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Reference Management for Steady-State Transitions Under Constrained Model Predictive Control / Reference Management for Steady-State TransitionsLam, David 12 1900 (has links)
There are increasing economic incentives within the chemical process industry towards demand driven operation with product diversification, requiring flexible operation in responsive plants. In continuous processes, this is realized through steady-state transitions but requires consideration of process dynamics arising from operation that is inherently transient in nature. The steady-state economic optimum is typically defined at the intersection of constraints, and requires multivariable control with optimal constraint handling capabilities. Thus, constrained model predictive control is well-suited to realize the profit potential at the economic optimum. In this thesis, feasible and optimal steady-state transitions are achieved using reference management with consideration of the closed-loop dynamics of constrained model predictive control. The supervisory control scheme is used to determine the optimal setpoint trajectory which is subsequently tracked by regulatory control, incorporating feedback for the rejection of high frequency disturbances and eliminating steady-state offset in the presence of model mismatch. The separation of economic and control objectives enables the lower level to be tuned for stability and the upper level to be tuned for performance. The mathematical formulation results in a multi-level optimization problem with an economic objective function at the upper level, and a series of control performance objective functions arising from constrained model predictive control at the lower levels. The solution strategy proposed converts the multi-level optimization problem into a single-level optimization problem using the Karush-Kuhn-Tucker conditions, and solves the resulting complementarity conditions using an interior point approach. Alternative objective formulations are investigated based on maximizing profit during transient operation. The first formulation is typically based on a quadratic objective function minimizing the transition time, indirectly improving economic operation by reducing the amount of off-specification product produced. The second formulation is based on the explicit consideration of economics. The profit calculated during transient operation is based on the difference between the revenue generated by the production of acceptable product within specified univariate product quality bands, and the operational costs of raw materials and utilities. The resulting linear objective function is further extended to incorporate control performance considerations to improve conditioning for gradient based optimization. The proposed methodology is applied to a single-input single-output linear system, demonstrating the potential benefits of simultaneous rather than sequential optimization in terms of computational efficiency and solution reliability. Alternative objective function and constraint formulations are investigated, and the effect on the optimal solution assessed. In particular, the possibility of indeterminacy is shown and handled using hierarchical optimization. The methodology is also demonstrated on additional examples including non-minimum phase systems and multi-input multi-output linear systems. Application to a multi-input multi-output nonlinear system corresponding to styrene polymerization using the proposed methodology is detailed. The set of differential and algebraic equations defining the process is discretized using orthogonal collocation on finite elements. The optimal operation during grade transitions based on explicit consideration of economics is determined, and additional improvements realized by manipulating the production rate. Finally, reference management with online re-optimization is investigated for a single-input single-output linear system based on a bias update, and the improvement in closed-loop performance assessed for output disturbances and model mismatch. The methodology is also demonstrated on a multi-input multi-output system based on a linear model when applied to the nonlinear process. The proposed methodology developed for steady-state transitions may also be applied to batch operation, startups and shutdowns. Future extensions include analysis of closed-loop stability due to the incorporation of feedback within the cascade control scheme, and the explicit consideration of uncertainty. / Thesis / Master of Applied Science (MASc)
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"We Shall Have to Make the Best of It:" The Conversion of Dennis SciamaHunt, James Christopher 14 October 2005 (has links)
The cosmologist Dennis W. Sciama (1926-1999) was a long-standing advocate of the steady state model of the universe. This theory, originally proposed in 1948 by Hermann Bondi, Thomas Gold, and Fred Hoyle, suggested that the universe was eternal, and unchanging on the largest scales. Contrary to the popular image of a scientist as a dispassionate, unbiased investigator of nature, Sciama fervently hoped the steady state model to be correct. In addition, and also pace the stereotypical image of a scientist, Sciama was motivated significantly by "extrascientific" or aesthetic factors in his adoption of the model. Finally, Sciama, in a stark contrast to the naive falsificationism usually presented as a virtue of the "scientific method," went through a several-year period of attempting to "save" the model from hostile data.
However, Sciama abandoned the model in 1966 due to increasingly reliable data relating to the distribution of quasars. Thus the Sciama case also stands as a counterexample to irrationalist criticisms of science, according to which scientists can and will always find ways to hold on to their "pet" theories until they die, regardless of contradictory data. Sciama's conversion also sheds light on the iterative process that goes on as scientists localize and attempt to repair faults in their theories. / Ph. D.
