The need for modern electricity infrastructures and more capable grid components brings attention to distributed energy storage systems because of their bidirectional power flow capability. This dissertation focuses on three different aspects of distributed energy storage system applications in distribution networks. It starts with flywheel energy storage system modeling and analysis for application in microgrid facilities. Then, a market-based optimal controller is proposed to enhance the operational profit of distributed energy storage devices in distribution networks. Finally, impact of multiple distributed energy storage devices on harmonic propagation in distribution networks is investigated. This dissertation provides a comparison between batteries and flywheels for the ride-through application in critical microgrid facilities like data centers. In comparison with batteries, the application of FES for power security is new. This limits the availability of experimental data. The software tool developed in this dissertation enables analysis of short-term, ride-through applications of FES during an islanded operation of a facility microgrid. As a result, it can provide a guideline for facility engineers in data centers or other types of facility microgrids to design backup power systems based on FES technology. This dissertation also presents a real-time control scheme that maximizes the revenue attainable by distributed energy storage systems without sacrificing the benefits related to improvements in reliability and reduction in peak feeder loading. This optimal control algorithm provides a means for realizing additional benefits by utilities by taking advantage of the fluctuating cost of energy in competitive energy markets. The key drivers of the economic optimization problem for distributed energy storage systems are discussed. In this dissertation, the impact of distribution network topology on harmonic propagation due to the interaction of multiple harmonic sources is investigated. Understanding how multiple harmonic sources interact to increase or decrease the harmonic distortion is crucial in distribution networks with a large number of Distributed Energy Resources. A new index, Index of Phasor Harmonics (IPH), is proposed for harmonic quantization in multiple harmonic source cases. The proposed IPH index presents more information than commonly used indices. With the help of the detailed distribution network model, topological impacts of harmonic propagation are investigated. In particular, effects of mutual coupling, phase balance, three phase harmonic sources, and single phase harmonic sources are considered. / Ph. D.

No description available.

No description available.

No description available.

High-impedance faults (HIFs) on distribution feeders are abnormal electrical conditions that cannot be detected by conventional protection schemes. These faults pose a threat on human lives when neighboring objects become in contact with the line's bare and energized conductors. An accurate electrical model for a HIF is implemented to investigate typical patterns in the line's current that allow for the detection of these faults. The occurrence of HIFs is detected with harmonic-current phase analysis and localized with recloser-sectionalizer technology as presented in this work. A sectionalizer algorithm is then presented showing the decision criteria for HIF declaration and shown to discriminate against nominal behavior in distribution feeders of similar harmonic content. Finally, it is shown that the algorithm will not produce a misreading when a current transformer enters saturation. / Master of Science

Com o déficit de energia que atualmente preocupa o setor elétrico brasileiro, ameaçando os consumidores com a possibilidade de novos racionamentos, surge a perspectiva de aumento de produção de energia, através da criação de usinas eólicas para suprir essa demanda. Entretanto, esta forma de geração, sabidamente, provoca distorções na qualidade de energia fornecida, principalmente quanto à geração de harmônicas, que acabam por interferir diretamente nas cargas podendo provocar danos a equipamentos e instalações. Por esse motivo, este trabalho visa analisar a contribuição desse tipo de geração no sistema elétrico e discutir, com base em estudos experimentais realizados em modelos de aerogeradores e diretamente em unidades geradoras instaladas em plantas de geração eólica, as perturbações harmônicas geradas pelo controle de tensão e frequência do sistema. A metodologia utilizada será a de medição das distorções harmônicas, através de analisadores de qualidade de energia, instalados primeiramente em modelos laboratoriais dos principais tipos de aerogeradores existentes no mercado, medindo as perturbações em diversas situações de carga, obedecendo ao estabelecido na norma NBR-IEC- 61400-21/2010 Medição e Avaliação da Qualidade de Energia de Aerogeradores Conectados a Rede. / With the energy deficit that currently worries the Brazilian electric sector, threatening consumers with the possibility of further rationing comes the prospect of increased energy production through the creation of wind farms to meet this demand. However, this form of generation is known to distort the quality of power supplied, especially as the generation of harmonics, which ultimately interfere directly in the loads can cause damage to equipment and facilities. Therefore, this study aims to analyze the contribution of this type of generation on the electrical system and discuss, based on experimental studies in directly generating units installed in wind generation plants, disturbances generated by harmonic voltage and frequency control system. The methodology will be the measurement of harmonic distortion through power quality analyzers, installed primarily in laboratory models of the main types of wind turbines on the market, measuring disturbances in various loading conditions, obeying the established standard NBR-IEC-61400-21/2010 - Measurement and Evaluation of Power Quality of Wind Turbines Connected Network.

