[pt] O aumento do consumo de energia elétrica leva os sistemas de distribuição a operar próximo do seu limite, podendo ocorrer situações de máximo fluxo de potência ativa e reativa nos ramos, ou seja, problemas de estabilidade de tensão. A mudança da topologia da rede permite encontrar uma configuração em que os índices de estabilidade de tensão estão distantes do ponto de máximo carregamento do sistema, reduzir as perdas técnicas e tornar a distribuição de carga nos alimentadores mais uniforme. Contudo, o número de possibilidades de chaveamento cresce com o aumento da dimensão da rede elétrica e a busca pela solução ótima requer esforço computacional elevado. O uso do algoritmo heurístico de Busca Tabu permite direcionar a busca por novas configurações de qualidade, armazenando suas características e proibindo a adição e/ou remoção de atributos por um período, evitando que a busca termine em um valor mínimo (máximo) local. Os resultados das análises em diferentes níveis de carregamento, que representam a operação do sistema radial de distribuição com carga leve, pesada e crítica, mostram que o algoritmo de Busca Tabu adotado neste trabalho consegue maximizar a margem de potência da barra crítica do sistema, levando o ponto de operação original à uma distância maior do ponto de máximo carregamento do sistema, na região normal de operação e minimizando as perdas técnicas. Com isso, evita-se que o sistema opere no ponto de máximo carregamento ou, na pior das hipóteses, na região anormal de operação, onde as ações de controle têm efeito oposto ao esperado. / [en] The increase of the consumption of electric energy takes the distribution systems to operate next to its limits, which might cause situation of maximum active and reactive power flow in the branches, that is, problems of voltage stability. The change of the topology of the network allows to find a configuration where de voltage stability indexes are far from de maximum loading point, improve voltage profile, reduce power losses and load balancing. However, the number of possible switching grows with the dimension of network and searching for optimal solution requires high computational effort. Using Tabu Search heuristics allows guiding the search for new configuration of high quality, being storing its characteristics and forbidding the addition and/or removal of attributes for a period, avoiding that the search finishes in a local minimum (maximum) value. The results in different loading levels, that represent the operation of radial distribution system with normal, weighed and critical load, show that the Tabu Search algorithm maximizes the voltage stability margin, leading the original operation point to a new one that is far from the maximum loading point, in the normal region of operation. With this, it is prevented that the system operates next to the maximum loading point or, in the worse case, in the abnormal region of operation, where the actions of control have opposing effect to the waited one.

Short circuit, electrical overloads, power line losses and electrical injury, but also circuit breaker and fuse, leakage current protector, power transformation and protection against electric shock. All these terms are connected with the mystery of operation in eletric power distribution systems. Let us join electricity on its journey from power station to everyone's socket. What do we experience on this adventurous journey? Sometimes there may be even a risk of death! Fortunately, thanks to the sophisticated application of physical principles of electricity and magnetism, most of the threats are avoided. Will we be able to uncover the veil of physical electricity site or will it defend its secrets?

Neste trabalho, apresenta-se um método para o Planejamento de Redes de Distribuição Secundária. O modelo básico desenvolvido baseia-se em técnica de programação dinâmica a fim de selecionar a política de evolução de trocas de transformadores de distribuição e rede secundária, com mínimo custo operacional dentro de limites de qualidade de serviço, para o atendimento de carga crescente no tempo em uma área de estudo restrita. Inicialmente, apresenta-se a filosofia básica do método, incluindo-se os dados necessários, critérios de planejamento e metodologia para o cálculo elétrico de redes secundárias. Em sequência, são apresentados três modelos para a solução do problema; tais modelos são diferenciados pela eliminação progressiva de hipóteses simplificativas. Nos dois primeiros modelos, a carga e seu crescimento são supostos uniformemente distribuídos ao longo dos trechos da rede secundária. No terceiro modelo, a distribuição da carga dos pontos presentes na rede secundária, durante o período de estudo, é estabelecida por procedimento randômico, com o único vínculo de serem mantidos os mercados globais de demanda e número de consumidores na área em estudo. Posteriormente, estabelece-se um exemplo de aplicação que permite proceder à comparação entre os três modelos desenvolvidos. Finalizando o trabalho, são estabelecidas as conclusões, possibilidades de aplicação do método em diversos estudos do sistema de Distribuição Secundária e são tecidos comentários sobre tópicos para ulterior desenvolvimento. / This work focuses on a method for the Planning of Secondary Distribution Systems. The basic model deals with dynamic programming in order to get an optimized design - Distribution Transformer and Secondaries - which presents the lowest operation cost within service quality limits in order to supply growing load on a restricted area. Initially the basic concepts of the method are presented, including the establishment of the data base, planning criteria and methodology in order to get operating conditions at secondary networks. Concerning this method, three computational models were established. These models differ form each other as far as some of the simplified hypothesis are eliminated. The first two models consider a uniform distribution of loads along the secondary system. The third model establishes a randomic distribution of loads on the restricted studying area. Following an application example, comparison is proceeded among the developed models. Eventually the conclusions, some possible applications of the method on Distribution system studies and research topics for further developments are settled.

