Power Quality Improvement and Low Voltage Ride through Capability in Hybrid Wind-PV Farms Grid-Connected Using Dynamic Voltage Restorer

© 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission.This paper proposes the application of a dynamic voltage restorer (DVR) to enhance the power quality and improve the low voltage ride through (LVRT) capability of a three-phase medium-voltage network connected to a hybrid distribution generation system. In this system, the photovoltaic (PV) plant and the wind turbine generator (WTG) are connected to the same point of common coupling (PCC) with a sensitive load. The WTG consists of a DFIG generator connected to the network via a step-up transformer. The PV system is connected to the PCC via a two-stage energy conversion (dc-dc converter and dc-ac inverter). This topology allows, first, the extraction of maximum power based on the incremental inductance technique. Second, it allows the connection of the PV system to the public grid through a step-up transformer. In addition, the DVR based on fuzzy logic controller is connected to the same PCC. Different fault condition scenarios are tested for improving the efficiency and the quality of the power supply and compliance with the requirements of the LVRT grid code. The results of the LVRT capability, voltage stability, active power, reactive power, injected current, and dc link voltage, speed of turbine, and power factor at the PCC are presented with and without the contribution of the DVR system.Peer reviewe

Voltage Profile and Power Quality Improvement in Photovoltaic Farms Integrated Medium Voltage Grid using Dynamic Voltage Restorer

© 2020 The Author(s). This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-sa/4.0/).In this paper, we have presented a simulation study to analyze the power quality of three phases medium voltage grid connected with distribution generation (DG) such as photovoltaic (PV) farms and its control schemes. The system uses two-stage energy conversion topology composed of a DC to DC boost converter for the extraction of maximum power available from the solar PV system based on incremental inductance technique and a three-level voltage source inverter (VSI) to connect PV farm to the power grid. To maintain the grid voltage and frequency within tolerance following disturbances such as voltage swells and sags, a fuzzy logic-based Dynamic Voltage Restorer is proposed. The role of the DVR is to protect critical loads from disturbances coming from the network. Different fault conditions scenarios are tested and the results such as voltage stability, real and reactive powers, current and power factor at the point of common coupling (PCC) are compared with and without the DVR system.Peer reviewe

Effets des défauts de soudure aluminothermique sur le comportement mécanique des rails

L’assemblage des rails de chemin de fer se fait généralement à travers un procédé de soudage par aluminothermie. Ce procédé consiste en la coulée de métal de jonction entre les deux extrémités de rails à assembler. La qualité de cet assemblage dépend étroitement des conditions de la réalisation qui sont généralement difficiles à respecter. En effet, les techniques classiques de contrôle des rails, mettent souvent, en évidence la présence des défauts de soudure dans la jonction. Selon les observations, ces défauts peuvent être classés en deux types : défauts d’adhésion (ou défauts de collage) et défauts de porosité (ou défauts de soufflures multiples). Chacun de ces défauts, peut constituer un site privilégié de concentration des contraintes. Selon le niveau de ces contraintes, des éventuels processus d’endommagement risquent de se développer et mettant le rail hors service. Il semble donc nécessaire de modéliser le comportement mécanique de ces soudures avec ces défauts en vue de les classer par leur criticité. Dans cette étude, nous avons donc modélisé avec un même chargement et avec les mêmes conditions aux limites, la jonction de soudure pour chaque type de défaut. Les résultats obtenus sont très concluants et permettent de bien orienter l’approfondissement de notre analyse coté paramètres de soudage

Effect of Curcuma longa Aqueous Extract on Male Fertility in Aluminum Exposed Wistar Rats

