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Littérature scientifique sur le sujet « Load stability »

Auteur : Grafiati

Publié le 1 février 2024

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Articles de revues sur le sujet "Load stability"

Ackerman, Jeffrey, Karna Potwar et Justin Seipel. « Suspending loads decreases load stability but may slightly improve body stability ». Journal of Biomechanics 52 (février 2017) : 38–47. http://dx.doi.org/10.1016/j.jbiomech.2016.12.001.

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Mohd Rosli, Hazwani, Hazlie Mokhlis, Nurulafiqah Nadzirah Mansor, Norazliani Md Sapari, Syahirah Abd Halim, Li Wang et Mohamad Fani Sulaima. « A Binary Archimedes Optimization Algorithm and Weighted Sum Method for UFLS in Islanded Distribution Systems Considering the Stability Index and Load Priority ». Energies 16, n^o 13 (3 juillet 2023) : 5144. http://dx.doi.org/10.3390/en16135144.

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This study proposes an under-frequency load-shedding (UFLS) scheme based on a binary Archimedes Optimization Algorithm (BAOA) and the Weighted Sum Method (WSM) to maintain the stability of an islanded distribution system. These methods consider stability indices and load priorities to ensure effective load shedding during frequency deviations. The BAOA determines the optimal load shedding based on the stability index and power mismatch that minimizes the impact on critical loads while maintaining system stability in an islanded distribution system. The WSM determines the rank of the load to be shed based on four criteria: the load priority, the load category, the stability index, and the load size. Each load is assigned a weight based on its priority. These weight variables determine the order in which loads are shed during frequency deviations. The effectiveness of the proposed UFLS was tested on an 11 kV Malaysian distribution network with two mini hydro distributed generation systems. A comparative study was conducted based on five result outputs, including the number of loads shed, the size of the loads shed, the frequency undershoot, the frequency overshoot, and the time taken to achieve a stable frequency in three cases: base load, peak load, and peak load with photovoltaics (PV). The proposed UFLS showed the best results for 11 of 15 outputs (73.3%) for islanding events and 9 of 15 outputs (60%) for overloading events. The voltage profile and stability index, also, were improved after the proposed UFLS was applied.

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Singh, Lovepreet, Arun Kaushal et Amritpal Digra. « A review on stability of polyhouse structures ». INTERNATIONAL JOURNAL OF AGRICULTURAL SCIENCES 17, AAEBSSD (15 juillet 2021) : 319–25. http://dx.doi.org/10.15740/has/ijas/17-aaebssd/319-325.

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Naturally ventilated polyhouse is popular all over the world for growing high value cropssuch as capsicum, tomato, lettuce, herbs etc. and these polyhouses are available in different designs as per different climatic conditions. Structure failure is the major problem faced by farmers throughout the world. The several studies carried out throughout the world shows that the single design of polyhouse cannot be adopted throughout the country due to different agro-climatic conditions.As per differentstudies, polyhousestability designs are analyzed for dead load, live load, snow load, wind load and load combination and Loads were calculated by adoptingdifferent National Standards. Moreover, Truss members, columns and foundation stability analysis is carried out by considering dead loads, live loads and wind loads in most of the studies. Support reactions arealso calculated on truss joints and column joints. The optimum design of any polyhouse generally depends on its structural design, specific mechanical and physical properties of the individual structural components i.e., foundation, hoops, lateral support, polygrip, assembly and end frame. From all the studies it is reported that in most parts of the world, wind is the major force responsible for the failure of any polyhouse structure.

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Lee, Wei-Jen, Mo-Shing Chen et Lucas B. Williams. « Load Model for Stability Studies ». IEEE Transactions on Industry Applications IA-23, n^o 1 (janvier 1987) : 159–65. http://dx.doi.org/10.1109/tia.1987.4504881.

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Arif, Hina, et Jaan Lellep. « Stability of nanobeams and nanoplates with defects ». Acta et Commentationes Universitatis Tartuensis de Mathematica 25, n^o 2 (17 novembre 2021) : 221–38. http://dx.doi.org/10.12697/acutm.2021.25.15.

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The sensitivity of critical buckling load and critical stress concerning different geometrical and physical parameters of Euler-Bernoulli nanobeams with defects is studied. Eringen’s nonlocal theory of elasticity is used for the determination of critical buckling load for stepped nanobeams subjected to axial loads for different support conditions. An analytical approach to study the impact of discontinuities and boundary conditions on the critical buckling load and critical stress of nanobeams has been developed. Critical buckling loads of stepped nanobeams are defined under the condition that the nanoelements are weakened with stable crack-like defects. Simply supported, clamped and cantilever nanobeams with steps and cracks are investigated in this article. The presented results are compared with the other available results and are found to be in a close agreement.

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Kiss, László. « Stability of pinned-rotationally restrained arches ». Theoretical and Applied Mechanics, n^o 00 (2020) : 10. http://dx.doi.org/10.2298/tam200402010k.

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The article aims to find the buckling loads for pinned-rotationally restrained shallow circular arches in terms of the rotational end stiffness, geometry and material distribution. The loading is a concentrated vertical force placed at the crown. A geometrically nonlinear model is presented which relates not only the axial force but also the bending moment to the membrane strain. The nonlinear load-strain relationship is established between the strain and load parameters. This equation is then solved and evaluated analytically. It turns out that the stiffness of the end-restraint has, in general, a significant effect on the lowest buckling load. At the same time, some geometries are not affected by this. As the stiffness becomes zero, the arch is pinned-pinned and as the stiffness tends to infinity, the arch behaves as if it were pinned-fixed and has the best load-bearing abilities.

