kV DC Traction Research Articles

Testing Algorithms for Controlling the Distributed Power Supply System of a Railway Signal Box

Trends in the use of renewable energy sources to power buildings do not bypass objects for which maintaining a power supply is critical. This also applies to railway signal boxes. The aim of the research work was to test the multisource power supply system for a railway signal box with power electronic converter systems and a DC bus, built as part of the research project. The assumption for powering the railway signal box building was to use renewable sources, energy storage devices, and a 3 kV DC traction network as the second required power supply grid. Both power grids were connected by power electronic converters, and the power values of the converters were set based on the calculated power balance values using the values measured at the system nodes and the set constraints. The tests primarily tested the response of the power supply system to changes in load power and power generated by the photovoltaic source, as well as the charge level of the energy storage devices. The correctness of the control algorithm’s operation was assessed based on the recorded power values in the power supply system nodes. The tests were carried out for 60 scenarios that covered all normal and emergency operating conditions. During the tests, delays in response to changes in the power supplied to the converters and the values of circular power flow between the power grid connections were recorded. The recorded delays ranged from 2 to about 50 s and the circular power flows did not exceed 1500 W. Based on the results of the tests, it was found necessary to improve the power measurement system in the power supply system nodes and to improve the quality of communication and the transmission time of measurement data transmission time.

Cost‐effective upgrade of the Dutch traction power network: Moving to Bi‐directional and controllable 3 kV DC substations for improved performance

AbstractTraction power networks can significantly influence a country's national grid due to their significant power consumption and numerous coupling points. To modernise the ageing Dutch traction power networks and enhance their impact on the utility grid, this study explores practical and cost‐effective approaches for upgrading existing 1.5 kV DC traction substations (TS) in the Netherlands into 3 kV bi‐directional DC TS. After evaluating the benefits of a 3 kV bi‐directional DC, two novel topologies are proposed that re‐use the existing substation's components and reduce the need for higher investments. These topologies incorporate parallel voltage source converters (VSCs) to recuperate braking energy from the DC grid and transfer it back to the AC grid. Furthermore, the study investigates additional use cases for the VSCs, including improving DC TS's reliability during faults, reducing harmonics through active power filtering, compensating for reactive power, and supporting the integration of renewable energy sources into the DC grid. A comprehensive control strategy for the VSCs is also proposed based on a thorough analysis of their working methodology and functional modes. The feasibility and effectiveness of the proposed solutions are validated through scenario analysis relevant to the Netherlands' traction network, utilising both a Simulink model and an Opal‐RT real‐time simulator. This study serves as a starting point for the various stakeholders of the Dutch traction network in their journey towards modernising the current traction power supply. It has the potential to serve as a reference for reusing existing railway infrastructures to provide ancillary services and support the energy transition.

Distributed Module-Based Power Supply Enhancement System for 3 kV DC Traction

This paper presents a conception of 3 kV DC traction power system based on distribution sources, as an alternative to traditional traction substation. The system consists of supplying modules (SM) installed along the electrified railway line, the distance between adjacent SMs are much shorter, than between traditional traction substations in 3 kV system. Each SM consists of energy storage system (ESS), and could be charged from adjacent, traditional traction substation via catenary, via medium voltage supplying lines, renewable power sources or by energy recuperation. In the article, the main parameters of the proposed supplying system operation have been compared with parameters of the system with traditional traction substation. For this purpose, in a case study, comparison analysis has been carried out for energy losses in catenary, 15-min peak power demand as well as the cost of the system installation. At the end, the reliability analysis has been carried out for proposed distribution power supply system and for traditional one.

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

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

SiC-Based Power Electronic Traction Transformer (PETT) for 3 kV DC Rail Traction

The design of rolling stock plays a key role in the attractiveness of the rail transport. Train design must strictly meet the requirements of rail operators to ensure high quality and cost-effective services. Semiconductor power devices made from silicon carbide (SiC) have reached a level of technology enabling their widespread use in traction power converters. SiC transistors offering energy savings, quieter operation, improved reliability and reduced maintenance costs have become the choice for the next-generation railway power converters and are quickly replacing the IGBT technology which has been used for decades. The paper describes the design and development of a novel SiC-based DC power electronic traction transformer (PETT) intended for electric multiple units (EMUs) operated in 3 kV DC rail traction. The details related to the 0.5 MVA peak power medium voltage prototype, including the electrical design of the main building blocks are presented in the first part of the paper. The second part deals with the implementation of the developed SiC-based DC PETT into a regional train operating on a 3 kV DC traction system. The experimental results obtained during the testing are presented to demonstrate the performance of the developed 3 kV DC PETT prototype.

