IET Electrical Systems in Transportation
Print ISSN
2042-9738
Online ISSN 2042-9746
Online ISSN 2042-9746
IET Electrical Systems in Transportation is aimed at all aspects of electrical power systems in modern transport applications including generation, storage, distribution and utilisation. The scope extends to all sectors of transportation: aerospace, marine (including sub-sea), automotive or land-based and rail. The central theme of the journal is to focus on the system and sub-system aspects of electrical energy including system architectures and integration, energy management, control and protection.
Latest content
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Reactive power compensation in railways based on AC boost choppers
- Author(s): G. Raimondo; P. Ladoux; A. Lowinsky; H. Caron; P. Marino
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p.
169
–177
(9)
In this study, a new topology, using AC choppers is proposed for reactive power compensation in 25 kV/50 Hz railway networks. The low losses of these converters compared to other solutions such as voltage-sourced inverters-based STATCOMs, makes this approach attractive for high-power, single-phase systems such as railway networks. A possible solution based on the controlled impedance concept working in boost mode is proposed and applied to a substation in the French rail network. Design method presented end simulation results which confirm the performance of this low-cost and low-loss solution. Finally, the experimental results achieved on a 1.2 MVAR prototype are presented.
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Permanent-magnet synchronous motor drive system for electric vehicles using bidirectional Z-source inverter
- Author(s): P. Liu; H.P. Liu
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p.
178
–185
(8)
Permanent-magnet synchronous motors (PMSM) are capable of providing high torque-to-current ratios, high power-to-weight ratios, high efficiency and robustness. Owing to these advantages, PMSM are widely used in modern variable speed AC drives, especially in electric vehicle (EV) and hybrid EV applications. In this study, a novel PMSM drive system with a bidirectional Z-source inverter (ZSI) is proposed and tested. By introducing ZSI to the drive system, the DC-link voltage is controllable so that PMSM can operate at high speed without field weakening. The operating principle and modulation method of ZSI are described in this study. After presenting the constraints of the motor maximum line current amplitude and maximum available voltage, a modified vector controlled scheme of PMSM drive is developed by considering voltage boosting. Finally, the feasibility and effectiveness of the proposed system are verified by several simulation and experiment results.
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Electric cars as part of electricity distribution – who pays, who benefits?
- Author(s): J. Lassila; V. Tikka; J. Haakana; J. Partanen
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p.
186
–194
(9)
The nature of transport and energy use is radically changing along with the upward trend of electric vehicles (EVs). This poses a challenge for the existing electricity distribution infrastructure. Key questions are: what efforts are required to guarantee that the network infrastructure has sufficient capability to deliver energy and power to the customers, and how does this development affect the network value and distribution fees? In this study, this challenge is approached from the economic perspective of an electricity distribution company. In this study, a generic model to analyse the network effects of EVs is presented. One significant result is that depending on the EV charging methods, the power demand (peak load) may increase dramatically or remain almost at the present level. Correspondingly, the required network reinforcements and distribution fees can be tens of percents lower than today or they can be higher, depending on how much intelligence is integrated into the charging process.
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Channel evaluation for power line communication in plug – in electric vehicles
- Author(s): S. Barmada; M. Raugi; R. Rizzo; M. Tucci
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p.
195
–201
(7)
In this study, an analysis of the use of the DC grid of electric vehicles as a communication channel for broadband power line communications (PLC) is presented. A measurement campaign of channel frequency responses is reported for different access points inside the vehicle, and also between the vehicle and the external grid during battery charging. The noise produced by the motor drive and the AC/DC converter is measured and characterised in time and frequency domain. A wavelet-based method is used to create a simulation model of the channel frequency responses, which is used together with the measured noise andis used to perform a performance analysis of the channels by calculating the symbol error rate using a multicarrier communication scheme. From the analysis, the authors conclude that a broadband PLC onboard electric vehicle is feasible if advanced PLC schemes are used.
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Modelling of lithium-ion battery for online energy management systems
- Author(s): S.X. Chen; H.B. Gooi; N. Xia; M.Q. Wang
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p.
202
–210
(9)
This study presents a new equivalent lithium-ion (Li-ion) battery model for online energy management system. It has an equilibrium potential E and an equivalent internal resistance Rint. The equilibrium potential E is expressed as a function of state-of-charge (SOC), current and temperature. The equivalent internal resistance Rint includes R1 and R2. R1 is defined as the resistance, which can be formulated by the discharging current and temperature. R2 is defined as the resistance which is because of the change of temperature. The adaptive extended Kalman filter is employed to implement the online energy management system based on the proposed Li-ion battery model. The SOC is considered as the state variable for the charging or discharging process of the Li-ion battery. The covariance parameters of the processing noise and observation errors are updated adaptively. The SOC of the Li-ion battery can be predicted by the online measured voltage and current in the online energy management system. The effectiveness and robustness of the proposed Li-ion battery model is validated. Experimental results show that the estimated SOC is accurate for various operating conditions. A comparison between the proposed method and other SOC estimation methods is also shown in the experimental results and analysis section.
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Quantification of complexity of power electronics based systems
- Author(s): T. El-mezyani; R. Wilson; M. Sattler; S.K. Srivastava; C.S. Edrington; D.A. Cartes
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p.
