Dissertations / Theses on the topic 'Distribution systems'

The 5th generation mobile telecommunication system (5G) is currently being specified and developed, with large expectations on throughput and efficiency. While 4G and more specifically LTE might constitute a basis of the design of the network, there are some parts that should be improved. One thing to improve is the static signalling that occurs very frequently in a 4G network, of which system information such as synchronization signals, detection of network frequencies, operators, configurations etc. is a part. It has been shown that the static signalling requires both much energy and time-frequency resources. Since the system information is not intended for a single user it is always broadcast so that any user, and any amount of users can read it when needed. 5G will use a technique called massive MIMO, where the base station is equipped with a large number of antennas which can be used to direct signals in space, called beamforming. This thesis presents a new method for distribution of system information that can utilize the beamforming capabilities of massive MIMO. A simple model together with simulated user channel statistics from urban 4G scenarios are used to show that the new method outperforms the classical method of only broadcasting the information, with respect to time-frequency resources. Especially if there are high requirements on the latency of the system information, the new method results in a large gain.

The development of a distribution system simulator that can model new power electronic devices as well as new novel distribution schemes, such as DC distribution has been donehere. The simulator adopts the Electro-Magnetic Transient Programs (EMTP) platform to facilitate the simulation. Basic power electronic building blocks have been developed to extend the capabilities of the EMTP. These blocks include a rectifier module, a DC buck converter module, a 3-phase inverter module and a single-phase inverter module. The paper shows simulation of a new distribution scheme for naval ships to illustrate that such a simulator facilitates the study of new distribution system designs, especially theprotection and control issues associated with new designs.

Distribution systems (DS) are the last stage of any large power system, delivering electricity to the end-users. Conventionally, simplicity of DS operation has been a priority over its optimality. However, with the recent advancements in the automation and measurement infrastructures, it is now possible to improve the efficiency of DS operation. In this dissertation, a load modeling procedure is proposed which takes advantage of the data available at the smart meters. An algorithm is proposed to decompose the load at each customer level using the smart meter measurements. The proposed load model represents the voltage dependence of loads according to the load composition. Based on the voltage-dependent load model, a linear power flow formulation is developed for DS analysis. The linear current flow equations are then proposed which calculate the branch flows directly without requiring the nodal voltages. Sensitivity factors in terms of current transfer and branch outage distribution factors are also derived using the linear power flow concept. The advantages of having a set of linear equations describing the system statics are demonstrated in a variety of DS optimization problems, such as topological reconfiguration, capacitor placement, and volt-VAR optimization. Using the linear current flow equations, the mixed-integer nonlinear programming problem of DS reconfiguration is reformulated into a mixed-integer quadratic/linear programming problem, which substantially reduces the computational burden of the nonlinear combinatorial problem. Besides developing a direct mathematical optimization approach, a fast heuristic method is also developed here for the minimum-loss network reconfiguration based on the minimum spanning tree problem. This heuristic method provides a good suboptimal solution to initialize the direct mathematical optimization approaches such as branch-and-cut algorithm used for solving combinatorial problems. Based on planar graph theory, an efficient mathematical formulation for the representation of the radiality constraint in reconfiguration problems is introduced. It is shown that this formulation is advantageous over the available methods in terms of accuracy and computational efficiency. The proposed algorithms are tested using a variety of DS benchmarks and promising results are achieved.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

