation results with an industrial transformer’s certified performance. Furthermore, a case study involving a comparison of the results with the field measurement data of an actual Korean railway system demonstrated the efficacy of the model.

Correction to: PSO-Based Initial SOC and Capacity Optimization for Stationary Energy Storage Systems in DC Electric Railway System

Correction to: PSO-Based Initial SOC and Capacity Optimization for Stationary Energy Storage Systems in DC Electric Railway System

PSO-Based Initial SOC and Capacity Optimization for Stationary Energy Storage Systems in DC Electric Railway System

PSO-Based Initial SOC and Capacity Optimization for Stationary Energy Storage Systems in DC Electric Railway System

Improving the efficiency of the railway electric power system

The railway productivity can be increased by increasing the efficiency of the electric power system, the main elements of which are traction substations, overhead contact systems and electric locomotives. The paper analyzes the technical infrastructure of the electric power system of the railway and evaluates the energy efficiency of the equipment. To assess the energy efficiency of the system elements, the revised law of conservation of energy in the electromagnetic field, spectral analysis of electrical quantities and mathematical computer modeling of electromagnetic processes in the system are used. The proposed energy characteristics of the elements of the electric power system made it possible to determine the reasons that hinder the further development of the throughput and carrying capacity of the railway. In order to eliminate the negative impact of inductive resistance of the system elements on the energy indicators of the traction supply and the AC electric rolling stock, the feasibility of the use of high voltage DC electric traction has been proved. Through the complete and continuous use of the voltage of the electricity system for electric traction, it is possible to ensure movement in the intersubstation zone of three linked multiple trains instead of one and increase the speed of trains by 20%. Using high-voltage direct current, the efficiency of electric traction of trains can be in-creased by 7% compared to electric traction of trains using alternating current by reducing the current by 40% in the overhead contact system.

Harmonic Mitigation in Electric Railway Systems Using Improved Model Predictive Control

An electric multiple unit (EMU) high-speed train is the dynamic load that degrades the power quality in an electric railway system. Therefore, a power quality improvement system using an active power filter (APF) must be considered. Due to the oscillating load current in the dynamic load condition, a fast and accurate harmonic current-tracking performance is required. As such, this paper proposes the design of a model predictive control (MPC) since the minimization of cost function in the MPC process can suitably determine APF switching states. The design technique of MPC is based on the APF mathematical model. This controller was designed to compensate the time delay in the digital control. Moreover, the synchronous detection (SD) method applied the reference current calculations, as shown in this paper. To verify the proposed MPC, the overall control of APF was implemented on a eZdsp F28335 board by using the hardware-in-the-loop technique. The testing results indicated that the proposed MPC can provide a fast and accurate harmonic current-tracking response compared with the proportional-integral controller. In the load changing condition, the MPC was still effective in providing a good result after compensation. The percentage of total harmonic distortion, the percentage current unbalance factor, and the power factor would also be kept within the IEEE Standard 519 and IEEE Standard 1459.