Voltage Stability Analysis with High Distributed Generation (DG) Penetration

Interest in Distributed Generation (DG) in power system networks has been growing rapidly. This increase can be explained by factors such as environmental concerns, the restructuring of electricity businesses, and the development of technologies for small-scale power generation. DG units are typically connected so as to work in parallel with the utility grid; however, with the increased penetration level of these units and the advancements in unit’s control techniques, there is a great possibility for these units to be operated in an autonomous mode known as a microgrid. Integrating DG units into distribution systems can have an impact on different practices such as voltage profile, power flow, power quality, stability, reliability, and protection. The impact of the DG units on stability problem can be further classified into three issues: voltage stability, angle stability, and frequency stability. As both angle and frequency stability are not often seen in distribution systems, voltage stability is considered to be the most significant in such systems. In fact, the distribution system in its typical design doesn’t suffer from any stability problems, given that all its active and reactive supplies are guaranteed through the substation. However, the following facts alter this situation: • With the development of economy, load demands in distribution networks are sharply increasing. Hence, the distribution networks are operating more close to the voltage instability boundaries. • The integration of distributed generation in distribution system introduces possibility of encountering some active/reactive power mismatches resulting in some stability concerns at the distribution level. Motivated by these facts, the target of this thesis is to investigate, analyze and enhance the voltage stability of distribution systems with high penetration of distributed generation. This study is important for the utilities because it can be applied with Connection Impact Assessment (CIA ). The study can be added as a complement assessment to study the impacts of the installation of DG units on voltage stability. In order to accomplish this target, this study is divided into three perspectives: 1) utilize the DG units to improve the voltage stability margin and propose a method to allocate DG units for this purpose, 2) investigate the impact of the DG units on proximity to voltage stability 3) conduct harmonic resonance analysis to visualize the impacts of both parallel and series resonance on the system’s stability. These perspectives will be tackled in Chapter 3, Chapter 4, and Chapter 5, respectively. Chapter 3 tackles placing and sizing of the DG units to improve the voltage stability margin and consider the probabilistic nature of both the renewable energy resources and the load. In fact, placement and sizing of DG units with an objective of improving the voltage stability margin while considering renewable DG generation and load probability might be a complicated problem, due to the complexity of running continuous load flow and at the same time considering the probabilistic nature of the load and the DG unit’s resources. Therefore, this thesis proposes a modified voltage index method to place and size the DG units to improve the voltage stability margin, with conditions of both not exceeding the buses’ voltage, and staying within the feeder current limits. The probability of the load and DG units are modeled and included in the formulation of the sizing and placing of the DG units. Chapter 4 presents a model and analysis to study the impact of the DG units on proximity to voltage instability. Most of the modern DG units are equipped with power electronic converters at their terminals. The power electronic converter plays a vital role to match the characteristics of the DG units with the requirements of the grid connections, such as frequency, voltage, control of active and reactive power, and harmonic minimization. Due to the power electronics interfacing, these DG units have negligible inertia. Thus, they make the system potentially prone to oscillations resulting from the network disturbances. The main goal of this chapter is to model and analyze the impact of distributed generation DG units on the proximity of voltage instability, with high penetration level of DG units. Chapter 5 studies the harmonic resonance due to the integration of DG units in distribution systems. Normally, the harmonic resonance phenomenon is classified as a power quality problem, however, this phenomenon can affect the stability of the system due to the parallel and series resonance. Thus, the main goal of this chapter is to study and analyze the impact of the integration of distributed generation on harmonic resonance by modeling different types of DG units and applying impedance frequency scan method

Design of Robust Digital Pole Placer for Car Active Suspension with Input Constraint

This chapter deals with the problem of state feedback control for an active quarter-car suspension system with control input constraint. The dynamics of the suspension system is first formed in terms of the control objectives: ride comfort, suspension deflection, and maximum actuator control force. The control task is formulated as robustly placing the closed poles in a desired region against different passenger load. Since digital computers are widely used in the vehicle industry, a new saturated controller design method is presented for regional pole-placement of uncertain discrete time systems. The constraint of control input saturation is considered in the design phase. The desired dynamic performance for uncertain discrete-time systems is represented by the settling time and damping ratio. A sufficient condition is derived to place the poles in a desired region. The design is formulated in terms of linear matrix inequality optimization. The effectiveness of the proposed design is illustrated by applying it to a quarter?car active suspension system. Different road tests for the proposed controller are carried out: step and bump disturbances. The proposed design achieves the desired oscillation damping due to road disturbances in addition to passenger comfort. The results are compared with the passive suspension system

