Active Power Compensation in the Interconnected Power System by Using Doubly Fed Induction Generator Based on Wind Turbine

ABSTRACT: The active power compensation has become the major concern for the power system engineers. A small change in the active power flow gives negative impact on the entire power system parameters. As the electrical power system is the most complex man made structure, hence, it's tough to maintain consistency though out the system, all day. To make the system stable proper monitoring is required or sometimes an auxiliary system can also be a good option, which can support the primary system during undesirable conditions. The recent developments indicate, for the electric power generation, wind energy forms are being utilized in a big way. These wind farms are not only playing vital role for the energy production but also contributing for the regulation of active and reactive power flow on the grid. This paper presents active power compensation of the grid with the help of Doubly Fed Induction Generator based on Wind Turbine. In this process, two converters are connected back to back, which are known as rotor side converter and grid side converter, have been used and the controlling of stator and rotor current can be achieved by the proper functioning of these two converters

An Assessment of the Hydrological Trends Using Synergistic Approaches of Remote Sensing and Model Evaluations over Global Arid and Semi-Arid Regions

Drylands cover about 40% of the world’s land area and support two billion people, most of them living in developing countries that are at risk due to land degradation. Over the last few decades, there has been warming, with an escalation of drought and rapid population growth. This will further intensify the risk of desertification, which will seriously affect the local ecological environment, food security and people’s lives. The goal of this research is to analyze the hydrological and land cover characteristics and variability over global arid and semi-arid regions over the last decade (2010–2019) using an integrative approach of remotely sensed and physical process-based numerical modeling (e.g., Global Land Data Assimilation System (GLDAS) and Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) models) data. Interaction between hydrological and ecological indicators including precipitation, evapotranspiration, surface soil moisture and vegetation indices are presented in the global four types of arid and semi-arid areas. The trends followed by precipitation, evapotranspiration and surface soil moisture over the decade are also mapped using harmonic analysis. This study also shows that some hotspots in these global drylands, which exhibit different processes of land cover change, demonstrate strong coherency with noted groundwater variations. Various types of statistical measures are computed using the satellite and model derived values over global arid and semi-arid regions. Comparisons between satellite- (NASA-USDA Surface Soil Moisture and MODIS Evapotranspiration data) and model (FLDAS and GLDAS)-derived values over arid regions (BSh, BSk, BWh and BWk) have shown the over and underestimation with low accuracy. Moreover, general consistency is apparent in most of the regions between GLDAS and FLDAS model, while a strong discrepancy is also observed in some regions, especially appearing in the Nile Basin downstream hyper-arid region. Data-driven modelling approaches are thus used to enhance the models’ performance in this region, which shows improved results in multiple statistical measures ((RMSE), bias (ψ), the mean absolute percentage difference (|ψ|)) and the linear regression coefficients (i.e., slope, intercept, and coefficient of determination (R2))

Synergistic Use of Remote Sensing and Modeling for Estimating Net Primary Productivity in the Red Sea With VGPM, Eppley-VGPM, and CbPM Models Intercomparison

Primary productivity (PP) has been recently investigated using remote sensing-based models over quite limited geographical areas of the Red Sea. This work sheds light on how phytoplankton and primary production would react to the effects of global warming in the extreme environment of the Red Sea and, hence, illuminates how similar regions may behave in the context of climate variability. study focuses on using satellite observations to conduct an intercomparison of three net primary production (NPP) models--the vertically generalized production model (VGPM), the Eppley-VGPM, and the carbon-based production model (CbPM)--produced over the Red Sea domain for the 1998-2018 time period. A detailed investigation is conducted using multilinear regression analysis, multivariate visualization, and moving averages correlative analysis to uncover the models\u27 responses to various climate factors. Here, we use the models\u27 eight-day composite and monthly averages compared with satellite-based variables, including chlorophyll-a (Chla), mixed layer depth (MLD), and sea-surface temperature (SST). Seasonal anomalies of NPP are analyzed against different climate indices, namely, the North Pacific Gyre Oscillation (NPGO), the multivariate ENSO Index (MEI), the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO), and the Dipole Mode Index (DMI). In our study, only the CbPM showed significant correlations with NPGO, MEI, and PDO, with disagreements relative to the other two NPP models. This can be attributed to the models\u27 connection to oceanographic and atmospheric parameters, as well as the trends in the southern Red Sea, thus calling for further validation efforts

Multidecadal Analysis of Beach Loss at the Major Offshore Sea Turtle Nesting Islands in the Northern Arabian Gulf

