Improvement of DFIG-based WECS performance using SMES unit

Doubly Fed Induction Generators (DFIGs) are widely used in variable speed wind turbine owing to its superior advantages that include ability to extract more energy from turbine, capability to control activeand reactive power independently and the usage ofreduced converter rating that reduces its overall cost.The application of DFIG in large wind energyconversion systems (WECS) has reached 55% of theworldwide total wind capacity during the year 2012. Onthe other side fluctuating output power, weak fault ridethrough capability and high sensitivity to griddisturbances are the main issues that affect DFIGperformance. In this paper, superconducting magneticenergy storage (SMES) unit is proposed to improve theoverall performance of a DFIG-based WECS duringvoltage sag disturbance in the grid side. A new controlapproach for SMES unit using hysteresis currentcontroller (HCC) along with proportional integral (PI) controller is introduced. Simulations results reveal the effectiveness of the proposed SMES controller in improving the overall performance of the WECS system under study

Application of SMES unit to improve DFIG power dispatch and dynamic performance during intermittent misfire and fire-through faults

The number of wind turbines connected to power grids has significantly increased during the last decade. This is mainly due to the convincing revolution in power electronic technology and the growing concern about greenhouse effect that is intensified due to the burning of fossil fuels. Variable speed wind energy conversion systems (WECS) such as doubly fed induction generators (DFIG) are dominating the wind energy market due to their superior advantages over fixed speed-based WECS that include more captured energy, less mechanical stress and acoustical noise. DFIG is interfaced to the ac network through grid side voltage source converter (GSC) and rotor side voltage source converter (RSC) to enable the variable speed operation of the wind turbine and to provide reactive power support to the ac grid during disturbance events. Converter switching malfunction such as misfire and fire-through may influence the power dispatch capability of the DFIG. In this paper, a super conducting magnetic energy storage (SMES) unit is utilized to improve the power dispatch and dynamic performance of DFIG-based WECS during internal converter switching malfunctions such as misfire and fire-through faults. Simulation results without and with SMES connected to the system are presented, compared and analyzed

Application of UPFC to Improve the FRT Capability of Wind Turbine Generator

Variable speed wind turbine generators installation has been significantly increased worldwide in the last few years. Faults at the grid side may call for the disconnection of the wind turbine from the grid as under such events, wind turbine generator (WTG) may not comply with the recent developed grid codes for wind energy conversion systems (WECS). In this paper, a unified power flow controller (UPFC) is applied to improve the fault ride through (FRT) capability of doubly fed induction generator (DFIG)-based WECS during voltage swell and voltage sag at the grid side. Simulation is carried out using MATLAB/Simulink software. Results show that UPFC can effectively improve the FRT capability of DFIG-based WECS and hence maintaining wind turbine connection to the grid during certain levels of voltage fluctuation at the grid side

Application of UPFC to Improve the LVRT Capability of Wind Turbine Generator

Variable speed wind turbine generators installation has been significantly increased worldwide in the last few years. Voltage sag at the grid side may call for the disconnection of the wind turbine from the grid as under such faults it may not comply with the recent developed grid codes for wind energy conversion systems (WECS). In this paper, a Unified Power Flow Controller (UPFC) is applied to improve the low voltage ride through (LVRT) capability of doubly fed induction generator (DFIG)-based WECS during voltage sag at the grid side. Simulation is carried out using MATLAB/Simulink software. Results show that UPFC can significantly improve the LVRT capability of DFIG-based WECS and hence maintaining wind turbine connection to the grid during certain levels of voltage sag at the grid side

Investigation of near flicker source impact on the dynamic performance of FCWECS

The number of full converter wind energy conversion system (FCWECS) connected to existing electricity grids has significantly increased worldwide during the last two decades. One of the common power quality issues associated with wind turbine generator (WTG) is the voltage flicker which can be caused due to wind gust. It is pivotal for the existing or the new construction of the WTG to comply with the power quality standards. Although, with the advance in WTG technology and control systems, the flicker due to wind speed fluctuation can be mitigated, flicker can still be caused as a result of load pulsation such as arc furnaces, resistive welding machines and compressors. In this paper, the near flicker source impact on the connected WTG performance is investigated and the compliance of the WTG with the recent grid codes under such disturbance is highlighted