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Shape Factors for the Pseudo-Steady State Flow in Fractured Hydrocarbon Wells of Various Drainage Area GeometriesJanuary 2017 (has links)
abstract: Pseudo-steady state (PSS) flow is an important time-dependent flow regime that
quickly follows the initial transient flow regime in the constant-rate production of
a closed boundary hydrocarbon reservoir. The characterization of the PSS flow
regime is of importance in describing the reservoir pressure distribution as well as the
productivity index (PI) of the flow regime. The PI describes the production potential
of the well and is often used in fracture optimization and production-rate decline
analysis. In 2016, Chen determined the exact analytical solution for PSS flow of a
fully penetrated vertically fractured well with finite fracture conductivity for reservoirs
of elliptical shape. The present work aimed to expand Chen’s exact analytical solution
to commonly encountered reservoirs geometries including rectangular, rhomboid,
and triangular by introducing respective shape factors generated from extensive
computational modeling studies based on an identical drainage area assumption. The
aforementioned shape factors were generated and characterized as functions for use
in spreadsheet calculations as well as graphical format for simplistic in-field look-up
use. Demonstrative use of the shape factors for over 20 additional simulations showed
high fidelity of the shape factor to accurately predict (mean average percentage error
remained under 1.5 %) the true PSS constant by modulating Chen’s solution for
elliptical reservoirs. The methodology of the shape factor generation lays the ground
work for more extensive and specific shape factors to be generated for cases such as
non-concentric wells and other geometries not studied. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2017
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Capacidade máxima de acúmulo de carbono em solos cultivados com cana-de-açúcar / Maximum capacity of carbon accumulation in soils cultivated with sugarcaneCarolina Braga Brandani 27 August 2013 (has links)
Um dos principais entraves na cultura da cana-de-açúcar quanto à sustentabilidade do solo é o manejo da cultura e da colheita. O objetivo deste estudo foi avaliar os estoques de C e sua dinâmica em diferentes frações da MOS (matéria orgânica do solo) em áreas cultivadas com cana-de-açúcar sob os manejos com e sem queima e, sob adubação orgânica com diferentes períodos de adoção (4 e 12 anos), tendo uma área de vegetação nativa (Cerradão) como referência. As áreas localizam-se em Goianésia-GO, sendo todas representativas da classe dos Latossolos Vermelho-Amarelo distróficos. Foram avaliados os teores de C e N do solo e seus respectivos estoques, além dos teores de C e N e, das abundâncias isotópicas do 13C e 15N para as frações organominerais < 53 ?m, 75-53 ?m e 2000- 75 ?m (fração orgânica e organomineral) da MOS. De posse desses resultados, objetivou-se simular a capacidade máxima de acúmulo de C, a partir do modelo Century, enfatizando os manejos avaliados e texturas de solos contrastantes. Os teores de C foram maiores para o manejo orgânico-4, em relação às demais áreas de cana-de-açúcar avaliadas. Os estoques de C e N foram maiores para as áreas em que o teor de argila foi superior; com queima e orgânica-4. Devido as diferenças entre texturas foram calculados os estoques em função dos ajustes quanto à massa de solo e teores de argila, utilizando-se como referência a vegetação nativa. Dessa forma os maiores estoques foram observados para o manejo orgânica-12. Os resultados para o conteúdo de C da biomassa microbiana (C-BM) mostrou aumento dos em função da melhoria do manejo. Em relação aos teores de C e N das frações da MOS, os manejos orgânicos (orgânica-12 e -4) resultaram nos maiores valores observados, principalmente para a fração organomineral <53 ?m à 5 cm de profundidade. Tais resultados refletiram diretamente sobre os valores de 13C, sua respectiva proporção de C derivado do resíduo C4 e, do 15N, indicando, respectivamente, maior acúmulo e proporção de C proveniente da cultura de canade- açúcar nas frações da MO, além de evidenciar, a partir do 15N, comportamento, quanto ao grau de humificação da MO, mais próximo ao observado para a vegetação nativa. Os resultados do estudo de modelagem enfatizaram a importância da textura do solo bem como as práticas de manejo para o acúmulo de C no solo. Os sistemas de manejo conservacionistas ao contrário da queima resultaram em estoques de C superiores em 78 % e 98 %, quando simulado solo com maior e menor teores de argila, respectivamente. Os resultados suportaram o uso do modelo Century em aplicações práticas de acúmulo de C em solos cultivados com cana-deaçúcar, principalmente, para os estoques de C e os ?13C dos solos avaliados, indicando que o modelo Century pode ser uma