Traction Power Substation Research Articles

Localization Method for Insulation Degradation Area of the Metro Rail-to-Ground Based on Monitor Information

Since rail-to-ground insulation decreases, large-level direct currents (DCs) leak from railways and form metro stray currents, corroding the buried metal. To locate the rail-to-ground insulation deterioration area, a location method is proposed based on parameter identification methods and the monitored information including the station rail potentials, currents at the traction power substations (TPSs), and train traction currents and train positions. According to the monitoring information of two adjacent TPSs, the section location model of the metro line is proposed, in which the rail-to-ground conductances of the test section are equivalent to the lumped parameters. Using the rail resistivity and traction currents as the known information, the rail-to-ground conductances are calculated with the least square method (LSM). The rail-to-ground insulation deterioration sections are identified by comparing the calculated conductances with thresholds determined by the standard requirements and section lengths. Then, according to the section location results, a detailed location model of the degradation section is proposed, considering the location distance accuracy. Using the genetic algorithm (GA) to calculate the rail-to-ground conductances, degradation positions are located by comparing the threshold calculated with the standard requirements and location distance accuracy. The location method is verified by comparing the calculation results under different degradation conditions. Moreover, the applications of the proposed method to different degradation lengths and different numbers of degradation sections are analyzed. The results show that the proposed method can locate rail-to-ground insulation deterioration areas.

Integrated procedure to design optimal hybrid renewable power plant for railways’ traction power substation

The paper suggests a 3-steps methodology, integrated in a unique-procedure, to optimally design a hybrid RPP (Renewable Power Plant) to be installed in the available areas of railway’s power plants. The procedure takes into account power profiles and time schedule of trains, traction line’s features, sizing and siting of TPSSs (Traction Power Substations) and features of renewable sources as PV (Photovoltaic) and wind turbines for optimizing the siting of the RPP, considering the investment convenience. The optimal sizing of a hybrid power plant is based on mixed-integer linear programming (MILP) taking into account the energy absorbed by TPSSs, the physical and geometric constraints and the operating and maintenance costs of RPP. The integrated procedure has been tested on a real case study regarding a new 3 kV DC railway located in the South of Italy. The main results show that a hybrid RPP with 4980 PV panels and 3 wind turbines installed in a TPSS area, adopting a capital cost of 645,000 €/MW for PV panels and 3000 €/kW for wind farms, ensures an annual revenue of 227,439 €, with a total investment of 897,400 €. Results show that the available areas in TPSS should be the target of relevant investments to support a new sustainable and green power traction supply system.

Analysis of the Timetable Impact on Energy Consumption of a Subway Line

This paper analyzes the timetable impact on the energy consumption of a subway line. In most timetable studies, simplified models are used and can lead to misestimation of the braking energy and thus the energy transfer between braking vehicles and accelerating vehicles. In this paper, specific attention is paid to the models of the vehicles, the traction power substation, and the rail supply network to enable an accurate estimation of the energy consumption. The energetic macroscopic representation formalism is used to organize the models of the subsystems so they have the right interactions. The developed model is validated by experimental tests on a real subway line. The error on the global energy consumption is lower than 2.2%. The model is then employed to examine the influence of the vehicle time interval on energy consumption. A 10-second adjustment in this time interval can result in a substantial 22% decrease in energy consumption for the analyzed real subway line.

Разработка мероприятий по устранению резонансных явлений на частотах высших гармоник на линии электропередачи 35 кВ

