Minimisation of the wind perturbations impact on the generation of electricity by variable speed wind turbines

Wind energy is seriously growing in response to environmental problems of traditional energy sources and aerogenerator technological improvements. The part of this kind of energy is each day more important in windy regions. Thus, the wind turbine power quality impact on the grid increases. Moreover, wind energy cost is still too high to compete with traditional sources on less windy sites. More intelligence can be introduced into wind turbines control to resolve these problems. This control must be done taking into account the whole wind turbine behaviour. Perturbations from wind have to be also considered. The thesis objective is to design control laws of a pitch regulated variable speed wind turbine, taking into account wind perturbations and four optimisation criterions. These criterions are: improvement of the power quality supply, of the energetic efficiency and of the control robustness and reduction of the aerogenerator drive-train fatigue loads. There are simulation models allowing the study of wind turbine control laws, but wind perturbations impact on the whole system is not generally considered with high precision. Here, a pitch regulated variable speed wind turbine simulation model is presented. Interaction between wind and wind turbine is accurately examined. This simulation model has been validated with real data of a 180 kW aerogenerator and with information from some papers. A pitch regulated variable speed wind turbine has different operating zones. Here, three zones are studied: one corresponding to medium wind speeds where turbine rotational speed is variable, the second related to higher speeds where aerogenerator rotates at nominal speed and the last related to wind speeds where the power captured by the turbine is limited with pitch control. Beside wind turbine general control strategy, different control designs are examined in each zone. Linear models allowing to study the system dynamical behaviour are obtained on different operating points from the non-linear simulation model. Some of these models are used as control models. Robust numerical regulators are synthesised in each operating zone. These regulators are then tested on the simulation model. Different controls are compared observing their behaviour in relation to the four control criterions linked to the thesis objective. A simulation model is practical to test control laws, but it is better to run also trials of these laws on a test bench before implementing them on a real wind turbine. Here, the aerogenerator studied in the thesis is emulated on a 15 kW test bench. After this, experimental trials are realised on this bench. The results in simulation and test bench trials show that advanced control laws allow improving the behaviour of a pitch regulated variable speed wind turbine. (author)