With increasing global change pressures such as urbanization and climate change, cities of the future will experience difficulties in efficiently managing scarcer and less reliable water resources. However, projections of future global change pressures are plagued with uncertainties. This increases the difficulty in developing urban water systems that are adaptable to future uncertainty. A major component of an urban water system is the distribution system, which constitutes approximately 80-85% of the total cost of the water supply system (Swamee and Sharma, 2008). Traditionally, water distribution systems (WDS) are designed using deterministic assumptions of main model input variables such as water availability and water demand. However, these deterministic assumptions are no longer valid due to the inherent uncertainties associated with them. Hence, a new design approach is required, one that recognizes these inherent uncertainties and develops more adaptable and flexible systems capable of using their active capacity to act or respond to future alterations in a timely, performance-efficient, and cost-effective manner. This study develops a framework for the design of flexible WDS that are adaptable to new, different, or changing requirements. The framework consists of two main parts. The first part consists of several components that are important in the pre and post--processing of the least-cost design methodology of a flexible WDS. These components include: the description of uncertainties affecting WDS design, identification of potential flexibility options for WDS, generation of flexibility through optimization, and a method for assessing of flexibility. For assessment a suite of performance metrics is developed that reflect the degree of flexibility of a distribution system. These metrics focus on the capability of the WDS to respond and react to future changes. The uncertainties description focuses on the spatial and temporal variation of future demand. The second part consists of two optimization models for the design of centralized and decentralized WDS respectively. The first model generates flexible, staged development plans for the incremental growth of a centralized WDS. The second model supports the development of clustered/decentralized WDS. It is argued that these clustered systems promote flexibility as they provide internal degrees of freedom, allowing many different combinations of distribution systems to be considered. For both models a unique genetic algorithm based flexibility optimization (GAFO) model was developed that maximizes the flexibility of a WDS at the least cost. The efficacy of the developed framework and tools are demonstrated through two case study applications on real networks in Uganda. The first application looks at the design of a centralized WDS in Mbale, a small town in Eastern Uganda. Results from this application indicate that the flexibility framework is able to generate a more flexible design of the centralized system that is 4% - 50% less expensive than a conventionally designed system when compared against several future scenarios. In addition, this application highlights that the flexible design has a lower regret under different scenarios when compared to the conventionally designed system (a difference of 11.2m3/US$). The second application analyzes the design of a decentralized network in the town of Aura, a small town in Northern Uganda. A comparison of a decentralized system to a centralized system is performed, and the results indicate that the decentralized system is 24% - 34% less expensive and that these cost savings are associated with the ability of the decentralized system to be staged in a way that traces the urban growth trajectory more closely. The decentralized clustered WDS also has a lower regret (a difference of 17.7m3/US$) associated with the potential future conditions in comparison with the conventionally centralized system and hence is more flexible.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California

Un système de systèmes est un système dont les composants sont eux-mêmes des systèmes indépendants, tous communiquant pour atteindre un objectif commun. Lorsque ces systèmes sont mobiles, il peut être difficile d'établir des connexions de bout-en-bout. L'architecture mise en place dans de telles situations est appelée réseau tolérant aux délais. Les données sont transmises d'un système à l'autre – selon les opportunités de communication, appelées contacts, qui apparaissent lorsque deux systèmes sont proches – et disséminées dans l'ensemble du réseau avec l'espoir que chaque message atteigne sa destination. Si une donnée est trop volumineuse, elle est découpée. Chaque fragment est alors transmis séparément.Nous supposons ici que la séquence des contacts est connue. On s'intéresse donc à des applications où la mobilité des systèmes est prédictible (les réseaux de satellites par exemple). Nous cherchons à exploiter cette connaissance pour acheminer efficacement des informations depuis leurs sources jusqu'à leurs destinataires. Nous devons répondre à la question : « Quels éléments de données doivent être transférés lors de chaque contact pour minimiser le temps de dissémination » ?Nous formalisons tout d'abord ce problème, appelé problème de dissémination, et montrons qu'il est NP-difficile au sens fort. Nous proposons ensuite des algorithmes pour le résoudre. Ces derniers reposent sur des règles de dominance, des procédures de prétraitement, la programmation linéaire en nombres entiers, et la programmation par contraintes. Une partie est dédiée à la recherche de solutions robustes. Enfin, nous rapportons des résultats numériques montrant l'efficacité de nos algorithmes
Systems of systems are supersystems comprising elements which are themselves independent operational systems, all interacting to achieve a common goal. When the subsystems are mobile, these may suffer from a lack of continuous end-to-end connectivity. To address the technical issues in such networks, the common approach is termed delay-tolerant networking. Routing relies on a store-forward mechanism. Data are sent from one system to another – depending on the communication opportunities, termed contacts, that arise when two systems are close – and stored throughout the network in hope that all messages will reach their destination. If data are too large, these must be split. Each fragment is then transmitted separately.In this work, we assume that the sequence of contacts is known. Thus, we focus on applications where it is possible to make realistic predictions about system mobility (e.g. satellite networks). We study the problem of making the best use of knowledge about possibilities for communication when data need to be routed from a set of systems to another within a given time horizon. The fundamental question is: "Which elements of the information should be transferred during each contact so that the dissemination length is minimized"?We first formalize the so-called dissemination problem, and prove this is strongly NP-Hard. We then propose algorithms to solve it. These relies on different dominance rules, preprocessing procedures, integer-linear programming, and constraint programming. A chapter is dedicated to the search for robust solutions. Finally experimental results are reported to show the efficiency of our algorithms in practice