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Cagan, J., et L. A. Taber. « Large Deflection Stability of Spherical Shells With Ring Loads ». Journal of Applied Mechanics 53, n^o 4 (1 décembre 1986) : 897–901. http://dx.doi.org/10.1115/1.3171878.

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Large deflections of shallow and deep spherical shells under ring loads are studied. The axisymmetric problem is solved through a Newton-Raphson technique on discretized nonlinear shell equations. Comparison of computed load-deflection curves to experimental data from both thick and thin shells generally shows good agreement in peak loads and the type of instability. For a point load, the load increases monotonically with deflection; as the ring radius increases, transition-type (snap-through) and then local buckling occurs. In addition, the pre- and post-buckled mechanical behaviors of the shell are examined.

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Holbein, Mary Ann, et Mark S. Redfern. « Postural Stability While Holding Loads in Various Postures ». Proceedings of the Human Factors and Ergonomics Society Annual Meeting 37, n^o 10 (octobre 1993) : 697–700. http://dx.doi.org/10.1177/154193129303701011.

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Stability while handling loads is an important issue in the prevention of injuries. This study investigated the effects of load positioning on recovery from an unexpected balance disturbance while standing upright holding loads. Fifteen subjects were tested while holding a box in one of five postures. An empty box and a 25 lb box were tested. Subjects stood on a posture platform while perturbations of the supporting surface were induced. Postural sway was recorded via center of pressure displacements calculated from three dimensional foot forces. It was found that laden standing with the heavier load resulted in increased sway magnitude and slower sway velocities than unladen standing. The load position also affected stability. Raising the center of gravity of the body-and-load system appears to increase sway. These results require consideration when designing safe material handling tasks, especially if the supporting surface is unstable or if slip potential is present.

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LaGoy, Alice D., Caleb Johnson, Katelyn F. Allison, Shawn D. Flanagan, Mita T. Lovalekar, Takashi Nagai et Chris Connaboy. « Compromised Dynamic Postural Stability Under Increased Load Carriage Magnitudes ». Journal of Applied Biomechanics 36, n^o 1 (1 février 2020) : 27–32. http://dx.doi.org/10.1123/jab.2018-0473.

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Warfighter performance may be compromised through the impact of load carriage on dynamic postural stability. Men and women may experience this impact to differing extents due to postural stability differences. Therefore, the authors investigated the effect of load magnitude on dynamic postural stability in men and women during a landing and stabilization task. Dynamic postural stability of 32 subjects (16 women) was assessed during the unilateral landing of submaximal jumps under 3 load conditions: +0%, +20%, and +30% body weight. Dynamic postural stability was measured using the dynamic postural stability index, which is calculated from ground reaction force data sampled at 1200 Hz. Two-way mixed-measures analysis of variance compared dynamic postural stability index scores between sexes and loads. Dynamic postural stability index scores were significantly affected by load (P = .001) but not by sex or by the sex by load interaction (P > .05). Dynamic postural stability index scores increased between the 0% (0.359 ± 0.041), 20% (0.396 ± 0.034), and 30% (0.420 ± 0.028) body weight conditions. Increased load negatively affects dynamic postural stability with similar performance decrements displayed by men and women. Men and women warfighters may experience similar performance decrements under load carriage conditions of similar relative magnitudes.

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Le, Trong Nghia, Hoang Minh Vu Nguyen, Thai An Nguyen, Trieu Tan Phung, Thi Thu Hien Huynh et Quang Tien Nguyen. « Optimize Ranking and Load Shedding in Microgrid Considering Improved Analytic Hierarchy Process Algorithm and Power Stability Index ». Mathematical Problems in Engineering 2023 (29 novembre 2023) : 1–14. http://dx.doi.org/10.1155/2023/6074287.

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This paper proposes a load shedding model for the island microgrid based on the ranking of loads and the power stability index (PSI). Loads are ranked based on the improved analytic hierarchy process (AHP) algorithm. Real-time measurement systems have the function of collecting data for very important, important, and less-important loads at each bus load. From this data, the improved AHP method is applied to rank the loads. The advantage of this method is that the subjectivity is eliminated and not depending on the expertise of the system operator when implementing the traditional AHP method. Besides, the minimum amount of load shedding power is calculated, taking into account both primary and secondary control methods. The objective is to minimize the impact on power consumers and ensure that the frequency returns to an acceptable range. In addition, when implementing load shedding, voltage quality, and stability are considered. The PSI serves as a crucial parameter for assessing the voltage stability of microgrid buses. This index is combined with load ranking weights to obtain combined weights for the load shedding plan. Consequently, the proposed load shedding plan prioritizes minimizing damage to customers, improving voltage quality and stability, and ensuring frequency is within permissible limits. The 16-bus microgrid system is applied to compare with traditional methods and to prove the efficiency of the suggested technique.

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Thèses sur le sujet "Load stability"

Dai, F. « Load modelling for power system stability studies ». Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578290.

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Monnin, Jared P. « Impact of load type on microgrid stability ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76821.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
CD-ROM contains PDF of thesis and MDL file.
Both MIT Institute Archives and Barker Library copy: with CD-ROM.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references.
Microgrids show great promise as a means of integrating distributed generation sources into the public grid distribution system. In order to provide uninterrupted,high quality power to local loads, microgrids must have the ability to operate independently of or in parallel with the local utility. Transitioning between independent operation, also called "islanded" operation, and utility connected operation can induce stability problems in the microgrid, especially when islanding is fault induced. Software simulation suggests that induction motor loads on the microgrid significantly decrease stability during fault induced islanding. To validate the software simulations and to investigate the impact of load type on microgrid stability, we have built a hardware system that simulates the operation of a microgrid.
by Jared P. Monnin.
M.Eng.