Improvement of the system of contactless automatic regulation of voltage of converter traction units of traction substations

The article discusses the problem of increasing the energy efficiency of the 3 kV DC traction power supply system on the railways of the Russian Federation. As one of the ways to amplify it, the authors consider a system of contactless automatic voltage regulation under load of converting units of traction substations, where reactor controlled devices serve as the regulatory body. As one of the directions for improving the system, the use of thyristors in the design of a controlled device is proposed. The article presents the functional diagrams of contactless automatic voltage control systems with thyristor-reactor and thyristor controlled devices, shows the external characteristics of the converter unit with these systems. To calculate the economic efficiency when introducing contactless automatic voltage control systems with reactor, thyristor-reactor and thyristor controlled devices, a methodology has been developed based on calculating the savings in reduced costs, as well as the payback period when replacing a contactless automatic voltage control system under load with a reactor controlled device by a system with thyristor-reactor and system with thyristor.

Influence of contact gaps on the conditions of vehicles supply and wear and tear of catenary wires in a 3 kV DC traction system

Influence of contact gaps on the conditions of vehicles supply and wear and tear of catenary wires in a 3 kV DC traction system

Interaction between a DC Traction System and an AC Power System Through Earth-return Circuits

The article describes a problem that occurs in electrified railway transportation, involving the interaction between the earth-return circuits of different power systems. One of the analysed circuits is the earth-return circuit of a high-voltage power grid, the other is the return path of a 3 kV DC traction power supply system. The paper presents the results of the field tests carried out so far and discusses a mathematical model developed in the Matlab-Simulink environment with the aim of determining the interaction between both of the said systems. Keywords: earthing, traction substation, traction return system

Mathematical model of traction vehicle movement

The article presents a mathematical model of electric traction vehicle movement in a given power supply area. Starting from the presentation of the basic features of the 3 kV DC traction power supply system used in Poland, the author presents a simulation model of electric traction vehicles movement, which allows to determine the mobility and current - voltage possibilities on a selected railway line. The obtained simulation results fully confirm the possibility of using the model as an aid in the design, modernization or diagnostics of existing railway lines and train traffic.

Digital control model for electric traction vehicles

The driving force of an electric traction vehicle depends on the vehicle’s power and the amount of electricity consumed. However, a particularly important parameter in the 3 kV DC traction is the voltage on its pantograph, which closely connects the traction vehicle and the power system. In turn, the voltage level depends on the power supply parameters of the railway line and the quantity as well as quality and location of other electric traction vehicles in the considered area. The article presents a digital model of movement for electric traction vehicles in the given power supply area.

Simulation of the traffic of electrical traction vehicles as an auxiliary equipment for designing or diagnostics of existing railway lines

The driving force of an electric traction vehicle depends on the vehicle's power and the amount of electricity consumed. However, a particularly important parameter in the 3 kV DC traction is the voltage on its pantograph, which closely connects the traction vehicle and the power system. In turn, the voltage level depends on the power supply parameters of the railway line and the quantity as well as quality and location of other electric traction vehicles in the considered area. The article presents a digital model of movement for electric traction vehicles in the given power supply area.

Lean implementation for rail substation processes

PurposeTraction substations are an integral part of the railway infrastructure. In order to ensure that machinery and equipment is available and utilised at full capacity, intelligent maintenance methods should be implemented. The purpose of this paper is to focus on the development of lean maintenance strategies implemented on traction substations and offer the maintenance manager an alternative maintenance method to be utilised during optimisation initiatives.Design/methodology/approachThe rail company under consideration has various improvement options, the maintenance supply chain is a priority. The existing maintenance process of 3 kVDC traction substations is examined and all operations and activities directly and indirectly associated with maintenance are analysed with lean methodologies. The analysis of maintenance operations and activities reveals that some of these operations and activities are non-value-adding and, therefore, regarded as waste. These activities only prolong the maintenance process without adding value to the process. Alternative operations and activities are suggested and simulated.FindingsThe application of lean indicates that the maintenance process could be optimised to deliver on a more efficient process, which would improve the quality of maintenance by ensuring that maintenance is timeously carried out. Through reducing the downtime caused by maintenance, the availability of the system is preserved and the railway lines could be used to capacity.Research limitations/implicationsThe research is limited to 3 kVDC traction substations and the associated maintenance process, as this was the area of opportunity for the company. The track and overhead traction equipment maintenance is not included.Practical implicationsThe practical application of this research is in optimisation of the value chain for maintenance, specifically in the rail industry.Originality/valueThis research could be applied by maintenance managers to effectively implement if a run-to-failure (RTF) maintenance philosophy is being utilised. The research offers maintenance techniques within the RTF maintenance scope which reduces the maintenance cycle and equipment downtime.

Diagnostics of the 3 Kv DC Traction Power Network

The railway traction network line is one of the technical elements ensuring proper operation of railway traffic. Due to its technical function and specificity, it is an essential element of the railway infrastructure. That is, why diagnostics of traction networks is a very important issue. In the article, the authors presented issues related to the diagnostics of 3kVDC traction networks. An analysis of traction network faults for a group of power supply areas was also presented. Additionally, calculations of damage indicators in a selected, representative power supply area are presented. On the basis of made an analysis authors proposed solutions aimed at minimizing breakdowns in traction networks.