A stable and reliable electric power supply system is an inevitable pre-requisite for the technological and economic growth of any nation. Due to this, utilities must strive and ensure that the customer’s reliability requirements are met and the regulators requirements satisfied at the lowest possible cost. It is known fact around the world that 90% of the of the customer service interruptions are caused due to failure in distribution system. Therefore, it is worth considering reliability worth assessments as it provides an opportunity to incorporate the cost or losses incurred by the utilities customer as a result of power failure and this must be considered in planning and operating practices. The system modeling and simulation study is carried out on one of the district’s distribution system which consists of 33kV and 11kV network in Bhutan. The reliability assessment is done on both 11 and 33kV system to assess the performance of the present system and also predictive reliability analysis for the future system considering load growth and system expansion. The alternative which gives low SAIDI, SAIFI and minimum breakeven costs are being assessed and considered. The reliability of 33kV system could be further improved by installation of load break switch, auto recloser and connecting with line coming from other district (reserve) at reasonable break even cost. The decision base could be further improved by having Bhutan’s context interruption cost. However, the questionnaire’s which may be used in Bhutan to acquire interruption costs from the customers are being proposed. The utility should have their own reliability improvement strategy depending upon their needs and requirements of the regulators. Although there is no magic bullet in managing power quality issues, utilities can maximize network performance and better serve customers by diligently addressing trouble prone areas. In order to achieve this objective, a computer program NetBas/Lesvik is used to run load flow and reliability analysis, thus selecting the alternatives either based on reliability indices or on cost benefit ratio.

Thesis (S.M. in System Design and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-112).
Electrical and electronic components have a prominent role in today's vehicles. Particularly during the last two decades, functionality has been added at an exponential rate, resulting in increased complexity, especially of the Electrical Distribution System (EDS), which is the backbone of the Electrical and Electronic System (EES). Increased content and complexity of electrical systems, together with pressure to reduce the design cycle time - to bring a larger variety of products to the market and at a faster pace - are forcing car companies to re-evaluate their existing electrical development processes. One of the ways that car makers have devised to accomplish this is a common EES architecture strategy, which consists in combining communization, standardization, reusability and best practices to create flexible EES architectural concepts that will be used in a higher number of derivative vehicles. This common architecture has several benefits, the most important being: reduction of development costs and time, which translates in less time for putting the products in the market; architecture, concepts and components reuse; rapid platform modifications, to adapt to market changes and regional preferences. The EES architecture choice for a vehicle is the result of the implementation of the desired functions in hardware and software. Many considerations need to be taken into account: costs, network capabilities, modularity, manufacturing, energy management, weight, among several others. The present work aims to explain these considerations, as well as the elements of the common EES, and in particular their impact on the EDS. Another important aspect for the successful implementation of the common architecture is the EDS development process. Despite the availability of a wide range of software tools, the current EDS approach is intensely manual, relying on design experts to define and maintain the interrelationships and complexities of the core design definition. There is a need to redefine the process, from concept to manufacture using a systems engineering approach, which would yield key benefits, like shorten development time, produce accurate harness manufacturing prints, reduce wiring costs by synchronizing all input and output data. An analysis of the tools and methods for design and validation of wire harnesses will be presented in the last two chapters of this thesis.
by Marcia E. Azpeitia Camacho.
S.M.in System Design and Management

Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1992 and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.
Thesis Advisor: Kirtley, James L., Jr. "May 1992." Description based on title screen as viewed on March 30, 2009. Includes bibliographical references (p. 73-74). Also available in print.

