Electric Traction System Research Articles

Control and Analysis of an Integrated Bidirectional DC/AC and DC/DC Converters for Plug-In Hybrid Electric Vehicle Applications

The plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. The PHEV battery would be recharged from the power grid at home or at work and would thus allow for a reduction in the overall fuel consumption. This paper proposes an integrated power electronics interface for PHEVs, which consists of a novel Eight-Switch Inverter (ESI) and an interleaved DC/DC converter, in order to reduce the cost, the mass and the size of the power electronics unit (PEU) with high performance at any operating mode. In the proposed configuration, a novel Eight-Switch Inverter (ESI) is able to function as a bidirectional single-phase AC/DC battery charger/ vehicle to grid (V2G) and to transfer electrical energy between the DC-link (connected to the battery) and the electric traction system as DC/AC inverter. In addition, a bidirectional-interleaved DC/DC converter with dual-loop controller is proposed for interfacing the ESI to a low-voltage battery pack in order to minimize the ripple of the battery current and to improve the efficiency of the DC system with lower inductor size. To validate the performance of the proposed configuration, the indirect field-oriented control (IFOC) based on particle swarm optimization (PSO) is proposed to optimize the efficiency of the AC drive system in PHEVs. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point, where the PSO is applied to evaluate the optimal flux. Moreover, an improved AC/DC controller based Proportional-Resonant Control (PRC) is proposed in order to reduce the THD of the input current in charger/V2G modes. The proposed configuration is analyzed and its performance is validated using simulated results obtained in MATLAB/ SIMULINK. Furthermore, it is experimentally validated with results obtained from the prototypes that have been developed and built in the laboratory based on TMS320F2808 DSP.

A Dual-Loop Control Strategy of Railway Static Power Regulator Under V/V Electric Traction System

For power quality in V/V traction system of the 350-km/h high-speed railway, a kind of railway static power conditioner (RPC) is discussed, which is used to carry out the comprehensive compensation of negative sequence and harmonic currents in the traction substation. In order to improve the control effect and performance of RPC, a dual-loop control strategy is constructed for RPC. Taking into account the disturbance and variation of electrified railway environment, a recursive proportional-integral control based on fuzzy algorithm is adopted to realize a fast and smooth tracking to the reference current. An energy-balance control is proposed to suppress the fluctuation of dc-link voltage and maintain the stability of RPC, which is an accurate and adaptive feedback control based on corresponding parameters. Finally, the correctness of the analysis proposed in this paper has been confirmed by the simulation and experiment results.

The Study for the Electronic Control Technology of the Electric Power Traction System in the Bridge/Shipping Crash Testing Laboratory

The electric power traction system in the Bridge/Shipping Crash Testing Laboratory, is the foundation of the crash test between the shipping and the bridge. In order to make sure the process more quickly, stably, accurately, centralized-control method has been applied in the electric power traction system of the Bridge/Shipping Crash Testing Laboratory in The Changsha University of Science and Technology, so the test flow has been controlled and finished automatically, the test data could be collected and recorded automatically, safety alarm, protect automatically and the history data could be recorded on the real-time, the test report form could been formed automatically and the manage function will be worked and so on. The problem of complexity of the test flow, the difficulty of the induction about the logic relationship, the strong electromagnetism interfere in the big current equipment, the machine shock is strong and so on would be solved, the traction system in the crash test would be made more real and mature.

Simplified Power Converter for Integrated Traction Energy Storage

Electrical energy storage has a significant role to play in improving the performance of future electric traction systems. This paper proposes a new power electronics topology that integrates the energy storage power electronics with those of the inverter drive system. This topology reduces weight and component count compared with previous topologies but still allows the use of standard machines. Practical results from a laboratory test system are shown, and indicative energy savings for a full-sized system are presented. A study on a City Class Tram on the public transportation system in Blackpool, U.K., shows that clear energy savings may be made by employing ultracapacitor energy storage with the proposed topology.