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Vargas, Rios Leon Maximino. « Local voltage stability assessment for variable load characteristics ». Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/21424.

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Voltage stability problems originate when a generation-transmission system is not able to supply a load connected remotely from the generation centers. Knowledge of the load characteristics and the load composition are necessary tools for voltage stability assessment (VSA). This thesis presents methods and results to evaluate local voltage stability conditions, considering the actual static load characteristics. Simulation of a modern load, verified by experimental tests, such as a variable frequency drive feeding an induction motor (IM), shows that the real power characteristic is very similar to the directly-connected motor, while the reactive power characteristic is different. The effect on voltage stability is described. A small-scale voltage stability test is performed for a single IM under increasing mechanical load, fed by a source and series reactance. A set of slip dependent PV curves, which show variable power factor (PF) behavior, is obtained and compared with the assumption of constant PF loads for VSA. A comprehensive case study is performed, which presents an experimentally obtained IM load characteristic, resulting in variable PF as expected from the equivalent circuit model. The IM is aggregated by simulation in a bus fed by a Thevenin network, and a numerical method is proposed to compute a local PQV curve that considers the actual load characteristic. It is demonstrated that traditional PV curves for constant PF loads do not describe properly the aggregation of induction motor loads in a bus. A graphical approach of network and load PV characteristic intersections for this variable PF load, confirmed with a time domain simulation, shows that the point of matching impedance, typically assumed as the voltage stability limit, is not the power transmission limit (“nose”), and the latter is not the static voltage stability (loadability) limit. The methods and results developed in the case study are extended to other motor, heating and lighting types of loads. Their experimental characteristics are later combined by simulation in one distribution bus of a university building to perform static local VSA. Finally, some implementation ideas for on-line load characteristic estimation and PQV curve computation are described as part of the tools for local VSA.

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MORAES, ADELIO JOSE DE. « CONTRIBUITIONS TO THE LOAD MODELLING FOR TRANSIENT STABILITY STUDIES ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1992. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8361@1.

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UNIVERSIDADE FEDERAL DE UBERLÂNDIA
Este trabalho, relacionado com a área de modelagem de cargas para estudos de estabilidade transitória de sistemas elétricos, tem por objetivo discutir a adequação dos modelos clássicos normalmente utilizados, bem como o aprimoramento e desenvolvimento de representações para cargas com características específicas. Inicialmente, são enfocados os aspectos das representações clássicas de cargas e, através de desenvolvimentos teóricos e estudos computacionais, ressaltadas as adequações destas estratégias ao contexto atual. Reconhecendo algumas limitações quanto às técnicas para a obtenção dos parâmetros de motores de indução, apresenta- se procedimentos sistematizados para o tratamento destes componentes de carga. Tendo em vista a busca da melhoria de modelos e respostas aos questionamentos a respeito da relevância da inclusão dos efeitos da variação da freqüência sobre as cargas e parâmetros da rede, o trabalho prossegue com investigações nesta direção. Objetivando a análise do desempenho dos modelos simplificados de cargas através de funções algébricas, são discutidas as propostas atuais e verificadas suas adequações aos estudos de estabilidade. Finalmente, considerando a importância atual das cargas conversoras estáticas, são desenvolvidos modelos apropriados e realizados os estudos necessários à incorporação de unidades retificadoras em programas de estabilidade.
This work, involved with the load modeling for electrical system transiente stability analysis, aim to discuss the classical load models normally used, and to develop and improve representations of specific types of loads. Initially, aspects concerned with classical load representations are dealt with aiming to evaluate, through theoretical and computational analyses, the current employment of such models. Knowing that the techiques to obtain induction motor parameters are still deficient, this work presents some systematic procedures for the treatment of such loads. Additionally, it continues seeking improvements in electrical system component models and answers to the questions about the need for inclusion of the frequency variation effects on loads and network parameters. Moreover, it takes into account the tendencies of using simplified load models represented by algebraic expressions. Some recent proposals in this area are discussed and tested with a view to acess the perfomance of the models in stability studies. Finally, considering the present importance of static load converters, it is developed the related models and presented the necessary studies to include rectifier units in stability programs.

