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Perin, Igor, Walker, Geoff, & Ledwich, Gerard(2019)Load sharing and wayside battery storage for improving AC railway net-work performance, with generic model for capacity estimation, Part 1.IEEE Transactions on Industrial Electronics, 66(3), Article number:8365150 1791-1798.

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https://doi.org/10.1109/TIE.2018.2838066

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Abstract— Load sharing between feeder stations has the ability to significantly improve the performance of AC electric railways by reducing the number of the traction power network grid connections and minimizing losses and plant sizes. The existing Rail Power Conditioner (RPC) technology, traditionally used for load balancing, is investigated from the new perspective of providing reactive voltage support and active power sharing between stations. The concept is validated through a feasibility study conducted for a heavy haul AC railway network.

Index Terms—traction, power, network, railway, rail

power conditioner

I. INTRODUCTION

INCE their origins in the 1840s, electric railways have

evolved through the early DC traction power networks

to the now prevalent AC systems [1-3]. The original DC

networks are still in use in railways where power demand

and distance are not critical, such as metro and light rail,

while AC systems are preferred for applications requiring

long distances and high power, such as high speed

commuter and freight trains.

This paper focuses on the AC electric railway networks.

The AC traction network used for the French TGV railway

is presented by Roussel [4], and Nugent details the

Australian heavy haul electric railway, operating in central

Queensland [5].

The paper is the first part of a two paper set. Part 1

focuses on improving the performance of AC electric

railways through load sharing via Rail Power Conditioners.

The second part looks at further improvements through

wayside energy storage.

A. Traditional AC Traction Power System

Electric locomotives are supplied using an overhead line

(OHL) network, fed from the utility transmission or

Manuscript received 12 Oct 2017, revised 20 Mar 2018, accepted 02

May 2018.

I.Perin is with Aurizon, Brisbane, 4000, Australia (iperin@hotmail.com) G.R.Walker and G.Ledwich are with the School of Electrical

Engineering and Computer Science, Queensland University of Technology,

Brisbane, 4000, Australia (e-mail: geoffrey.walker@qut.edu.au, g.ledwich@qut.edu.au).

distribution grid, via feeder stations located alongside the

rail corridor. Track section cabins (TSCs) are positioned in

between feeder stations to facilitate sectioning.

AC locomotives are almost universally implemented as

single phase electric loads and, consequently, the entire

traction power network is a single phase system. Each

feeder station contains typically two single phase power

transformers fed from a pair of phases sourced from the

three phase HV grid side. The adjacent power transformers

are always connected to alternate phases of the utility grid to

avoid feeding the entire traction network from a single pair

of phases. This prevents paralleling of any two adjacent

power transformers, be it at one feeder station or at

neighboring feeder stations, meaning that each power

transformer feeds a radial section, isolated from the rest of

the network.

This is illustrated in Figure 1, where the power

transformer from Feeder Station 1, connected to phases B, C

feeds the section between Feeder Station 1 and the Track

Section Cabin and similar applies to Feeder Station 2 power

transformer connected to phases C, A. The bus section

breakers at both Feeder Stations and the Track Section

Cabin are normally open with neutral sections preventing

the locomotives from bridging two adjacent feeding

segments. Train loads can never be shared by two or more

power transformers. This feeding arrangement is commonly

referred to as the “V/V” connection.

B. Rail Power Conditioners

The single phase railway network invariably creates load

unbalance in the upstream three phase utility grid. Special

transformer connections have been developed over the years

to alleviate the problem of unbalanced loads [6, 7]. A

commonly used arrangement is the Scott transformer,

installed between a three phase source grid and two single

phase legs of the traction network. If the two single phase

legs are equally loaded, the Scott transformer presents a

balanced three phase load to the source side. In practice, the

two load legs are rarely equally loaded, therefore the special

transformer connection, at best, only alleviates the

unbalance problem.

Load Sharing and Wayside Battery Storage for Improving AC Railway Network Performance, with Generic Model for Capacity Estimation,

Part 1

Igor Perin, Aurizon, Geoffrey R Walker, Gerard Ledwich, Queensland University of Technology (QUT)

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IV. CONCLUSIONS

The RPC components and their ratings are dependent on the

particulars of the network, the traffic and the relative location

of the installation.

As the study demonstrates, in this case, reactive support

alone is insufficient, as it fails to adequately improve the

voltage profile and even slightly exacerbates the overloading

of the Norwich Park transformer. The addition of the active

power exchange normalizes the voltage, eliminates the

overloading of the Norwich Park transformer and significantly

reduces the MVA requirements of the converters and the

combined MVAr delivered by the RPC.

The position of the RPC system in this case is determined by

the location of the existing Peak Downs feeder station. A more

convenient location could reduce the component sizing.

Mobile installations, allowing for accurate selection of the

most convenient location to deal with outages would be of

particular interest.

Further improvements in terms of RPC component sizing,

and network performance could be achieved through wayside

large scale energy storage. The energy storage solution is

beyond the scope of this paper and is investigated in a further

publication.

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Igor Perin (M’09) was born in Belgrade, Serbia in 1969. He received his M.S. degree in electrical engineering from the University of Belgrade, Serbia, in 1995. Since 2013, he has been a PhD candidate with the Queensland University of Technology, Brisbane, Australia. From 1995 to 2000, he was with Energoprojekt, working on electrical power projects in Nigeria, Botswana and Serbia. From 2001 to 2002, he was with UGL in Sydney, Australia, and from 2002 and 2006 he

worked for Powerlink, Brisbane, Australia. Between 2006 and 2008 he worked for WorleyParsons in Brisbane, Australia. Since 2008 he has worked as Senior Electrical Engineer with Aurizon, Brisbane, Australia. His research interests include railway electrification using FACTS technologies and energy storage. Mr. Perin has published a number of papers in the fields of Static Frequency Converters and Rail Power Conditioners for traction power networks.

Geoffrey R. Walker (M’98) was born in Brisbane, Australia in 1969. He received the B.E. degree (Communications and Electronics) and the Ph.D. degree in multilevel converter modulation and control from The University of Queensland (UQ), Brisbane, in 1990 and 1999, respectively. Geoff joined the Queensland University of Technology (QUT) as an Associate Professor in 2013, and currently serves as the leader of the

Power Engineering discipline. From 2008 to 2013, he worked as a senior electrical engineering consultant in Aurecon’s Transmission and Distribution group, Brisbane, across various areas including rail traction, earthing studies, electricity transmission planning, and

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renewable energy project design and review. From 1998 to 2007, he was the power electronics lecturer at the University of Queensland. Geoff’s research interests centre on grid interactive power electronic converters such as dSTATCOMs, PV inverters, battery inverters and EV chargers – their design, optimization, and interaction with the LV grid. A second group of project are tied to high power, high bandwidth multilevel converters. Geoff has previously worked in and maintains an active interest in the pro-audio and industrial electronics sectors.

Gerard Ledwich (SM’89) received the Ph.D. degree in electrical engineering from the University of Newcastle, Newcastle, Australia, in 1976. He has been Chair Professor in electrical asset management at Queensland University of Technology (QUT), Brisbane, Australia, since 1998. He was the Head of the Electrical Engineering Department, University of

Newcastle, from 1997 to 1998. Previously, he was with the University of Queensland from 1976 to 1994. His research interests are in the areas of power systems, power electronics, and controls. Dr. Ledwich is a Fellow with the Institute of Engineers, Australia.