Induced Voltage Calculation in Electric Traction Systems: Simplified Methods, Screening Factors, and Accuracy

In modern electric traction systems, the calculation of induced voltage on internal and external conductors is always required for both interference and people and equipment safety. The International Telegraph and Telephone Consultative Committee (CCITT) method is based on simplified relationships, which are integrated by suitable screening factors (representing and hiding the traction system complexity). Focus is on the determination of these factors and the accuracy, which are evaluated with simulation and experimental data. The considered systems are rail return, return conductor, and autotransformer (AT) 2 × 25-kV traction systems with victim cables of various lengths; the influence of the most relevant electric parameters (soil resistivity and conductance to earth of the return circuit conductors) is considered. The results confirm the relevance of the conductance to earth and of the position of the current injection point. The induced voltage is approximately proportional to the length, with a slight increase for shorter victim cables. The calculated AT screening factor is always smaller than the values suggested by the standards by a factor of 2 in the worst case. For the influence of separation of the inducing and victim circuits, the adopted methods agree in finding a critical distance around 6-8 m; at larger distances, CCITT values are slightly optimistic. Measured results confirm that the CCITT coefficients are all conservative by a factor of 2-4 (except the AT coefficient for total length exposure), whereas the multiconductor transmission line (MTL) results agree with a worst-case margin of 13%.

REACTIVE POWER DEVICES IN SYSTEMS OF ELECTRIC TRACTION

A comparative characteristic of different concepts and expressions for determination of reactive power in the circuits with non-sinusoidal electric values has been given. For the first Ukrainian electric locomotives of DE1 type with the system of DC electric traction, the values of reactive power after Budeany, Fryze, and also the differential, integral and generalized reactive powers have been determined. Some measures on reducing its consumption by the DC electric rolling stock have been suggested.

INDICATORS OF QUALITY OF ELECTRIC ENERGY IN THE ELECTRIC TRACTION DC

The research results showing an opportunity to use a power quality rating in a system of direct current electric traction on a traction substation input and output are stated. It is demonstrated that these ratings essentially simplify the quality analysis of power coming into traction circuits.

Reliability management and assessment for the electric traction system on the Korea High-Speed Train

The Korea High-Speed Train (KHST) is complete and ready for commercial service. In preparation for commercial service, the reliability of the KHST was proven. In this article, a practical procedure is proposed to assess and manage the reliability of the prototype train traction system. The past data of a similar traction system are analysed in order to set the reliability target. The effectiveness of the procedure for reliability growth is shown. After the electric traction system is classified into subsystems, reliability analysis is carried out. Reliability block diagram and failure mode effect analyses are performed. The expressions for calculating the reliability are deduced and the mean kilometres between service failures are calculated using the previous failure rate data. Some practical criteria for the demonstration of reliability are proposed. Reliability growth is shown using a test run on a commercial line.

Advanced Integrated Bidirectional AC/DC and DC/DC Converter for Plug-In Hybrid Electric Vehicles

Hybrid electric vehicle (HEV) technology provides an effective solution for achieving higher fuel economy, better performance, and lower emissions, compared with conventional vehicles. Plug-in HEVs (PHEVs) are HEVs with plug-in capabilities and provide a more all-electric range; hence, PHEVs improve fuel economy and reduce emissions even more. PHEVs have a battery pack of high energy density and can run solely on electric power for a given range. The battery pack can be recharged by a neighborhood outlet. In this paper, a novel integrated bidirectional AC/DC charger and DC/DC converter (henceforth, the integrated converter) for PHEVs and hybrid/plug-in-hybrid conversions is proposed. The integrated converter is able to function as an AC/DC battery charger and to transfer electrical energy between the battery pack and the high-voltage bus of the electric traction system. It is shown that the integrated converter has a reduced number of high-current inductors and current transducers and has provided fault-current tolerance in PHEV conversion.

Magnetic field under the 3000 V DC electric overhead traction system

In the environment in which we live we are exposed to different kinds of radiation. Radiation is divided into ionising radiation as a result of radioactive decay and into non-ionising radiation, which is the consequence of electromagnetic waves. The use of electric power has penetrated every area of human activities. Its accompanying effects are electromagnetic waves, which expand into the space surrounding the installations for the generation, transmission and use of electric power. The research in the last 20 years has concentrated on the possibly harmful effects of low frequency (0–300 Hz) electromagnetic waves on man and the environment. However, not much research has been conducted into the magnetic fields under the electric overhead traction systems. Therefore, this paper is presenting the results of the calculation of the magnetic field under the electric overhead traction system on Slovenian railways.