importante ferramenta para estabelecer estratégias apropriadas de manejo para aumentar os estoques de C do solo ao longo do tempo. O longo período de avaliação mostrou que conceitos, como o \"steady state\" de C no solo, podem ser investigados via modelagem, como pelo uso do modelo Century. A partir desse estudo foi possível concluir que práticas de manejos conservacionistas tendem a aumentar os estoques de C e N do solo ao longo do tempo e, que esse aumento é fortemente influenciado pelo teor de argila no solo. / One of the main obstacles of sugarcane production in the soil sustainability is the crop management and harvesting. The aim of this study was to evaluate the carbon (C) stocks and dynamics in different SOM fractions in sugarcane systems with or without burning, and under organic fertilization with different periods of adoption (4 and 12) and an area of native vegetation (Cerradão) used as a reference. The study areas are located in Goianésia, GO, all representatives of Latossolos Vermelho-Amarelo distróficos (Oxisols Hapludox distrofic). We evaluated C and N soil contents and natural isotopic abundances 13C e 15N to organominerals fractions < 53 ?m, 75-53 ?m e 2000-75 ?m (organic and organomineral fractions) of SOM. With these results, we aimed to simulate the maximum accumulation of C, by using the Century model, emphasizing different management practices and contrasting soil textures. The C contents were higher for organic-4, in relation to the other areas of sugarcane evaluated. The stocks of C and N were higher for areas where the clay content was higher (burning and organic-4). Due to the difference between soil texture we calculated stocks according to the adjustments on the equivalent mass of soil and clay content, with reference to the native vegetation and thus the largest stocks were observed for organic-12. The C from microbial biomass (C-BM) showed increased in the (C-BM) levels, due to improved management. Regarding the levels of C and N fractions of SOM, the organic-12 and organic-4 resulted in the highest values, especially for OM fraction < 53 ?m (organomineral) to 5 cm depth. These results reflected directly on the values of 13C, the respective proportion of C derived from C4 residue and the 15N, indicating, respectively, greater accumulation and proportion of C derived from the sugarcane in SOM fractions, and evidence from the 15N closer behavior to that observed for native vegetation, relative of OM humification degree. The results of the modeling study emphasized the importance of soil texture and management practices for soil C accumulation. The conservation management system resulted in higher C stocks, by 78% and 98% when simulated soil with higher and lower clay contents, respectively. The results supported the use of the Century model in practical applications of C accumulation in soils cultivated with sugarcane, especially for C stocks and 13C of soils evaluated, indicating that the Century model can be an important tool to establish appropriate management strategies to increase soil C stocks over time. The long period of evaluation showed that concepts such as the \"steady state\" of soil carbon, can be investigated via modeling. We concluded that the practices of the conservation tillage systems tend to increase the stocks of C and N in the soil over time, and this increase is strongly influenced by the clay content in the soil.
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Capacidade máxima de acúmulo de carbono em solos cultivados com cana-de-açúcar / Maximum capacity of carbon accumulation in soils cultivated with sugarcaneBrandani, Carolina Braga 27 August 2013 (has links)
Um dos principais entraves na cultura da cana-de-açúcar quanto à sustentabilidade do solo é o manejo da cultura e da colheita. O objetivo deste estudo foi avaliar os estoques de C e sua dinâmica em diferentes frações da MOS (matéria orgânica do solo) em áreas cultivadas com cana-de-açúcar sob os manejos com e sem queima e, sob adubação orgânica com diferentes períodos de adoção (4 e 12 anos), tendo uma área de vegetação nativa (Cerradão) como referência. As áreas localizam-se em Goianésia-GO, sendo todas representativas da classe dos Latossolos Vermelho-Amarelo distróficos. Foram avaliados os teores de C e N do solo e seus respectivos estoques, além dos teores de C e N e, das abundâncias isotópicas do 13C e 15N para as frações organominerais < 53 ?m, 75-53 ?m e 2000- 75 ?m (fração orgânica e organomineral) da MOS. De posse desses resultados, objetivou-se simular a capacidade máxima de acúmulo de C, a partir do modelo Century, enfatizando os manejos avaliados e texturas de solos contrastantes. Os teores de C foram maiores para o manejo orgânico-4, em relação às demais áreas de cana-de-açúcar avaliadas. Os estoques de C e N foram maiores para as áreas em que o teor de argila foi superior; com queima e orgânica-4. Devido as diferenças entre