This thesis demonstrates the value of integrating electrical distribution engineering analysis with Geographic Information Systems (GIS). The 37-Node IEEE Feeder model was used as the base distribution system in this study. It was modeled separately, both in software capable of unbalanced load-flow and in an industry-standard GIS environment. Both tools utilized were commercially available, off-the shelf products indicative of those used in academia and in basic GIS installations. The foundational data necessary to build these models is representative of information required by a variety of utility departments for a multitude of applications. It is inherent to most systems within an enterprise-level, business-wide data model and therefore can be used to support a variety of applications. In this instance, infrastructure information is assumed to be managed and housed with the GIS. This data provides the required information as input for load-flow calculations. The engineering analysis is performed within DistributionSystem 4.01 and its output is passed back to the GIS in tabular format for incorporation. This thesis investigates the transfer of information between GIS and DistributionSystem 4.01 and demonstrates the extended display capabilities in the GIS environment. This research is implemented on a small scale, but is intended to highlight the need for standardization and automatic integration of these systems as well as others that are fundamental to the effective management of electrical distribution systems.
Master of Science

Modern power distribution systems (PDS) utilize multiple converters, making power flow undergo several conversions between source and the load. Use of high frequency AC (HFAC) in PDSs eliminates a few stages of converters in addition to the smaller sized capacitors and inductors being used; making the converters much lighter in weight offering a variety of solutions for the weight critical applications such as spacecraft, aircraft and electric vehicle onboard PDSs. HFAC converters with resonant filters have been widely used in the past despite of being tuned to a single frequency. Thus, the variable frequency operation as well as parallel connection of multiple converters had been less efficient. This part of the research work focusses on development of a bi-directional AC-AC converter that could work within a range of grid parameters. The proposed two-stage converter constructed with wide bandgap power switches, a high-performance microcontroller, low-pass filters which operates at high switching frequencies provide the desired variable frequency and voltage operation capability. A major drawback in HFAC PDS had been the excessive power loss and voltage drop due to skin effect and proximity effect of conductors. This part of the research work investigates the development of new cable types with hollow core cross-sections. This would minimize skin effect losses by shifting much of the conducting material to the skin depth, keeping the weight increase to a minimal. Feasibility studies performed using PSCAD software showed improved performance of cables upto 100kHz; enabling using such as in wireless power transmission applications.

Considering various applications of Pump as Turbine (PAT) as an effective source of reducing the equipment cost in small hydropower plants as well as the selecting process of appropriate location and suitable machinery are the main concerns of this study. Vary range of PAT settings criteria has been propound by taking into account the State-of-the-Art researches. The purpose of this study is to establish the effectiveness of pump as turbine, considering all the possible obstacles such as producer’s market interests, accessibility of technical information and mechanical limitation. Cutting-edge scientific researches concerning PAT have been proposed by implementation of various approaches. The most challenging criteria of PAT, which is selecting the appropriate machinery, has been investigated subsequently. A comparative methodology to model the effectiveness of PATs, both numerical and experimental, has been developed based on the efficiency. The mechanical reliability of the hydropower devices in situ, prototype and numerical investigation have been reviewed. These results have been obtained through measurements and optimization of the simulated system by means of characteristic methods against the established PAT system in many different case studies. Water Distribution Networks (WDNs) allow to obtain a widespread and globally significant amount of produced energy by exploiting the head drop due to the network pressure control strategy for leak reductions. Replacing PAT in water distribution networks regarding to all the possible obstacles, will reduce the final cost and will improve the expected efficiencies, as much as the reduction of environmental impacts. This study definitively answers the question whether PAT is an effective alternative in WDNs. The comparative approach also aims for a better understanding of the impact of PAT on the transition to renewable energy systems.

In this thesis, different types of chemical and physical distribution coefficients are identified, examined and used to describe the fate and transport pathways of substances in aquatic systems.

Observations from field experiments in streams with non-reactive and reactive tracers constituted the basis for development of an advection-dispersion model. Differences in the concentrations in both the water and sediment data for the tracers were due to the particle affinity of the reactive tracer. This difference in behaviour could be described by including an instantanous and a kinetically controlled sorption, which included distribution coefficients, in the water column (Kd) and in the streambed sediment (KB), respectively.

The results presented in this thesis also include a model for the lake characteristic concentration of suspended particulate matter (SPM). The SPM-model can be used to describe mass flows of particles in lakes. The traditional distribution (or partition) coefficient Kd has been found to be unsuitable for interpretations of the particle association of solutes and also for distributing solute mass flows. Instead, the particulate or the dissolved fraction, PF and DF, defined as ratios of the particulate or dissolved concentration to the total concentration respectively, is recommended for mass-balance calculations. A new PF-model for phosphorus has meant that this part is no longer the most sensitive part of predicting concentrations of phosphorus in lakes using a more extensive dynamic model.

New methods have also been developed to describe the shape of lakes. Together with the mixing depth of lakes, the shape of a lake can be transformed into a distribution coefficient that physically determines the portion of a lake that is exposed, both areally and vertically, to continuously mixing.