The multi-criteria optimization method for implementation of a regenerative inverter in a 3 kV DC traction system

This article presents a method supporting the decision-making process for implementation of a regenerative inverter in a 3kV DC traction system. The method in question consists of two steps. The first one is based on the solution of power flow (PF) problem in the novel model of DC power supply system with the limited overhead contact system (OCS) receptivity. The second step consists in execution of an optimization-oriented procedure. The optimization criteria are defined as follows: net energy drawn from a traction substation, cost of inverter implementation and energy loss in a supplying medium voltage grid. The optimized variables are rated power of the inverter and its location as well as other parameters of the inverter, which may be selected optionally. The optimization procedure is based on a genetic algorithm (GA), the results are presented as Pareto-fronts. Among the Pareto-optimized solutions, the single solution is chosen based on the criteria of a payback period.

Comprehensive approach to risk assessment and evaluation regarding constructioning of the first 25 kV 50 Hz AC traction power supply sections in Poland

Railway lines in Poland are either equipped with 3 kV DC traction system or not electrified for traction purpose. Presently maximum line speed is 200 km/h while maximum train speed is 250 km/h. Speeding up limit for 3 kV DC traction is estimated to be around 220-230 km/h. Already present in Poland trains for 250 km/h are equipped with three electric power supply systems: 3 kV DC used in Poland, 15 kV 16,7 Hz AC used in Germany, and 25 kV 50 Hz AC foreseen to be used in Poland on high speed lines. Introducing 25 kV 50 Hz AC traction power supply will be associated with safety challenges, which have to be taken into account already during constructioning, starting even at the predesigned phase. Two key questions arise. First of all question regarding methodology, which should be used for safety level acceptance and secondly how to ensure that all safety aspects will be taken into account. Answering first question for railway safety experts seems to be easy – let’s apply risk assessment and evaluation methodology described by EU regulation under Railway Safety Directive. The challenge is however to define risk acceptance criteria which will be required, and that is analysed in the paper. The second challenge is even more challenging. Author proposes using 10-by-10 safety matrix which was defined by the author in previous publications [9, 10]. Its concept as well as principles for its application for new type of power supply is also presented in the paper.

Case study of stationary energy storage device in a 3 kV DC traction system

The paper presents the results of economic study of energy storage system (ESS) implemented in 3 kV DC power supply system. Two conceptions of ESS have been investigated: ESS with supercapacitor (SC) and hybrid ESS (HESS) with SC and LFP battery. The investigated locations of energy storage systems are considered among existing traction substations in two railway lines with different density of train operation. The considered aims of energy storage system implementation are decreasing of energy consumption by maximum regenerative energy utilization and reduction of peak 15- min power demand of traction substation. The paper presents a method of regenerative power estimation depending on the location of the considered ESS implementation point. Also the method of optimal location selection of ESS in terms of minimization of Simple Payback Time (SPBT) of investment is presented. Besides the influence of initial cost value as well as energy price on the SPBT value are investigated. The results are compared between two railway lines with different number of trains operating.

The method of selection of the setpoint high speed feeder switch of 3,3kV DC with microprocessor-based protection systems

In the article a new procedure of choice of minimum current jump for action of fast-acting switches of 3.3 kV DC traction substations intended for the use in the microprocessor protection system of feeders is described. This procedure is more perfect than existing one on the current increment and uses the results of mathematical simulation of the traction electric supply system.

A frequency domain model for 3 kV DC traction DC-side resonance identification

Frequency-dependent effects in railway traction power systems arise from the impedance of substation and locomotive line filters and the traction line. Harmonic noise from traction drives and substations can excite resonances and produce overcurrent or overvoltage conditions at critical points in the network. In this paper, the harmonic feeding impedances of a 3 kV DC traction system seen from the rectifier substation, locomotive drive converter and pantograph terminals are presented. Several substation and locomotive filters are considered with a frequency-dependent traction line. Resonances attributed to the substation filter, locomotive filter and traction line are separate and distinct, the line introducing poles and zeros in the audio frequency (AF) range which vary in frequency and magnitude with locomotive position. >

Analysis And CAD Of Electric Vehicle PowerElectronic Converters As A Source OfElectromagnetic Disturbances

The problem of disturbances caused by the converters of an electric traction vehicle is discussed in this paper. As there have been projects to introduce new types of rolling stock in a suburban railway line in Silesia (the south-western part of Poland), some introductory analyses have been done in order to estimate the electromagnetic disturbances which could be caused by the vehicles' converters. As a type of rolling stock, supplied by a 3 kV DC traction system , a multiple unit with a.c. motors and a voltage inverter have been taken into consideration. Specialized software for the simulation of the power electronic and electrical machines PC-NAP have been used. A complex model of the system has been worked out which includes:power utility system, DC traction substation 12-pulse rectifiers, traction contact line, vehicle input filters,power electronic converters and asynchronous traction motors. The parameters of the subsystems were calculated according to the measurements carried out by the authors or were taken as specified by manufacturers. The results of analyses and simulations are presented and discussed