Génie électrique
Arc Welding Current Control Using Thyristor Based Three-Phase Rectifiers Applied to Gas Metal Arc Welding Connected to Grid Network
The purpose of the welding operation is to ensure the continuity of the materials to be assembled in large industrial sectors. This study aims to suggest a topology of the Thyristor based three-phase rectifiers applied to the Gas Metal Arc Welding (GMAW) process connected to the grid network, the output currents are controlled and using various pulsed forms such as square, annealing, and spike pulse operations and investigate and compare between the effects of the three references welding currents structures on the welding current, welding voltage, droplet diameter, and welding quality. To have the best pulse operation, the amplitude and frequency are kept the same for all operations, the application of meshing graphs in the references of welding currents structures, welding current, welding voltage, and droplet diameter can illustrate a clear comparison between them. The simulation results show that the square pulse operation is the best among them. The Single-Sided Amplitude Spectrum (SSAS) method is also applied to the welding current and droplet diameter of the three operations under slow and rapid droplet detachment rates to estimate the droplet detachment frequency. The results show the great success of the SSAS in estimating the precise frequency. Voir les détails
Mots clés : Gas Metal Arc Welding, three-phase rectifier, grid network, SSAS method, welding current, welding voltage, droplet diameter, detachment frequency
CONTRIBUTION À LA RÉCONFIGURATION D’ONDULEUR ÀTOLÉRANCE DE PANNE APPLIQUÉE AU PARC ÉOLIEN CONNECTÉAU RÉSEAU ÉLECTRIQUE
Cet article propose une nouvelle technique de diagnostic basée sur les vecteurs de Park associés aux coordonnées polaires pour ladétection et la localisation des défauts de circuit- ouvert (CO), ainsi que l’intégration de l’onduleur reconfigurable à tolérance depanne afin de permettre la continuité de service du système du parc éolien. Le modèle utilisé est celui d'une éolienne à vitessevariable couplée à une génératrice asynchrone à double alimentation (GADA) connecté au réseau électrique via unconvertisseur à tolérance de panne pour améliorer les performances après l’apparition du défaut. Ce convertisseur est utilisé àbase d’IGBT pour l’obtention d’une précision acceptable avec des fréquences de commutation élevées. Ce modèle est bienadapté pour l'observation des harmoniques et la performance dynamique du système de contrôle sur des périodes de tempsrelativement courtes (généralement des centaines de millisecondes à une seconde). Cette méthode permet d'extraire l'énergiemaximale du vent lors d’une faible vitesse du vent en optimisant la vitesse de la turbine tout en minimisant les contraintesmécaniques sur la turbine pendant les rafales de vent. Pour illustrer l’amélioration de diagnostic des défauts en circuit ouvert duconvertisseur à tolérance de panne, plusieurs résultats sont présentés et discutés dans cet article. Voir les détails
Mots clés : Génératrice asynchrone à double alimentation (GADA) Turbine, Onduleur, diagnostic, détection, localisation, Reconfiguration, défaut, Circuit- ouvert, Insulated gate bipolar transistor (IGBT).
Modeling and Fuzzy MPPT Controller Design for Photovoltaic Module Equipped with a Closed-Loop Cooling System
Electrical energy generated by a photovoltaic (PV) panel depends heavily on two climatic conditions: total solar irradiance and absolute temperature. If high intensity of the solar illumination contributes positively to increasing electrical power, a high degree of absolute temperature has, by contrast, a negative effect on its electrical characteristic. In this paper, the electrical efficiency provided by a conventional PV panel is enhanced using the proposed photovoltaic thermal (PVT) panel. The latter contains serpentines fed by a water tank, which allows cooling its PV cells at high temperature. Accordingly, the desired enhancement needs two main requirements: an efficient PVT panel model that accurately describes the actual PVT panel behavior and an efficient controller that correctly tracks the maximum power point tracking (MPPT). For this reason, a number of experimental test data is firstly recorded from an actual ISOFOTON I-50-PVT module under different climatic conditions. Afterward, the recorded data are fitted by the Curve Fitting Toolbox (CF-Tool), creating therefore a 2-dimensional lookup table, used in the following step. Next, the fuzzy logic control (FLC) strategy is employed to synthesize the proposed MPPT-FLC controller, which should ensure a good extraction of the maximal electrical power. To validate the effectiveness of the proposed MPPT-FLC controller based on a 2-dimensional lookup table, the obtained performance is compared, in terms of electrical power and duty cycle, to those provided by an MPPT-FLC controller for a conventional PV panel in various climatic conditions. Voir les détails