The Master's Thesis research focuses on analyzing the possibilities of using Direct Current distribution systems to distribute power to end users. Considering the shift in load types in the past few decades and also a growing demand of distributed generation, DC distribution can potentially offer higher efficiencies and cost savings to utilities. The incorporation of DC distribution offers the opportunity to eliminate multiple conversion stages for devices which are powered using DC electricity. The integration of power sources such as photovoltaics and fuel cells, which produce DC power, offer further incentives to consider the use of DC systems. Using DC systems can help eliminate the conversion losses associated with rectifiers and inverters which would be part of the infrastructure if AC distribution was used. In the literature, the study of DC distribution has been limited to customized systems. The objective of this research is to analyze DC distribution when applied to systems based on standard IEEE test feeder systems. The IEEE 13 node test feeder and the IEEE 37 node test feeder will be used as the basis for the analysis. Issues such as associated costs, protection and integration of appliances will also be addressed.

Unprecedented expansion of native direct current (DC) powered equipment (computers and consumer electronics) has increased household DC electricity consumption over the past decade. Since power utilities deliver alternating current (AC) rather than DC, the conversion process (rectifier) used to supply DC loads is very inefficient. The research investigates the suitability of employing conventional AC wiring to distribute DC power to supply loads directly, in particular around outlet/switch arcing issues. The problem of arcing in DC system is very predominant and needs to be addressed to meet safety requirements while improving the efficiency of the system. In order to overcome the arcing issues, an alternative flat DC wiring system is proposed which offers improved transient electrical and thermal characteristics for household wiring. The flat wire solution employs the same raw materials and provides improvements in parasitic values associated with arcing while reducing thermal resistance. The proposed flat wire geometry is expected to achieve reduction of arcing and improve the overall efficiency of the distribution system. Simulations of the two preliminary AC and DC systems are provided for typical domestic loads and switching events. These characteristics are verified by conducting similar tests on house wiring system prototype created in the lab. Furthermore, the switching behaviour is observed on loading the system through the outlet.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

We are building a Big Data Management System (BDMS) called AsterixDB at UCI. Since AsterixDB is designed to operate on large volumes of data, the results for its queries can be potentially very large, and AsterixDB is also designed to operate under high concurency workloads. As a result, we need a specialized mechanism to manage these large volumes of query results and deliver them to the clients. In this thesis, we present an architecture and an implementation of a new result distribution framework that is capable of handling large volumes of results under high concurency workloads. We present the various components of this result distribution framework and show how they interact with each other to manage large volumes of query results and deliver them to clients. We also discuss various result distribution policies that are possible with our framework and compare their performance through experiments.

We have implemented a REST-like HTTP client interface on top of the result distribution framework to allow clients to submit queries and obtain their results. This client interface provides two modes for clients to choose from to read their query results: synchronous mode and asynchronous mode. In synchronous mode, query results are delivered to a client as a direct response to its query within the same request-response cycle. In asynchronous mode, a query handle is returned instead to the client as a response to its query. The client can store the handle and send another request later, including the query handle, to read the result for the query whenever it wants. The architectural support for these two modes is also described in this thesis. We believe that the result distribution framework, combined with this client interface, successfully meets the result management demands of AsterixDB.

When islanding occurs, power supply from the main grid is interrupted which causes a problem when distributed generators continue to provide power into distributed networks. An islanding situation should be detected accurately soon after the island is formed. Because failure to trip the islanded distributed resource can lead to a number of problems for the resource and the connected load. Although ROCOF islanding detection method is the most commonly employed anti-islanding protection technique, it provides fast detection and easily implementation. It is sensitive to the system disturbance. Therefore, the application of the ROCOF relay to detect system islanding has been limited. This thesis proposes a solution to enhance the performance of the ROCOF relay by cooperation with rate of change of power or v2/p interlock function. During system load variation, the false operation of ROCOF relay can be blocked effectively. It is validated by applied in grid-connected synchronous generator, Doubly-fed Induction generator (both simulation and experiment) and microgrid. The principle of rate of change of power or v2/p interlock function are presented in this thesis. The new interlock function v2/p with ROCOF relays works well for different types of DGs within a short detection time without introducing perturbation into the system, which are the advantages over other active and hybrid islanding detection methods. The performances characteristics of ROCOF relays for DGs islanding detection (i.e. frequency measuring methods, measuring windows, generator inertia constant, relay settings and load power factor) are investigated. In addition, two other islanding detection methods (impedance measurement (active method) and the Total Harmonic Method) are applied to the grid-connected DFIG distributed system, the comparison and effectiveness of these two methods utilized in islanding and load changing conditions are also discussed.

