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An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0003-2109-060X
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.ORCID iD: 0000-0001-7330-146X
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0002-8189-2420
2013 (English)In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 30, 23-40 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation overtime. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

Place, publisher, year, edition, pages
2013. Vol. 30, 23-40 p.
Keyword [en]
Optimization, Railway, Power systems, Special ordered sets of type 2 (SOS2), MINLP, Moving loads
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-107033DOI: 10.1016/j.trc.2013.01.009ISI: 000318387500002Scopus ID: 2-s2.0-84875241859OAI: oai:DiVA.org:kth-107033DiVA: diva2:574490
Note

QC 20130610. Updated from submitted to published.

Available from: 2012-12-06 Created: 2012-12-05 Last updated: 2017-12-07Bibliographically 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.
Series
Trita-EE, ISSN 1653-5146 ; 2012:062
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
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)
Opponent
Supervisors
Note

QC 20121206

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

Open Access in DiVA

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