One of the problems to ensure the quality of electricity and reliability of the network is significant deviation of the voltage curve from sinusoidal in some active electricity transmission lines of the energy system of the Irkutsk region. The purpose of the research is to develop organizational and technical measures to eliminate resonance phenomena at higher harmonics that occur in the active 35 kV electrical line connected to a traction power substation. The object of the research is non-sinusoidal mode of the 35 kV electric power transmission line connected to the medium voltage winding of the three-winding traction transformer. The authors have used technological research methods of calculation using an equivalent circuit of the existing linear circuit of an electrical power system with a traction substation. The software “Calculation program of non-symmetric and non-sinusoidal modes of the electric power system” and Microsoft Excel are used for the research. The authors have developed a 110–35–10 kV “Consumer 1 – Consumer 2 – Consumer 3” model using the software “Calculation program of non-symmetric and non-sinusoidal modes of the electric power system”. The calculation results are processed using Microsoft Excel. Non-sinusoidal electrical modes of the equivalent circuit of the electrical power system and the power transmission lines are calculated. Calculation of non-sinusoidal modes of a 35 kV line is carried out to show the distribution of higher harmonic voltages along the line. It is established that the quality indicators of electricity in terms of non-sinusoidal voltages in most nodes of the 35 kV power transmission line do not comply with GOST 32144-2013. Calculation and analysis of non-symmetric and non-sinusoidal modes of the network have shown resonance voltage increase along the line on the odd harmonics frequencies and elimination of resonance factor when installing the compensation reactor at the beginning of the 35 kV line. Based on the calculation results, the diagrams of harmonics power-voltage curve from 3 to 39 are compiled. Based on the results obtained, the authors have proposed technical measures such as installation of a compensation reactor at the beginning of the electrical power system line to prevent resonance factor to improve the electrical power quality in terms of voltage unsinusoidality in the consumers busbars connected to the 35 kV line. The proposed measures will improve the electrical power quality in busbars of consumers and satisfy the requirements of GOST 32144-2013.

Comparison of regenerative braking energy recovery of a DC third rail system under various operating conditions

Conducting simulations prior to real-world testing is essential for the planning and development of rail systems. However, accurately representing the train trajectory characteristics resulting from the railway power system and the dynamic load changes based on the train position can be challenging. The power exchange between trains and the fluctuating rail resistance between them add to the computational complexity. Given these challenges, the aim of this study is to develop a comprehensive model of DC third rail systems based on the operational requirements and parameters of the MRT Line 2 Malaysia. Moreover, the simulation method should be adaptable to investigate potential energy savings through regenerative braking systems, thereby maximizing the energy efficiency of electric railways. This study outlines the development of a framework that models the power flow within an electric rail network using a specific case study example. A simulation is presented with 15 trains operating on a double rail track to validate the model for multiple train operations. Notably, the simulation methodology developed in this research is unique compared to other approaches found in relevant literature. It integrates both the power system and train trajectory, incorporating actual system information from a practical DC third rail system to generate precise trajectory outcomes. The results show that implementing a regenerative braking energy recovery system in all traction power substations (TPSSs) has the potential to achieve significant electrical energy savings of up to 55.75% for the entire system.

Balancing the Active Power of a Railway Traction Power Substation with an sp-RPC

The railway system is one of the safest, most efficient, and environmentally friendly means of land transport for people and goods. However, as the demand for mobility has increased, the current railway system has shown some weaknesses, requiring an increase in catenary power in order to be able to supply power to longer trains and faster locomotives, as well as to increase rail traffic. This paper proposes a control algorithm to be implemented in a sectioning post-Rail Power Conditioner (sp-RPC). The sp-RPC is connected to the neutral section between two traction power substations (TPS). With the control algorithm, it is possible to minimize the existing unbalance of the active powers of each TPS. In a regenerative braking condition, this surplus energy can be used to assist the traction of another locomotive on the existing overhead line. In this way, it is possible to increase the capacity of the overhead line. The analysis was performed with computer models using a modular multilevel converter (MMC) topology for the sp-RPC. Quantitative results for different consumption events of the locomotives and the analysis of the response to these variations are presented.

Dynamic stray current evaluation model of metro system considering reversible DC traction power system

ABSTRACT Stray current of DC metro system will accelerate metal corrosion. Therefore, it is necessary to evaluate it. With the application of inverter feedback devices in recent years, stray current is more complex due to the DC traction power system is reversible. To evaluate stray current more accurately, the dynamic evaluation model is proposed in this paper. Firstly, traction power substation (TPS) is equivalent to controlled source, considering the diverse operating characteristics. Based on this, the dynamic evaluation model is built with multiple trains running and TPSs operation. Then, considering the nonlinear and multivalued function characteristics of TPS, the solution method is proposed. The problem of slow convergence or even non-convergence in the stray current solving process of the metro system considering reversible DC traction power system is solved. The model is validated by the field test data. Finally, the model is used to obtain dynamic stray current. Result shows that stray current level tends to be higher as traction trains and braking trains run separately and concentratedly in different areas of the line.

