Electric Traction System Research Articles

Implementation of vector control on electric vehicle traction system

BackgroundNowadays, electric vehicle development takes a great attention in vehicle industry and researches, due to demising supplies of fuel, less pollution, and developing many resources of generating electricity as renewable energy and clean resources.ResultsThis research is a part of the Autotronics Research Lab (ARL), applying researches on autonomous and electric vehicles. The main aim of the research is to apply vector control method on traction control system of electric vehicle (mini golf cart) by using two hub motors on the rear wheels while the two front wheels are used for steering; it is assumed that the controlled vehicle is fitted with some equipment which can used in autonomous driving.Simulation results show the output response of speed and torque of the vehicle motors and vehicle speed while the vehicle is moving in a straight line or during steering and also show the fusion between vector control and power steering algorithm.ConclusionsThe system preforms the efficiency, safety, accuracy, and more controllability of electric vehicle traction system, leading to more stability in vehicle speed, lower troubleshoots, and less error in unstable surfaces and bad roads.

Synchronized Switching Modulation to Reduce the DC-Link Current in SRM Drives

Switched Reluctance Machines (SRM) are emerging as a possible alternative in terms of cost and supply stability to rare earth based electric vehicle traction systems. However, because of the huge amounts of energy stored and transferred back and forth between the DC source and the SRM, large DC-link capacitors must be used as buffers, which increases overall costs and size. This paper proposes a novel modulation technique which forces the exchange of energy between phases while decreasing the energy transfer between the DC bus and the SRM. This means lower DC bus currents (capacitor size and cost reduction) and lower Joule-effect conduction losses (better efficiency). The proposed modulation has been validated experimentally in a test bench and compared with the conventional torque-sharing function.

Saliency enhancement and torque ripple reduction of wound field synchronous machine by injecting optimum harmonic in rotor shape

This paper presents a new rotor shape design with optimum reverse 3rd harmonic for wound field synchronous machines to effectively enhance the saliency ratio and reduce the torque ripple in a micro electric vehicle traction system. Due to the enhanced saliency ratio, the reluctance torque is expected to be improved. The air gap flux density distribution is reshaped by the new rotor shape method, which benefits the low torque ripple. By contrast, the reverse 3rd harmonic injection is much more suitable than the general 3rd harmonic injection for increasing the effective air gap length along the q-axis for a high saliency ratio. Subsequently, three amplitudes of the reverse 3rd harmonic are studied and it is found that the optimum reverse 3rd harmonic is 1/6 of the fundamental one. To verify the effectivity of the proposed design, the original model and the ICS model are compared. Finally, all the motor characteristics, such as back electromotive force, cogging torque, and electromagnetic torque, are predicted using a 2-D finite-element method with the aid of JMAG-Designer.

КОНЦЕПТУАЛЬНЫЙ ПОДХОД К ПРОБЛЕМЕ ОБОСНОВАНИЯ ЭКОНОМИЧЕСКОЙ ЭФФЕКТИВНОСТИ ТРЕХФАЗНОЙ СИСТЕМЫ ЭЛЕКТРИЧЕСКОЙ ТЯГИ ПЕРЕМЕННОГО ТОКА

The paper proposes a conceptual approach to economic efficiency substantiation of three-phase alternating current system of electric traction in comparison with one-phase alternating current system of electric traction. It is based on quasi-optimal values of indicators of electric traction system that are necessary for feasibility study and assessment of integral criterion of efficiency, for which, in turn, it is necessary to compare systems by reduced expenditures. Saving of reduced expenditures should also consider out-of-transport effect that is very important for system effect of interaction between railway transport and other enterprises.