Water crises are predicted to be amongst the risks of highest concern for the next ten years, due to availability, accessibility, quality and management issues. Knowledge of the microbial communities indigenous to drinking water is essential for treatment and distribution process control, risk assessment and infrastructure design. Drinking water distribution systems (DWDSs) ideally should deliver to the consumer water of the same microbial quality as that leaving a treatment plant (“biologically stable” according to WHO). At the start of this Ph.D. program water microbiology comprised conventional culturedependent methods, and no studies were available on microbial communities from source to tap. A method combining 16S rRNA gene pyrosequencing with flow cytometry was developed to accurately detect, characterize, and enumerate the microorganisms found in a water sample. Studies were conducted in seven fullscale Dutch DWDSs which transport low-AOC water without disinfectant residuals, produced from fresh water applying conventional treatment. Full-scale studies were also conducted at the desalination plant and DWDS of KAUST, Saudi Arabia where drinking water is produced from seawater applying RO membrane treatment and then transported with chlorine residual. Furthermore, biological stability was evaluated in a wastewater reuse application in the Netherlands. When low-AOC water was distributed without disinfectant residuals, greater bacterial richness was detected in the networks, however, temporal and spatial variations in the bacterial community were insignificant and a substantial fraction of the microbiome was still shared between the treated and transported water. This shared fraction was lower in the system transporting water with chlorine residual, where the eukaryotic community changed with residence time. The core microbiome was characterized and dominant members varied between the two systems. Biofilm and deposit-associated communities were found to drive tap water microbiology regardless of water source and treatment scheme. Network flushing was found to be a simple method to assess water microbiology. Biological stability was not associated with safety. The biological stability concept needs to be revised and quantified. Further research is needed to understand microbial functions and processes, how water communities affect the human microbiome, and what the “drinking” water microbiome is like in undeveloped countries. / The research presented in this doctoral dissertation was financially supported by and conducted in collaboration with Delft University of Technology (TU Delft) and Evides Waterbedrijf in the Netherlands.

[pt] A Geração Distribuída (GD) tem modificado profundamente a estrutura clássica dos sistemas elétricos. No Brasil, o modelo tarifário adotado pela regulação atual, denominado Sistema de Compensação de Energia, estabelece que a energia injetada pela GD na rede da distribuidora desconta integralmente a energia consumida, com todas suas componentes tarifárias. Em voga, a discussão para novas regras a respeito das formas de remuneração e valoração da GD envolve por um lado as distribuidoras, que alegam que o atual mecanismo de compensação não remunera adequadamente o uso do sistema de distribuição e, por outro lado, consumidores que optam pela GD, pontuam seus benefícios à sociedade e defendem o atual modelo. Neste sentido, é proposta nesta tese de doutorado uma nova metodologia de quantificação e alocação de benefícios e custos da GD em sistemas de distribuição, que gere um sinal tarifário capaz de traduzir os efeitos da sua localização e presença na rede. A concepção básica abrange a identificação, contabilidade e partilha do que são denominadas na metodologia proposta como funções, que representam características tarifáveis e consideradas adequadas na averiguação da remuneração da GD. Neste trabalho, as funções que serão avaliadas representam o impacto da GD no uso, nas perdas, no pico de carga e na confiabilidade da rede de distribuição. A alocação entre os geradores é realizada utilizando-se o Valor Shapley da Teoria de Jogos Cooperativos. Para aplicação da metodologia proposta, dois sistemas testes e um sistema real de distribuição são utilizados e os resultados obtidos são amplamente discutidos. / [en] Distributed Generation (DG) has deeply changed the classical structure of electrical power systems. In Brazil, the tariff model adopted by the current regulation, called the Energy Compensation System, establishes that the energy injected by DG into the distribution grid fully discounts the energy consumed, with all its tariff components. In vogue, the discussion for new rules regarding the forms of remuneration and valuation of DG involves, on the one hand, distributors, who claim that the current compensation mechanism does not adequately remunerate the use of the distribution system, and, on the other hand, consumers who choose for DG, point out its benefits to society and defend the current model. In this sense, this doctoral thesis proposes a new method for quantifying and allocating DG benefits and costs in distribution systems, which generates a tariff signal capable of translating the effects of its location and presence in the network. The basic concept covers the identification, accounting and sharing of what are called in the proposed method as functions, which represent chargeable characteristics and considered adequate in the study of DG remuneration. In this work, the functions that will be evaluated represent the DG impact on the usage, losses, peak load and reliability of the distribution network. The allocation between generators is performed using the Shapley Value of Cooperative Game Theory. In order to apply the proposed method, two test systems and a real distribution system are used and the obtained results are widely discussed.