Performance of Retrieval Information System For Medical Images

Problem statement : In this article the principles of building knowledge and retrieval information system will be applied to medical images in some studied hospital. Since there is a huge number of medical images this system will organizes and manages the operation of retrieving and displaying such images to the persons who need such images in short time and in high quality services. Approach : From relevance assessments we can compute measures of retrieval performance such as: Recall (R), discrimination DC, and Precision. Results: both recall and precision of the system are linearly depend on relevant items correctly retrieved. Conclusion : Number of retrieved images from huge total number of medical images in some hospital determine the systems' recall, discrimination, and precision of the retrieval information system

Distribution Systems Efficiency

This paper constructing a measurement system for determining the efficiency of the distributed system. This efficiency depends on many parameters like number of terminals, number of customers and kind of information, number of nodes, and number of messages. It is found that the efficiency depends strongly on number of messages sent or received inside the distributed system, as the number of messages increased the efficiency decreased. Keywords: distributed system, terminals, efficiency

Morphological and imaging evaluation of the metacarpophalangeal and metatarsophalangeal joints in healthy and lame donkeys

The donkey is of socio-economic value yet imaging techniques in both healthy and abnormal limbs are a limiting factor in research and medicine. The objective was to determine anatomical features of both healthy and clinically abnormal donkey metacarpophalangeal and metatarsophalangeal joints (n=13) using anatomical dissection, casting, x-ray and computed tomography. The joint capsule contained two palmar/plantar and two dorsal recesses. The proximal-palmar or plantar recess was larger than the distodorsal recess and potential sites of approaches to the recesses were determined. Soft tissue structures were distinguished using computed tomography at 300mA which was superior to 120mA. This methodology gave better assessments of the synovial tendon sheath, joint recesses and cruciate, collateral and short sesamoidean ligaments. Computed tomography provided outstanding discrimination between the cortex and medulla of the third metacarpal, the proximal sesamoid bones, the proximal phalanx and excellent details of the osseous structures. Although the joints appeared free from exostosis using x-ray; the position and extension of exostosis in pathologically affected donkeys (a novel finding) was revealed using computed tomography with 300mA in comparison to 120mA. The study also provided an anatomical record of the metacarpophalangeal and metatarsophalangeal joints using the latest technology which could impact on clinical situations including anesthesia injection sites

Mapping subnational HIV mortality in six Latin American countries with incomplete vital registration systems

BackgroundHuman immunodeficiency virus (HIV) remains a public health priority in Latin America. While the burden of HIV is historically concentrated in urban areas and high-risk groups, subnational estimates that cover multiple countries and years are missing. This paucity is partially due to incomplete vital registration (VR) systems and statistical challenges related to estimating mortality rates in areas with low numbers of HIV deaths. In this analysis, we address this gap and provide novel estimates of the HIV mortality rate and the number of HIV deaths by age group, sex, and municipality in Brazil, Colombia, Costa Rica, Ecuador, Guatemala, and Mexico.MethodsWe performed an ecological study using VR data ranging from 2000 to 2017, dependent on individual country data availability. We modeled HIV mortality using a Bayesian spatially explicit mixed-effects regression model that incorporates prior information on VR completeness. We calibrated our results to the Global Burden of Disease Study 2017.ResultsAll countries displayed over a 40-fold difference in HIV mortality between municipalities with the highest and lowest age-standardized HIV mortality rate in the last year of study for men, and over a 20-fold difference for women. Despite decreases in national HIV mortality in all countries-apart from Ecuador-across the period of study, we found broad variation in relative changes in HIV mortality at the municipality level and increasing relative inequality over time in all countries. In all six countries included in this analysis, 50% or more HIV deaths were concentrated in fewer than 10% of municipalities in the latest year of study. In addition, national age patterns reflected shifts in mortality to older age groups-the median age group among decedents ranged from 30 to 45years of age at the municipality level in Brazil, Colombia, and Mexico in 2017.ConclusionsOur subnational estimates of HIV mortality revealed significant spatial variation and diverging local trends in HIV mortality over time and by age. This analysis provides a framework for incorporating data and uncertainty from incomplete VR systems and can help guide more geographically precise public health intervention to support HIV-related care and reduce HIV-related deaths.Peer reviewe

Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018

Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations.Peer reviewe