8 research outputs found
Toward Teaching Methods that Develop Learning and Problem Solving Skills in Engineering Students
No full textProblem solving skills and abilities are critical in life and more specifically in the engineering field. Unfortunately, significant numbers of South African students who are accessing higher education are lacking problem solving skills and this results into poor academic performance jeopardizing their progress especially from first to second year. On the other hand, teaching problem solving to under-prepared first year learners is a challenge to academics that are required to think in innovative ways about teaching and learning strategies in order to respond in an efficient manner to South Africa’s high demand for quality engineering graduates. This paper discusses two successful sample lessons of how higher-order thinking skills can be integrated into the content of a so called “bottle-neck” subject namely Electrical Engineering 1 (EE1), with the goal of enhancing problem solving skills and consequently improve under-prepared learners’ performance. The importance of developing active student engagement practice as well as conceptual understanding is highlighted
Voltage control and stability analysis in a multi-machine power system with increasing penetration of intermittent renewable energy generation.
Get PDFMasters Degree. University of KwaZulu-Natal, Durban.Among multiple distributed generation (DG) supply means, photovoltaic (PV) and wind technologies are the most important and widely used renewable energy sources (RES) throughout the world. However, solar intermittency and the stochastic nature of radiation on one hand and grid integration-related issues on the other are fundamental concerns in the development and smooth deployment of solar energy contribution to conventional power systems networks. In addition, given that they modify both the structure and the operation of the distribution networks, RES increase uncertainty in power system operations, thus affecting power systems variables such as the voltage profiles and direction of network power flows. It is also largely established that a high penetration of DGs at the distribution end is associated amongst others, with voltage rises at PV buses that may lead to the violation of grid codes, if not adequately mitigated. There is a need to investigate both the effect and the impact of increasing penetration of these intermittent RES on, particularly, voltage and frequency stability power systems and the utilization thereof of such sources to improve voltage stability margins and predict voltage stability conditions. This research work investigated voltage control and stability conditions at Solar PV buses through various case studies and scenarios simulated using the Power Factory® tool, both in static and dynamic analysis modes. A modified standard IEEE 9-Bus Sub-transmission system was used to assess the voltage profile, system loadability and system stability. The comparison and discussion of the results obtained from the integration of the Solar PV and FACTS devices under various scenarios revealed that their respective impacts and abilities to improve voltage stability differ. The results confirmed that under any operating conditions, reactive power control remains the most effective method to control voltage stability and power transfer capability, especially in the context where an increasing penetration of renewable and inertia-less generating sources is planned. The results further revealed that there is a specific location and a specific siting architecture for a given size of PV that produces the best results for voltage stability, as well as improved system stability and loadability conditions for a given load distribution profile in a particular network. Lastly, the results demonstrated the effectiveness of the use of a Battery Energy Storage System (BESS) in achieving voltage control and regulation in distribution networks highly penetrated by PV generation, subsequently enabling greater RE penetration
Voltage Profile and Power Losses Analysis on a Modified IEEE 9-Bus System with PV Penetration at the Distribution Ends
No full textOperational Issues of Contemporary Distribution Systems: A Review on Recent and Emerging Concerns
No full textDistribution systems in traditional power systems (PS) constituted of passive elements and the distribution issues were then limited to voltage and thermal constraints, harmonics, overloading and unbalanced loading, reactive power compensation issues, faults and transients, loss minimization and frequency stability problems, to name a few. Contemporary distribution systems are becoming active distributed networks (ADNs) that integrate a substantially increasing amount of distributed energy resources (DERs). DERS include distributed generation (DG) sources, energy storage resources and demand side management (DSM) options. Despite their evidenced great benefits, the large-scale deployment and integration of DERs remain a challenge as they subsequently lead to the network operational and efficiency issues, hampering PS