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Online ISSN 2042-9746 Print ISSN 2042-9738

IET Electrical Systems in Transportation

Volume 2, Issue 3, September 2012

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Volume 2, Issue 3

September 2012

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    • Electric vehicles' impact on British distribution networks
      • Author(s): P. Papadopoulos ; S. Skarvelis-Kazakos ; I. Grau ; L.M. Cipcigan ; N. Jenkins
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 91 –102
      • DOI:  10.1049/iet-est.2011.0023
      • Type: Article
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      • p. 91 –102 (12)
        Battery charging of electric vehicles (EVs) will increase the power demand in distribution networks. It is anticipated that this will cause voltage drops, thermal overloads and an increase in losses. The severity of the impact will depend on the EV owners’ behaviour. A generic three-phase low voltage (LV) residential distribution network model was used to evaluate the effects of EV battery charging on distribution networks, the effect of a smart charging regime for EVs as well as the contribution of dispersed micro-generation (mGen) sources. The uncertainties associated with the residential loads, m-Gen and EV owners’ behaviour, were addressed with a probabilistic approach. A case study was performed for the year 2030 using both deterministic and probabilistic approaches. The probabilistic assessment showed the importance of the above uncertainties.
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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
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 103 –109
      • DOI:  10.1049/iet-est.2011.0048
      • Type: Article
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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
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 110 –118
      • DOI:  10.1049/iet-est.2011.0013
      • Type: Article
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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
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 119 –129
      • DOI:  10.1049/iet-est.2011.0051
      • Type: Article
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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
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 130 –138
      • DOI:  10.1049/iet-est.2011.0053
      • Type: Article
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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.
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      Load flow analysis and future development study for an AC electric railway
      • Author(s): S.V. Raygani ; A. Tahavorgar ; S.S. Fazel ; B. Moaveni
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 139 –147
      • DOI:  10.1049/iet-est.2011.0052
      • Type: Article
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      • p. 139 –147 (9)
        This study presents a forward/backward sweep (FBS) load flow method for AC autotransformer (AT)-fed electrical railway networks considering dynamic movement of trains. Field measurements of Tehran–Golshahr suburban railway are compared with simulation results. Moreover, effects of the time headway reduction on this suburban railway and its transmission power supply system are investigated. Then, to minimise power losses, two methods of the reactive power compensation are studied; the pulse-width-modulated (PWM) trains and a static var compensator (SVC). For the aforementioned cases, fluctuations of the displacement factors (DISF), defined in p–q–r theory are simulated at the point of common coupling (PCC). MATLAB software is used for programming and simulations.
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      Multi-objective design of a hybrid propulsion system for marine vessels
      • Author(s): E.A. Sciberras  and  R.A. Norman
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 148 –157
      • DOI:  10.1049/iet-est.2011.0011
      • Type: Article
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      • p. 148 –157 (10)
        Hybrid vehicles offer the advantages of both conventional and electric vehicles. Improved fuel consumption is generally the main driver for these systems with the option of silent, emission-free operation also being a big advantage. Marine hybrid vehicles however, do not experience significant recovery of energy via regeneration, because of their operating profiles. Fuel savings can be realised by optimal component operation rather than free-energy recovery, yet this requires correct component sizing considering the typical usage over a scenario. In this study, a model is built to calculate the fuel consumption of a hybrid motoryacht over a given day-cruise scenario. A genetic algorithm is then applied to optimise the component sizing of this hybrid system with respect to minimisation of fuel consumption and total installation weight.
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      Generation control system for improving design and stability of medium-voltage DC power systems on ships
      • Author(s): V. Arcidiacono ; A. Monti ; G. Sulligoi
      • Source: IET Electrical Systems in Transportation, Volume 2, Issue 3, p. 158 –167
      • DOI:  10.1049/iet-est.2011.0016
      • Type: Article
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      • p. 158 –167 (10)
        Voltage stability in medium-voltage DC (MVDC) power systems on ships is a key design goal. MVDC bus voltage stability can be impaired because of the presence of power electronic converters that can induce negative incremental resistance instabilities. This study presents a control strategy that stabilises MVDC bus voltage in the presence of destabilising constant power load converters. A state-feedback adaptive control is designed by linearisation and implemented using controlled interface converters connecting the MVAC alternators to the MVDC bus. Large signal stability of the control system is assessed using Lyapunov techniques. The proposed control is verified against both average-simplified and detailed time-domain numerical simulations, thus providing a two-way comparison.
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