Patient Satisfaction Survey as a Tool Towards Quality Improvement

Over the past 20 years, patient satisfaction surveys have gained increasing attention as meaningful and essential sources of information for identifying gaps and developing an effective action plan for quality improvement in healthcare organizations. However, there are very few published studies reporting of the improvements resulting from feedback information of patient satisfaction surveys, and in most cases, these studies are contradictory in their findings. This article investigates in-depth a number of research studies that critically discuss the relationship of dependent and independent influential attributes towards overall patient satisfaction in addition to its impact on the quality improvement process of healthcare organizations

Information Mastery, Effective Health Care, Evidence-Based Practice and the Otolaryngologist

Objectives: The objectives of this study were to study the information-seeking behaviour of otolaryngologists in Oman, and their willingness to learn and acquire evidence-based practice (EBP) skills. Methods: A cross-sectional survey was carried out by distribution of a questionnaire to 63 otolaryngologists (ranging from residents to consultants) employed in Oman who attended a national otolaryngology meeting in January 2010. Results: Forty-nine completed questionnaires were received; 57% of the respondents had more than 10 years’ experience, and 60% were from tertiary care; 38.8% “totally agreed”, and 36.7% “partially agreed” that EBP would improve the quality of care and thus provide effective health care to patients. More than 46.9% had 1–5 questions per week, 18.4% had 11 or more questions per week at the point-of-care; 69.4% were willing to acquire information mastery skills. There was a statistical correlation between the number of years of experience, the number of questions, and willingness to acquire information mastery skills. Conclusion: In day-to-day clinical practice, web-based resources are of increasing significance. Most otolaryngologists in Oman not only believed that it is essential to acquire information mastery skills, but also that effective health care depends on such skills and on EBP. Most were willing to acquire these skills. In the future, these skills will be vital in helping otolaryngologists deliver effective health care solutions. 

Schwannoma of the Cervical Symphathetic Chain : First case report from Oman

Schwannomas are benign, encapsulated and slow-growing nerve sheath tumours arising from Schwann cells. The schwannoma arising from the cervical sympathetic chain (SCSC) is a very rare tumour. It usually presents as a slow growing, painless and asymptomatic neck mass, hence preoperative clinical diagnosis is difficult. Radiological investigation and fine needle aspiration cytology make only a small contribution to its preoperative diagnosis, histopathological examination being much more useful. We report here the first case report of SCSC from Oman. It occurred in a 45 year-old female and was successfully excised

Multiple Mini-interview Consistency and Satisfactoriness for Residency Program Recruitment: Oman Evidence

Objectives: Standard interviews are used by most residency programs to assess non-cognitive skills, but variability in the interviewer’s skills, interviewer bias, and context specificity limit reliability. We sought to investigate the consistency and satisfactoriness of the multiple mini-interview (MMI) model for resident selection into an otorhinolaryngology head and neck surgery residency program. Methods: This pilot study was done in an independent academic residency training center for 15 applicants, in seven eight-minute MMI stations with eight raters for the 2015–2016 academic year. The raters included the chief resident and education committee chairman in one of the stations. Candidates were assessed on two items: medical knowledge (two standardized case scenarios) and behavioral knowledge (personality and attitude, professionalism, communication, enthusiasm to the specialty, and English proficiency). Results: Of 15 candidates, 10 (66.7%) were female and five (33.3%) were male; five were recommended for selection, and five were kept on the waiting list. The reliability, intraclass correlation coefficient (ICC), of the scores obtained from seven items of MMI was 0.36 (95% confidence interval (CI): -0.31–0.75; p = 0.110). However, the ICC of the medical interview was 0.54 (95% CI: 0.45–0.84; p = 0.090). The correlation between behavioral items score and MMI total score was r = 0.135 (p = 0.150). Conclusions: The interview evaluation/survey form given to candidates and interviewers has shown that MMI is a fair and effective tool to evaluate non-cognitive traits. Both candidates and interviewers prefer MMI to standard interviews. The MMI process for residency interviews can generate reliable interview results using only seven stations and is acceptable and preferred over standard interview modalities by residency program applicants and faculty members