texturas foram calculados os estoques em função dos ajustes quanto à massa de solo e teores de argila, utilizando-se como referência a vegetação nativa. Dessa forma os maiores estoques foram observados para o manejo orgânica-12. Os resultados para o conteúdo de C da biomassa microbiana (C-BM) mostrou aumento dos em função da melhoria do manejo. Em relação aos teores de C e N das frações da MOS, os manejos orgânicos (orgânica-12 e -4) resultaram nos maiores valores observados, principalmente para a fração organomineral <53 ?m à 5 cm de profundidade. Tais resultados refletiram diretamente sobre os valores de 13C, sua respectiva proporção de C derivado do resíduo C4 e, do 15N, indicando, respectivamente, maior acúmulo e proporção de C proveniente da cultura de canade- açúcar nas frações da MO, além de evidenciar, a partir do 15N, comportamento, quanto ao grau de humificação da MO, mais próximo ao observado para a vegetação nativa. Os resultados do estudo de modelagem enfatizaram a importância da textura do solo bem como as práticas de manejo para o acúmulo de C no solo. Os sistemas de manejo conservacionistas ao contrário da queima resultaram em estoques de C superiores em 78 % e 98 %, quando simulado solo com maior e menor teores de argila, respectivamente. Os resultados suportaram o uso do modelo Century em aplicações práticas de acúmulo de C em solos cultivados com cana-deaçúcar, principalmente, para os estoques de C e os ?13C dos solos avaliados, indicando que o modelo Century pode ser uma importante ferramenta para estabelecer estratégias apropriadas de manejo para aumentar os estoques de C do solo ao longo do tempo. O longo período de avaliação mostrou que conceitos, como o \"steady state\" de C no solo, podem ser investigados via modelagem, como pelo uso do modelo Century. A partir desse estudo foi possível concluir que práticas de manejos conservacionistas tendem a aumentar os estoques de C e N do solo ao longo do tempo e, que esse aumento é fortemente influenciado pelo teor de argila no solo. / One of the main obstacles of sugarcane production in the soil sustainability is the crop management and harvesting. The aim of this study was to evaluate the carbon (C) stocks and dynamics in different SOM fractions in sugarcane systems with or without burning, and under organic fertilization with different periods of adoption (4 and 12) and an area of native vegetation (Cerradão) used as a reference. The study areas are located in Goianésia, GO, all representatives of Latossolos Vermelho-Amarelo distróficos (Oxisols Hapludox distrofic). We evaluated C and N soil contents and natural isotopic abundances 13C e 15N to organominerals fractions < 53 ?m, 75-53 ?m e 2000-75 ?m (organic and organomineral fractions) of SOM. With these results, we aimed to simulate the maximum accumulation of C, by using the Century model, emphasizing different management practices and contrasting soil textures. The C contents were higher for organic-4, in relation to the other areas of sugarcane evaluated. The stocks of C and N were higher for areas where the clay content was higher (burning and organic-4). Due to the difference between soil texture we calculated stocks according to the adjustments on the equivalent mass of soil and clay content, with reference to the native vegetation and thus the largest stocks were observed for organic-12. The C from microbial biomass (C-BM) showed increased in the (C-BM) levels, due to improved management. Regarding the levels of C and N fractions of SOM, the organic-12 and organic-4 resulted in the highest values, especially for OM fraction < 53 ?m (organomineral) to 5 cm depth. These results reflected directly on the values of 13C, the respective proportion of C derived from C4 residue and the 15N, indicating, respectively, greater accumulation and proportion of C derived from the sugarcane in SOM fractions, and evidence from the 15N closer behavior to that observed for native vegetation, relative of OM humification degree. The results of the modeling study emphasized the importance of soil texture and management practices for soil C accumulation. The conservation management system resulted in higher C stocks, by 78% and 98% when simulated soil with higher and lower clay contents, respectively. The results supported the use of the Century model in practical applications of C accumulation in soils cultivated with sugarcane, especially for C stocks and 13C of soils evaluated, indicating that the Century model can be an important tool to establish appropriate management strategies to increase soil C stocks over time. The long period of evaluation showed that concepts such as the \"steady state\" of soil carbon, can be investigated via modeling. We concluded that the practices of the conservation tillage systems tend to increase the stocks of C and N in the soil over time, and this increase is strongly influenced by the clay content in the soil.