The presented thesis investigates the identification of burst locations in water distribution systems (WDS) by analysis of field and simulation experimental data. This required the development of a new hybrid method of burst detection and sizing, and also a burst location identification algorithm. Generally, existing practice relies on a combination of some simple procedure and experience of the involved staff and cannot be easily automated. The practical methods are based on direct manifestation of burst on the surface or on systematically surveying suspected areas e.g. by using listening sticks, such methods are very time consuming. The proposed burst location algorithm is based on comparing data by means of statistical analysis of field data with results of water network simulation. An extended network hydraulic simulator is used to model pressure dependent leakage terms. The presence of a burst changes the flow pattern and also pressure at network nodes which may be used to estimate the burst size and its location. The influence of such random factors as demand flows and background leakage on the process of burst detection is also considered. The field data is from a generalised fixed area and variable area (FAVOR) test where inlet pressure is being stepped up and down and the following variables are measured: inlet flow, inlet pressure (head) and pressure at a number of selected sensitive nodes. The method has three stages and uses two different models, one is inlet flow model (IFM) to represent the total inlet flow and another is the extended hydraulic model to simulate different burst locations. Initially the presence of a potential burst is investigated. If this is confirmed precise values of the demand, background leakage flow and burst flow in IFM are subsequently estimated. They are used to identify the burst site at the third stage of the method. The method can be easily adapted for practical use. It requires data from experiments carried out at night between 1am and 5am and involves placing typically about 20 temporary loggers to collect the measurements during this period. It also requires the availability of a hydraulic model which normally is in the possession of a water company. The program has been implemented in the Matlab package and is easy to use. The current methodology is tuned to identify a single burst but can be generalised to identify locations of multiple bursts.

The upgrade of urban water distribution systems (UWDS) amidst uncertain global change pressures is a challenging problem. To deal with this dilemma water utilities require approaches that enable UWDS to be transitioned at a minimal technical and socio-economic impact as uncertainties become known. A review of approaches for upgrading UWDS shows that existing cost models are skewed towards operation and maintenance costs without consideration for future transitionability. This thesis describes approaches for the sustainable transition of UWDS and their application on case studies. The thesis develops a conceptual framework for the analysis of UWDS transitions. It then develops a Socio-economic Impact Indicator (SII) framework based on Multi Criteria Decision Analysis and the Analytical Hierarchical Process to estimate impacts in an urban area due to UWDS transitions. It also develops an approach for modelling socio-technical transitions based on multinomial logistic regression. The thesis then develops an UWDS transition design approach that considers not only operation and maintenance costs (leakage and burst costs) but also transitionability and future socio-technical impacts costs. The developed approaches have been tested on case studies as proof of concept. Maximum cost saving can be realised when existing UWDS are upgraded with consideration of future UWDS transitionability.

Water distribution systems are often susceptible to failure events, mainly due to component malfunctions, increase in demand and pollution events. However, levels of service to the consumers cannot be compromised. Therefore, to understand the behaviour of distribution systems, performance assessment is important. In this thesis, problem of failure events in water distributions system is discussed and the causes of failure are described. Component failures are selected to simulate the extreme situations in the distribution systems. Random nature of the component failures are simulated by way of employing a Monte Carlo technique based on the failure probabilities of the components. The methodology was illustrated with an example application. Appropriateness of existing network analysis methods to simulate failure events is analysed and their shortcomings identified. To demonstrate the impact of component failures, they are simulated with the hydraulic network analysis model. The traditional demand driven network analysis approach is not sensitive to pressure variations in the system. Therefore, simulating failures with demand driven analysis methods produces inaccurate flows at the nodes. The pressure dependent demand analysis on the other hand, is capable of accommodating the flow redistributions in the water distribution network, caused by failure events. The pressure dependent functions used in the analysis are meant to predict the flows that are consumed by the secondary networks (tree network supplied from primary node). However, representing the secondary network behaviour by using only a few coefficients (as in the PDD functions) do not always results in correct predictions. An alternative method that is based on micro level models (secondary networks) is proposed. Micro level models try to simulate the exact network conditions, taking into account of the consumers piping arrangements. Applying micro level models to a large real network will be a tedious process, as the size of the network will increase by many folds. To avoid the difficulties in the micro level modeling, a method based on artificial neural networks (ANN) is introduced. The ANNs mimic the behaviour of secondary networks in the micro level model. Therefore, instead of physically attaching the secondary networks, ANNs are incorporated with the analysis. The ANN based network analysis model predicts the pressure dependent demand outflows at the nodes. The behaviour of water distribution system is evaluated using performance measures. Existing performance indicators are reviewed and their shortcomings identified. New measures are proposed that give better insights into the behaviour of the system and also the failure experience of the consumers. The improved performance assessment method is applied to a case study network and results were explained.