Indirect Extrusion: A Multifaceted Approach of Sub-surface Tubular Expansion

Extrusion and indirect extrusion is a very old manufacturing process used in multitudes of applications mainly focused on transportation, household and power industries. Indirect extrusion has found an interesting application in petroleum industry, which resulted in resolving many unsolvable issues over the last few decades. The current and expected future global demand for hydrocarbons became a driving force for researchers to find new comprehensive and cheaper solutions for hydrocarbon production. The challenges faced in oil and gas fields, while drilling, constructing and operating new and old vertical/horizontal wells, are many. The use of indirect extrusion for in-situ expansion of sub-surface tubulars used in wells revolutionized the drilling and completion as opposed to one and half decade back. The emergence of solid expandable tubular technology has changed the basics of how we design and construct wells. The original development of the technology was to overcome the challenges faced by the petroleum industry to reach ultra-deep reservoirs, off-shore drilling, drilling in high-pressure/difficult zones and repair/maintenance of old/ageing wells. However, it gained significant interest of researchers and operators in providing solutions to wide-range problems. The development of a computational framework using finite element method (FEM) enabled to determine the force required for expansion and resulting dimensional changes in final product, which is of direct assistance to the field engineers. The effect of friction and stress variations along contact surface is also determined

Harmonics Temporal Profile in High-Voltage Networks: Case Study

This chapter presents a case study about harmonics measurements in high-voltage networks. Measurements were conducted at two locations in the main interconnected system (MIS) of Oman. Voltage and current THDs were recorded for a period of 1 week. The power quality analyzer was set to record required data for a period of 1 week, and the observation period for each recorded value is 10 minutes. At the first location, the grid station (132/33) is feeding industrial as well as other customers. The second grid station (220/132/33 kV) is dedicated to large industrial customers including arc furnaces and rolling mills. The power quality analyzer was installed at the 132 kV side of power transformers at both locations. Recorded data are analyzed, and temporal harmonics profiles are studied. A clear temporal variation of harmonics similar to that of aggregate load and local voltage profiles was observed at the grid station feeding mixed residential and industrial loads. However, this correlation between system load and harmonics profile diminishes at the grid station dedicated for heavy industrial loads

The Reality of Including Pre-University Education Policies at the Sultanate of Oman for the Purposes of the Fourth Goal of the Sustainable Development Goals 2030 واقع تضمين سياسات التعليم قبل الجامعي في سلطنة عُمان لغايات الهدف الرابع من أهداف التنمية المستدامة 2030

Abstract: The study aimed to identify the reality of including pre-‎university education policies in the Sultanate of Oman ‎for the purposes of the fourth goal of the sustainable ‎development goals (2030) according to the dimensions ‎set by the study (compulsory of education, educational justice and quality of education).The study applied the descriptive methodlogy and used the qualitative ‎method through the content analysis form to analyze a ‎number of educational documents in the Sultanate of ‎Oman. The results showed that the ‘Quality of ‎Education’ dimension obtained the first rank as the ‎most included dimension in the documents subject of ‎analysis with a general mean of (13.6), whereas the ‎dimension ‘compulsory of education’ came second, ‎while the ‘educational justice’ dimension ranked last. ‎The study recommended the importance of paying ‎more attention from educational policy ‎makers to pre-‎school education، and caring about ‎special education to ‎achieve justice in education. ملخص: هدفت الدراسة إلى التعرف إلى واقع تضمين سياسات التعليم قبل الجامعي في سلطنة عمان لغايات الهدف الرابع ‏من أهداف التنمية المستدامة 2030‏ وفق ‏الأبعاد التي حددتها: ‏(إلزامية التعليم، والعدالة في التعليم، ‏والجودة في التعليم). ‏واعتمد على المنهج الوصفي، واستُخدم الأسلوب النوعي؛ إذ تمت الاستعانة باستمارة ‏تحليل المحتوى لتحليل عدد من الوثائق التعليمية (فلسفة التعليم في سلطنة عمان، والاستراتيجية الوطنية للتعليم ‏‏2040، والخطة الخمسية التاسعة ‏لوزارة التربية والتعليم (2016-2020). وأظهرت النتائج أن بُعد (الجودة في ‏التعليم) حصل على الرتبة الأولى كأكثر الأبعاد تضميناً في الوثائق موضوع التحليل بمتوسط ‏عام (13.6)، فيما ‏حل بُعد (إلزامية التعليم) في الرتبة الثانية بمتوسط عام بلغ (6.3)، وحل بُعد (العدالة في التعليم) في الرتبة الأخيرة ‏بمتوسط عام ‏بلغ (6.0).‏ وفي ضوء هذه النتائج تمت التوصية بأهمية أن يقوم صناع السياسة التعليمية بزيادة الاهتمام بالتعليم ‏ما قبل المدرسي، وإتاحته مجاناً للمجتمع، والعناية بتعليم التربية الخاصة لتحقيق العدالة في التعليم بما يسهم في ‏تحقيق غايات الهدف الرابع للتعليم.

Reflections on the Academic Accreditation of the MD Programme of the College of Medicine & Health Sciences, Sultan Qaboos University, Oman

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