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Untersuchungen zur Validität und Praktikabilität des mathematisch bestimmten maximalen Laktat-steady-states bei radergometrischen BelastungenHauser, Thomas 27 February 2013 (has links) (PDF)
Das maximale Laktat-steady-state (MLSS) gilt als ein physiologischer Parameter der Ausdauerleistungsfähigkeit. Bereits in den 1980er Jahren entwickelte Mader (1984) auf Basis der Michaelis-Menten-Kinetik eine Berechnungsmethode zur Bestimmung der Leistung im MLSS. Diese Methode setzt die Kenntnis der maximalen Reaktionsgeschwindigkeiten von Glykolyse und Atmung voraus. Die Goldstandard-Methode zur Ermittlung der Leistung im MLSS sind mehrere 30-minütige konstante Dauerbelastungen. Das hauptsächliche Ziel der vorliegenden Arbeit bestand in dem Vergleich der berechneten mit der empirisch ermittelten Leistung im MLSS. 57 männliche Probanden unterzogen sich zunächst in randomisierter Reihenfolge einem Test zur Bestimmung der maximalen Laktatbildungsrate sowie der maximalen Sauerstoffaufnahme. Im Anschluss absolvierten die Testpersonen mehrere 30 minütige Dauertests zur empirischen Ermittlung der Leistung im MLSS. Die ermittelten Ergebnisse zeigen, dass zwischen beiden Testmethoden eine hochsignifikante Korrelation (r = 0,89; p< 0,001) sowie eine mittlere Differenz von -13 Watt vorliegt. Ausgehend von den ermittelten Ergebnissen kann der Schluss gezogen werden, dass die Leistung im MLSS, ermittelt unter Verwendung der Methode nach Mader (1984) im Mittel mit der empirisch ermittelten Leistung im MLSS sehr gut übereinstimmt. Neben der angeführten Hauptstudie, wurde in der vorliegenden Arbeit weiterhin die Reliabilität und Tag-zu-Tag-Variabilität der Leistung im MLSS, der Einfluss der Testdauer auf die Laktatbildungsrate sowie die Praktikabilität der berechneten Leistung im MLSS in einem Einzelzeitfahren näher untersucht.
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Energetics in Canoe SprintLi, Yongming 11 May 2015 (has links) (PDF)
This study reviewed first the development of race result in canoe sprint during the past decades. The race results of MK1-1000 and WK1-500 have increased 32.5 % and 42.1 %, respectively, a corresponding 5.0 % and 6.5 % increase in each decade. The development of race results in canoe sprint during the past decades resulted from the contributions of various aspects. The recruitment of taller and stronger athletes improved the physiological capacity of paddlers. Direct investigation on energy contribution in canoe sprint enhanced the emphasis on aerobic capacity and aerobic endurance training. Advancement of equipment design improved the efficiency of paddling. Physiological and biomechanical diagnostics in canoe sprint led to a more scientific way of training. Additionally, other aspects might also have contributed to the development of race results during the past decades. For example, the establishment of national team after World War II provided the possibility of systematic training, and the use of drugs in the last century accelerated the development of race results in that period.
Recent investigations on energetics in high-intensity exercises demonstrated an underestimate of WAER % in the table provided by some textbooks since the 1960s. An exponential correlation between WAER % and the duration of high-intensity exercises was concluded from summarizing most of the relevant reports, including reports with different methods of energy calculation. However, when reports with the MAOD and Pcr-La-O2 methods were summarized separately, a greater overestimate of WAER % from MAOD was found compared to those from Pcr-La-O2, which was in line with the critical reports on MAOD. Because of the lack of investigation of the validity of the comparisons between MAOD and Pcr-La-O2, it is still not clear which method can generate more accurate results and which method is more reliable.
With regard to kayaking, a range of variation in WAER % was observed. Many factors might contribute to the variation of WAER % in kayaking. Therefore, the methods utilized to calculate the energy contributions, different paddling conditions, and the level of performance were investigated in kayaking. The findings indicated that the method utilized to calculate the energy contributions in kayaking, rather than paddling condition and performance level of paddlers, might be the possible factor associated with WAER %. Some other possible factors associated with WAER % still need to be further investigated in the future.
After verifying the dependence of WAER % on the method of energy calculation, but not on paddling condition and performance level of paddlers, energy contributions of kayaking were investigated for the three racing distances on a kayak ergometer with junior paddlers. Energetic profiles in kayaking varied with paddling distances. At 500 m and 1000 m the aerobic system was dominant (with WAER % of 57.8 % and 76.2 %), whereas at 200 m the anaerobic system was dominant (with WAER % of 31.1-32.4 %). Muscular volume seemed to have an influence on absolute energy productions. The anaerobic alactic system determined the performance during the first 5 to 10 s. The anaerobic lactic system probably played a dominant role during the period from the 5th-10th s to 30th-40th s. The aerobic system could dominate the energy contribution after 30–40 s. This energetic profile in kayaking could provide physiological support for developing the training philosophy in these three distances. Additionally, the method introduced by Beneke et al. seemed to be a valid method to calculate the energy contributions in maximal kayaking.