To assess the effects of Curcuma longa aqueous extract (CE) on fertility in male rats exposed to Aluminum chloride (AlCl3), Twenty four male rats, 3 months old, divided into 4 groups (n=6) were used. Animal from the first group received, by the oral route, water-containing AlCl3 at the dose of 34 mg/kg body weight (BW). Rats from the second group received both AlCl3 at the same dose in combination with oral treatment of CE at a dose of 200 mg/kg BW. The third group received only an oral administration of CE with the same dose. Rats from the fourth group, without any treatment, served as control. After 4 weeks of experimentation, AlCl3 exposure showed a significant decrease in sperm concentration (4.58±0.65 × 106 cells /ml), and percentage of viability (61.53±23.63 %), and an increase of morphological abnormalities (26.11±17.84 %). A significant decreased in serum testosterone levels (0.31±0.26 ng/ml) and an increase of testicular malondialdehyde (MDA) level (0.16±0.015 μM/g) were also observed. Histological examination of the testes showed degeneration of the seminiferous tubules, germ line cells, and interstitial cells. However, CE treatment concomitant to AlCl3 showed that the rate of morphological abnormalities (19±2.65 %) is significantly decreased compared to AlCl3 group, with a significant increase in serum testosterone (1.17±0.24 ng/ml) and a significant decrease in MDA (0.11±0.003μM/g) level. Microscopic examination revealed a significant regeneration of seminiferous tubules and interstitial cells. This study demonstrated an ameliorative effect of Curcuma longa aqueous extract in testicular tissue and sperm quality. Keywords: Curcuma longa, Aluminum, fertility, testosterone, malondialdehyde (MDA), sperm

Sliding mode sensorless control of an asynchronous motor based on an MRAS-type observer

This work deals with the problem of speed control of a sensorless asynchronous motor. Conventional control laws by PI or PID for example, although still widely used, may prove to be insufficient or unsuitable. We then develop control laws by state feedback, their use nevertheless requires the measurement of the state vector. However, in many cases, sensors for measuring all the physical quantities are not available, essentially for cost reasons. An observer, which is a mathematical object, makes it possible to reconstruct this state vector from the only physical measurements available. In this context, we will propose the use of the sliding mode technique, which is a recursive control method and represents a tool for the study of dynamic stability. We will then approach the observers and in particular those resulting from the theory of the reference model (MRAS). In this proposed work, we are interested in the study of the asynchronous motor by the application of the sliding mode which is a relatively recent technique for nonlinear systems. It is combined with the vector control principle with oriented rotor flux to design robust machine control laws. The motor state quantities are estimated by the MRAS algorithm. A comparison of the performances is established to come out with general conclusions and in particular with regard to the use of the observer to estimate the quantities of state of the engine to control it later by this technique

A Review of Microsatellite Markers and Their Applications in Rice Breeding Programs to Improve Blast Disease Resistance

Over the last few decades, the use of molecular markers has played an increasing role in rice breeding and genetics. Of the different types of molecular markers, microsatellites have been utilized most extensively, because they can be readily amplified by PCR and the large amount of allelic variation at each locus. Microsatellites are also known as simple sequence repeats (SSR), and they are typically composed of 1–6 nucleotide repeats. These markers are abundant, distributed throughout the genome and are highly polymorphic compared with other genetic markers, as well as being species-specific and co-dominant. For these reasons, they have become increasingly important genetic markers in rice breeding programs. The evolution of new biotypes of pests and diseases as well as the pressures of climate change pose serious challenges to rice breeders, who would like to increase rice production by introducing resistance to multiple biotic and abiotic stresses. Recent advances in rice genomics have now made it possible to identify and map a number of genes through linkage to existing DNA markers. Among the more noteworthy examples of genes that have been tightly linked to molecular markers in rice are those that confer resistance or tolerance to blast. Therefore, in combination with conventional breeding approaches, marker-assisted selection (MAS) can be used to monitor the presence or lack of these genes in breeding populations. For example, marker-assisted backcross breeding has been used to integrate important genes with significant biological effects into a number of commonly grown rice varieties. The use of cost-effective, finely mapped microsatellite markers and MAS strategies should provide opportunities for breeders to develop high-yield, blast resistance rice cultivars. The aim of this review is to summarize the current knowledge concerning the linkage of microsatellite markers to rice blast resistance genes, as well as to explore the use of MAS in rice breeding programs aimed at improving blast resistance in this species. We also discuss the various advantages, disadvantages and uses of microsatellite markers relative to other molecular marker types