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Elaboration of the Minimum Capacitor for an Isolated Self Excited
Induction Generator Driven by a Wind Turbine
Fadi Ouafia, Abbou Ahmed
Mohammadia School of Engineers, Mohammed V University, Avenue Ibn Sina, Rabat, Morocco
Department of electrical engineering Mohammed V University, Rabat, Morocco
Keywords:
Wind turbine, Induction generator, self-excitation, excitation capacitance required, wind speed, magnetiz-
ing inductance, steady state, real parts of the roots, voltage build up, no load, prime mover, synchronous speed.
Abstract:
In this paper, a detailed procedure is elaborated, based on evaluation of the roots in the characteristic equation
of the stator current, to determine the proper capacitor bank that will be used to reach the self-excitation. For
that, a d-q model of the self-excited induction generator under no load is presented using Matlab-Simulink
to verify if the self-excitation comes true or not. This study illustrates furthermore, the influence of the
magnetizing inductance on the voltage buildup.
1 INTRODUCTION
A wind turbine with Self-excited Induction Genera-
tor SEIGs is a subject that is gaining renewed inter-
est with the increasingly frequent use of the asyn-
chronous generator. In the field of renewable ener-
gies, in general, and that of wind turbines, in particu-
lar, has largely contributed to the development of the
induction machine as a Self-excited Induction Gen-
erator thanks to its several advantages such as: very
reliable and relatively inexpensive compared to other
types of generators. It also has some mechanical char-
acteristics which makes it very suitable for the conver-
sion of wind energy (sliding of the generator as well
as a certain capacity of overload), very high lifetime;
non-existent maintenance (bearings ...), very simple,
rugged, and produces high power per unit mass (N.
M. Okana and al., 2015), (A.Abbou and al., 2013).
The self excited machine, in its operation in generator
mode, poses a particular problem : it cannot start it-
self as a generator and needs an external source to per-
form this operation which is called self-excitation : it
requires excitation current to magnetize the core and
produce the rotating magnetic field. This current is
supplied from an external source, for grid connected
systems; however, this current is supplied from a bat-
tery of capacitors, for isolated system which is our
case. When a charged capacitor is connected and the
generator is driven by a prime mover, a transient ex-
citing current will flow and produce a rotated mag-
netic flux, so as a result, the power will be generated
and supplied to the external source.
Several approaches have been reported in previous
studies to determine the sufficient value of the ca-
pacitance to stimulate a self excited induction gener-
ator (A.K and al., 1990), (N.H.Mal and al., 1986), (
N.H.Malik and al., 1987), (M.Orabi and al., 2000),
(S.S.Murthy al., 1982). Most of these approaches ap-
ply loop equations in the steady state model of per
phase equivalent circuit such us : Nodal Admittance
Approach, Loop Impedance Approach, and LC Res-
onance Principal. These kinds of approaches give the
appropriate capacitance corresponding to the mini-
mum capacitance in steady state analysis, but they are
inapplicable for transient analysis.
The main purpose of this study is to present a new
approach to determine the minimum capacitance re-
quired for excitation in a SEIG. For this, we should,
first look behind its process and extract an accurate al-
gorithm that will serve us to achieve the aim. For this,
we have, first, recalled the basic concepts for mod-
elling of RLC circuit, since this one is similar to the
self-excited induction generator. Then, a review of the
characteristic stator equation of the SEIG, the roots of
this equation is discussed as well as the choice of the
accurate capacitance.
264
Ouafia, F. and Ahmed, A.
Elaboration of the Minimum Capacitor for an Isolated Self Excited Induction Generator Driven by a Wind Turbine.
DOI: 10.5220/0009774302640270
In Proceedings of the 1st International Conference of Computer Science and Renewable Energies (ICCSRE 2018), pages 264-270
ISBN: 978-989-758-431-2
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