Energy contributions in canoeing were similar to those in kayaking. The relative energy contributions on open water canoeing were 75.3 ± 2.8 % of aerobic, 11.5 ± 1.9 % of anaerobic lactic, and 13.2 ± 1.9 % of anaerobic alactic at maximal speed of simulated 1000 m. Further, the C of canoeing seemed also to be similar to the reported findings in kayaking, with a function of y = 0.0242 * x2.1225. Training programs could be designed similarly for kayaking and canoeing with regard to energetic profile.
In order to extend the findings on energetics in canoe sprint to other exercises, energy contributions in kayaking, canoeing, running, cycling, as well as arm cranking were compared with the same duration. Results indicated that WAER % during maximal exercises with the same duration seemed to be independent of movement patterns, given similar VO2 kinetics during the maximal exertion. The exponential relationship between WAER % and duration in maximal exercises could be supported by excluding the influence from movement patterns.
Additionally, MLSS in kayaking was investigated. The blood lactate value of MLSS was found to be 5.4 mM in kayaking, which could expand the knowledge of MLSS in different locomotion. The MLSS in kayaking might be attributed to the involved muscle mass in this locomotion, which could result in a certain level of lactate removal, and allow a certain level of equilibrium between lactate production and removal. LT5, instead of LT4, was recommended for diagnostics in kayaking, given an incremental test as used in this study.
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Exploration of a Scalable Holomorphic Embedding Method Formulation for Power System Analysis ApplicationsJanuary 2017 (has links)
abstract: The holomorphic embedding method (HEM) applied to the power-flow problem (HEPF) has been used in the past to obtain the voltages and flows for power systems. The incentives for using this method over the traditional Newton-Raphson based nu-merical methods lie in the claim that the method is theoretically guaranteed to converge to the operable solution, if one exists.
In this report, HEPF will be used for two power system analysis purposes:
a. Estimating the saddle-node bifurcation point (SNBP) of a system
b. Developing reduced-order network equivalents for distribution systems.
Typically, the continuation power flow (CPF) is used to estimate the SNBP of a system, which involves solving multiple power-flow problems. One of the advantages of HEPF is that the solution is obtained as an analytical expression of the embedding parameter, and using this property, three of the proposed HEPF-based methods can es-timate the SNBP of a given power system without solving multiple power-flow prob-lems (if generator VAr limits are ignored). If VAr limits are considered, the mathemat-ical representation of the power-flow problem changes and thus an iterative process would have to be performed in order to estimate the SNBP of the system. This would typically still require fewer power-flow problems to be solved than CPF in order to estimate the SNBP.
Another proposed application is to develop reduced order network equivalents for radial distribution networks that retain the nonlinearities of the eliminated portion of the network and hence remain more accurate than traditional Ward-type reductions (which linearize about the given operating point) when the operating condition changes.
Different ways of accelerating the convergence of the power series obtained as a part of HEPF, are explored and it is shown that the eta method is the most efficient of all methods tested.
The local-measurement-based methods of estimating the SNBP are studied. Non-linear Thévenin-like networks as well as multi-bus networks are built using model data to estimate the SNBP and it is shown that the structure of these networks can be made arbitrary by appropriately modifying the nonlinear current injections, which can sim-plify the process of building such networks from measurements. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017
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Energetics in Canoe SprintLi, Yongming 10 February 2015 (has links)
This study reviewed first the development of race result in canoe sprint during the past decades. The race results of MK1-1000 and WK1-500 have increased 32.5 % and 42.1 %, respectively, a corresponding 5.0 % and 6.5 % increase in each decade. The development of race results in canoe sprint during the past decades resulted from the contributions of various aspects. The recruitment of taller and stronger athletes improved the physiological capacity of paddlers. Direct investigation on energy contribution in canoe sprint enhanced the emphasis on aerobic capacity and aerobic endurance training. Advancement of equipment design improved the efficiency of paddling. Physiological and biomechanical diagnostics in canoe sprint led to a more scientific way of training. Additionally, other aspects might also have contributed to the development of race results during the past decades. For example, the establishment of national team after World War II provided the possibility of systematic training, and the use of drugs in the last century accelerated the development of race results in that period.
