Performance analysis of doubly-fed induction generator (DFIG)- based wind turbine with sensored and sensorless vector control

PhD ThesisConventional energy sources are limited and pollute the environment. Therefore more attention has been paid to utilizing renewable energy resources. Wind energy is the fastest growing and most promising renewable energy source due to its economically viability. Wind turbine generator systems (WTGSs) are being widely manufactured and their number is rising dramatically day by day. There are different generator technologies adopted in wind turbine generator systems, but the most promising type of wind turbine for the future market is investigated in the present study, namely the doubly-fed induction generator wind turbine (DFIG). This has distinct advantages, such as cost effectiveness, efficiency, less acoustic noise, and reliability and in addition this machine can operate either in grid-connected or standalone mode. This investigation considers the analysis, modeling, control, rotor position estimation and impact of grid disturbances in DFIG systems in order to optimally extract power from wind and to accurately predict performance. In this study, the dynamic performance evaluation of the DFIG system is depicted the power quantities (active and reactive power) are succeed to track its command signals. This means that the decouple controllers able to regulating the impact of coupling effect in the tracking of command signals that verify the robust of the PI rotor active power even in disturbance condition. One of the main objectives of this study is to investigate the comparative estimation analysis of DFIG-based wind turbines with two types of PI vector control using PWM. The first is indirect sensor vector control and the other type includes two schemes using model reference adaptive system (MRAS) estimators to validate the ability to detect rotor position when the generator is connected to the grid. The results for the DFIG-based on reactive power MRAS (QRMRAS) are compared with those of the rotor current-based MRAS (RCMRAS) and the former scheme proved to be better and less sensitive to parameter deviations, its required few mathematical computations and was more accurate. During the set of tests using MATLAB®/SMULINK® in adjusting the error between the reference and adaptive models, the estimated rotor position can be obtained with the objective of achieving accurate rotor position information, which is usually measured by rotary encoders or resolvers. The use of these encoders will conventionally lead to increased cost, size, weight, and wiring ii complexity and reduced the mechanical robustness and reliability of the overall DFIG drive systems. However the use of rotor position estimation represents a backup function in sensor vector control systems when sensor failure occurs. The behavioral response of the DFIG-based wind turbine system to grid disturbances is analyzed and simulated with the proposed control strategies and protection scheme in order to maintain the connection to the network during grid faults. Moreover, the use of the null active and reactive reference set scheme control strategy, which modifies the vector control in the rotor side converter (RSC) contributes to limiting the over-current in the rotor windings and over-voltage in the DC bus during voltage dips, which can improve the Low Voltage Ride-through (LVRT) ability of the DFIG-based wind turbine system.my home country of Iraq and its Ministry of Planning for providing a scholarship for my study

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030