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MOROTE, CARLOS HUGO SOTO. « STABILITY AND DEFORMATION OF SOIL SLOPES UNDER SEISMIC LOAD ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9532@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O comportamento sísmico de taludes tem sido um tópico de grande interesse da engenharia geotécnica nos últimos 40 anos. Durante este período, a prática da engenharia nesta área evoluiu do emprego de técnicas elementares para procedimentos numéricos bastante complexos. A abordagem mais simples é a análise pseudo-estática na qual o carregamento do terremoto é simulado por uma aceleração horizontal estática equivalente atuando na massa de solo deslizante, utilizando-se um procedimento de equilíbrio limite (método das fatias), geralmente conservativo. O parâmetro que descreve o comportamento dinâmico do solo é referido como coeficiente sísmico k, e sua seleção depende fortemente da experiência e normas técnicas locais, porque não há maneira simples e segura de se escolher um valor adequado. O segundo procedimento é conhecido como método de Newmark, que envolve o cálculo de uma aceleração de escoamento, definida como a força inercial necessária para o fator de segurança atingir 1 em uma análise pseudo-estática pelo método de equilíbrio limite. O procedimento então usa os registros de aceleração do terremoto de projeto e o integra duplamente no tempo para calcular os deslocamentos permanentes acumulados. O terceiro método é referido como análise de Makdisi- Seed, que procura definir a estabilidade sísmica do talude em termos de deslocamentos aceitáveis em vez de um fator de segurança tradicional através de uma versão modificada do método de Newmark. Esta técnica apresenta uma maneira racional de calcular uma aceleração de escoamento média, necessária para produzir um valor do coeficiente de segurança do talude igual a 1. Gráficos específicos foram também desenvolvidos para estimativa dos deslocamentos permanentes, tendo sido bastante aplicados em aterros rodoviários, barragens e aterros sanitários. Finalmente, o mais sofisticado método para análise de estabilidade sísmica de taludes é conhecido como análise dinâmica, que normalmente incorpora modelos de elementos finitos e relações tensão x deformação complexas numa tentativa de obter melhores representações para o comportamento mecânico de taludes sob cargas cíclicas Os resultados destas análises podem incluir a história no tempo dos deslocamentos e tensões, bem como das freqüências naturais, efeitos de amortecimento, etc. Este trabalho apresenta uma comparação entre os métodos mencionados anteriormente, analisando o comportamento sísmico dos taludes da estrutura de contenção dos resíduos de lixiviação de minério de urânio, na Bahia, e dos taludes do bota-fora sul da mina de cobre Toquepala, situada no Peru.
The seismic stability of slopes has been a topic of considerable interest in geotechnical engineering for the past 40 years. During that period, the state of practice has moved from simples techniques to more complicated numerical procedures. The simplest approach is the pseudo-static analysis in which the earthquake load is simulated by an equivalent static horizontal acceleration acting on the mass of the landslide, according to a generally conservative limit equilibrium analysis. The ground motion parameter used in a pseudo-static analysis is referred to as the seismic coefficient k, and its selection has relied heavily on engineering judgment and local code requirements because there is no simple method for determining an appropriate value. The second main procedure is known as the Newmark displacement analysis which involves the calculation of the yield acceleration, defined as the inertial force required to cause the static factor of safety to reach 1 from the traditional limit equilibrium slope stability analysis. The procedure then uses a design earthquake strong-motion record which is numerically integrated twice for the amplitude of the acceleration above the yield acceleration to calculate the cumulative displacements. These displacements are then evaluated in light of the slope material properties and the requirements of the proposed development. The third method is referred to as the Makdisi-Seed analysis sought to define seismic embankment stability in terms of acceptable deformation instead of conventional factors of safety, using a modified Newmark analysis. Their method presents a rational means to determine yield acceleration, or the average acceleration required to produce a factor of safety of unity. Design curves were developed to estimate the permanent earthquake- induced deformations of embankments, which have since been applied to sanitary landfill and highway embankments. Finally, the most sophisticated method for seismic slope stability calculations is known as the dynamic analysis, which normally incorporates a finite element model and a rather complex stress-strain behavior for geological materials in an attempt to obtain a better representation of the behavior of soils under cyclic loading. The results of the analysis can include a time history of displacements and stresses, as well as natural frequencies, effects of damping, etc. This work presents a comparison of the results obtained by the aforementioned approaches, considering the seismic behavior of the slopes of an uranium lixiviation pad situated in Bahia, Brazil, and the South embankment of the waste landfill of the Toquepala Mine, Peru.

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Genet, Benjamin. « On monitoring methods and load modeling to improve voltage stability assessment efficiency ». Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210258.

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Power systems must face new challenges in the current environment. The energy market liberalization and the increase in the loading level make the occurrence of instability phenomena leading to large blackouts more likely. Existing tools must be improved and new tools must be developed to avoid them.

The aim of this thesis is the improvement of the voltage stability assessment efficiency. Two orientations are studied: the monitoring methods and the load modeling.

The purpose of the monitoring methods is to evaluate the voltage stability using only measurements and without running simulations.

The first approach considered is local. The parameters of the Thevenin equivalent seen from a load bus are assessed thanks to a stream of local voltage and current measurements. Several issues are investigated using measurements coming from complete time-domain simulations. The applicability of this approach is questioned.

The second approach is global and uses measurements acquired by a Wide-Area Measurement System (WAMS). An original approach with a certain prediction capability is proposed, along with intuitive visualizations that allow to understand the deterioration process leading to the collapse.

The load modeling quality is certainly the weak point of the voltage security assessment tools which run simulations to predict the stability of the power system depending on different evolutions. Appropriate load models with accurate parameters lead to a direct improvement of the prediction precision.

An innovative procedure starting from data of long measurement campaigns is proposed to automatically evaluate the parameters of static and dynamic load models. Real measurements taken in the Belgian power system are used to validate this approach.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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Regulski, Pawel Adam. « Estimation of parameters of dynamic load models for voltage stability studies ». Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/estimation-of-parameters-of-dynamic-load-models-for-voltage-stabily-studies(db6176e0-c7df-4ad6-83f7-5772eb9f8421).html.

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Current environmental and economic trends have forced grid operators to maximize the utilization of the existing assets, which is causing systems to be operated closer to their stability limits than ever before. This requires, among other things, better knowledge and modelling of the existing power system equipment to increase the accuracy of the assessment of current stability margins.This research investigates the possibility of improving the quality of load modeling. The thesis presents a review of the traditional methods for estimation of load model parameters and proposes to use Improved Particle Swarm Optimization. Different algorithms are tested and compared in terms of accuracy, reliability and CPU requirements using computer simulations and real-data captured in a power system.Estimation of frequency and power components has also been studied in this thesis. A review of the existing methods has been provided and the use of an Unscented Kalman Filter proposed. This nonlinear recursive algorithm has been thoroughly tested and compared against selected traditional techniques in a number of experiments involving computer-generated signals as well as measurements obtained in laboratory conditions.

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Karimishad, Amir. « Transient stability-constrained load dispatch, ancillary services allocation and transient stability assessment procedures for secure power system operation ». University of Western Australia. Energy Systems Centre, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0028.