Об оценке коммутационной способности тяговых двигателей грузовых электровозов

An important direction in the development of JSC Railways is increasing the volume of freight traffic over the railway network. A number of measures are being taken to achieve the predicted strategic indicators in the locomotive complex. The most large-scale activities include research and experimental works aimed at improving the traction properties of electric locomotives in the Eastern polygon, which is one of the most heavily loaded sections of the Russian railway network. This is an important link connecting Southeast Asia and Europe. The conditions under which the railway transport operates require, among the priority tasks, efficient use of the locomotive fleet with high operational reliability to ensure safe train traffic. The Eastern polygon uses a system of electric traction powered by the 25 kV, 50 Hz AC voltage. Freight trains are driven by 2ES5K and 3ES5K electric locomotives equipped with pulsating current commutator traction machines. In implementing the required traction forces, the traction electric drive of such locomotives has a number of limitations. One of them is the quality of switching on the traction motor commutator. Achieving better reliability of traction motors, which are regarded as the weak link of electric locomotives, is a topical problem. The number of their failures due to faults of direct and pulsating current traction motors is at the level of 20--22%. The greatest difficulty is to increase the switching reliability. A switching quality criterion for traction electric motors of electric locomotives is proposed, which takes into account the degree to which the armature reaction magnetomotive force is compensated in the switching zone. The width of the sparkless operation region cannot fully characterize the traction electric motor switching capacity. Its calculation takes into account the spark voltage under the brush, the effect of electromagnetic factors on the switching, the design of additional poles, and the kind of load current. The accomplished calculations have shown that the proposed switching reliability quality criterion objectively characterizes the switching quality in the limiting mode and is consistent with the long-term experience of their operation in AC electric locomotives.

Комплексная оценка тягово-экономических показателей вагонов метрополитена с альтернативными системами тягового электропривода

Комплексная оценка тягово-экономических показателей вагонов метрополитена с альтернативными системами тягового электропривода

Overview of DC and AC Electric Railway Systems Considering Energy Efficiency Enhancement Methods

In this paper both DC and AC railway electric power feeding systems are reviewed and discussed. The advantage and disadvantage of these systems are also compared. One major problem of such systems is that they take the lion share of electricity consumption compared to non-traction systems. Therefore, most of the new technologies focus on enhancing Energy efficiency of railway systems. This paper discusses the main operation methodologies for reducing the consumption of electric traction systems. These methods include using renewable energy resources (RER), such as solar Photovoltaic (PV) panels and wind turbines, and regenerative braking. Moreover, the most common energy storage devices such as batteries, super-capacitors and flywheels. They are used in railway systems for storing the excess energy from RER or the return energy during regenerative braking (Batteries, super-capacitors and flywheel) are also explained. In addition, challenges of the right storage system selection for specific applications are briefly discussed.

Performance enhancement of electric vehicle traction system using FO‐PI controller

This work improves the performance of an electric vehicle (EV) traction system by using non-linear fractional-order proportional–integral (FO-PI) controller. The functionality of FO-PI controller is benchmarked against integer-order proportional–integral (IO-PI) controller. A 400 V, 6.6 Ah Li-ion battery bank is designed to power an indirect field-oriented induction motor driven prototype EV traction system. The appeal of this study is to reveal the simplicity, robustness, and effectiveness of FO-PI speed regulator for EV traction system. The efficacy of FO-PI speed regulator for EV applications is validated through rigorous experimentation. The FO-PI controller due to its non-linear nature proves to be more robust and effective under variation of a system's parameters and external disturbances as compared to IO-PI controller. Furthermore, the experimental results show that FO-PI control strategy provides higher torque per amp output while maintaining better voltage and state-of-charge profiles of the Li-ion battery bank.

Analysis of in-service composite insulators used in overhead railway traction

Polymeric based Composite insulators are extensively used for overhead rail electric traction system; these insulators play an important role in the traction electrification which supply power to the locomotives of train. Traction insulators are subjected to a variety of stresses, like mechanical, electrical, environmental, etc., these stresses act in unison, degradation and subsequent failure of traction insulator influences the safety of traction power supply system. To understand the phenomena of degradation and in-service aging, experimental investigations are conducted on in service traction insulators to identify and analyze the structural changes occurred in the field for a specified time, the insulators are of composite silicone polymeric materials rated for 25 kV. The electrical performance on the insulator samples is investigated using leakage current analysis and surface resistance measurements under normal and fog/moisture conditions using a specifically designed fog test chamber. The structural changes are studied by using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX), Fourier Transform Infra-Red (FTIR) and wettability measurements. The study highlights the in-depth analysis conducted on the performance of service insulators compares with the fresh, also suggests mitigation methods to overcome the probable failures in the field. Some interesting results obtained from the study are analyzed and presented.

