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.

A smart grid cost/benefit analysis answers a series of economic questions that address the incremental benefits of each stage or decision point. Each stage of the economic analysis provides information about the incremental benefits of that stage with respect to the previous stage. With this approach stages that provide little or no economic benefits can be identified. In this study there are series of applications,-including quasi-steady state power flows over time-varying loads and costs of service, Monte Carlo simulations, reconfiguration for restoration, and coordinated control - that are used to evaluate the cost-benefits of a series of smart grid investments. In the electric power system planning process, engineers seek to identify the most cost-effective means of serving the load within reliability and power quality criteria. In order to accurately assess the cost of a given project, the feeder losses must be calculated. In the past, the feeder losses were estimated based upon the peak load and a calculated load factor for the year. The cost of these losses would then be calculated based upon an expected, fixed per-kWh generation cost. This dissertation presents a more accurate means of calculating the cost of losses, using hourly feeder load information and time-varying electric energy cost data. The work here attempts to quantify the improvement in high accuracy and presents an example where the economic evaluation of a planning project requires the more accurate loss calculation. Smart grid investments can also affect response to equipment failures where there are two types of responses to consider -blue-sky day and storm. Storm response and power restoration can be very expensive for electric utilities. The deployment of automated switches can benefit the utility by decreasing storm restoration hours. The automated switches also improve system reliably by decreasing customer interruption duration. In this dissertation a Monte Carlo simulation is used to mimic storm equipment failure events, followed by reconfiguration for restoration and power flow evaluations. The Monte Carlo simulation is driven by actual storm statistics taken from 89 different storms, where equipment failure rates are time varying. The customer outage status and durations are examined. Changes in reliability for the system with and without automated switching devices are investigated. Time varying coordinated control of Conservation Voltage Reduction (CVR) is implemented. The coordinated control runs in the control center and makes use of measurements from throughout the system to determine control settings that move the system toward optimum performance as the load varies. The coordinated control provides set points to local controllers. A major difference between the coordinated control and local control is the set points provided by the coordinated control are time varying. Reduction of energy and losses of coordinated control are compared with local control. Also eliminating low voltage problems with coordinated control are addressed. An overall economic study is implemented in the final stage of the work. A series of five evaluations of the economic benefits of smart grid automation investments are investigated. Here benefits that can be quantified in terms of dollar savings are considered here referred to as "hard dollar" benefits. Smart Grid investment evaluations to be considered include investments in improved efficiency, more cost effective use of existing system capacity with automated switches, and coordinated control of capacitor banks and voltage regulators. These Smart Grid evaluations are sequentially ordered, resulting in a series of incremental hard dollar benefits. Hard dollar benefits come from improved efficiency, delaying large capital equipment investments, shortened storm restoration times, and reduced customer energy use. The evaluation shows that when time varying loads are considered in the design, investments in automation can improve performance and significantly lower costs resulting in "hard dollar" savings. / Ph. D.

Orientador: Rubén Augusto Romero Lázaro / Resumo: Neste projeto de pesquisa, é abordado o problema de desligamento ótimo de linhas de transmissão, chamado de Problema OTS, para otimizar os custos de operação de um sistema de energia elétrica, isto é, para minimizar os custos de operação da geração para atender um perfil de demanda especificado. Foram priorizados tópicos de pesquisas considerados problemáticos na otimização do problema OTS, tópicos identificados através de uma revisão bibliográfica das publicações mais relevantes relacionadas com o problema OTS. Assim, um tópico abordado na pesquisa é o desenvolvimento de estratégias para reduzir o número relativamente elevado de linhas de transmissão que são desligadas, já que o desligamento de muitas linhas de transmissão produzem uma redução de custo insignificante. Outro tópico abordado é o problema de geração de soluções ótimas que produzem ilhamento do sistema elétrico ou até a formação de vários setores do sistema de energia elétrica operando de forma independente. O terceiro tópico é o desenvolvimento de um modelo matemático que representa as linhas iguais conectadas em paralelo entre duas barras por uma linha simples equivalente. Finalmente, é iniciada a análise teórica para encontrar os argumentos consistentes que permitam explicar os motivos pelos quais o desligamento de uma linha de transmissão melhora a operação de um sistema de energia elétrica contradizendo a lógica fundamental existente entre os engenheiros de operação. Esse tópico, chamado de paradoxo de Brae... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this research project, the optimal transmission switching (OTS) problem is addressed to optimize the operating costs of an electric power system, i.e., to minimize the generation costs to meet a specified demand profile. Priority was given to topics of research considered problematic in the optimization of the OTS problem, that were identified through a review of the most relevant publications related to the OTS problem. Thus, a topic addressed in the work is the development of strategies to reduce the relatively high number of disconnected transmission lines, since disconnecting many transmission lines produces insignificant cost reduction. Another topic addressed is the problem of generating optimal solutions that produce islanding of the electrical system or even the formation of several sectors of the electric power system operating independently. The third topic is the development of a mathematical model that represents the equal lines connected in parallel between two buses by an equivalent simple line. Finally, the theoretical analysis to find consistent arguments that allow explaining the reasons why the disconnection of a transmission line may improve the operation of an electric power system contradicting the fundamental logic existing among the operation engineers, is introduced. This topic, called the Braess paradox, is not addressed in any of the references reviewed during the development of this research project. In all of these proposals, the fundamental ide... (Complete abstract click electronic access below) / Doutor