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Power distribution systems have underwent a lot of significant changes in the last two decades. Wide-scale integration of Distributed Energy Resources (DERs) have made the distribution grid more resilient to abnormal conditions and severe weather induced outages. These DERs enhance the reliability of the system to bounce back from an abnormal situation rather quickly. However, the conventional notion of a radial system with unidirectional power flow does not hold true due to the addition of these DERs. Bidirectional power flow has challenged the conventional protection schemes in place. The most notable effects on the protection schemes can be seen in the field of islanding or Loss of Mains(LOM) detection and general fault identification and isolation. Adaptive protection schemes are needed to properly resolve these issues. Although, previous works in this field have dealt with this situation, a more comprehensive approach needs to be taken considering multiple topologies for developing adaptive protection schemes. The most common protective devices widely deployed in the distribution system such as overcurrent relays, reverse power relays at Point of Common Coupling(PCC), fuses, reclosers and feeder breakers need to studied in implementing these schemes. The work presented in this dissertation deals with simulation based and analytical approaches to tackle the issues of islanding and adaptive protection schemes. First we propose a multiprinciple passive islanding detection technique which relies on local PCC measurements, thus reducing the need of additional infrastructure and still ensuring limited Non Detection Zone (NDZ). The next step to islanding detection would be to sustain a islanded distribution system in order to reduce the restoration time and still supply power to critical loads. Such an approach to maintain generator load balance upon islanding detection is studied next by appropriate shedding of non-critical and low priority critical loads based upon voltage sensitivity analysis. Thereafter, adaptive protection schemes considering limited communication dependency is studied with properly assigning relay settings in directional overcurrent relays (DOCRs), which are one of the most widely deployed protective devices in distribution systems by catering to multiple topologies and contingencies. A simulation based technique is discussed first and then an analytical approach to solve the conventional optimal relay coordination problem using Mixed Integer Linear Programming (MILP) with the usage of multiple setting groups is studied. All these approaches make the distribution more robust and resilient to system faults and ensure proper fault identification and isolation, ensuring overall safety of system. / Doctor of Philosophy / With widespread integration of inverter-based distributed energy resources (DERs) in the distribution grid, the conventional protection and control schemes no longer hold valid. The necessity of an adaptive protection scheme increases as the DER penetration in the system increases. Apart from this, changes in system topology and variability in DER generation, also change the fault current availability in the system in real-time. Hence, the protection schemes should be able to adapt to these variations and modify their settings for proper selectivity and sensitivity towards faults in the system, especially in systems with high penetration of DERs. These protection schemes need to be modified in order to properly identify and isolate faults in the network as well as correctly identify Loss of Mains (LOM) or islanding phenomenon. Special attention is needed to plan the next course of action after the islanding occurrence. Additionally, the protective devices in distribution system should be utilized to their maximum capability to create an adaptive and smart protection system. This document elaborately explains the research work pertaining to these areas.