Defining energy indicators for detecting short circuits in a dc electric traction system

It has been proposed to use power losses as an additional energy parameter to complement basic energy indicators in determining the short circuit mode in a traction power grid. Three techniques have been reported to determine the transitional characteristics of an electrical network, which are based on methods of approximation, discrete electrical engineering, and spectral analysis. The need to construct these methods is predetermined by the non-stationarity and nonlinearity of electrical parameters for traction networks, which could form uncertainty in the moment of a short circuit occurrence.The input data to determine the energy characteristics and losses are the functions of transitional voltage and transitional current, measured at the clamps of the switchgear to which power conductors of the traction network are connected. Based on the experimental measurements and the reported methods, we have calculated basic energy parameters of the network, as well as losses, at different short circuits.Results of our calculations show that during short circuits in a traction network the quantitative values of energy indicators and unproductive losses make it possible to unambiguously assess the mode of network operation. The obtained results also make it possible to determine the actual load on protective switching devices at short circuits in a traction network.The proposed methods could be applied when developing computer models of traction networks in order to study them and perform engineering calculations. They could also be applied while designing new or reconstructing current DS traction networks, in order to more accurately substantiate design solutions. In addition, the proposed methods could be employed when constructing new or improving the existing samples of protective switching equipment

A brief study on the implementation of transformers for track electrification

ABSTRACTIn the current state, the electric traction system is the cheapest and efficient medium for both personnel and material transportation. As electric locomotives are connected as loads, they introduce power quality problems due to their dynamic speed and load conditions. The power quality of these new high-capability swift-flying trains needs to be improved. In order to increase the power quality of systems, the transformers are designed. The objective of the work is to design an electric traction system that reduces the unsymmetrical voltages of electrification systems by using two different transformers in the Simulink environment.

Dynamism of Parasite Capacitance of AC Electric Traction Line Inside the Railway Tunnels

Air pollution by the fossil fuel-driven vehicles in the urban and suburban sections in the developed countries forced the adoption of electric traction in railways. Subsequently, traffic dense rail routes in many developing countries were also switched over to high voltage electric traction to reduce their dependency on petroleum products. Developing countries are the main beneficiaries of the high voltage electric railway traction system. As a result of the operational constraints evolved in maintaining partially electrified rail routes, developing countries are trending to electrify more rail routes at geographically challenged areas also. Tunnels constructed for metro railways in urban sections also raise the similar geographical challenges. Power supply interruption happened due to persisting earth fault on electric traction system even for a short duration will paralyze the rail network to a large extent. Hence precisely pin pointing the fault distance is essential to ensure the railway system reliability. Undesirable variations occurred in line parameters due to the bare conductors for the electric traction inside railway and metro train tunnels for very long stretches due to proximity of earth potential, and the subsequent nuisance crept in line fault distance locating algorithm studied through the experimentations conducted in actual working condition for re-modelling high voltage ac electric railway traction to precisely pin pointing the fault distance of it are presented in this paper.

Improving energy characteristics of ac electric rolling stock by using the three-level active four-quadrant rectifiers

In order to minimize the reactive power and higher harmonics of currents, as well as to improve the electromagnetic compatibility of electrical traction networks and systems of railroad automation, modern electric rolling stock of alternating current employ active four-quadrant rectifiers. The classical topology of a given converter is the two-level full-bridge active rectifier that ensures a power factor close to unity and the recuperation of energy to a power network. However, the high switching frequency predetermines high dynamic losses in power transistors and a low value for efficiency.It appears promising to use the three-level active four-quadrant rectifiers with a power factor correction. It has been proposed in the current work to apply a system of control over a three-level active rectifier with the two-channel equal-shifted sinusoidal PWM. The advantage of the proposed algorithm, as compared with known, is the improvement of quality of the input current and a decrease in the frequency of switching power switches, which leads to a decrease in power losses and an increase in the rectifier efficiency. The paper reports results of comparative analysis of dependences of power losses and efficiency on the switching frequency of power switches for the two-level and three-level active rectifier with the proposed control system, which confirmed the feasibility of the proposed control system. The software package MATLAB 2017b was used for simulation modeling of the two-level and three-level active rectifier, based on which we analyzed the quality parameters of electric energy, established the dependence of a harmonic distortion coefficient of the input current of an active rectifier on the switching frequency of power switches. Our study has proven the technical and economic expediency of using a circuit of the three-level active rectifier with a control system based on the two-level equal-shifted sinusoidal PWM.