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[Truncated abstract] The present thesis is devoted to the development of new methods for transient stability-constrained optimal power flow, probabilistic transient stability assessment and security-constrained ancillary services allocation. The key objective of the thesis is to develop novel dispatch and assessment methods for power systems operation in the new environment of electricity markets to ensure power systems security, particularly transient stability. A new method for economic dispatch together with nodal price calculations which includes transient stability constraints and, at the same time, optimises the reference inputs to the Flexible AC Transmission System (FACTS) devices for maintaining power systems transient stability and reducing nodal prices is developed. The method draws on the sensitivity analysis of time-domain transient stability simulation results to derive a set of linearised stability constraints expressed in terms of generator active powers and FACTS devices input references. '...' The low computing time requirement of the two-point estimate method allows online applications, and the use of detailed power systems dynamic model for time-domain simulation which offers high accuracy. The two-point estimate method is integrated in a straightforward manner with the existing transient stability analysis tools. The integrated software facility has potential applications in control rooms to assist the system operator in decision making process based on instability risks. The software system when implemented on a cluster of processors also makes it feasible to re-assess online transient stability for any change in system configuration arising from switching control. The method proposed has been tested on a representative power system and validated using the Monte Carlo simulation. In conjunction with the energy market, by which forecasted load demand is met by generator dispatch, ancillary services are required in relation to control for secure system operation and power quality. The final part of the thesis has a focus on the key aspect of allocating these ancillary services, subject to an important constraint that the dispatch of the ancillary services will not impair the system security achieved in the load dispatch. With this focus and requirement, the thesis develops a new dispatch formulation in which the network security constraints are represented in the optimal determination of generator active power schedule and allocation of ancillary services. Contingencies considered include power demand variations at individual load nodes from the values specified for the current dispatch calculation. The required changes in generator active powers to meet the new load demands are represented by additional control variables in the new dispatch formulation which augment those variables in the traditional OPF dispatch calculation. Based on the Lagrange function which includes the extended set of security constraints, the formulation derives the optimality condition to be satisfied by the dispatch solution, together with the marginal prices for individual ancillary service providers and LMPs. The effects of the security constraints are investigated and discussed. Case studies for representative power systems are presented to verify the new dispatch calculation procedure.

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Garmroodi, Doiran Mehdi. « Sensitivity Analysis for Future Grid Stability Studies ». Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15978.

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The increasing penetration of converter-interfaced generators (CIGs) has raised concerns about the stability and security of future grids (FGs). These resources affect power systems dynamics in many ways including reducing system inertia, interacting with existing generators, changing power flow paths, etc. In this thesis, we carry out a sensitivity study to explore the structural impacts from CIGs on the damping and frequency stability of power systems. Initially, we study the impact of the intermittent power from wind turbine generators (WTGs) on the damping of the electromechanical oscillations in power systems. It will be shown that the inability of WTGs to provide synchronizing and damping torque to the system jeopardize the small signal stability of power systems. Stable operation regions, in terms of wind penetration and tie-line power, are derived and the impact of load flexibility on these regions are discussed. Next, we have studied the impact of the inertia distribution on the damping of the inter-area modes in power systems. It is shown that tie-line power has a significant role on the damping of the inter-area modes. Moreover, we show that dynamic voltage control and inertia emulation can be utilized to improve the damping of the system. By developing an oscillatory recovery model for power system loads, we have also studied the impact of load oscillations on the damping of the inter-area modes. It is shown that the load dynamics can have a significant influence on the electromechanical oscillations of power systems. Finally, the frequency support capability of WTGs is investigated and the performance of different techniques in utilizing the kinetic energy of the WTGs to assist the frequency stability of power systems is evaluated. A novel time-variable droop characteristic is proposed to enhance the contribution of WTGs in supporting system frequency.

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Jadric, Ivan. « Modeling and Control of a Synchronous Generator With Electronic Load ». Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36549.

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Design and analysis of a system consisting of a variable-speed synchronous generator that supplies an active dc load (inverter) through a three-phase diode rectifier requires adequate modeling in both time and frequency domain. In particular, the system's control-loops, responsible for stability and proper impedance matching between generator and load, are difficult to design without an accurate small-signal model. A particularity of the described system is strong non-ideal operation of the diode rectifier, a consequence of the large value of generator's synchronous impedance. This non-ideal behavior influences both steady state and transient performance. This thesis presents a new, average model of the system. The average model accounts, in a detailed manner, for dynamics of generator and load, and for effects of the non-ideal operation of diode rectifier. The model is non-linear, but time continuous, and can be used for large- and small-signal analysis. The developed model was verified on a 150 kW generator set with inverter output, whose dc-link voltage control-loop design was successfully carried out based on the average model.
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Livres sur le sujet "Load stability"

L, Kollár, dir. Structural stability in engineering practice. London : Taylor and Francis, 1999.

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Lajos, Kollár, dir. Structural stability in engineering practice. London : E & FN Spon, 1999.

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Kong, Kit N. A. The influence of load dynamics on power system small-signal stability. Manchester : UMIST, 1998.

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Stability under wind load of loose-laid external roof insulation boards. Watford : Building Research Establishment, 1985.

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Power system analysis : Short-circuit load flow and harmonics. 2^e éd. Boca Raton : CRC Press, 2012.

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Power system analysis : Short-circuit load flow and harmonics. New York : Marcel Dekker, 2002.

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Wen, Yi-Kwei. Structural load modeling and combination for performance and safety evaluation. Amsterdam : Elsevier, 1990.

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Structural Engineering Institute. Technical Committee on Load and Resistance Factor Design. Task Committee on Effective Length., dir. Effective length and notional load approaches for assessing frame stability : Implications for American steel design. New York : The Society, 1997.