Optimal Motion of a Rolling Stock Fleet Under Traction Power System Constraints

The operators of the railway industry [i.e., traction system operator (TSO) and railway system operator (RSO)] are currently involved in a major process of energy transition. Aimed at improving both environmental sustainability and energy efficiency, technological infrastructures are being updated and new operating solutions are studied. Moreover, the business opportunities offered by the new rail market are forcing operators to search for power quality solutions. In this article, an efficiency strategy is proposed for optimally moving a fleet of trains while taking power quality indices into account. A method to relate the traction power requirements to the electrical variables of the railway infrastructure is formulated in terms of the power flow approach. Our numerical simulations focus on the real case of Metro Line 1 in the southern Italian city of Naples. The energy problem of moving the trains on the track is solved by including a set of constraints at the point of common interaction between railway market operators. Specifically, repetitive train starts and their speed profiles are optimally managed in terms of power requirements at traction power substations (TPSs) using power quality constraints. This strategy allows improvements in energy efficiency without compromising the quality of the railway service.

LCL-filter design and analysis for PWM recuperating system used in DC traction power substation

Voltage source inverter (VSI) had been used in dc traction power substation to deliver the trains braking energy back to the utility grid. To mitigate low order harmonics components, pulse-width-modulation (PWM) technique is commonly used in VSI controlled. As a result, the ac voltage and current waveforms may contain high frequency ripples. This paper proposes to mitigate the high frequency harmonics using LCL-filter with series <em>R</em>-damper. This filter offers good attenuation on harmonics with smaller size compare to other passive filter topologies. Theoretical analysis and simulation verification are conducted in designing the proposed filter. System level simulation had also been carried out. Sinusoidal grid current and voltage waveforms are recorded (THD<2%). This paper also includes damping losses analysis in conjunction with resonance peak suppression in designing the <em>R</em>-damper.

Подбор силовых трансформаторов с разными напряжениями короткого замыкания для параллельной работы

Parallel operation of transformers (TR) is one of the key solutions for improving the reliability of power supply, production, traction power substations, port production capacities. TR operation influences the cost effectiveness of different cycles of equipment operation and no-load losses when the equipment is not operated. Creating the most economical cycle of operation of the entire port infrastructure is considered, which will ensure not only the equipment operation, but also maintainability with trouble-free power supply cycle. TR operation requires the precise calculation and necessary conditions for switching, which allows to conduct prompt repair of equipment, proper control of the operation of each TR and each node separately. A complete shutdown of equipment with its further conservation during the period when the equipment is not needed is found possible. There were carried out calculations for the TR parallel operation, which prove the economic benefits of TR parallel operation. Some formulas are derived from the theoretical foundations of electrical engineering. Many calculations present the empirical studies in the field of transformer engineering and power networks. Practical solutions are summarized in tables, where TR options with different passport data are presented. There has been found which of the TRs on the market meet the condition of parallel connection. There are considered the TRs most convenient for gaining the required power. The research results can facilitate the choice of TR when designing new power supply sections and upgrading existing ones. It has been stated that the TR models designed for operation in difficult geoclimatic conditions, on the offshore platforms, in zones of extreme cold and high temperatures are not presented. TR of this design require a separate study due to the specific working conditions.

Traction power substation balance and losses estimation in AC railways using a power transfer device through Monte Carlo analysis

The high dynamic power requirements present in modern railway transportation systems raise research challenges for an optimal operation of railway electrification. This paper presents a Monte Carlo analysis on the application of a power transfer device installed in the neutral zone and exchanging active power between two sections. The main analyzed parameters are the active power balance in the two neighbor traction power substations and the system power losses. A simulation framework is presented to comprise the desired analysis and a universe of randomly distributed scenarios are tested to evaluate the effectiveness of the power transfer device system. The results show that the density of trains and the relative branch length of a traction power substation should be considered in the evaluation phase of the best place to install a power transfer device, towards the reduction of the operational power losses, while maintaining the two substations balanced in terms of active power.

