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For economical reasons, wind turbine systems must be located in favourable sites generating a higher pro- ductivity. These are often located in areas with weak electric grid infrastructures. The constraints related to this type of grids limit the penetration levels of wind energy. These constraints are mainly related to power quality in the grid as well as the economical aspects of the project. In this study, we take into account the slow voltage variations and the flicker phenomenon. The models used are based on the development of a set of relations derived from engineering knowledge related to both technical and economical points of view. The maximal penetration level of a fixed speed wind turbine system is determined for a given grid. The power control has been investigated to improve wind turbine system integration. Obtained results show the necessity to adapt technological choices to the requirements of weaker grids. Penetration levels and wind turbine cost may be greatly improved using variable speed systems

An accurate estimation of rotational effects is critical during the preliminary design of wind turbines. For this purpose, different stall delay models were developed based on the centrifugal pumping mechanism. However, their generality is not yet thoroughly evaluated. In this work, we investigated the causal relationship between the radial flow, the pressure reduction, and forces augmentation. Three stall delay models, which represent different solutions of the centrifugal pumping mechanism, were verified and modified to accurately predict the radial flow, the pressure coefficient, and normal and tangential force coefficients. Then, the three modified stall delay models were calibrated using the radial flow data available from the literature. Finally, they were validated against the experimental data of the NREL phase VI and MEXICO rotors. The results showed that the centrifugal pumping produces a small chordwise pressure gradient in the separated boundary layer, which produces a small augmentation in the normal and tangential force coefficients. In contrast, the measured pressure coefficient and the normal and tangential force coefficients showed a large augmentation compared to the three modified stall delay models. Consequently, the lack of generality of current stall delay models is mainly due to the centrifugal pumping assumption. Furthermore, the verification and calibration of these stall delay models allowed us to isolate large errors in the model's output due to the model's assumptions. Thus, the importance of a rigorous verification and calibration before performing the validation.

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This study presents a decision-support tool for preliminary design of a horizontal wind turbine system. The function of this tool is to assist the various actors in making decisions about choices inherent to their activities in the field of wind energy. Wind turbine cost and site characteristics are taken into account in the used models which are mainly based on the engineering knowledge. The present tool uses a constraint-modelling technique in combination with a CSP solver (numerical CSPs which are based on an arithmetic interval). In this way, it generates solutions and automatically performs the concept selection and costing of a given wind turbine. The data generated by the tool and required for decision making are: the quality index of solution (wind turbine), the amount of energy produced, the total cost of the wind turbine and the design variables which define the architecture of the wind turbine system. When applied to redesign a standard wind turbine in adequacy with a given site, the present tool proved both its ability to implement constraint modelling and its usefulness in conducting an appraisal.