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H, Acquaviva Thomas, et Lewis Research Center, dir. Static stability of the space station solar array FASTMast structure. Cleveland, Ohio : NASA Lewis Research Center, 1995.

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Bankhead, Natasha. Analysis of bank stability and potential load reduction along reaches of the Big Sioux River, South Dakota. Oxford, Mississippi : United States Department of Agriculture, National Sedimentation Laboratory, 2009.

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Chapitres de livres sur le sujet "Load stability"

Cutsem, Thierry, et Costas Vournas. « Load Aspects ». Dans Voltage Stability of Electric Power Systems, 93–133. Boston, MA : Springer US, 1998. http://dx.doi.org/10.1007/978-0-387-75536-6_4.

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Zhu, Yue. « Power System Load Models and Load Modelling ». Dans Power System Loads and Power System Stability, 19–47. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-37786-1_2.

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Gouaisbaut, Frédéric, Isabelle Queinnec et Sophie Tarbouriech. « Stability of Load Balancing Control ». Dans Applications of Time Delay Systems, 77–95. Berlin, Heidelberg : Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-49556-7_5.

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Horne, M. R. « The Rankine-Merchant Load and its Application ». Dans Summation Theorems in Structural Stability, 111–39. Vienna : Springer Vienna, 1995. http://dx.doi.org/10.1007/978-3-7091-2912-8_3.

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Zhu, Yue. « Factors Affecting Load Model Parameter Ranking ». Dans Power System Loads and Power System Stability, 109–28. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-37786-1_6.

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Sharma, Prashant Kumar, Akash Sharma et Rajive Tiwari. « Load Shedding Technique for Maintaining Voltage Stability ». Dans Lecture Notes in Electrical Engineering, 305–14. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-4795-9_29.

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Simitses, George J. « Dynamic Stability Under Constant Load of Finite Duration ». Dans Dynamic Stability of Suddenly Loaded Structures, 54–67. New York, NY : Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3244-5_3.

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Rusakov, A. I. « Three-Hinged Arches under Live Static Load ». Dans Fundamentals of Structural Mechanics, Dynamics, and Stability, 49–58. First edition. | Boca Raton : CRC Press, 2021. : CRC Press, 2020. http://dx.doi.org/10.1201/9780429155291-8.

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Kumar, G. Naveen. « Characterizing Voltage-Dependent Loads and Frequency-Dependent Loads for Load Stability Analysis ». Dans Smart Buildings Digitalization, 207–16. Boca Raton : CRC Press, 2021. http://dx.doi.org/10.1201/9781003201069-13.

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Zhu, Yue. « Required Accuracy Level of Critical Load Model Parameters ». Dans Power System Loads and Power System Stability, 129–42. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-37786-1_7.

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Actes de conférences sur le sujet "Load stability"

Kolakowski, Zbigniew, Andrzej Teter et Wojciech Smagowski. « On using load–axial shortening plots to determine approximate buckling load of real plate structure ». Dans PROCEEDINGS OF THE 15TH STABILITY OF STRUCTURES SYMPOSIUM. Author(s), 2019. http://dx.doi.org/10.1063/1.5086136.

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Zhang, Xinran, et David J. Hill. « Load Stability Index for Short-term Voltage Stability Assessment ». Dans 2019 IEEE Power & Energy Society General Meeting (PESGM). IEEE, 2019. http://dx.doi.org/10.1109/pesgm40551.2019.8973754.

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Burgess, Kevin L., et Kevin M. Passino. « Stability Analysis of Load Balancing Systems ». Dans 1993 American Control Conference. IEEE, 1993. http://dx.doi.org/10.23919/acc.1993.4793321.

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Fu, Xu, et Xifan Wang. « Load Shedding Scheme Ensuring Voltage Stability ». Dans 2007 IEEE Power Engineering Society General Meeting. IEEE, 2007. http://dx.doi.org/10.1109/pes.2007.385850.

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Morison, Kip, Hamid Hamadani et Lei Wang. « Load Modeling for Voltage Stability Studies ». Dans 2006 IEEE PES Power Systems Conference and Exposition. IEEE, 2006. http://dx.doi.org/10.1109/psce.2006.296379.

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Kedziora, Slawomir, et Muhammad Omer Anwaar. « Concrete-filled steel tubular (CFTS) columns subjected to eccentric compressive load ». Dans PROCEEDINGS OF THE 15TH STABILITY OF STRUCTURES SYMPOSIUM. Author(s), 2019. http://dx.doi.org/10.1063/1.5086135.

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Li, Shao-hua, Hsiao-dong Chiang et Sheng Liu. « Analysis of Composite Load Models on Load Margin of Voltage Stability ». Dans 2006 International Conference on Power System Technology. IEEE, 2006. http://dx.doi.org/10.1109/icpst.2006.321595.

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Subhana, Arik, et Nahid-Al-Masood. « Estimation of Frequency Stability Considering Load Levels and Load Frequency Relief ». Dans 2020 IEEE International Women in Engineering (WIE) Conference on Electrical and Computer Engineering (WIECON-ECE). IEEE, 2020. http://dx.doi.org/10.1109/wiecon-ece52138.2020.9397973.

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Zhu, S. Z., J. H. Zheng, L. Li, S. D. Shen et G. M. Luo. « Effect of load modeling on voltage stability ». Dans 2000 Power Engineering Society Summer Meeting. IEEE, 2000. http://dx.doi.org/10.1109/pess.2000.867617.

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Wu, G. Y., C. Y. Chung, K. P. Wong et C. Rehtanz. « Interruptible load management to preserve voltage stability ». Dans 7th IET International Conference on Advances in Power System Control, Operation and Management (APSCOM 2006). IEE, 2006. http://dx.doi.org/10.1049/cp:20062116.