Com o déficit de energia que atualmente preocupa o setor elétrico brasileiro, ameaçando os consumidores com a possibilidade de novos racionamentos, surge a perspectiva de aumento de produção de energia, através da criação de usinas eólicas para suprir essa demanda. Entretanto, esta forma de geração, sabidamente, provoca distorções na qualidade de energia fornecida, principalmente quanto à geração de harmônicas, que acabam por interferir diretamente nas cargas podendo provocar danos a equipamentos e instalações. Por esse motivo, este trabalho visa analisar a contribuição desse tipo de geração no sistema elétrico e discutir, com base em estudos experimentais realizados em modelos de aerogeradores e diretamente em unidades geradoras instaladas em plantas de geração eólica, as perturbações harmônicas geradas pelo controle de tensão e frequência do sistema. A metodologia utilizada será a de medição das distorções harmônicas, através de analisadores de qualidade de energia, instalados primeiramente em modelos laboratoriais dos principais tipos de aerogeradores existentes no mercado, medindo as perturbações em diversas situações de carga, obedecendo ao estabelecido na norma NBR-IEC- 61400-21/2010 Medição e Avaliação da Qualidade de Energia de Aerogeradores Conectados a Rede. / With the energy deficit that currently worries the Brazilian electric sector, threatening consumers with the possibility of further rationing comes the prospect of increased energy production through the creation of wind farms to meet this demand. However, this form of generation is known to distort the quality of power supplied, especially as the generation of harmonics, which ultimately interfere directly in the loads can cause damage to equipment and facilities. Therefore, this study aims to analyze the contribution of this type of generation on the electrical system and discuss, based on experimental studies in directly generating units installed in wind generation plants, disturbances generated by harmonic voltage and frequency control system. The methodology will be the measurement of harmonic distortion through power quality analyzers, installed primarily in laboratory models of the main types of wind turbines on the market, measuring disturbances in various loading conditions, obeying the established standard NBR-IEC-61400-21/2010 - Measurement and Evaluation of Power Quality of Wind Turbines Connected Network.

This research is concerned with the self-adaptive numerical solution of the neutral particle radiation transport problem. Radiation transport is an extremely challenging computational problem since the governing equation is seven-dimensional (3 in space, 2 in direction, 1 in energy, and 1 in time) with a high degree of coupling between these variables. If not careful, this relatively large number of independent variables when discretized can potentially lead to sets of linear equations of intractable size. Though parallel computing has allowed the solution of very large problems, available computational resources will always be finite due to the fact that ever more sophisticated multiphysics models are being demanded by industry. There is thus the pressing requirement to optimize the discretizations so as to minimize the effort and maximize the accuracy. One way to achieve this goal is through adaptive phase-space refinement. Unfortunately, the quality of discretization (and its solution) is, in general, not known a priori; accurate error estimates can only be attained via the a posteriori error analysis. In particular, in the context of the finite element method, the a posteriori error analysis provides a rigorous error bound. The main difficulty in applying a well-established a posteriori error analysis and subsequent adaptive refinement in the context of radiation transport is the strong coupling between spatial and angular variables. This research attempts to address this issue within the context of the second-order, even-parity form of the transport equation discretized with the finite-element spherical harmonics method. The objective of this thesis is to develop a posteriori error analysis in a coupled space-angle framework and an efficient adaptive algorithm. Moreover, the mesh refinement strategy which is tuned for minimizing the error in the target engineering output has been developed by employing the dual argument of the problem. This numerical framework has been implemented in the general-purpose neutral particle code EVENT for assessment.

Within scope of this work, double-fourier analysis method of rapid calculation and detailed simulation method, which are used to investigate DC bus current harmonics in two level and three level three-phase inverters systematically, will be emphasized and two methods will be compared via applying different modulation techniques. In addition, DC bus currents will be investigated visually for various working conditions and modulation methods. After that, analysis methods will be applied and harmonic spectrums will be determined. After all, it will be showed that calculated harmonic spectrums could be treated as unified harmonics around certain frequencies and these unified harmonics could be reached easily via looking at predetermined table. Moreover, it will also be showed that unified harmonic values could be used to determine harmonic current components that are necessary for sizing DC bus capacitor and could be used in various inverter analysis.

Diffusion MRI (dMRI) measurements allow us to infer the microstructural properties of white matter and to reconstruct fiber pathways in-vivo. High angular diffusion imaging (HARDI) allows for the creation of more and more complex local models connecting the microstructure to the measured signal. One of the challenges is the derivation of meaningful metrics describing the underlying structure from the local models. The aim hereby is to increase the specificity of the widely used metric fractional anisotropy (FA) by using the additional information contained within the HARDI data. A local model which is connected directly to the underlying microstructure through the model of a single fiber population is spherical deconvolution. It produces a fiber orientation density function (fODF), which can often be interpreted as superposition of multiple peaks, each associated to one relatively coherent fiber population (bundle). Parameterizing these peaks one is able to disentangle and characterize these bundles. In this work, the fODF peaks are approximated by Bingham distributions, capturing first and second order statistics of the fiber orientations, from which metrics for the parametric quantification of fiber bundles are derived. Meaningful relationships between these measures and the underlying microstructural properties are proposed. The focus lies on metrics derived directly from properties of the Bingham distribution, such as peak length, peak direction, peak spread, integral over the peak, as well as a metric derived from the comparison of the largest peaks, which probes the complexity of the underlying microstructure. These metrics are compared to the conventionally used fractional anisotropy (FA) and it is shown how they may help to increase the specificity of the characterization of microstructural properties. Visualization of the micro-structural arrangement is another application of dMRI. This is done by using tractography to propagate the fiber layout, extracted from the local model, in each voxel. In practice most tractography algorithms use little of the additional information gained from HARDI based local models aside from the reconstructed fiber bundle directions. In this work an approach to tractography based on the Bingham parameterization of the fODF is introduced. For each of the fiber populations present in a voxel the diffusion signal and tensor are computed. Then tensor deflection tractography is performed. This allows incorporating the complete bundle information, performing local interpolation as well as using multiple directions per voxel for generating tracts. Another aspect of this work is the investigation of the spherical harmonic representation which is used most commonly for the fODF by means of the parameters derived from the Bingham distribution fit. Here a strong connection between the approximation errors in the spherical representation of the Dirac delta function and the distribution of crossing angles recovered from the fODF was discovered. The final aspect of this work is the application of the metrics derived from the Bingham fit to a number of fetal datasets for quantifying the brain’s development. This is done by introducing the Gini-coefficient as a metric describing the brain’s age.