DC traction power substation using eighteen-pulse rectifier transformer system

<span lang="EN-US">Twelve-pulse rectification system had been widely integrated in today’s DC traction power sub-station (DC-TPSS). This configuration had successfully mitigated low order harmonic distortion. As some research findings had confirmed that the dc voltage and current ripple factors may further minimize by increasing the number of rectification pulses to 18, 24, or 36. This paper had presented a simulation study to investigate the prospect of implementing an eighteen-pulse rectification system in a DC-TPSS. The theory of phase-shifting transformer used to produce an 18-pulse rectifier is presented with simulation verification. Simulation result shows that 3.69% of grid current distortion index is recorded without installing any filters. In addition, the dc voltage and current ripple may also be further reduced for about 30% compared to a conventional twelve-pulse rectification system.</span>

Electrical Railway Dynamical Versus Static Models for Infrastructure Planning and Operation

Simulation tools are essential to design the infrastructure and plan the trains operations of electrical railway systems. Traditionally, the train model (that estimates the electrical, mechanical and kinematical behaviors of the vehicles) and electrical network model (that estimates the electrical behavior of the energy supply network) are developed separately. Then, they are simulated together to estimate the interactions between both subsystems. The paper objective is to compare different models to highlight the impacts on the interactions between the vehicles and the railway electrical network, which are crucial to have accurate estimations of the system behavior. For this purpose, a new dynamical model, which is based on a systemic approach and a causality analysis, is compared to a conventional static model, which is based on a cartesian approach and a power flow analysis. The dynamical model is accurate and has been experimentally validated but requires a long computational time. The static model is fast to compute and give a good estimation of the energy consumption for conventional railway systems. However, it is not always able to estimate the power flows within the DC network, and especially when all traction power substations are blocked.

Analysis on Rail Potential Distribution Characteristics Considering OVPD in Metro System

By the field investigation of the metro system, it is found that there is relatively serious corrosion in the terminal of the metro line, and overvoltage protection device (OVPD) often operates when the metro system is in the valley level. In order to analyze the causes of these conditions and alleviate the related problems caused by high rail potential. In this paper, establish a simulation model of metro system by CDEGS software, and consider the influence of the track-to-track cross bond on rail potential. It is analyzed that the causes of high rail potential in the terminal of the metro line and high rail potential operating small number of trains in the metro line. And it is analyzed that the influence on the rail potential of metro line, the influence on OVPD outside the power supply section, the influence on the station grounding gird where the OVPD is, caused by OVPD operation. The results show that the rail potential can be reduced to some extent by setting the track-to-track cross bond. No traction power substation (TPS) in the terminal of the metro line increases the rail potential. When the braking train supplies power to the accelerating train outside the power supply section in the metro line, the rail potential of some part of the line increases. The OVPD operation increases the ground potential around the station grounding gird, and may lead to the continuous operation of other OVPD in the metro line.

Comparison of Energy Recovery Solutions on a Suburban DC Railway System

Conventional dc railway systems are usually supplied by nonreversible traction power substations. This means that regenerative braking energy cannot be sent back to the electric power grid. Therefore, this energy can only be sent to nearby consuming trains or be burned by the rheostatic or mechanical brakes. However, due to the low service frequency and the manual driving control in some suburban sections, trains synchronization is not always possible, and most of the braking energy is lost. Thus, there is great potential for energy recovery. This could be achieved with the addition of energy recovery devices. In this article, a dc railway system is modeled and simulated to compare the benefits of a reversible substation and two energy storage systems (wayside and onboard). Then, the model is validated with real measures taken on a French railway system. Finally, the simulation is used to compare the benefits of adding each device on a suburban section. Results show a reduction of up to 30% of the total supplied energy.

Dual-loop generalized predictive control method for two-phase three-wire railway active power quality controller

One of the most challenging topics in electric railway networks (ERNs) is power quality (PQ) problems caused by single-phase feeding of time-varying and high-power locomotives. During previous years, many techniques and compensators have been offered to alleviate these problems. Railway active power quality controller (RAPQC) is considered as one of the most efficient approaches. Due to the time-variant, uncertainty and distorted features of ERNs, the controlling of RAPQCs has always been a substantial concern to experts. This paper presents, a new robust control system for two-phase three-wire RAPQC (ThRAPQC) based on generalized model predictive control integrated with modified instantaneous reactive power theory (GMPC-MIRP). A dual-loop balancing system has been adopted in the proposed control system to equalize the active powers of traction power substation (TPSS) adjacent feeders, compensate reactive powers and suppress harmonic simultaneously. The performance of the proposed method in comparison with the conventional Fryze-Buchholz-Depenbrock (FBD)-based current strategy together with hysteresis current controller (FBD-HCC) has been evaluated through the detailed simulations and Opal-RT 5600-based laboratory setup results. The fast response, high precision, lower fluctuation in reference current tracking and high capability of working in distorted conditions are the outstanding privileges of the proposed method that are confirmed by the output results.