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Rapports d'organisations sur le sujet "Load stability"

Guarino, V. J. Stability of EB when cryostat load is applied. Office of Scientific and Technical Information (OSTI), septembre 2004. http://dx.doi.org/10.2172/832935.

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Guarino, V. J. Stability of EB when cryostat load is applied. Office of Scientific and Technical Information (OSTI), septembre 2004. http://dx.doi.org/10.2172/834028.

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Dagle, J. E., D. W. Winiarski et M. K. Donnelly. End-use load control for power system dynamic stability enhancement. Office of Scientific and Technical Information (OSTI), février 1997. http://dx.doi.org/10.2172/484515.

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Walshire, Lucas, Joseph Dunbar et Benjamin Breland. Stability analysis of Old River Low Sill Structure. Engineer Research and Development Center (U.S.), septembre 2022. http://dx.doi.org/10.21079/11681/45349.

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An updated stability analysis was performed on the Old River Low Sill Structure due to a change in the operating conditions from historic river sedimentation. Sedimentation of the Mississippi River channel since the 1973 spring flood has caused higher river stages at lower discharges. Numerical methods used included nonlinear analysis of pile group stability, seepage analyses, and limit equilibrium methods. The structure’s foundation was compromised during the 1973 flood, and emergency repairs were conducted to prevent scouring and undermining of the foundation by the flood scour. Rehabilitation included the reconstruction of a failed wing wall on the left abutment, rock and riprap fill in the forebay channel, and emergency grouting to fill the scour hole beneath the structure. An operating restriction was emplaced to limit the differential head across the structure due to flood damage. Taking these conditions into account, results from an updated analysis showed that full headwater uplift caused increased tension in the piles, while the increased body load caused increased compressive loads in the piles. Review of piezometric monitoring and the seepage analyses showed that full headwater uplift is unlikely, indicating the foundation grouting adequately sealed the scour hole beneath the structure. Analysis results exhibited lower magnitude compression and tension loads in the piles with design load cases compared to previous analyses. Recommendations from these analyses indicate that increased monitoring and additional investigation may support increasing the differential head limitation.

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Wang, Yao, Jeehee Lim, Rodrigo Salgado, Monica Prezzi et Jeremy Hunter. Pile Stability Analysis in Soft or Loose Soils : Guidance on Foundation Design Assumptions with Respect to Loose or Soft Soil Effects on Pile Lateral Capacity and Stability. Purdue University, 2022. http://dx.doi.org/10.5703/1288284317387.

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The design of laterally loaded piles is often done in practice using the p-y method with API p-y curves representing the behavior of soil at discretized points along the pile length. To account for pile-soil-pile interaction in pile groups, AASHTO (2020) proposes the use of p-multipliers to modify the p-y curves. In this research, we explored, in depth, the design of lateral loaded piles and pile groups using both the Finite Element (FE) method and the p-y method to determine under what conditions pile stability problems were likely to occur. The analyses considered a wide range of design scenarios, including pile diameters ranging from 0.36 m (14.17 inches) to 1.0 m (39.37 inches), pile lengths ranging from 10 m (32.81 ft) to 20 m (65.62 ft), uniform and multilayered soil profiles containing weak soil layers of loose sand or normally consolidated (NC) clay, lateral load eccentricity ranging from 0 m to 10 m (32.81 ft), combined axial and lateral loads, three different pile group configurations (1×5, 2×5, and 3×5), pile spacings ranging from 3 to 5 times the pile diameter, two different load directions (“strong” direction and “weak” direction), and two different pile cap types (free-standing and soil-supported pile caps). Based on the FEA results, we proposed new p-y curve equations for clay and sand. We also examined the behavior of the individual piles in the pile groups and found that the moment applied to the pile cap is partly transferred to the individual piles as moments, which is contrary to the assumption often made that moments are fully absorbed by axial loads on the group piles. This weakens the response of the piles to lateral loading because a smaller lateral pressure is required to produce a given deflection when moments are transferred to the head of the piles as moments. When the p-y method is used without consideration of the transferred moments, unconservative designs result. Based on the FEA results, we proposed both a new set of p-multipliers and a new method to use when moment distribution between piles is not known, using pile efficiency instead to calculate the total capacity of pile groups.

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Cowell, Luke, Alejandro Camou, Ivan Carlos et Dustin Truesdel. PR-283-16201-R01 Improved SoLoNOx Taurus 60 Control Algorithm to Reduce Part Load Emissions. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), août 2018. http://dx.doi.org/10.55274/r0011510.

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An executed NDA is required from Solar Turbines to have access to this document. The low load control algorithm for Solar Turbines' TaurusTM 60-7802S has been modified and evaluated in a field trial at the TransCanada Glenville Compressor Station. The algorithm has been modified to extend the bleed valve operating range to lower engine speed settings covering operation from idle to 50% load. The pilot fuel schedule has also been optimized with the new bleed valve schedule. The new control algorithm is designated as Enhanced Emissions Control (EEC). A Mobile Emissions Lab (MEL) and three site visits for extensive low load emissions mapping were used to document the emissions performance of the test unit over 20 months from August 2016 to April 2018. Data was collected over a wide ambient temperature range from -7 to 97 �F. The field trial has demonstrated that the new algorithm results in a significant reduction in NOx, CO and UHC emissions from idle to 50% load. Reductions in CO and UHC emission of 35 to 99% were demonstrated from idle to 50% load. NOx emissions reductions were slightly less ranging from 50 to 20% from idle to 50% load, respectively. The emissions performance above 50% load were unchanged when comparing the EEC to the production algorithm. Continuous emission measurements indicate that emissions of NOx and CO above 50% load were very consistent with average levels of 10 and 2 ppm, respectively. No clear emission variation trends were evident with ambient temperature or engine speed (load). By extending the load range with temperature control, by modulating the bleed valve, the engine heat rate was increased slightly from idle to 50% load. No measurable impact on heat rate was detected from 50 to 100% load. An improved BAM 2.0 with Active Control was included in the field trial. The BAM 2.0 demonstrated reliable performance and hardware durability over the test period. The Active Control also performed as designed to modulate the pilot fuel flow to maintain combustion stability as required, typically at cold ambient conditions with no measurable effect on emissions.