Power generation from solar energy has significantly increased, and the growth is projected to continue in the foreseeable future. The main challenge of dealing with solar energy is its intermittent nature. The received irradiation energy of the sun on the earth's surface can fluctuate in a matter of seconds and cause voltage issues to power systems. Considering the high growth rate of solar photovoltaic (PV) resources, it is essential to be prepared to encounter and manage their high penetration levels. Currently, simplified approaches are used to model the impacts of cloud shadows on power systems. Using outdated standards also limits the penetration levels more than required. Approximately 40% of the new PV installations are residential, or installed at a low voltage level. Currently, all components between utility distribution transformers and customers/loads are either ignored or modeled with oversimplification. Furthermore, large PV systems require a considerable amount of land. However, point sensor models are currently used to simulate those systems. With a point model, the irradiance values measured at a point sensor are used to represent the output of a large PV system. However, in reality, clouds cover photovoltaic resources gradually and if the solar arrays are widespread over a large geospatial area, it takes some time for clouds to pass over the solar arrays. Finally, before 2014, participation of small-scale renewable resources was not allowed in controlling voltage. However, they can contribute significantly in voltage regulation. The main objective of this dissertation is to address the abovementioned issues in order to increase the penetration levels as well as precisely identify and locate voltage problems. A time-series analysis approach is used in modeling cloud motion. Using the time-series approach, changes of the received irradiation energy of the sun due to cloud shadows are simulated realistically with a Cloud Motion Simulator. Moreover, the use of the time-series approach allows implementation of new grid codes and standards, which is not possible using the old step change methods of simulating cloud impacts. Furthermore, all electrical components between utility transformers and customers are modeled to eliminate the inaccuracy due to using oversimplified models. Distributed PV models are also developed and used to represent large photovoltaic systems. In addition, the effectiveness of more distributed voltage control schemes compared to the traditional voltage control configurations is investigated. Inverters connect renewable energy resources to the power grid and they may use different control strategies to control voltage. Different control strategies are also compared with the current practice to investigate voltage control performance under irradiation variations. This dissertation presents a comprehensive approach to study impacts of solar PV resources. Moreover, simulation results show that by using time-series analysis and new grid codes, as well as employing distributed PV models, penetration of solar PV resources can increase significantly with no unacceptable voltage effects. It is also demonstrated that detailed secondary models are required to accurately identify locations with voltage problems. / PHD / Power generation from solar energy has significantly increased, and the growth is projected to continue in the foreseeable future. The main challenge of dealing with solar energy is its intermittent nature. The received irradiation energy of the sun on the earth’s surface can fluctuate in a matter of seconds and cause voltage issues to power systems. Considering the high growth rate of solar photovoltaic (PV) resources, it is essential to be prepared to encounter and manage their high penetration levels. Currently, simplified approaches are used to model the impacts of cloud shadows on power systems. Using outdated standards also limits the penetration levels more than required. Approximately 40% of the new PV installations are residential, or installed at a low voltage level. Currently, all components between utility distribution transformers and customers/loads are either ignored or modeled with oversimplification. Furthermore, large PV systems require a considerable amount of land. However, point sensor models are currently used to simulate those systems. With a point model, the irradiance values measured at a point sensor are used to represent the output of a large PV system. However, in reality, clouds cover photovoltaic resources gradually and if the solar arrays are widespread over a large geospatial area, it takes some time for clouds to pass over the solar arrays. Finally, before 2014, participation of small-scale renewable resources was not allowed in controlling voltage. However, they can contribute significantly in voltage regulation. The main objective of this dissertation is to address the above mentioned issues in order to increase the penetration levels as well as precisely identify and locate voltage problems. A time-series analysis approach is used in modeling cloud motion. Using the time-series approach, changes of the received irradiation energy of the sun due to cloud shadows are simulated realistically with a Cloud Motion Simulator. Moreover, the use of the time-series approach allows implementation of new grid codes and standards, which is not possible using the old step change methods of simulating cloud impacts. Furthermore, all electrical components between utility transformers and customers are modeled to eliminate the inaccuracy due to using oversimplified models. Distributed PV models are also developed and used to represent large photovoltaic systems. In addition, the effectiveness of more distributed voltage control schemes compared to the traditional voltage control configurations is investigated. Inverters connect renewable energy resources to the power grid and they may use different control strategies to control voltage. Different control strategies are also compared with the current practice to investigate voltage control performance under irradiation variations. This dissertation presents a comprehensive approach to study impacts of solar PV resources. Moreover, simulation results show that by using time-series analysis and new grid codes, as well as employing distributed PV models, penetration of solar PV resources can increase significantly with no unacceptable voltage effects. It is also demonstrated that detailed secondary models are required to accurately identify locations with voltage problems.

Doctor of Philosophy / Computing and Information Sciences / Scott A. DeLoach / As sensor prices drop and computing devices continue to become more compact and powerful, computing capabilities are being embedded throughout our physical environment. Connecting these devices in cyber-physical systems (CPS) enables applications with significant societal impact and economic benefit. However, engineering CPS poses modeling, architecture, and engineering challenges and, to fully realize the desired benefits, many outstanding challenges must be addressed. For the cyber parts of CPS, two decades of work in the design of autonomous agents and multiagent systems (MAS) offers design principles for distributed intelligent systems and formalizations for agent-oriented software engineering (AOSE). MAS foundations offer a natural fit for enabling distributed interacting devices. In some cases, complex control structures such as holarchies can be advantageous. These can motivate complex organizational strategies when implementing such systems with a MAS, and some designs may require agents to act in multiple groups simultaneously. Such agents must be able to manage their multiple associations and assignments in a consistent and unambiguous way. This thesis shows how designing agents as systems of intelligent subagents offers a reusable and practical approach to designing complex systems. It presents a set of flexible, reusable components developed for OBAA++, an organization-based architecture for single-group MAS, and shows how these components were used to develop the Adaptive Architecture for Systems of Intelligent Systems (AASIS) to enable multigroup agents suitable for complex, multigroup MAS. This work illustrates the reusability and flexibility of the approach by using AASIS to simulate a CPS for an intelligent power distribution system (IPDS) operating two multigroup MAS concurrently: one providing continuous voltage control and a second conducting discrete power auctions near sources of distributed generation.