Undocumented historical losses of sea turtle nesting beaches worldwide could overestimate the successes of conservation measures and misrepresent the actual status of the sea turtle population. In addition, the suitability of many sea turtle nesting sites continues to decline even without in-depth scientific studies of the extent of losses and impacts to the population. In this study, multidecadal changes in the outlines and area of Jana and Karan islands, major sea turtle nesting sites in the Arabian Gulf, were compared using available Kodak aerographic images, USGS EROS Declassified satellite imagery, and ESRI satellite images. A decrease of 5.1% and 1.7% of the area of Jana and Karan islands, respectively, were observed between 1965 and 2017. This translated to 14,146 m2 of beach loss at Jana Is. and 16,376 m2 of beach loss at Karan Is. There was an increase of island extent for Karan Is. from 1965 to 1968 by 9098 m2 but comparing 2017 with 1968, Karan Is. lost as much as 25,474 m2 or 2.6% of the island extent in 1968. The decrease in island aerial extent was attributed to loss of beach sand. The southern tips of the island lost the most significant amount of sand. There was also thinning of beach sand along the middle and northern sections that exposed the rock outcrops underneath the beach. The process of beach changes of both islands was tracked by the satellite imagery from Landsat 1,3,5,7 and Sentinel-2 during 1972 to 2020. Other factors including the distribution of beach slope, sea level changes, as well as wind & current from both northward and eastward components were analyzed to show its impact on the beach changes. The loss of beach sand could potentially impact the quality and availability of nesting beach for sea turtles utilizing the islands as main nesting grounds. Drivers of beach loss at the offshore islands are discussed in the context of sea level rise, dust storms, extreme wave heights and island desertification

Study of enhancement in the dielectric and electrical properties of WO3-doped LiF nano-composite

We report the dielectric and electrical behavior of thermally evaporated lithium fluoride (LiF)-tungsten trioxide (WO3) (x wt% WO3-doped LiF; x = 0, 1, 3, 5, 7, 10) nano-composite thin films at room temperature over a wide range of frequencies from 0.1 Hz to 1 MHz. Among the various doping concentrations of WO3, the 5 wt% WO3-doped LiF nano-composite thin film reaches to the maximum dielectric constant similar to 25, compared with those of pure LiF similar to 9 thin film. The electrical studies of the films have been done by complex impedance spectroscopy and show the presence of grain and grain boundaries contribution in the films for all doping concentrations. The relaxation behavior in the nano-composite films has been observed in the dielectric curve at low frequencies which is superimposed by electrode polarization. The non-Debye type of relaxation in the films has been observed in the impedance and modulus curve. The peaks appearing at low frequencies for each doping concentration in loss tangent spectrum show the presence of relaxing dipoles in the films. An increment in the ac conductivity has been observed with doping concentration up to 5%. The ac conductivity curves obey the jump relaxation power law where an electrode polarization effect can be seen at low-frequency region

Study of enhancement in the dielectric and electrical properties of WO3-doped LiF nano-composite

We report the dielectric and electrical behavior of thermally evaporated lithium fluoride (LiF)-tungsten trioxide (WO3) (x wt% WO3-doped LiF; x = 0, 1, 3, 5, 7, 10) nano-composite thin films at room temperature over a wide range of frequencies from 0.1 Hz to 1 MHz. Among the various doping concentrations of WO3, the 5 wt% WO3-doped LiF nano-composite thin film reaches to the maximum dielectric constant similar to 25, compared with those of pure LiF similar to 9 thin film. The electrical studies of the films have been done by complex impedance spectroscopy and show the presence of grain and grain boundaries contribution in the films for all doping concentrations. The relaxation behavior in the nano-composite films has been observed in the dielectric curve at low frequencies which is superimposed by electrode polarization. The non-Debye type of relaxation in the films has been observed in the impedance and modulus curve. The peaks appearing at low frequencies for each doping concentration in loss tangent spectrum show the presence of relaxing dipoles in the films. An increment in the ac conductivity has been observed with doping concentration up to 5%. The ac conductivity curves obey the jump relaxation power law where an electrode polarization effect can be seen at low-frequency region

Evaluation of downwelling diffuse attenuation coefficient algorithms in the Red Sea

Que faut-il entendre par « musique » ? La référence à la musique est omniprésente dans les Lettres d’un voyageur, au point qu’elle contribue à l’unité thématique du recueil. Encore faut-il préciser ce qui, pour George Sand, appartient au domaine de la musique : pour une nature aussi profondément auditive que la sienne, sont musique les chants d’oiseaux aussi bien que l’écho des montagnes, les musiques populaires aussi bien que des formes plus codifiées comme la romance (qui connut à l’époque ..