Mots clés : Photovoltaic thermal system, 2-Dimensional lookup table, fuzzy logic control, Maximum Power Point Tracking
Les techniques de reconnaissance de Formes Application : à la reconnaissance de l’écriture Arabe
Le domaine de la reconnaissance de l’écriture arabe manuscrite a reçu un intérêt de recherche intensif aux cours des deux dernières décennies et se concrétise aujourd’hui par un grand nombre d’applications opérationnelles. Malgré ces avancées, le problème reste ouvert à la recherche et à l’expérimentation à cause des caractéristiques morphologiques complexes du manuscrit arabe qui sont à l’origine de la défaillance des traitements. Les travaux de recherches présentés dans cette thèse s’inscrivent dans ce cadre et constituent une contribution au domaine de la reconnaissance de l’écriture arabe manuscrite. Dans un premier temps, nous proposons une approche globale basée sur une combinaison parallèle de classifieurs pour la reconnaissance hors ligne de mots arabe manuscrits. Le système développé s’articule autour de quatre modules distincts : prétraitement, extraction de primitives, classification basée sur deux types de classifieurs : SVM et k plus proches voisins flou et un module de combinaison. Des expériences ont été effectuées sur des images de la base de référence INF/ENIT ont montré l’efficacité du système proposé.En second temps, nous présentons un nouvel algorithme de segmentation en caractères des mots arabes manuscrits. Cet algorithme est fruit d’une coopération entre un ensemble de règles morphologiques spécifiques à l’écriture arabe (AMS) et un classifieur SVM mono classe, dont la tache principale consiste à accepter ou rejeter les points de segmentation primaires générées par le module AMS. Il a montré de bons résultats de segmentation sur des mots extraits de la base de données de référence IFN/ENIT. Voir les détails
Mots clés : reconnaissance de l’écriture arabe manuscrite ; combinaison de classifieurs ; séparateurs à vaste marge ; k plus proches voisins flou ; la transformée en cosinus discrète, histogrammes des gradients orientés ; segmentation.
Bearing Fault Diagnosis Using De-noising Techniques Based on EMD Combined with Coefficients Correlation
The vibration signals of a rolling bearing contain important information which can be used in early defect detection and diagnosis. This signal is usually noisy and the information about the fault can be lost. In this paper, a new denoising method based on Empirical Mode Decomposition Iterative Interval Thresholding and estimation of the correlation coefficient (EMD-corIIT) is presented. The results are compared with others proposed methods. The application of this technique to the experimental results shows that this method can extract effectively the fault features of rolling bearing compared with the others cited methods. Voir les détails
Mots clés : Denoising EMD, thresholding, vibration signal, Bearing Fault, Correlation Coefficients
Effect of Zinc/Cadmium Proportion in the Properties of CdS LayersDeposited by Chemical Bath Depostion Method
Cadmium poisoning and the cost of panel recovery which is very expensive and difficult in the buffer layersof CdS in solar cell, for these two drawbacks, we do a search on the effect of proportion of zinc/cadmium inthe properties layers of CdS. For this, our studies study the properties of CdxZn1-xS layers deposited bychemical bath (CBD). CdZnS thin films were synthesized by chemical bath deposition (CBD) with differentdeposition protocols to optimize deposition parameters such as temperature, deposition time, ionconcentrations and pH. The surface morphology, structural, optical and chemical properties of the CdZnS thinfilms were studied by SEM, XRD, Raman and UV-visible spectrophotometer. The transmittance is 80% inthe visible region 300 nm - 800 nm; the crystalline structure is hexagonal for x ≥ 0.5 and cubic for x≤0.5, thegrain size is between 85.7 and 100 nm. It is observe that the transmittance and the shape change with theconcentration of zinc in the solution; this result favours the application of these films in solar cells application. Voir les détails
Mots clés : CdZnS, chemical bath, SEM, Raman, solar cells, thin films.