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Vélez, Rómulo Andrés, Alejandro Fereño Caceres, Wilson Daniel Bravo Torres, Daniela Astudillo Rubio et Jacinto José Alvarado Cordero. Primary stability with the osseodensification drilling technique for dental implants in low density bone in humans : a systematic review. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, septembre 2022. http://dx.doi.org/10.37766/inplasy2022.9.0066.

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Review question / Objective: - Does the osseodensification drilling technique increase primary stability in low-density bone? - The aim of the present investigation was to evaluate primary stability in dental implants in people with low density bone using the osseodensification technique. Condition being studied: The replacement of missing teeth through dental implants is currently the most practiced in dental clinics. The main criterion for determining the success of an implant is osseointegration, which is a direct structural and functional connection between vital bone and the prosthetic load-bearing surface of an implant. In the same way, primary stability must be obtained for a good lasting clinical result of the implant and to achieve this purpose, the bone density must be evaluated where the dental implant is to be placed. Salah Huwais in 2013 introduced a new osteotomy procedure (Oseodensification) for site preparation without removal and bone preservation. The Osseodensification process produces an autograft layer around the implant with the osteotomy surface, the autologous bone comes into contact through an endosteal device that accelerates osseointegration due to the nucleation of osteoblasts in the instrumented bone adjacent to the implant and has a greater primary stability due to contact between the device and the bone.

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Sutipatanasomboon, Arpaporn. Ultimate guide on Clegg Impact Testers. ConductScience, juillet 2022. http://dx.doi.org/10.55157/cs20220727.

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A Clegg Impact Tester, also known as a Clegg Hammer, is a portable device invented by Dr. Baden Clegg to assess surface shock absorption and bearing capacity. It measures the strength of soils, aggregates, and synthetic materials for roads and sports surfaces. The tester consists of a compaction hammer, guiding tube, and piezoelectric accelerometer. It quantifies a surface's ability to withstand structural load and offers insights into strength, stiffness, and stability. The hammer is dropped from a specific height, and its impact is measured. Clegg Impact Testers are used for various applications, including road quality, turf safety, athletic tracks, and stall surfaces. Factors to consider when choosing one include hammer weight, readout range, power source, and additional features.

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Kerber, Steve, Daniel Madrzykowski, James Dalton et Robert Backstrom. Improving Fire Safety by Understanding the Fire Performance of Engineered Floor Systems and Providing the Fire Service with Information for Tactical Decision Making. UL Firefighter Safety Research Institute, mars 2012. http://dx.doi.org/10.54206/102376/zcoq6988.

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This research project was a collaboration of several research organizations, product manufacturers and fire service representatives to examine hazards associated with residential flooring systems to improve firefighter safety. Funding for this project was provided through the National Institute of Standards and Technology’s American Recovery and Reinvestment Act Grant Program. The main objective of this study was to improve firefighter safety by increasing the level of knowledge on the response of residential flooring systems to fire. Several types (or series) of experiments were conducted and analyzed to expand the body of knowledge on the impact of fire on residential flooring systems. The results of the study have been prepared to provide tactical considerations for the fire service to enable improved decision making on the fire scene. Experiments were conducted to examine several types of floor joists including, dimensional lumber, engineered I-joists, metal plate connected wood trusses, steel C-joists, castellated I-joists and hybrid trusses. Experiments were performed at multiple scales to examine single floor system joists in a laboratory up through a full floor system in an acquired structure. Applied load, ventilation, fuel load, span and protection methods were altered to provide important information about the impact of these variables to structural stability and firefighter safety. There are several tactical considerations that result from this research that firefighters can use immediately to improve their understanding, safety and decision making when sizing up a fire in a one or two family home. This report summarizes the results from each of the experimental series and provides discussion and conclusions of the results.

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Riveros, Guillermo, Felipe Acosta, Reena Patel et Wayne Hodo. Computational mechanics of the paddlefish rostrum. Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/41860.

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Purpose – The rostrum of a paddlefish provides hydrodynamic stability during feeding process in addition to detect the food using receptors that are randomly distributed in the rostrum. The exterior tissue of the rostrum covers the cartilage that surrounds the bones forming interlocking star shaped bones. Design/methodology/approach – The aim of this work is to assess the mechanical behavior of four finite element models varying the type of formulation as follows: linear-reduced integration, linear-full integration, quadratic-reduced integration and quadratic-full integration. Also presented is the load transfer mechanisms of the bone structure of the rostrum. Findings – Conclusions are based on comparison among the four models. There is no significant difference between integration orders for similar type of elements. Quadratic-reduced integration formulation resulted in lower structural stiffness compared with linear formulation as seen by higher displacements and stresses than using linearly formulated elements. It is concluded that second-order elements with reduced integration and can model accurately stress concentrations and distributions without over stiffening their general response. Originality/value – The use of advanced computational mechanics techniques to analyze the complex geometry and components of the paddlefish rostrum provides a viable avenue to gain fundamental understanding of the proper finite element formulation needed to successfully obtain the system behavior and hot spot locations.

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