Modélisation et commande d’un générateur éolien à double excitation isolé en vue de l’amélioration de son rendement et de la diminution de la fatigue mécanique

This subject contributes to the modeling and control of a wind conversion system based on a Double Excitation Synchronous Generator (DESG). The degree of freedom provided by the wound excitation allows the improvement of the energy efficiency on the operation’s cycles with random solicitations, as it is the case for wind turbines.The aim of this research is to implement robust control techniques for the DESG in order to optimize its aerodynamic efficiency and to reduce its mechanical loads. In this context, a hybrid generator connected to an isolated load for wind applications is presented. First, linear models are established. These models are used to set up the appropriate control structures from both an electrical and mechanical point of view. At the same time, very complete nonlinear models are developed allowing a validation in an advanced simulation platform taking into account the space harmonics of the generator, the switching effects of the converters and the torsional effects on the shaft. Moreover, a 3 kW wind emulator is built to evaluate the contribution of the hybrid generator in the wind conversion systems field and then improve the synthesized controllers. Two robust control strategies for a hybrid machine are implemented and a comparison between a CRONE controller and a H∞ controller is presented. Satisfying results are obtained with a better performance for the CRONE regulator compared to H∞ one. In addition to the problem of optimizing the production of the wind energy conversion system, attempts have also been made to reduce the generator harmonic distortion ratios by using two solutions: passive filtering and reduction of the electromagnetic torque ripple by acting on the excitation current. Although there are improvements at high rotation speeds, these solutions are not sufficient for a connection of the proposed architecture to the grid.Once the applicability of the DESG in the wind energy field has been proven in the case of a 3 kW wind conversion system, we have considered a more realistic case. To this end, we have interfaced the developed advanced electric model with an aeroelastic model available on the FAST software, to take into account the mechanical couplings and the flexibilities. The turbine chosen for the study is the WindPACT 1.5MW turbine. In this part, robust controllers dealing with the reduction of mechanical fatigue are developed.The model of WindPACT turbine based on the hybrid generator is finally connected to the grid and the control laws necessary for this connection are implemented and validated under the Matlab Simulink platform.