Robust Fuzzy On–Off Synthesis Controller for Maximum Power Point Tracking of Wind Energy Conversion
Due to the major discrepancy between the exigent demands regarding the electrical energy quality and the irregular nature of the wind, which is characterized by random and instantaneous speed variations, it is vital to determine the optimal operating point that maximizes the efficiency of the obtained electrical energy in the grid from wing generators. The present paper addressed the above-mentioned problem by introducing a fuzzy logic control system in the standard on–off control strategy. The purpose is to maximize the power point tracking of wind energy and to reduce the mechanical loads in which variable wind speed is considered. This idea has the ability to drive the conversion system to its optimal operating point, thereby solving the switching component problem (also referred to as the chattering problem) of the standard on–off control strategy. To examine the validity of the proposed idea, the obtained results are compared with those given by the standard on–off control strategy wherein our method can ensure a better dynamic behavior of the wind energy conversion system. Voir les détails
Mots clés : Wind Energy Conversion System (WECS), Maximum Power Point Tracking (MPPT), Standard and fuzzy on–off controller, Induction generator (IG)
Particle Swarm Optimization Based Maximum Power Point Tracking Algorithm for Photovoltaic Energy Conversion System
In order to extract the maximum power from PV system, the maximum power point tracking (MPPT) method is one of the most popular and widely used and it has always been applied in photovoltaic energy conversion system. However, this method exhibits fluctuations among the maximum power point (MPP) due to the nature of unpredicted and changes of the environmental parameters. Therefore, it is significant to include an intelligent controller that can track the maximum peak regardless of parameters variations such as: irradiation and temperature. This paper describes the design and development of particle swarm optimization (PSO) based maximum power point tracking (MPPT) algorithm for photovoltaic energy conversion system. The proposed MPPT is simple, flexible, accurate and efficient in maximum photovoltaic power tracking. In this work, MATLAB/Simulink simulation package is used to simulate the performance of the proposed MPPT algorithm. The performance of the proposed PSO algorithm is evaluated by comparing it with the conventional P&O method in terms of tracking speed and accuracy. The simulation results demonstrate that the tracking capability of the PSO algorithm is more efficient, comparing to the traditional one, particularly under parameters variation conditions. Voir les détails
Mots clés : Photovoltaic systems, Maximum Power Point Tracking (MPPT), Particle Swarm Optimization (PSO), perturb and observe (P&O)
Corrosive effects of the electromagnetic induction caused by the high voltage power lines on buried X70 steel pipelines
This paper diagnoses the corrosive effects of the electromagnetic induction caused by double circuit high voltage power lines (HVPL) on the buried X70 steel pipelines. To achieve this objective, firstly the electromagnetic interference between the double circuit HVPL and the X70 steel pipeline (the distribution of the magnetic field and the induced AC current densities in the buried X70 steel pipeline) and the factors affecting this interference such as the vertical distance between the double circuit HVPL and the X70 steel pipeline, and the conductor phase sequence orientation were studied. Then, electrochemical measurements were used to characterize the corrosion polarization properties of X70 steel in simulated soil at various AC current densities. The results show that with an increase in the AC current density, the corrosion rate of the X70 steel increased, indicating that the induced AC current density has accelerated the corrosion degree of X70 steel, by comparison with that in the absence of the AC current density. We can conclude from these results that the electromagnetic induction caused by the double circuit high voltage power lines affects the electrochemical characteristic of the X70 steel pipeline and accelerates the corrosion of the pipeline. Voir les détails
Mots clés : Electromagnetic induction, high voltage power line, induced AC current density, X70 steel pipeline, corrosion, Finite element method.
A new time–frequency method for identificationand classification of ball bearing faults
In order to fault diagnosis of ball bearing that is one of the most critical components ofrotating machinery, this paper presents a time–frequency procedure incorporating a newfeature extraction step that combines the classical wavelet packet decomposition energydistribution technique and a new feature extraction technique based on the selection ofthe most impulsive frequency bands. In the proposed procedure, firstly, as a pre-processing step, the most impulsive frequency bands are selected at different bearing conditionsusing a combination between Fast-Fourier-Transform FFT and Short-Frequency Energy SFEalgorithms. Secondly, once the most impulsive frequency bands are selected, the measured machinery vibration signals are decomposed into different frequency sub-bands byusing discrete Wavelet Packet Decomposition WPD technique to maximize the detectionof their frequency contents and subsequently the most useful sub-bands are representedin the time-frequency domain by using Short Time Fourier transform STFT algorithm forknowing exactly what the frequency components presented in those frequency sub-bandsare. Once the proposed feature vector is obtained, three feature dimensionality reductiontechniques are employed using Linear Discriminant Analysis LDA, a feedback wrappermethod and Locality Sensitive Discriminant Analysis LSDA. Lastly, the Adaptive NeuroFuzzy Inference System ANFIS algorithm is used for instantaneous identification andclassification of bearing faults. In order to evaluate the performances of the proposedmethod, different testing data set to the trained ANFIS model by using different conditionsof healthy and faulty bearings under various load levels, fault severities and rotatingspeed. The conclusion resulting from this paper is highlighted by experimental resultswhich prove that the proposed method can serve as an intelligent bearing fault diagnosissystem. Voir les détails
Mots clés : Vibration signal processing Bearing fault diagnosis Bearing faults LDA, LSDA, ANFIS, WPD