A Remotely Controlled Onboard Measurement System for Optimization of Energy Consumption of Electrical Trains

Reduction in energy consumption in electrical railway traction systems has become a vital need. The effort spent in providing better quality services implies increasing speed and, therefore, an increase in energy consumption. Various techniques are usually adopted to improve train performances. They span from modifying the vehicle structure to improving the motor. In this paper, a different way to reduce power absorption is presented, which is based on an appropriate interpretation of the traction diagram, along with the absorption curves. Measurement data are available by means of an onboard monitoring system that measures all the electromechanical quantities of the train course and sends them through a network connection to a remote control station. The evaluation of measurement uncertainty, the procedure to obtain the optimized protocol for train operation, and the experimental data obtained when the optimized protocol is applied are also presented.

Components For Hybrid Vehicles: Results of the IEA Annex VII “Hybrid Vehicle” Phase III

This paper describes the experiences made inside the Annex VII “Hybrid Vehicle” Phase III of the IEA Implement Hybrid & Electric Vehicle. In particular, the paper focuses on the Components that have been investigated by the working group. The development of a vehicle with an electric traction system, like HEV has to deal with the introduction of components which are not present in Conventional Vehicle (CV), or which, even if present in CV, they must undergo modifications for an HEV application, like for instance the cooling compressor.The working-group has singled out 4 main interesting areas which have these critical components: Fuel Converters, Drives, Energy Storage, and Auxiliaries. The issues related to these areas must be properly solved for achieving the needed HEV’s performances. Inside the Annex VII the experts have discussed it, and the paper gives an overview of this process.

Two Enthusiasts

Beginning in San Francisco in 1873, cable railways spread to nearly every large American city and several overseas. Los Angeles had three systems, the most successful of which began operation on Temple Street in 1886. Frederick Wood and John Fowler, who managed the Temple Street Cable Railway, were responsible for several mechanical innovations that they hoped would be adopted by other lines. To demonstrate these, they kept a section of cable track and conduit above ground, and in the summer of 1892 they posed alongside this section. Unfortunately—but probably not yet obvious to them—by 1892 cable railways were on the verge of being rendered obsolete by Frank Sprague's system of electric traction and thus the demand for mechanical novelty had vanished. Total cable railway mileage nationwide peaked the next year at 305; by the time the Temple Street line was converted to electricity in 1902 the total was down to 100, and ten years after that it was down to 20, nearly all of it on the steep hills of San Francisco. For cable-car enthusiasts like Wood and Fowler, Sprague had spoiled the fun.

A Double Excited Synchronous Machine for Direct Drive Application—Design and Prototype Tests

This paper presents the analytical, numerical, and experimental results obtained with a double excited synchronous machine (DESM) prototype designed and constructed for an electric vehicle traction system. To obtain a wide speed range, the flux-weakening technique is implemented. Analytical design, 2-D finite element method (FEM) analysis, thermal analysis, and prototype construction of the DESM are discussed, and the performances are assessed with experimental data.

Simplified Modeling of 2$\,\times\,$25-kV AT Railway System for the Solution of Low Frequency and Large-Scale Problems

An electric traction system supplied at 2times25 kV with autotransformers is considered. The conductors arrangement is that of the new European High Speed Railway Line under construction. The system is analyzed with a validated multiconductor transmission line model with the aim of model simplification with reduction of the number of conductors and use of the lumped-circuit model. The scope is that of load-flow and voltage stability problems, which may be large-scale problems and benefit from model simplification and reduction of computational effort

Genetic algorithm approach for the determination of the electrical parameters of railway traction lines

