IEEE Electrification Magazine - September 2016 - 14

Discussion
All of railway power supply solutions presented here
have examples of field implementation. Table 2 compares the different solutions. SVCs are an established
technology, but they need very large passive components and operate at a low device switching frequency,
which necessitates large filters. STATCOMs operate as
active power filters, but they require an additional
transformer due to the low-voltage ratings of IGBTs and
GTOs. The main advantage of SVCs and STATCOMs is
that they can be retrofitted to existing substations with
minimal interruption of the service.
Full-power static converter feeder stations offer the
best performance. Although they are the most effective
solution when frequency conversion is required, they are
associated with high costs for 50- or 60-Hz railway lines.
However, they do not require a supply from a dedicated
high-voltage transmission line and can be connected to
the public grid without introducing a load imbalance or
significant harmonics. This can be translated into land
savings as well as auxiliary equipment and switchgear
rated for lower voltages, and it makes them more attractive for new railways rather than for retrofitting existing
feeder stations.
Cophase power supplies and STATCOMs have similar
performances, but cophase supplies can omit neutral
sections between consecutive parts of a track and
require a lower-power rating for the full compensation
of the negative sequence of the input current. Similarly
to STATCOMs and SVCs, cophase supplies can be retrofitted easily as they can be added in parallel to existing transformers.
Another factor to consider is that the regulations on
grid imbalance vary in different countries, and a full negative sequence compensation is not always required. The
SVC, STATCOM, and cophase converter ratings can be
optimized to meet only regulation standards, which will
reduce the installation cost. In contrast, the full-power
converter solution has to be rated for the full traction
load but does not require the same design for conventional short circuit levels as it can have much lower fault
levels due to the controllability of the voltage on the
overhead line side. Moreover, the greater flexibility of the
power control offered by static converters is a key factor
for the introduction of smart railways, where electric railways will be fully integrated in the power system and
help improve its operations by integrating storage devices, contributing to the voltage and frequency regulation,
and optimizing the use of electrical power for trains.

For Further Reading
N. Lang, "Electrifying history," ABB Rev., no. 2, pp. 88-94, 2010.
J. A. P. Lopes, C. L. Moreira, and A. G. Madureira, "Defining
control strategies for MicroGrids islanded operation," IEEE
Trans. Power Syst., vol. 21, no. 2, pp. 916-924, 2006.
Y. Horita, N. Morishima, M. Kai, M. Onishi, T. Masui, and M.
Noguchi, "Single-phase STATCOM for feeding system of

I E E E E l e c t r i f i cati o n M agaz ine / SEPTEMBER 2016

Tokaido Shinkansen," in Proc. 2010 Int. Proc. Power Electronics
Conf., Sapporo, Japan, pp. 2165-2170.
H. Wang, Y. Liu. K. Yan, Y. Fu, and C. Zhang, "Analysis of static VAr compensators installed in different positions in electric
railways," IET Electr. Syst. Transp., vol. 5, no. 3, pp. 129-134, 2015.
J. Ranneberg, "Transformerless topologies for future stationary AC-railway power supply," in Proc. 2007 European Conf.
Power Electronics and Applications, Aalborg, Denmark, pp. 1-11.
M. Winkelnkemper, A. Korn, and P. Steimer, "A modular direct converter for transformerless rail interties," in
Proc. 2010 IEEE Int. Symp. Industrial Electronics, Bari, Italy,
pp. 562-567.
Z. Shu, S. Xie, and Q. Li, "Single-phase back-to-back converter for active power balancing, reactive power compensation, and harmonic filtering in traction power system," IEEE
Trans. Power Electron., vol. 26, no. 2, pp. 334-343, 2011.
M. Chen, Q. Li, C. Roberts, S. Hillmansen, P. Tricoli, N. Zhao,
and I. Krastev, "Modelling and performance analysis of
advanced combined co-phase traction power supply system
in electrified railway," IET Gener. Transm. Distrib., vol. 10, no. 4,
pp. 906-916, 2016.

Biographies
Ivan Krastev (ixk879@bham.ac.uk) received his M.Eng.
degree in electronics and electrical engineering in 2012
from the University of Birmingham, United Kingdom,
and is currently pursuing a Ph.D. degree in electrical engineering. His research interests include modular multilevel
converters, energy storage for hybrid electric vehicles, and
boost inverters. He is a Student Member of the IEEE.
Pietro Tricoli (p.tricoli@bham.ac.uk) received his M.Eng.
degree in electrical engineering in 2002 and his Ph.D.
degree in electrical engineering in 2005 from the University of Naples Federico II, Italy. He is currently a lecturer in
electrical power and control at the University of Birmingham, United Kingdom. His research interests include
modeling and control of traction converters, ac and dc
electrification systems, power converters for wind, and
photovoltaic generation. He is a Member of the IEEE and
the IEEE Industrial Electronics Society.
Stuart Hillmansen (s.hillmansen@bham.ac.uk)
received his B.S. degree in physics in 1996, his M.S. degree
in advanced mechanical engineering in 1997, and his
Ph.D. degree in mechanical engineering in 2001 from
Imperial College, London. He is currently a senior lecturer
in electrical energy systems at the University of Birmingham, United Kingdom. His research interests include railway traction systems, ac and dc electrification systems,
novel traction technologies, system optimization, and
driver control.
Minwu Chen received his B.S. and Ph.D. degrees in
electrical power systems from Southwest Jiaotong University, Chengdu, China, in 2004 and 2009, respectively.
He is currently an associate professor with the Department of Electrical Engineering, Southwest Jiaotong University. His research interests include power quality
control and monitoring and optimizing traction power
supply systems.

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2016