211
–222
(12)
Power electronics are becoming increasingly important in modern ship board power systems. They are used for development and implementation of controls and to interface different electrical modules such as loads, batteries and generators that produce, store or consume energy. Power electronic systems are suitable for control because they provide fast operation in the range of microseconds. However, fast control operations can also add complexity to the system. Unintended complex dynamics can arise if the system (inertia) is unable to adapt to the control actions. This article studies the complexity and emergent phenomena that may develop in a ship board power system because of the power electronic components, coupling between these components, as well as feedback mechanisms such as control loops and those of human and environmental origin. A statistical complexity measure, referred to as structural complexity, is used to quantify the degree of complexity that arises during the system evolution. This metric of complexity is computed using permutation entropy and ordinal patterns. A modified procedure for structural complexity called multivariable structural complexity is developed to compute the system wide complexity. This multivariable structural complexity is also used to assist the modelling process and the decision of the best model candidate that captures observed aspects of complexity from the system data history. Various case studies on complexity quantification are conducted on simulated data from a noise coupled buck converter, two parallel connected buck converters and an electric ship board power system.
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Preliminary evaluation of the energy-saving effects of the introduction of superconducting cables in the power feeding network for DC electric railways using the multi-train power network simulator
- Author(s): R. Takagi
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p.
103
–109
(7)
Thanks to the recent developments, the superconducting cables using high-temperature superconducting (HTS) materials are now expected to reduce feeding losses in the power supply network for DC electric railways. However, by connecting the HTS cables with the normal conducting wires electrically, heat intrusion is inevitable; to suppress heat intrusion to an acceptable level, interconnection becomes a large and costly installation. This means that the use of HTS cables as the replacement for normal conducting feeder wires in the DC railway feeding network is unrealistic because of the need for frequent interconnections between the feeder and contact wires. By combining the results obtained by a number of cases of multi-train simulation and a preliminary estimate of the refrigeration losses, the author shows that, by using HTS cables to replace some of the feeding substations, rather than the feeder wires, the introduction of HTS cables in the feeding network of DC electric railways may have positive effects of saving energy.
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Electrothermal modelling of the railroads catenaries
- Author(s): J.Ph. Mattera; R. Glises; Ph. Baucour; A. Vaudrey; S. Verschelde; D. Chamagne
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p.
110
–118
(9)
Feeding catenaries sometimes induces mechanical problems because of high temperature gradients, particularly for power supply voltage of continues tensions from 750 to 3000 V, contrary to the supplies in alternative tensions used of the order of 25 000 V. One of the major reasons of these problems comes from both high temperatures reached in operating configurations and surrounding conditions. The authors of this study have developed a simple nodal method allowing to estimate the temperatures reached in the volume of the contact wires taking into account the surrounding conditions of thermal exchanges with the atmosphere, so by radiation that convection. The exchanges of the external surface of the wire with the external air are there developed in an original way by taking into account the incidence of the wind with regard to the axis of the catenaries.
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Fault location for aircraft distribution systems using harmonic impedance estimation
- Author(s): Q. Zhou; M. Sumner; D. Thomas
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p.
119
–129
(11)
The demands for ‘more electric aircraft’ will increase the power distribution requirements of future aircraft electrical distribution systems. To increase safety and reduce aircraft maintenance times on the ground, there is also a need for system condition monitoring to quickly identify and locate any electrical faults which may develop. The work presented in this study forms an initial study into the use of power system harmonic impedance measurement for identifying and locating faults within power cables. The method is passive – that is, it does not require the injection of any test signals – and can be embedded into a centralised equipment controller to provide intelligent, real-time diagnostics. The method estimates the harmonic line–line self-impedance at strategic points in the distribution system by measuring load voltage and current at different load distribution points within the network. By combining the harmonic line–line self-impedance estimates the faults can be identified and located within a few cycles. This can, therefore, provide a ‘backup protection’ system, which does not require bus current measurement. It can also provide a measure of the fault location and could therefore be a significant aid to aircraft maintenance. The study derives the theoretical basis of the scheme and provides experimental results from a laboratory prototype to demonstrate the validity of this approach to detect and locate faults within the system.
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Synchronisation control of trains on the railway track controlled by the moving block signalling system
- Author(s): R. Takagi
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p.
130
–138
(9)
It has been widely expected that moving block signalling will realise greater line capacity through shortened headways between trains. However, under the condition in which all trains are individually and manually controlled, the actual effect of introducing moving block signalling is marginal. To make full use of moving block systems, the author proposes a new scheme in which a train that follows another with minimum distance defined by the signalling system will keep the condition for a certain period of time through synchronisation control. This scheme will ensure that the minimum headways between trains will always be achieved through automatic control. In this study, the calculation result of the deceleration at which a train that follows another with the theoretical minimum distance is first shown. Then, the calculation and simulation results are shown for cases in which multiple trains simultaneously start moving or simultaneously start braking. Finally, as examples of possible applications of this scheme for the realisation of advanced rail services, the following three services are discussed together with the simulation results: (i) minimisation of departure-to-arrival headway at a platform, (ii) group operation of express trains and (iii) group operation of local trains.
