IEEE Electrification Magazine - September 2014 - 15

100

(A)

50
0
-50
-100

1.52

(A)

iac

1.54

1.56

1.58

1.6

1.56

1.58

1.6

Time (s)
(a)

iab

60
40
20
0
-20
-40
-60
1.52

1.54
Time (s)
(b)

Figure 19. (a) The line currents and (b) the injected currents i ab and i ca .

Direct converters
provide a link
between the source
and the load without
additional storage
elements.

Nevertheless, to avoid over-voltages,
it is necessary to choose the filtering
elements with regard to preexisting
harmonics in the network.
As far as the application in ac traction lines is concerned, simulation
results validated the operation of this
novel topology, and a 1.2-Mvar prototype
of the compensator was built and tested
at the SNCF's test platform, confirming
the analytical study and system performance. Although a STATCOM solution
using cascaded VSIs could be considered, the ac chopper
topology, presented in Figure 5, exhibits lower semiconductor
losses. Furthermore, a low-loss voltage-unbalance compensator based on the CCI concept was proposed, and the case
study of a real French substation was undertaken. Despite the
limited compensation domain of the presented topology, the
study highlights its feasibility in railway substations. In fact, in
this kind of application, average compensation is sufficient to
respect the utility's requirements. The semiconductor power
losses and energy-storage requirements compared to the
widely used VSI topology make the proposed solution very
attractive for railway operators. A very simple control can be
achieved by varying only the chopper duty cycles, without the
need for control loops for other variables. The simulation
results confirmed the operation of the novel topology under
real conditions. At present, an industrial solution of the chopper-controlled Steinmetz circuit is under development and
will be tested in 2016.

compensators based on PWM AC
choppers," Eur. Power Electron. J., vol.
21-23, pp. 22-32, Sept. 2011.
G. Raimondo, P. Ladoux, A. Lowinsky, H. Caron, and P. Marino, "Reactive
power compensation in railways based
on acboost choppers," IET J. Electr. Syst.
Transport., vol. 2, no. 4, pp. 169-177,
Dec. 2012.
P. Ladoux, G. Raimondo, H. Caron,
and P. Marino, "Chopper-controlled
Steinmetz circuit for voltage balancing in railway substations," IEEE Trans. Power Electron.,
vol. 28, no. 12, pp. 5813-5822, Dec. 2013.
G. Raimondo. (2012, Feb.). Power quality improvements
in 25 kV 50 Hz railways substation based on chopper controlled impedances. Ph.D. thesis, Institut National Polytechnique de Toulouse, France. [Online]. Available:
http://ethesis.inp-toulouse.fr/archive/00001820/01/raimondo.pdf

biographies
Philippe Ladoux (philippe.ladoux@laplace.univ-tlse.fr) is a
full professor at the Plasma and Conversion of Energy
Research Laboratory, University of Toulouse, France.
Joseph Fabre (joseph.fabre@laplace.univ-tlse.fr) is a postdoctoral researcher at the Plasma and Conversion of Energy
Research Laboratory, University of Toulouse, France.
Hervé Caron (herve.caron@sncf.fr) is an engineer at the
Department of Fixed Installations for Traction Power Supply in the French National Railways Company.

For Further reading
P. Ladoux, Y. Chéron, A. Lowinsky, G. Raimondo, and
P. Marino, "New topologies for static reactive power

IEEE Elec trific ation Magazine / s ep t em be r 2 0 1 4

http://www.ethesis.inp http://www.toulouse.fr/archive/00001820/01/rai

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2014