Voltage Difference Residual-Based Open-Circuit Fault Diagnosis Approach for Three-Level Converters in Electric Traction Systems

This paper proposes a voltage difference residual-based fault diagnosis approach for three-level converters in electric traction systems. Compared to the existing open-circuit fault diagnosis approaches, the proposed approach cannot only detect and identify the faulty devices among the transistors and clamp diodes in both of rectifier and inverter, but also hierarchically diagnose the leg-level and device-level faults. Furthermore, no additional sensors are required and all of specified parameters can be directly identified. Specifically, the current related term in the dc-link voltage difference equations are analyzed and modeled under the normal case and open-circuit fault cases in the transistors and clamp diodes, respectively. Subsequently, the estimation models of the dc-link voltage difference are developed, and then, the residuals and their evaluation functions between estimation and actual are generated. Furthermore, by analyzing the residual evaluation functions for various cases and building the current similarity functions, the hierarchical diagnosis algorithms are proposed to identify the leg-level and device-level faults. Finally, hardware-in-the-loop experiments are performed. The results show the effectiveness and robustness of the proposed approach.

Hierarchical Model Predictive Control for Coordinated Electric Railway Traction System Energy Management

The paper presents a railway energy management system based on hierarchical coordination of electric traction substation energy flows and on-route trains energy consumption. The railway system is divided into energy-efficient individual trains energy consumption management as lower level, and the price-efficient electric traction substation energy flows management as higher level. The levels are coordinated through parametric hierarchical model predictive control with the main goal of additionally increasing the energy efficiency and decreasing the operational costs of the overall system. Through interactions with the power grid on the higher level, the system is able to provide ancillary services and respond to various grid requests. At the same time, lower level trains driving profiles are adjusted to attain the minimal cost of system operation with timetables and on-route constraints respected. The developed algorithm is verified on a detailed real case study scenario put together with a railway operator and a trains manufacturer. The presented results show significant cost and energy consumption reductions achieved by simultaneous coordination of several trains supplied from the same traction substation.

Influence of electric traction system on power grid harmonics

This paper analyzes the traction power supply system and traction substation of electrified railway. Due to the use of a large number of power electronic devices, the electric locomotive has strong nonlinear characteristics. Focusing on harmonics, this paper studies the harmonics generated by AC-DC and AC-DC-AC electric locomotives respectively. Based on this, The mathematical model of the power supply system of electrified traction locomotive is established, and the harmonic model is established. The simulation results are in good agreement with the actual conditions.

Data-driven and deep learning-based detection and diagnosis of incipient faults with application to electrical traction systems

Incipient faults in electrical drive systems will evolve into faults or failures as time goes on. Successful detection and diagnosis of incipient faults can not only improve the safety and reliability but also provide optimal maintenance instructions for electrical drive systems. In this paper, an integration strategy of data-driven and deep learning-based method is proposed to deal with incipient faults. The salient advantages of the proposed method can be summarized as: (1) The moving average technique is firstly introduced into the canonical correlation analysis (CCA) framework, which makes the new residual signals more sensitive to incipient faults than the traditional CCA-based method; (2) Based on the defined residual signals, the new test statistics cooperating closely with Kullback–Leibler divergence (KLD) are proposed from the probability viewpoint, which can greatly improve the fault detectability; (3) It is of high computational efficiency because the estimation of probability density functions of residual signals is skilly avoided; (4) Based on the new developed test statistics, the fault matrices are defined and regarded as the input of convolutional neural network (CNN) whose feature extraction ability is highly improved compared with the traditional method, which helps to accurately diagnose of incipient faults; (5) The proposed method can be implemented without any priori knowledge on system information. Theoretical analysis and three sets of experiments on a practical electrical drive system demonstrate the effectiveness of the proposed method.

