Renewable energy was strongly encouraged. It doesn’t produce emissions either provided by the sun, wind, wa- terfalls or plant growth. They participate in the fight against the greenhouse effect and CO₂ emissions in the at- mosphere, facilitate rational management of local resources, and also create jobs. Solar (solar photovoltaic, solar thermal), hydro, wind, biomass, geothermal energy are inexhaustible resource of energy versus “energy stock” from fossil fuels deposits such us scarce oil, carbon, natural gas.

In this paper, study focuses on wind energy conversion systems. Indeed, wind energy has become a major pro- ducer of renewable electric energy.

A wind turbine generator system (WTGS) transforms the wind energy into electrical energy. In fact, wind turbines generate mechanical forces such as windmills of the past. Through their blades, wind turbine captures the wind kinetic energy and transforms it into mechanical one.

Then this later was transformed into electric energy by a generator.

There are many types of generator available for wind energy conversion; as example induction generator in all its forms like wound rotor asynchronous generator, dual stator induction generator, MADA, etc. The permanent magnet synchronous generator is selected for many reasons. A permanent magnet synchronous generator is cha- racterized by the absence of gearbox and reduced active weight, besides having a high power density and a high efficiency (disappearing of the copper losses in rotor).

Generally the wind turbine generator based on rotational speed can be splited into two types: fixed and varia- ble speed WTGS. Fixed speed turbines are easier to interface with the electrical grid. However, variable speed turbines are able to extract more energy from the wind and are the design preferred by the wind industry.

This paper interested to a variable speed WTGS. It has higher efficiency, especially at low wind speeds and also its power variations are lower than fixed speed turbines.

The paper analyzes a complete model of a variable wind turbine equipped with a permanent magnet synchron- ous generator it also proposes a vector control strategy to control the wind turbine generator. This strategy in- cludes a speed controller and two current controllers.

The wind conversion system model and the control schemes were verified using Matlab/Simulink. Simulations results are selected, dicussed and come to prove the obtained performances of the used controllers.

The wind energy captured by the blades was transformed by the wind turbine into mechanic energy.

The model studied is illustrated by Figure 1 that contains the wind model, an aerodynamic part and a me- chanical model.

The PMSG model can be written, in the d-q synchronously rotating reference frame, by the following equation system [1] [6]

where are the synchronous rotating reference frame; is the armature resistance;, are the ge- nerator inductance on the d-q axis;, are, respectively, the d- and q-axis components of current;, are the d- and q-axis voltage components, respectively, is the pole pairs number and is the permanent magnet flux.

In the d-q synchronously rotating reference frame, the electromagnetic torque is represented by [1] :

Vector control strategy is used to have more preferment results, to control the wind turbine.

As given in Equation (11) we have a problem of coupling between d- and q-axis, represented by the terms and. Vector control concept is recommended, in order to overcome this problem of coupling

Simulations are carried out, in order to prove the wind turbine model and the effectiveness of the proposed con- trol strategy. The block simulated is represented by Figure 7. It include, the different parts of the Wind Energy Conversion System [1] [11] such as the wind turbine model that has as input the electromagnetic torque and the mechanic rotational speed as output. The permanent magnet synchronous generator model which has three inputs; the two voltage components and and the electric rotational speed of the wind turbine. The control model take the quadrature current, the direct current and the reference electric wind tur- bine rotational speed as inputs.

The complete WECS bloc given by Figure 7 was built in Simulink and its simulation results are given by Figures 8-19. The wind turbine parameters and the PMSG one used in simulation are illustrated in the Appen- dix.

Simulations are carried with the following model:

Simulation results demonstrate the performances of the wind turbine model and the vector control strategy. In fact, the output mechanical rotational speed is assumed at the reference one; is null as desired, is proportional to. Therefore the value of the power coefficient can be better than the current one as shown by Figure 19 Cp isn’t the maximum one so the wind turbine power also isn’t in the max and the tip speed ratio isn’t optimal as given by Figure 18. The real but the optimum one is that illustrated by Figure 19 when Cp is maximum.

In this paper, the different bloc of the wind energy conversion system was studied and modeled. In fact, the model of the wind turbine has been presented, the permanent magnet synchronous generator using in variable speed wind turbine has been modeled, controlled and simulated. Using Matlab/Simulink, simulation results were carried when the proposed WECS model was confirmed and the performances of vector control strategy are substantiating.

We faced a number of problems, when making the different component model of the wind energy conversion system. First, the performances of the WECS are relied to the choice of pitch angle. Then, the aerodynamic power is related to the wind speed. And as assumed by simulation results, the coefficient power isn’t in its maximum, the speed ratio isn’t in the optimum one and the turbine power isn’t maximal. So, as results, trying to overcome these problems, we propose for the continuation of this chain of conversion energy controlling the pitch angle, studying and research of the maximum power point tracking to have more preferment results.