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MODEL DEVELOPMENT AND SIMULATION OF SMALL ISOLATED WIND
TURBINES
Jean-Daniel Langlois
ABSTRACT
The field of wind energy has experienced rapid growth over the past years. However,
the sector of small wind turbines, used mainly for battery charging applications in grid-
isolated installations, has not had the same level of technical and scientific support as the
large wind turbine sector. As such, it is necessary to develop some tools for the design,
analysis and optimization of small wind turbines adapted to their specific characteristics in
order to improve their performance. This work presents a method for power performance
evaluation of small wind turbines in order to evaluate the interaction between the rotor and
the permanent magnet alternator.
First of all, the modeling of each component of the system, that is the rotor, the alternator
and the battery, is carried out. After, a structured step-by-step method, taking the model of
each component, is presented in order to couple the rotor with the alternator. The model
of the rotor uses the coefficient power curve, which is a function of the tip speed ratio that
can be obtained analytically from the blade geometry. The model of the permanent magnet
alternator uses the Park transformation, which makes it possible to consider the anisotropy
of the alternator as well as the winding resistance. The proposed method makes it possible
to visualize the interaction between the rotor and the alternator and to calculate the power
curve of a wind turbine. Lastly, a temporal model is developed using Matlab/Simulink
in order to analyze the time-dependant behaviour of the system. The time-based model
requires the development of a time-series generator to give the wind speed and the power
consumption of the electric load. This time-based model makes it possible to verify if a
given wind turbine system is able to meet the requirements of a certain electric load for a
specific wind profile.
These tools are then used to measure the influence of the voltage variation of the battery,
during charge and discharge, on the power curve measurement and on the annual energy
production. In analyzing the coupling between the rotor and the generator, it is shown
power curve of the wind turbine can vary greatly depending on the battery voltage, but
thereafter, with a time-based simulation, one can see that this variation is of less impor-
tance during operation. However, it is shown that, during power performance testing, the
specific test conditions can lead to different measurements of the power curve. The work
is ended with a review of different methods to optimize the coupling between the rotor and
the alternator in order to maximize the energy production of the wind turbine.