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Railway power supply investment decisions considering the voltage drops: Assuming the future traffic to be known
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0003-2109-060X
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0002-8189-2420
2009 (English)In: 2009 15th International Conference on Intelligent System Applications to Power Systems, ISAP '09, 2009Conference paper (Other academic)
Abstract [en]

Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. The more distant the uncertain future is, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. Therefore a fast approximator that uses aggregated railway power supply system information has been developed. In particular the approximator studies the impacts of voltage drops on the traffic flow. The weaker the power system and the heavier the traffic, the greater the voltage drops. And the greater the voltage drops, the more limited the maximal attainable tractive force on the locomotives. That approximator is in this paper used as a constraint in the embryo of a railway power supply system investment planning program, where investment decisions are assumed to be realized immediately, and there is no preexisting power supply system to consider. The traffic forecasts are in this first approach assumed to be perfect. This stepwise creation of the planning program makes evaluating it easier. The basic investment planning model presented here constitutes the foundation for further improvements.

Place, publisher, year, edition, pages
Keyword [en]
Decision making, Mathematical modeling, Neural networks, Planning, Railway power supply, Approximators, Investment decisions, Investment planning, Power demands, Power supply, Power supply system, Power systems, Railway infrastructure, Tractive force, Traffic flow, Traffic forecasts, Voltage drop, Electric load forecasting, Electric power systems, Engines, Intelligent systems, Motor transportation, Railroad transportation, Railroads, Rails, Traffic surveys, Voltage control, Investments
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-36374DOI: 10.1109/ISAP.2009.5352887ScopusID: 2-s2.0-76549104711ISBN: 9781424450985OAI: diva2:430724
QC 20110712Available from: 2012-01-17 Created: 2011-07-12 Last updated: 2012-12-06Bibliographically approved
In thesis
1. Optimal Railroad Power Supply System Operation and Design: Detailed system studies, and aggregated investment models
Open this publication in new window or tab >>Optimal Railroad Power Supply System Operation and Design: Detailed system studies, and aggregated investment models
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Railway power supply systems (RPSSs) differ mainly from public power systems from that the loads are moving. These moving loads are motoring trains. Trains can also be regenerating when braking and are then power sources. These loads consume comparatively much power, causing substantial voltage drops, not rarely so big that the loads are reduced. By practical reasons most RPSSs are single-phase AC or DC. Three-phase public grid power is either converted into single-phase for feeding the railway or the RPSS is compartmentalized into separate sections fed individually from alternating phase-pairs of the public grid. The latter is done in order not to overload any public grid phase unnecessarily much.

This thesis summarizes various ways of optimally operating or designing the railway power supply system. The thesis focuses on converter-fed railways for the reasons that they are more controllable, and also has a higher potential for the future. This is also motivated in a literature-reviewing based paper arguing for the converter usage potential. Moreover, converters of some kind have to be used when the RPSS uses DC or different AC frequency than the public grid.

The optimal operation part of this thesis is mainly about the optimal power flow controls and unit commitments of railway converter stations in HVDC-fed RPSSs. The models are easily generalized to different feeding, and they cope with regenerative braking. This part considers MINLP (mixed integer nonlinear programming) problems, and the main part of the problem is non-convex nonlinear. The concept is presented in one paper. The subject of how to model the problem formulations have been treated fully in one paper.

The thesis also includes a conference article and a manuscript for an idea including the entire electric train driving strategy in an optimization problem considering power system and mechanical couplings over time. The latter concept is a generalized TPSS (Train Power Systems Simulator), aiming for more detailed studies, whereas TPSS is mainly for dimensioning studies. The above optimal power flow models may be implemented in the entire electric train driving strategy model.

The optimal design part of this thesis includes two aggregation models for describing reduction in train traffic performance. The first one presented in a journal, and the second one, adapted more useful with different simulation results was presented at a conference. It also includes an early model for optimal railway power converter placements.

The conclusions to be made are that the potential for energy savings by better operation of the railway power system is great. Another conclusion is that investment planning models for railway power systems have a high development potential. RPSS planning models are computationally more attractive, when aggregating power system and train traffic details.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xii, 77 p.
Trita-EE, ISSN 1653-5146 ; 2012:062
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-107037 (URN)978-91-7501-584-2 (ISBN)
Public defence
2012-12-17, sal Q2, Osquldasväg 10, KTH, Stockholm, 10:00 (English)

QC 20121206

Available from: 2012-12-06 Created: 2012-12-05 Last updated: 2013-02-25Bibliographically approved

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