Periodic System Approximation for Operational Modal Analysis of Operating Wind Turbine

International audienceThe inherent modelling of the operational wind turbines and rotating machines do not agree in general with the assumptions of the operational modal analysis (OMA) methods developed for civil engineering, where time invariant systems are considered. Current OMA methods for rotating machines introduce datapre-processing to adapt classical identification methods. However, they show strong limitations and rely on strong assumptions, such as the isotropy of the rotor, making them hardly applicable in practice. To overcome these limitations, this paper proposes to employ the Floquet theory of periodic system to approximate rotating systems as time invariant systems. Thus, classical identification methods can be used to retrieve the parametric signature of the periodic systems. This Floquet-based approximation gives a physical meaning to the identified eigenmodes. The proposed approach is validated on both a small numerical model and an aero-servo-elastic numerical model of a rotating 10MW wind turbine, with isotropic and anisotropic rotors, using the stochastic subspace identification to retrieve the modes and their uncertainty

Mode shape phase change detection in wind turbine under anisotropy variation

International audienceFault detection by modal analysis is a highly developed field in civil engineering. For wind turbines, a loss of isotropy for the rotor can be the consequence of a defect in the angle of attack (pitch) of the blades, or the accumulation of ice, or else the presence of structural defects resulting in a loss of stiffness on one or more blades. It is highly desirable to apply classical OMA techniques, and this despite the rotation of the blades. It is shown in this paper that it is possible to apply LTI approaches on wind turbines similarly to the methodology usually applied to standard civil engineering structures using an approximate Fourier modeling of the eigenmodes. The monitoring of anisotropy using the mode shapes of the estimated modes is validated with an example where a global loss of stiffness of 5% of a rotor blade is simulated

Détection d'anisotropie d'un rotor d'éolienne par suivi du changement de phase des modes propres

National audienceFault detection by modal analysis is a highly developed field in civil engineering. Despite the rotation of the blades, it is possible to apply it and develop similar approaches for wind turbines using a Fourier modeling of the eigenmodes. A loss of isotropy for the rotor can be the consequence of a defect in the angle of attack (pitch) of the blades, of the accumulation of ice or else the presence of structural defects resulting in a loss of stiffness on one or more blades. The monitoring of this effect using the deformations of the estimated modes is validated with an example where a global drop in stiffness of 5% of a rotor blade is simulated.La détection de défaut par analyse modale est un domaine très développé dans le génie civil. Malgré la rotation des pales, il est possible de l'appliquer et de développer des approches similaires pour les éoliennes en utilisant une modélisation des modes propres en base de Fourier. Une perte d'isotropie du rotor peut être la conséquence d'un défaut d'angle d'attaque (pitch) des pales, de l'accumulation de glace ou bien de la présence de défauts structurels entraînant une perte de raideur sur une ou plusieurs pales. La surveillance de ce phénomène à partir des déformées des modes estimés est validée avec un exemple où une baisse globale de raideur de 5% d'une pale du rotor est simulée

Suite de la discussion de la motion de M. Rabaud-Saint-Etienne sur la création de petits assignats, lors de la séance du 6 mai 1791

Germain d'Orsanville Ambroise François, Allarde Pierre-Gilbert Leroy, baron d'. Suite de la discussion de la motion de M. Rabaud-Saint-Etienne sur la création de petits assignats, lors de la séance du 6 mai 1791. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XXV - Du 13 avril 1791 au 11 mai 1791. Paris : Librairie Administrative P. Dupont, 1886. pp. 622-623

Mode shape phase change detection in wind turbine under anisotropy variation

International audienceFault detection by modal analysis is a highly developed field in civil engineering. For wind turbines, a loss of isotropy for the rotor can be the consequence of a defect in the angle of attack (pitch) of the blades, or the accumulation of ice, or else the presence of structural defects resulting in a loss of stiffness on one or more blades. It is highly desirable to apply classical OMA techniques, and this despite the rotation of the blades. It is shown in this paper that it is possible to apply LTI approaches on wind turbines similarly to the methodology usually applied to standard civil engineering structures using an approximate Fourier modeling of the eigenmodes. The monitoring of anisotropy using the mode shapes of the estimated modes is validated with an example where a global loss of stiffness of 5% of a rotor blade is simulated

Linear Time Invariant Approximation for Subspace Identification of Linear Periodic Systems Applied to Wind Turbines

International audienceIn this paper, subspace identification for wind turbines and more generally rotating periodic systems are investigated. Previous works have stressed the difficulty of modeling such systems as Linear Time Invariant and thus to apply classical Stochastic Subspace Identification. Such works plead for periodic or augmented theories. In this paper, the classical SSI can be applied to recover modal information that is related to the eigenstructure of the instrumented system despite the system excitation being modeled as non-stationary

Lifetime Prediction Modeling of Non-Insulated TO-220AB Packages with Lead-Based Solder Joints during Power Cycling

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