Traction Power Substation Load Analysis with Various Train Operating Styles and Substation Fault Modes

The simulation of railway systems plays a key role in designing the traction power supply network, managing the train operation, and making changes to timetables. Various simulation technologies have been developed to study the railway traction power network and train operation independently. However, the interactions between the load performance, train operation, and fault conditions are not fully understood. This paper proposes a mathematical modeling method to simulate the railway traction power network with a consideration of a multi-train operation, driving controls, under-voltage traction, and substation fault modes. The network voltage, power load demands, and energy consumption according to the existing operation are studied. The hotspots of the power supply network are identified based on an evaluation of the train operation and power demand. The impact of traction power substation (TPSS) outage and a short circuit on the power supply network have been simulated and analyzed. The simulation results have been analyzed and compared with those of a normal operation. A case study based on a practical metro line in Singapore is developed to illustrate the power network evaluation performance.

Impact of Railway Energy Efficiency on the Primary Distribution Power Grid

Electrified railway systems are the current focus of energy efficiency studies due to the increasing constraints of environmental sustainability policies. Railway System Operators (RSOs), also encouraged by market deregulation, are thus examining how to update infrastructures and vehicles and/or apply new operating strategies. Given the intrinsic relation between railway systems and their primary feeding grid, each measure applied to a railway system impacts directly on the power grid which supplies the system. Against this background, this paper aims to ascertain the impact of an energy efficiency strategy applied by the RSO system on its primary grid. The energy-efficient strategy is identified as to preserve timetable stability and service quality in a passenger-oriented perspective. Moreover, a method to model the interaction between the systems in terms of power flow exchanges is proposed. The model is used to verify how an eco-driving technique applied to a metro system affects the state variables of the distribution grid. In particular, the primary grid, the traction power substations and the railway system are modelled according to real data. The case study is the Metro Line 1 operating in the city of Naples (Italy). The numerical simulations are carried out with a two-step procedure: first, the power requirements of the rolling stock as a function of the imposed operating service are calculated by OpenTrack® software; the state variables of the distribution grid are then evaluated by means of the power flow approach.

Design a nine-level modular multilevel converter for DC railway electrification system

<p>A recuperating converter is highly demanded in traction power substation to deliver the braking energy generated by a traction vehicle. Conventional voltage source inverter had been implemented in the traction power station. However, large ac line filters must be installed to improve the quality of ac voltages and currents. This paper proposes to install a nine-level Modular Multilevel Converter (MMC) as a recuperating converter. The main aim is to eliminate the need of ac line filters while producing good quality of ac voltage and current waveforms. The MMC is designed and modelled using MATLAB/Simulink Simulation tool. A centralized control of balancing all the sub-module capacitor voltage level is proposed with Third Harmonic Voltage Injection Level Shifted Pulse Width Modulation (THVI-LSPWM) technique. The simulation results prove that with the application of MMC, good quality of ac voltages and currents are being produced. The Total Harmonic Distortion indexes are found less than 3.5 % without using any ac line filters in the system. In addition, the classic DC link capacitance has also being eliminated. </p>

Infinitesimal Method Based Calculation of Metro Stray Current in Multiple Power Supply Sections

The calculation of rail potential and stray current in the DC traction power system can guide the protection against the rail overvoltage problem and mitigate the electrolytic corrosion due to stray current. To obtain the accurate stray current distribution, the infinitesimal method based calculation of metro stray current in multiple power supply sections (PPSs) is studied in this paper. The through-type structure characteristics of power supply system and that of return current system which is constituted of rails - stray current collection mats - tunnel reinforcements - ground (RSTG) are considered in the proposed calculation method. In the traction power supply system, the currents injected into the rail by train, and absorbed by traction power substation (TPS) or regeneratively braking train, are solved by the power flow calculation which considers stray current. In the return current system, these currents are used as the boundary conditions for stray current calculation. Then the rail potential and stray current in multiple PPSs are solved by the infinitesimal method. The verification result shows that the proposed calculation method can effectively calculate the rail potential and stray current in multiple metro PPSs. At last, the novel calculation method is used to gain the dynamic stray current along the metro line and evaluate the influence factors of stray current.