New modeling approach of secondary control layer for autonomous single-phase microgrids     

Ahmed Bendib  Aissa Chouder  Kamel Kara  Abdelhammid Kherbachi  Said Barkat  Walid Issa 《Journal of The Franklin Institute》2019,356(13):6842-6874

In a microgrid (MG) topology, the secondary control is introduced to compensate for the voltage amplitude and frequency deviations, mainly caused by the inherent characteristics of the droop control strategy. This paper proposes an accurate approach to derive small signal models of the frequency and amplitude voltage at the point of common coupling (PCC) of a single-phase MG by analyzing the dynamics of the second-order generalized integrator-based frequency-locked loop (SOGI-FLL). The frequency estimate model is then introduced in the frequency restoration control loop, while the derived model of the amplitude estimate is introduced for the voltage restoration loop. Based on the obtained models, the MG stability analysis and proposed controllers’ parameters tuning are carried out. Also, this study includes the modeling and design of the synchronization control loop that enables a seamless transition from island mode to grid-connected mode operation. Simulation and practical experiments of a hierarchical control scheme, including traditional droop control and the proposed secondary control for two single-phase parallel inverters, are implemented to confirm the effectiveness and the robustness of the proposal under different operating conditions. The obtained results validate the proposed modeling approach to provide the expected transient response and disturbance rejection in the MG.  相似文献   

Dynamics of a stochastic multigroup SIQR epidemic model with standard incidence rates     

Qun Liu  Daqing Jiang  Tasawar Hayat  Ahmed Alsaedi 《Journal of The Franklin Institute》2019,356(5):2960-2993

In this paper, we consider a stochastic multigroup SIQR epidemic model with standard incidence rates. By using the stochastic Lyapunov function method, we establish sufficient conditions for the existence of a stationary distribution of the positive solutions to the model. Then we establish sufficient conditions for extinction of the diseases. A stationary distribution means that all the individuals can be coexistent and persistent in the long term. Finally, some examples and numerical simulations are introduced to illustrate our theoretical results.  相似文献   

Evaluating research performance of research institutes within Malaysian universities: an alternative assessment framework     

Ta  Goh Choo  Halim  Sharina Abdul  Azman  Norzaini  Komoo  Ibrahim  Mokhtar  Mazlin 《Tertiary Education and Management》2021,27(4):331-349

Tertiary Education and Management - Evaluation of research performance has significantly increased in importance, particularly in many emerging higher education systems. In Malaysia, the Malaysian...  相似文献   

Integrating design science research and design based research frameworks for developing education support systems     

Fahd  Kiran  Miah  Shah J.  Ahmed  Khandakar  Venkatraman  Sitalakshmi  Miao  Yuan 《Education and Information Technologies》2021,26(4):4027-4048

Education and Information Technologies - This paper proposes an integrated research framework that takes advantage of the similarities of design science research (DSR) and Design-based research...  相似文献   

Optimal sizing of piezo-actuators for minimum-deflection design of frames under uncertain loads     

Sarp Adali  Ibrahim S. Sadek  James M. Sloss 《Journal of The Franklin Institute》2007,344(5):698-710

Optimal piezo-actuator sizes and locations for a frame structure under bending load uncertainty are determined with the objective of minimizing the deflection under worst case of loading. The bending moments generated by the piezo-actuators are used for deflection control, i.e., to minimize the maximum deflection. The frame is subjected to a tip load which lies in an uncertainty domain with regard to its magnitude and direction. The specific uncertain loading studied in the present paper involves a load of given magnitude but of unknown direction, which should be determined to produce the highest deflection. The worst case of loading depends on the size and location of the actuators leading to a nested problem of optimization (design) and anti-optimization (uncertainty problem). Results are given for deterministic and uncertain loading conditions.  相似文献   

Book reviews     

Manzoor Ahmed  Myriam Bacquemaine 《Prospects》1987,17(1):149-157

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Cross-cultural counseling and psychotherapy: An existential-psychological approach     

Farah A. Ibrahim 《International journal for the advancement of counseling》1984,7(3):159-169

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Assessing the Emotional Intelligence of Gifted and Talented Adolescent Students in the Kingdom of Bahrain     

Najat Sulaiman Al-Hamdan  Fatima Ahmed Al-Jasim  Ahmed M. Abdulla 《Roeper Review》2017,39(2):132-142

This study assessed the differences in the emotional intelligence of gifted adolescent students and talented adolescent students in Bahrain. The sample consisted of 80 gifted adolescent students and 80 talented adolescent students in Grades 9 through 12. A multivariate analysis of variance (MANOVA) indicates that there were significant differences in emotional intelligence levels, as measured by the Bar-On Emotional Quotient Inventory, between gifted students and talented students in Bahrain in the direction of gifted students. There were differences between the gifted and the talented students in intrapersonal, adaptability, general mood subtest, and total emotional intelligence scores. Finally, gifted males had higher total emotional intelligence scores than gifted females; talented females had higher interpersonal scores than talented males.  相似文献   

Evaluating students experiences using a virtual learning environment: satisfaction and preferences     

Hamutoglu  Nazire Burcin  Gemikonakli  Orhan  Duman  Ibrahim  Kirksekiz  Ali  Kiyici  Mubin 《Educational technology research and development : ETR & D》2020,68(1):437-462

Educational technology research and development - Virtual learning environments (VLEs) are web-based software systems that enable students to interact with their teachers and classmates, access...  相似文献   

The challenge of basic education for all     

Manzoor Ahmed  Gabriel Carron 《Prospects》1989,19(4):559-572

UNICEF Representative in China. Author of several books and articles ou non-formal education, rural development and educational planning.  相似文献