Failure analysis of BMC insulators used for third rail traction system

Bulk molding compound (BMC) or Glass Reinforced plastic (GRP) composite insulators are extensively used for the third rail electric traction system. The performance of these insulators primarily depends on the local environmental conditions that cause degradation over a period of time. Degradation leads to partial arcing which grow more severe and can generate combustion that ignites flammable debris, smoke including fires resulting in service interruptions and safety risks of the third rail traction system. In the present investigations, exhaustive analysis is conducted to understand the root cause of degradation and arcing on the field aged insulators rated for 750Vdc. Leakage current and surface resistance measurements are conducted under dry, wet and contaminated conditions. Further to better interpret Physico-chemical analysis are conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX) and Fourier Transform Infra-Red (FTIR) spectroscopy to investigate surface morphology and chemical changes in the samples, also Thermo-Gravimetric Analysis (TGA) is performed to find the thermal characteristics of the insulator. Interesting results obtained from the investigations clearly present evidence to loss of epoxy material from the bulk eventually leading to the exposure of glass fibers causing degradation, arcing and failure of the insulators. The study further highlights the essential procedures to be edopted to locate, isolate, and better anticipate failures of BMC insulators used in third rail traction system.

Comprehensive approach to modeling dynamic processes in the system of underground rail electric traction

An analysis of tasks on improving energy efficiency of electric traction systems reveals the need for the introduction of new technologies, namely modern rolling stock with a traction asynchronous electric drive, as well as traction substations, based on new technologies. To solve this class of problems, we have defined the need for an integrated simulation model of the electric traction system that would ensure a sufficient level of its reliability.This work reports details of algorithms for calculating the parameters in order to develop a simulation model of the integrated electric traction system of an underground rail system, which consists of electricity supply subsystems, electric drive of rolling stock, and mechanical part of the traction transmission.In the programming environment Matlab/Simulink, based on the known, actual and refined, estimation parameters, we developed a simulation model of the system of traction electric supply to an underground rail with a two-way power to two tracks. We have constructed a simulation model of the modern traction electric drive of the underground rail cars with a vector system to control an asynchronous electric drive and a uni-mass mechanical part, capable of taking into consideration the impact of the coefficient of adhesion.We have compared results from the imitational simulation of dynamic processes with oscillograms for the actual operation modes of an underground rail system, which confirmed the adequacy of the model to the examined object. The correspondence between results obtained from simulation is confirmed by the oscillograms from analysis of voltage and current of the contact network, as well as by characteristics of the traction and braking modes of rolling stock.We have simulated processes of work of the power supply system, a nonstationary regime at deterioration of adhesion conditions, and a recuperative braking mode with energy transferred to other trains.Using the developed model of the integrated system of electric traction would contribute to a more detailed study into the mutual influence of elements in the electric traction system. That would make it possible to improve the efficiency of making technical decisions related to meeting safety requirements, preventing the disruptions of normal operation, and bringing down operating costs

Operating modes of electric energy storage systems on the Moscow Central Ring

Improving the performance of electric traction systems is associated with the use of new technologies, the introduction of which is preceded by an assessment of the technical efficiency of their work. Nowadays, electric energy storage systems in Russia have not found application in electric traction systems, but questions are being actively developed on advisability and possibility of their use. And electric traction load of electric traction system of the Moscow Central Ring is not an exception, which forms in the conditions of domination on the area of passenger traffic and frequent electric tractions stops. Electric energy of high level of return of electric trains was formed on the site. Obtaining the technical result of assessing the use of energy storage systems of electric energy is most expedient to perform on the basis of simulation modeling of the interaction of electric rolling stock and electric traction system in the conditions of the Moscow Central Ring. Modeling results allow receiving the main characteristics of storage units and voltage load graph, determining the duration of work episodes in charge and discharge modes, their number and appropriate total volumes of electric energy per day. The received results allow assessing requirements to the technical characteristics of storage systems in relation to work conditions in the electric traction system of the Moscow Central Ring and performing assessment of economic efficiency of this activity.