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The rapid evolution of wind energy in reducing CO2 emissions worldwide is undeniable, which is, in fact, expected to continue or even increase its impressive yearly capacity growth. In this regard, optimizing operations and maintenance of wind turbines (WTs) and farms is considered to be one of the options for reducing the levelized cost of electricity of wind energy. This can be achieved by developing innovative condition monitoring methods. To this end, the use of the windowed scalogram difference (WSD) algorithm, based on wavelets, is proposed as an alternative solution, combined with current signature analysis (CSA). The electric generator is one of the major contributors to WT failure rates and downtime, and doubly-fed induction generators (DFIGs) are the dominant technology in variable-speed WTs. In the present work, operational data on an in-service WT DFIG are analyzed over a period of eight months, in contrast to the majority of the studies in this field, which rely on laboratory or simulated data. The evolution of the fault, namely rotor mechanical asymmetry, at an early stage, is analyzed and quantified implementing WSD to the stator current signals, supported by the previous diagnosis achieved through CSA. The combination of CSA and WSD shows strong potential for diagnosing and tracking, respectively, incipient faults in in-service WT DFIGs.

Wind power plants are becoming a generally accepted resource in the generation mix of many utilities. At the same time, the size and the power rating of individual wind turbines have increased considerably. Under these circumstances, the sector is increasingly demanding an accurate characterization of vertical wind speed profiles to estimate properly the incoming wind speed at the rotor swept area and, consequently, assess the potential for a wind power plant site. The present paper describes a shape-based clustering characterization and visualization of real vertical wind speed data. The proposed solution allows us to identify the most likely vertical wind speed patterns for a specific location based on real wind speed measurements. Moreover, this clustering approach also provides characterization and classification of such vertical wind profiles. This solution is highly suitable for a large amount of data collected by remote sensing equipment, where wind speed values at different heights within the rotor swept area are available for subsequent analysis. The methodology is based on z-normalization, shape-based distance metric solution and the Ward-hierarchical clustering method. Real vertical wind speed profile data corresponding to a Spanish wind power plant and collected by using a commercialWindcube equipment during several months are used to assess the proposed characterization and clustering process, involving more than 100000 wind speed data values. All analyses have been implemented using open-source R-software. From the results, at least four different vertical wind speed patterns are identified to characterize properly over 90% of the collected wind speed data along the day. Therefore, alternative analytical function criteria should be subsequently proposed for vertical wind speed characterization purposes. The authors are grateful for the financial support from the Spanish Ministry of the Economy and Competitiveness and the European Union —ENE2016-78214-C2-2-R—and the Spanish Education, Culture and Sport Ministry —FPU16/0428

This paper presents a study of industry equipment electrical responses under voltage dips with different magnitude, duration and point-on-wave initiation. The analysis provides electrical sensitive curves for safe and reliable operation based on experimental tests performed over real AC-contactors, ground fault relays, variable speed drives, industrial computers and lighting loads. The presence of a relevant scatter-band where the sensitivity of some equipments in the presence voltage dips responds in a stochastic manner is analysed. The effect of the working temperature of the device is studied as well. A detailed description of the testing procedure is provided, proposing additional voltage dip parameters to characterize the equipment sensitivity in detail. In this way, existing standards and previously published contributions are reviewed and compared with the obtained results. The obtained results are useful for OEMs, Utilities as well as Uninterruptible Power Supply Manufacturers; where a more precise counting of equipment failures due to voltage dips is essential for an economic and technical assessment of power quality.

The available wind speed potential strongly depends on the existing wind profiles at different locations. In this way, the exploitation of this resource can be determined by the wind turbine power curve, relating both wind speed at the rotor hub and electric power from the wind turbine. According to the current international Standard for power performance, the wind speed at hub height is the main input parameter for the characterization of the power curve, being considered the air density as a secondary factor. Under this framework, the wind speed is considered as constant over the whole turbine swept rotor area. This assumption can achieve high level of accuracy for small wind turbines. However, current wind turbines are characterized by a large rotor diameter, being exposed to remarkable variations in wind speed with height. Moreover, this Standard will be modified in a short-term, with the aim of taking into account several wind measurements within the swept rotor area This paper reviews recent solutions to measure wind speed and direction based on remote sensing systems: SODAR and LIDAR technology. These systems are able to collect vertical wind profiles over a wide range of heights, providing a significant advantage in comparison with conventional approaches.

Hasta finales de septiembre de 2008, la energia solar fotovoltaica (FV) se concebia como un negocio muy atractivo en Espana, por lo que fueron muchos los que invirtieron en el sector FV. A partir de entonces, se publicaron una serie de modificaciones legales, algunas de ellas con caracter retroactivo, provocando cierto grado de inestabilidad en dicho sector. Por ello, en el presente trabajo se han analizado los cambios normativos sufridos por el sector FV espanol y, ademas, se ha estudiado el efecto de dichos cambios sobre una planta real. Algunos autores han analizado los principales cambios normativos sufridos por el sector FV en Espana.