The problem of electrical parameters identification in complex systems, and in particular in electric railway traction systems, is considered. Parameters are determined by an indirect approach: only the terminal variables (voltages and currents and, impedance and admittance, which can be readily calculated) are measured and the per-unit-length electrical parameters are determined using a multiconductor transmission line model of the track section under test. It will be shown that some parameters cannot be measured directly, that they are not constant with frequency and that they may depend on other external conditions. An indirect method for parameters identification is proposed through an adaptive algorithm (AA), so that the calculated terminal variables match the measured ones. The AA is based on a genetic algorithm (GA) approach, with details on pattern generation (through mutation and recombination) and determination of the degree of fitness and, as a consequence, of matching and stop criteria. There is a general accordance with model previsions, within common variations of the most critical properties of the test track.

Measurement of AT Electric Railway System Currents at Power-Supply Frequency and Validation of a Multiconductor Transmission-Line Model

An electric traction system supplied at 2 /spl times/ 25 kV with autotransformers (ATs) is considered. The conductors' arrangement is that of the new European High Speed Railway Line (HSRL) under construction: The overhead supply conductors in contact with the train pantograph are connected to a symmetrical circuit (the feeder) with the purpose of current balancing; the traction return current flows from the rolling stock axles back to the supply (i.e., substation) through the traction rails and additional return conductors. The test campaign carried on the Rome-Naples HSRL allowed the validation of the multiconductor transmission line model used for system analysis. Measurements were performed in normal system configuration (2 /spl times/ 25-kV supply) and degraded configuration (1 /spl times/ 25 kV with AT and feeder not operating). Metrological issues (accuracy and consistency) are detailed for the presented results.

Distribution of the Traction Return Current in AT Electric Railway Systems

The problem of determination of the accurate distribution of the return current in AT (autotransformer) electric traction systems (supplied at 2/spl times/25 kV) for High Speed Railways is considered. The path of the traction return current flowing from the rolling stock axles back to the supply (i.e., substation) is composed of the traction rails and additional earth potential conductors. The overhead supply conductors in contact with the train pantograph are connected to a symmetrical circuit (the feeder) with the purpose of current balancing. This arrangement and its influence on current to earth are considered: the return current divides among rails (as signalling disturbing current) and earth, depending on the value of the electric parameters of the system and the earth and on the circuit arrangement and on the relative position of system devices. The amplitude (as a percentage of the total return current) of the disturbing current may be high enough to cause interference to signalling. This work investigates the behavior of the return current in AT electric railway systems, on the basis of a reference system for the variation of the most important electrical parameters.

Hybrid Electric Sport Utility Vehicles

Drive-train hybridization improves the fuel economy and emissions of vehicles. This is the concept of hybrid electric vehicles (HEVs). Application of this concept in sport utility vehicles (SUVs), which consume more fuel as compared to passenger cars, will positively have a great impact. However, dynamic performances such as acceleration and gradeability also are of great importance in SUVs. Therefore, the optimum choice of the system hybridization level includes complex tradeoffs between the engine and electric propulsion motor on the one hand and fuel economy, performance, and cost on the other. In this paper, we classify SUVs as small, medium, and large vehicles. Effects of hybridization on the fuel economy and dynamic performances of each class of SUVs are investigated. Different hybridization levels, from mild to full hybrid electric traction systems, are examined.

Effects of Drivetrain Hybridization on Fuel Economy and Dynamic Performance of Parallel Hybrid Electric Vehicles

Hybrid electric vehicles have proved to be the most practical solution in reaching very high fuel economy as well as very low emissions. However, there is no standard solution for the optimal size or ratio of the internal combustion engine and the electric system. The optimum choice includes complex tradeoffs between the heat engine and electric propulsion system on one hand and cost, fuel economy, and performance on the other. Each component, as well as the overall system, have to be optimized to give optimal performance and durability at a low price. In this paper, we look at the effects of hybridization on fuel economy and dynamic performances of vehicles. Different hybridization levels from mild to full hybrid electric traction systems are examined. We also present the optimum level of hybridization for typical passenger cars. This study shows that low hybridization levels provide an acceptable fuel economy benefit at a low price, while the optimal level of hybridization ranges between 0.3 and 0.5, depending on the total vehicle power.