**Preface to "Modeling of Wind Turbines and Wind Farms"**

Wind turbine technology has matured over the years and is considered a reliable renewable energy technology. Furthermore, wind energy is a research field characterized by a high degree of interdisciplinarity, given the wide range of technical fields involved, such as aerodynamics, mechanics, meteorology, resource assessment, as well as electrical engineering addressing the generation, transmission, and the integration of wind power plants into the power systems.

The modeling of wind power plants (WPP), wind turbines (WT), and WT components is currently gaining key importance during the design stage, but also over their entire lifetime with respect to operation and maintenance. This book presents solutions to all these challenges, including the development, validation, and implementation of WT components, WTs, and WPP models in applications related to aerodynamics, mechanics, resource assessment, or wind power integration.

Half of the contributions deal with wind integration into power systems, analyzing and forecasting the effects on grid stability and reliability. Different power system agents, such as transmission system operators (TSOs) and distribution system operators (DSOs), are currently engaged in addressing transient analyses, WT frequency provision, WT reactive power capability, or new control strategies to deal with these issues. Assessment and validation of such models is also a major issue due to the importance and difficulty of collecting real data.

The remaining contributions deal with the other technical disciplines mentioned when talking about the interdisciplinarity of wind energy. Works are presented on modeling WT mechanical dynamics, aerodynamics and aeroelasticity, WT blades, WT failures and maintenance, WT lightning protection, wind energy prediction and forecasting, and wind farm (WF) design.

The technical contents will be of grea<sup>t</sup> help to researchers as well as practicing engineers in the wind and power industry. The contributions offer a broad view of the relevant, diversified and challenging problems involved in wind turbine technology modeling.

Finally, we would like to thank all the authors for the 25 contributions and the reviewers for the care taken in preparing and assessing the contents. Moreover, we acknowledge the support of the Spanish Ministry of Economy and Competitiveness and the European Union—FEDER Funds, ENE2016-78214-C2-1-R-.

> **Emilio Gomez-Lazaro, Estefania Artigao**

> > *Special Issue Editors*
