The paper presents methodologies to detect and locate short-circuit faults on the stator winding of VSI-fed PM brushless dc motors. Normal performance characteristics of the motor are obtained through a discrete-time lumped-parameter network model. The model is modified to accommodate shortcircuit faults in order to simulate faulty operation. Fault signatures are extracted from the waveforms of electromagnetic torque and phase-voltage summation using wavelet transform. Three independent detection techniques are introduced. Experimental measurements agree acceptably with simulation results, and validate the proposed methods. This work sets forth the fundamentals of an automatic fault detector and locator, which can be used in a fault-tolerant drive.Index Terms-Brushless dc motor, fault detection, wavelet transform.
Please cite this article in press as: Salem, F., Awadallah, M.A., Detection and assessment of partial shading in photovoltaic arrays. J. Electr. Syst. Inform. Technol. (2016), http://dx.
AbstractThe paper presents a methodology for detection and assessment of partial shading conditions in photovoltaic (PV) arrays based on artificial neural networks (ANN) as a preliminary step toward automatic supervision and monitoring. The PV array is modeled under normal and partial shading conditions for performance comparison. ANN is designed, trained, and tested for full identification of the partial shading condition. One ANN detects the presence of partial shading and distinguishes it from the uniform change in environmental conditions. If the first ANN detects partial shading on the PV array, other two ANN agents determine the shading factor and infers the number of shaded modules of the array, consequently. Results show excellent performance of ANN on the detection and assessment of partial shading.
In a deregulated power market with increasing penetration of distributed generators and renewable sources, energy storage becomes a necessity. Renewable energy sources are characterized by a fluctuating and intermittent nature, which simply means that energy may be available when it is not needed, and vice versa. Energy storage devices can help rectify the mismatch between generation and demand at any loading condition. Such devices can also provide some ancillary services, such as frequency regulation, voltage support, power quality improvement, transmission congestion relief, and system upgrade deferral. This paper presents an overview of the flywheel as a promising energy storage element. Electrical machines used with flywheels are surveyed along with their control techniques. Loss minimization and bearing system development are introduced. In addition, power system applications of flywheels are summarized. Finally, some outstanding technical difficulties are recommended for future research work.Résumé-Dans un marché d'énergie libéralisée avec une augmentation de la pénétration des générateurs distribués et des sources renouvelables, le stockage de l'énergie est devenu une nécessité. Les sources d'énergie renouvelables sont caractérisées par leur fluctuation et leur intermittence, ce qui signifie tout que l'énergie peut être disponible quand il n'est pas nécessaire, et vice versa. Les dispositifs de stockage d'énergie peuvent aider à remédier à l'inadéquation entre la production et la demande pour toute condition de chargement. Ces dispositifs peuvent aussi fournir quelques services annexes, comme la régulation de la fréquence, la régulation de tension, l'amélioration de la qualité de l'alimentation, l'allègement de la congestion de transmission, et le report des mises à niveau. Cet article présente un aperçu du volant comme un élément de stockage d'énergie prometteur. Les machines électriques utilisées avec des volants ainsi que leurs techniques de contrôle sont examinées. La minimisation des pertes et le développement du système de palier sont introduits. En plus, les applications du système d'alimentation de volants sont présentées brièvement. Enfin, quelques défis techniques demeurent en suspens pour les futurs travaux de recherche.
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