Electrotechnique
Fault Diagnosis of an Induction Generator ina Wind Energy Conversion System Using SignalProcessing Techniques
In this article, a contribution to fault diagnosis of an in-duction machine in a wind energy conversion system in closed-loopoperation using a combination between short-time Fourier transformand discrete wavelet transform algorithms is proposed. An on-linefault diagnostic technique based on stator currents analysis of thesquirrel-cage induction generator is proposed to detect and localizeabnormal electrical conditions that indicate, or may lead to, a statoror rotor failure in a squirrel-cage induction generator. This techniquealso permits identification of a fault severity factor and consequentlyhelps to determine the best choice of correctivemaintenance. Further-more, a generalized model of the squirrel-cage induction generatoris used to simulate both the rotor and stator faults, taking iron losses,main flux, and cross-flux saturation into account. The efficiency ofdiagnostic procedure in closed-loop operation of the wind energyconversion system under non-stationary operating conditions is illus-trated with simulation results. Voir les détails
Mots clés : fault diagnosis;, Induction Generator;, Wind Energy Conversion System;, Signal Processing Techniques
DIAGNOSTIC DES DEFAUTS MECANIQUES ETELECTROMAGNETIQUES SUR LES AEROGENERATEURS ÀBASE DE MACHINE ASYNCHRONE À DOUBLE ALIMENTATION
The use of doubly-fed induction machine in wind conversion systems occupies a verysignificant place. Therefore, the diagnosis of potential faults in these machines is nowadays a majorpriority for the industrialists in particular and for the scientists in general.Currently, the requirements of renewable energy, in terms of wind conversion system, is growingup due to the availability of the industrial processes became an economic argument than a meremarketing. However, the monitoring and the diagnosis require at the same time a better functionaland behavioral knowledge of the system in order to highlight, in an early stage, the conditionsleading to a failure situation.In this thesis, we are interested of the fault of the doubly-fed induction machine. Firstly, we willdevelop the doubly-fed induction machine model that can to represent the machine behavior invarious function modes and structural imbalances. Among the faults, the fault of static, dynamic andmixed eccentricity, and the phases openings faults, and the stator or rotor inter-turns short-circuit areconsidered.A spectral analysis of stator currents of the doubly-fed induction machine taken at the time ofthese faults will be presented subsequently.In the last part, we will develop an approach of monitoring allowing to obtain information on themachine state, the detection and the localization of the faults. Voir les détails
Mots clés : défauts mécaniques, électromagnétique, aérogénérateurs, GADA, modélisations
Condition Monitoring and Fault Detection in Wind Turbine Based on DFIG by the Fuzzy Logic
oubly-fed induction generator is widely used in wind turbine conversion systems. Several research works are being made to efficiently approve existing condition monitoring and fault detection techniques for these systems. The condition monitoring ofthese systems becomes more and more important, the main obstacle in this task is the lack of an accurate analytical model to describe a faulty DFIG in the majority of the research tasks. In this paper, we present the monitoring strategy of short-circuit fault between turns of the stator windings and open stator phases in doubly-fed induction generator by fuzzy logic technique. The stator condition monitoring is diagnosed based on the root mean square values of current magnitude in addition to the knowledgeexpressed in rules and membership function. The proposed strategy is verified using simulations performed via the model of Doubly-fed induction generator built in MatLab ® SIMULINK. Voir les détails
Mots clés : Wind turbine, DIFG, Monitoring, Detection fault, Fuzzy logic.
Parameters Identification for Jiles-Atherton Model using Genetic Algorithms
The aims of this work is the modeling of the hysteresis loop in ferromagnetic materials, and allowed to highlight of the difficulty that exists in the choice of an model, both accurate and fast, for implantation in a calculation code field. Through this work, we tried to implement the means to incorporate the hysteresis phenomenon; we proposed a procedure for the identification and optimization of the hysteresis loop by genetic algorithms (GA). The obtained results by this method permit to get the hysteresis loop using numerical simulation techniques. Experimental cycles on different samples allowed to us to identify the different optimized parameters and determine the GA approach on the calculation of various parameters of the hysteresis loop. Voir les détails
Mots clés : Hysteresis Loop, Ferromagnetic Materials, genetic algorithms (GA), Jiles-Atherton model
Parameters Identification for Jiles-AthertonModel using Genetic Algorithms
The aims of this work is the modeling of the hysteresis loop in ferromagneticmaterials, and allowed to highlight of the difficulty that exists in the choice of an model,both accurate and fast, for implantation in a calculation code field. Through this work, wetried to implement the means to incorporate the hysteresis phenomenon; we proposed aprocedure for the identification and optimization of the hysteresis loop by geneticalgorithms (GA). The obtained results by this method permit to get the hysteresis loopusing numerical simulation techniques. Experimental cycles on different samples allowedto us to identify the different optimized parameters and determine the GA approach on thecalculation of various parameters of the hysteresis loop. Voir les détails
Mots clés : Hysteresis Loop, Ferromagnetic Materials, genetic algorithms (GA), Jiles-Atherton Model.
