III
ABSTRACT
For a half a century, the increasing development of AC electrical traction railway networks in
France relied on the progress made in the infrastructure power supply an in the rolling stock. However,
over the past two decades, increased traffic and the introduction of modern locomotives were the cause
of electrical phenomena that have proven harmful to the operation of the railway network. The first
events that occurred induced serious faults on board locomotives. It was overvoltages resulting from
unfavourable interaction between the internal impedance of the infrastructure and the harmonics
generated by the electrical vehicles using thyristor controlled rectifiers. More recently, with the
massive introduction of active front-end locomotives (also called four-quadrant locomotives),
problems of low frequency oscillations and instability were observed causing power off locomotives
or disjunction of the sector sub-station. This now constitutes a major obstacle to the widespread use of
the new technology of IGBT rectifiers on board vehicles.
These disturbances of the electrical traction circuit affect the operation of the rail system
generally causing delays or traffic cancellations. They can also damage the energy quality of the
power upstream network at a level such that the supply sub-station must be disconnected. Thus, the
engineering management of the French National Railways – SNCF, has taken steps to understand and
avoid the occurrence of the observed phenomena. An internal collaboration between the Rolling Stock
Department and the Power Traction Fixtures Division was established as well as a partnership with
LAPLACE. This document is the result of this collaboration.
The objective of this thesis is to study and model the interactions between locomotives and fixed
installations for electric traction on the French rail network 25kV/50Hz. This script has two main
parts, which organized as follows:
The first part is devoted to the study of the phenomenon of very low frequency modulation of the
catenary voltage. The models of the two main components of the system, namely the single-phase
power and the active front-end locomotives are first presented. Studies conducted this way, help to
understand the origin of the phenomenon and then to develop a method to characterize the vehicle to
find the stability limits in problems sectors of the rail network. This led us to propose a general
representation of modern locomotives as an admittance matrix that can be obtained by direct
measurement on real machines.
The second part is the study of harmonic interactions causing overvoltages on the catenary.
Systematic analysis of the phenomenon is based on simulation tools of power electronics circuits using
a collection of specific elementary models. The first step consists in developing a “medium frequency”
model of the power network in order to highlight the resonance and anti-resonance frequencies of the
line/sub-station set. The second step is to model locomotives to take into account their harmonic
response. In the end, it becomes possible to know whether a particular machine will generate
deformations of the catenary voltage, by checking if any of the harmonic components of the consumed
current coincides with one of the characteristic resonances of the traction electric circuit.