network reliability and stability. This paper carries out a comprehensive literature survey based on the last decade’s research on operational challenges reported and focusing on dispatchable and non-dispatchable DGs grid integration, on various demand response (DR) mechanisms and, on battery energy storage system (BESS) charging and discharging challenges, with the aim to pave the way to developing suitable optimization techniques that will solve the coordination of multiple renewable sources, storage systems and DRs to minimize distribution systems’ operational issues and thus improve stability and reliability. This paper’s findings assist the researchers in the field to conduct further research and to help PS planners and operators decide on appropriate relevant technologies that address challenges inherent to DG grid integration
Loadability Assessment of a Photovoltaic Penetrated Grid to Offset Intermittency and Reduce Total Losses using Battery Energy Storage System
No full textApplication of diverse FACTS in AGC of multi-area interconnected energy systems
Get PDFThis article presents the simple and effective control design for active power regulation of modern energy delivery system. As an energy delivery system experiences the demand changes as per the demand of the modern energy users due to which the system frequency is highly troubled and fluctuating. To balance such demand changes and to stable the system occurrence fluctuations, the thyristor control phase shifter (TCPS) in synchronisation with super conducting magnetic energy storage (SMES) or TCPS in coordination with capacitive energy storage (CES) based model predictive control (MPC) technique are proposed. SMES-SMES and CES-CES configurations are also tested for energy delivery system. The effectiveness of the proposed system regulator design are guaranteed by analyzing the transient system performance under varying load pattern, sinusoidal load change and for system non-linearities. A comparative performance analysis between TCPS-SMES, TCPS-CES, SMES-SMES and CES-CES based MPC of energy system are tested and presented
Critical Aspects of AGC Emerging from Optimal Control to Machine Learning Techniques
Get PDFWith the emphasis towards renewable energy lot more advancement has been done in the field of electric energy system and it is expected that future energy system may have wind power dominating control areas or hydro power be it bulk hydro or micro hydro based power generations in order to cater the rising energy demands of the modern society. Hence, automatic generation control (AGC) plays a crucial role in the modern electrical energy system in order to maintain the frequency standards to nominal value besides maintaining the power interchange between the interconnected controls areas in order to distribute value and cost effective power. This paper presents the literature survey related to some of the critical aspects of AGC such as diverse sources power generations, hydro dominating control areas, wind power based power generations and applications of flexible alternating current transmission system (FACTS) in AGC. This paper also discusses the novel control designs based on the concept of optimal control, output vector feedback, model predictive control, robust control and finally the machine learning based AGC designs are explored and the critical gaps among the available research work are well presented and discussed
African neurosurgery research: a scientometric analysis of the top 115 most cited articles
No full textBackground The use of quantitative and qualitative scientometrics provides deductive and inductive insights into the landscape of research in a specic area. In this manuscript, the authors identied the major contributors of African neurosurgery and emerging terms.
Methods Articles on African neurosurgery were searched on Web of Science and 8 other repositories without language or date restrictions. The H-index, co-author, author country, time trend, and keyword analyses were done using Bibexcel and VOSviewer.
Results 115 articles on African neurosurgery were published in 36 journals by 90 rst authors. The journals with the most articles were World Neurosurgery (46, 40.0%), Journal of Neurosurgery Pediatrics (8, 7.0%), and Neurosurgery (7, 6.1%). There was a rapid increase in the number of articles from 2010 and the median number of citations was 8 (IQR: 4-16). Qureshi MM had the highest H-index score (6) while Warf BC (5, 4.3%), Adeleye AO (4, 3.5%), and El Khamlichi (4, 3.5%) contributed the most to the 115 articles. The articles by Lanzino G (1999), Warf BC (2011), and Warf BC (2005) were the most influential. The U.S.A. had the largest node and South Africa, Kenya and Uganda were the most impactful African countries. Pediatric neurosurgery dominated the keywords and global neurosurgery was an emerging term.
Conclusion The most cited articles on African neurosurgery are published in prestigious specialty journals and neurosurgeons from Southern and East Africa are the most impactful local researchers. Future research should analyze the differences between African regions