DIAGNOSTIC DES DEFAUTS MECANIQUES ET ELECTROMAGNETIQUES SUR LES AEROGENERATEURS A BASE DE MACHINE ASYNCHRONE A DOUBLE ALIMENTATION.
Face à l’épuisement des ressources énergétiques fossiles et aux problèmes environnementaux causés par l’émission des gaz à effet de serre lors de l’exploitation de ces ressources, d’autres ressources énergétiques alternatives ont été et doivent continuer à être développées. Parmi elles, une autre alternative, consiste à exploiter les énergies renouvelables, qui offrent la possibilité de produire de l’électricité proprement et surtout dans une moindre dépendance des ressources. Aujourd’hui, les éoliennes et particulièrement les offshores sont devenus compétitives en termes de coûts de production. Par conséquent, elles constituent une voie à ne pas négliger pour le développement de l’énergie éolienne. Sachant particulièrement, qu’elles peuvent connaître un développement économique et social durable. En effet, leur potentiel exploitable est considérable et la qualité des gisements est telle que des investissements rentables peuvent être envisageable. Dans cette thèse, nous nous intéressons principalement à leurs conceptions et l’étude des défauts éventuels afin d’éviter leurs arrêts intempestifs. Nous développons des modèles de comportement de la chaine éolienne à base d’une machine asynchrone à double alimentation (MADA). Nous nous intéressons à des modèles fins permettant la détection précoce et la localisation de défauts mécaniques et électromagnétiques éventuels. Voir les détails
Mots clés : énergies renouvelables, éolienne, machine asynchrone double alimentation (MADA), défauts mécaniques, défauts électromagnétiques, diagnostic, détection, localisation
Diagnostic & detection des cassures des barres du rotor d'une machine asynchrone a cage par l'analyse en ondelettes
In this thesis we used the wavelet technique for the diagnosis of the squirrel cage inductionmachines. This technique which offers a very fine analysis of the one-dimensional and twodimensionalsignals through decomposition in discrete wavelets or in wavelet packet is usedto extract the necessary information from the motor current of the machine. The resultobtained dismounts the effectiveness of the technique in the detection of the rotor defects andeven the detection of no-stationary where this characteristic is not available in the analysis byFFT. Voir les détails
Mots clés : Induction machine faults, squirrel cage induction machine modeling, wavelets technique
An Improved Method for Bearing Faults diagnosis
Envelope analysis is especially suitable for faultdiagnosis inducing periodic shocks or amplitude modulations suchas gears and bearings and has been applied widely for mechanicalfault detections over the last few decades. However, a criticallimitation of this technique is that it requires a prior knowledge onfiltering band. Due to this drawback, detecting machine defects atthe incipient stage when defect-characteristic components areweak in amplitude and without a distinctive spectral pattern posesa challenge to the conventional enveloping spectral analysistechnique .In order to overcome this limitation, this work gives anew signal processing approach for bearing faults diagnosis basedon Hilbert Transform (HT) and Fast Fourier Transform (FFT). Itis applied on real measurement signals collected from anexperimental vibration system. The monitoring results indicatethat the proposed method improves the bearing faults diagnosisrelatively to other common techniques. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Hilbert Transform (HT), Envelope Analysis (EA), Fast Fourier Transform (FFT)
CORROSION RESISTANCE EVALUATION OF DUPLEX STAINLESS STEEL 2205 INACIDIC AND CHLORIDE ENVIRONMENT
This work is mainly devoted to the study ofelectrochemical performance anticorrosive of stainless steel,2205 duplex by immersion in different study at roomtemperature and different concentrations of corrosive speciesenvironments. The chemical composition and morphologicalstructure of the stainless steel material, respectively, arecharacterized by X-ray fluorescence and by optical microscopy.Electrochemical tests are performed in three electrolytes,namely sodium chloride (NaCl) at 3 %, hydrochloric acid (HCl)3% and hydrochloric acid (HCl) 5%. The techniques used inthis study are potentiometric open circuit (OCP), linearpolarization (LP) and electrochemical impedance spectroscopy(EIS). The impedance spectra and the current - potential curvesobtained allowed the estimation of the rate of corrosion indifferent electrolytes and showed a change of the polarizationresistance (Rp) and the degradation kinetics of this materialdepending on the composition of the study areas. Voir les détails
Mots clés : duplex stainless steel, Pitting corrosion, PREN, Electrochemical impedance spectroscopy
Etude de l'éfficacité dans un système pointe-plan à la présence d'un isolant solide propre et pollué.
L'objectif de notre travail est l'étude par simulation numérique de l'efficacité des barrières isolantes propre et pollué, en fonction de leurs dimensions géométriques et leur position dans l'intervalle inter-électrodes en tenant compte de l'évolution de la décharge électrique. Voir les détails
Mots clés : décharges électriques, éléments finis, champ électriques, pollution isolateur, décharge d'arc