Recent investigations on energetics in high-intensity exercises demonstrated an underestimate of WAER % in the table provided by some textbooks since the 1960s. An exponential correlation between WAER % and the duration of high-intensity exercises was concluded from summarizing most of the relevant reports, including reports with different methods of energy calculation. However, when reports with the MAOD and Pcr-La-O2 methods were summarized separately, a greater overestimate of WAER % from MAOD was found compared to those from Pcr-La-O2, which was in line with the critical reports on MAOD. Because of the lack of investigation of the validity of the comparisons between MAOD and Pcr-La-O2, it is still not clear which method can generate more accurate results and which method is more reliable.
With regard to kayaking, a range of variation in WAER % was observed. Many factors might contribute to the variation of WAER % in kayaking. Therefore, the methods utilized to calculate the energy contributions, different paddling conditions, and the level of performance were investigated in kayaking. The findings indicated that the method utilized to calculate the energy contributions in kayaking, rather than paddling condition and performance level of paddlers, might be the possible factor associated with WAER %. Some other possible factors associated with WAER % still need to be further investigated in the future.
After verifying the dependence of WAER % on the method of energy calculation, but not on paddling condition and performance level of paddlers, energy contributions of kayaking were investigated for the three racing distances on a kayak ergometer with junior paddlers. Energetic profiles in kayaking varied with paddling distances. At 500 m and 1000 m the aerobic system was dominant (with WAER % of 57.8 % and 76.2 %), whereas at 200 m the anaerobic system was dominant (with WAER % of 31.1-32.4 %). Muscular volume seemed to have an influence on absolute energy productions. The anaerobic alactic system determined the performance during the first 5 to 10 s. The anaerobic lactic system probably played a dominant role during the period from the 5th-10th s to 30th-40th s. The aerobic system could dominate the energy contribution after 30–40 s. This energetic profile in kayaking could provide physiological support for developing the training philosophy in these three distances. Additionally, the method introduced by Beneke et al. seemed to be a valid method to calculate the energy contributions in maximal kayaking.
Energy contributions in canoeing were similar to those in kayaking. The relative energy contributions on open water canoeing were 75.3 ± 2.8 % of aerobic, 11.5 ± 1.9 % of anaerobic lactic, and 13.2 ± 1.9 % of anaerobic alactic at maximal speed of simulated 1000 m. Further, the C of canoeing seemed also to be similar to the reported findings in kayaking, with a function of y = 0.0242 * x2.1225. Training programs could be designed similarly for kayaking and canoeing with regard to energetic profile.
In order to extend the findings on energetics in canoe sprint to other exercises, energy contributions in kayaking, canoeing, running, cycling, as well as arm cranking were compared with the same duration. Results indicated that WAER % during maximal exercises with the same duration seemed to be independent of movement patterns, given similar VO2 kinetics during the maximal exertion. The exponential relationship between WAER % and duration in maximal exercises could be supported by excluding the influence from movement patterns.
Additionally, MLSS in kayaking was investigated. The blood lactate value of MLSS was found to be 5.4 mM in kayaking, which could expand the knowledge of MLSS in different locomotion. The MLSS in kayaking might be attributed to the involved muscle mass in this locomotion, which could result in a certain level of lactate removal, and allow a certain level of equilibrium between lactate production and removal. LT5, instead of LT4, was recommended for diagnostics in kayaking, given an incremental test as used in this study.
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Development and Deployment of Renewable and Sustainable Energy TechnologiesJung, Jae Sung 06 March 2014 (has links)
Solar and wind generation are one of the most rapidly growing renewable energy sources, and is regarded as an appealing alternative to conventional power generated from fossil fuel. This is leading to significant levels of distributed renewable generation being installed on distribution circuits. Although renewable generation brings many advantages, circuit problems are created due to its intermittency, and overcoming these problems is a key challenge to achieving high penetration.
It is necessary for utilities to understand the impacts of Photovoltaic (PV) generation on distribution circuits and operations. An impact study is intended to quantify the extent of the issues, discover any problems, and investigate alternative solutions. In this manner, system wide and local impact study are proposed in the dissertation.
1) System wide impact study
This study considers system effects due to the addition of Plug-in Hybrid Vehicles (PHEV) and Distributed Energy Resource (DER) generation. The DER and PHEV are considered with energy storage technology applied to the residential distribution system load. Two future year scenarios are considered, 2020 and 2030. The models used are of real distribution circuits located near Detroit, Michigan, and every customer load on the circuit and type of customer are modeled. Monte Carlo simulations are used to randomly select customers that receive PHEV, DER, and/or storage systems. The Monte Carlo simulations provide not only the expected average result, but also its uncertainty.
2) Local impact study
Analysis of high PV penetration in distribution circuits using both steady-state and quasi steady-state impact studies are presented. The steady-state analysis evaluates impacts on the distribution circuit by comparing conditions before and after extreme changes in PV generation at three extreme circuit conditions, maximum load, maximum PV generation, and when the difference between the PV generation and the circuit load is a maximum. The quasi steady-state study consists of a series of steady-state impact studies performed at evenly spaced time points for evaluating the spectrum of impacts between the extreme impacts. Results addressing the impacts of cloud cover and various power factor control strategies are presented. PV penetration levels are limited and depend upon PV generation control strategies and the circuit design and loading. There are tradeoffs in PV generation control concerning circuit voltage variations, circuit losses, and the motion of automated utility control devices. The steady state and quasi steady-state impact studies provide information that is helpful in evaluating the effect of PV generation on distribution circuits, including circuit problems that result from the PV generation.
In order to fully benefit from wind power, accurate wind power forecasting is an essential tool in addressing this challenge. This has motivated researchers to develop better forecast of the wind resources and the resulting power. As a solution for wind generation, frequency domain approach is proposed to characterize and analyze wind speed patterns in the dissertation.
3) Frequency Domain Approach
This study introduces the frequency domain approach to characterize and analyze wind speed patterns. It first presents the technique of and the prerequisite conditions for the frequency domain approach. Three years of wind speed data at 10 different locations have been used. This chapter demonstrates that wind speed patterns during different times and at different locations can be well characterized by using the frequency domain approach with its compact and structured format. We also perform analysis using the characterized dataset. It affirms that the frequency domain approach is a useful indicator for understanding the characteristics of wind speed patterns and can express the information with superior accuracy.
Among the various technical challenges under high PV penetration, voltage rise problems caused by reverse power flows are one of the foremost concerns. The voltage rises due to the PV generation. Furthermore, the need to limit the voltage rise problem limits PV generators from injecting more active power into the distribution network. This can be one of the obstacles to high penetration of PVs into circuits. As a solution for solar generation, coordinated control of automated devices and PV is proposed in the dissertation.
4) Coordinated Automated Device and PV Control
A coordinating, model-centric control strategy for mitigating voltage rise problems due to PV penetration into power distribution circuits is presented. The coordinating control objective is to maintain an optimum circuit voltage distribution and voltage schedule, where the optimum circuit operation is determined without PV generation on the circuit. In determining the optimum circuit voltage distribution and voltage schedule, the control strategy schedules utility controls, such as switched capacitor banks and voltage regulators, separate from PV inverter controls. Optimization addresses minimizing circuit losses and motion of utility controls. The coordinating control action provides control setpoints to the PV inverters that are a function of the circuit loading or time-of-day and also the location of the PV inverter. Three PV penetration scenarios are considered, 10%, 20%, and 30%. Baselines with and without coordinating controls for circuit performance without PV generation are established, and these baselines are compared against the three PV penetration scenarios with and without coordinating control. Simulation results are compared and differences in voltage variations and circuit losses are considered along with differences in utility control motion. Results show that the coordinating control can solve the voltage rise problem while minimizing circuit losses and reducing utility control motion. The coordinating control will work with existing PV inverter controls that accept control setpoints without having to modify the inverter controls.
5) Coordinated Local and Centralized PV Control
Existing distribution systems and their associated controls have been around for decades. Most distribution circuits have capacity to accommodate some level of PV generation, but the question is how much can they handle without creating problems. It proposes a Configurable, Hierarchical, Model-based, Scheduling Control (CHMSC) of automated utility control devices and photovoltaic (PV) generators. In the study here the automated control devices are assumed to be owned by the utility and the PV generators and PV generator controls by another party. The CHMSC, which exists in a hierarchical control architecture that is failure tolerant, strives to maintain the voltage level that existed before introducing the PV into the circuit while minimizing the circuit loss and reducing the motion of the automated control devices. This is accomplished using prioritized objectives. The CHMSC sends control signals to the local controllers of the automated control devices and PV controllers. To evaluate the performance of the CHMSC, increasing PV levels of adoption are analyzed in a model of an actual circuit that has significant existing PV penetration and automated voltage control devices. The CHMSC control performance is compared with that of existing, local control. Simulation results presented demonstrate that the CHMSC algorithm results in better voltage control, lower losses, and reduced automated control device motion, especially as the penetration level of PV increases. / Ph. D.
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