Les systèmes de distribution de contenu comme les caches web et les réseaux d’échanges de fichiers doivent pouvoir servir une population de clients à la fois très grande (centaines de milliers) et fortement dynamique (temps de connexion très courts). Ces caractéristiques rendent leur analyse très coûteuse par les approches traditionnelles comme les modèles markoviens ou la simulation. Dans cette thèse, nous proposons des modèles fluides simples permettant de s’affranchir de l’une des dimensions du problème. Dans la première partie, nous développons un modèle stochastique fluide pour les systèmes de caches distribués. Les documents stockés sont modélisés par un fluide augmentant avec les requêtes insatisfaites. Nous appliquons ce modèle aux « clusters » de caches et à Squirrel, un système de cache pair-à-pair. Dans les deux cas notre modèle permet de calculer efficacement et avec précision la probabilité de hit, et de mettre en évidence les paramètres clés de ces systèmes. Nous proposons également une approximation multiclasses pour modéliser la popularité des documents. Dans la seconde partie de cette thèse, nous étudions BitTorrent, un système d’échange de fichiers pair-à-pair. Nous proposons un modèle fluide multiclasses qui remplace les usagers par un fluide. Nous considérons deux classes d’usager pour modéliser les différences de débits d’accès ou de qualité de service. Nous obtenons une formule close pour le temps de téléchargement dans chaque classe. Nous montrons également comment allouer la bande passante à chaque classe pour offrir un service différencié
Content distribution systems (CDS) such as web caches and file sharing systems are large-scale distributed systems that may serve hundreds of thousands of users. These highly dynamic systems exhibit a very large state space which makes them difficult to analyze with classical tools such as Markovian models or simulation. In this thesis we propose macroscopic fluid models to reduce the complexity of these systems. We show that these simple models provide accurate and insightful results on the performance of CDS. In a first part, we propose a generic fluid model for distributed caching systems. The idea is to replace cached documents with fluid that increase with unsatisfied requests. Caches may go up and down according to a birth-death process. We apply this model to study two caching systems : cache clusters and P2P cooperative cache system called Squirrel. We derive an efficient and accurate expression of their hit probabilities and show how the model identifies the key tradeoffs of these systems. We also propose a multicasts approximation for taking into account document popularity. In the second part of the thesis we consider file sharing systems such as BitTorrent. We propose a two-class fluid model which replaces downloaders with fluids. This simple deterministic model may reflect the problem of service differentiation or bandwidth diversity for instance. We provide a closed-form expression of the average download time for each class under the word-case assumption that users leave the system immediately after completing their download. We also show how to allocate peers bandwidth between classes to achieve service differentiation

In contrast with traditional approaches based either on the analysis of a small specific area or on idealistic networks, the proposed methodology determines optimal network design policies by evaluating alternative planning strategies on statistically similar networks. The position of consumers influences the amount of equipment used to serve them. Therefore, simple geometric models or randomly placed points used in previous researches are not adequate. Using an algorithm based on fractal theory, realistic consumer sets are generated in terms of their position, type and demand to allow statistical evaluation of the cost of different design policies. In order to systematically deal with the problem of determining justifiable network investments, the concept of economically adapted distribution network was investigated and applied in the context of a loss-inclusive design promoting efficient investment policies from an overall social perspective. The network’s components are optimized, after yearly load flow calculations, based on the minimum life-cycle cost methodology, balancing annuitised capital investments and maintenance costs against the cost of system operation. Evaluating the cost of each particular design over statistically similar networks allows statistically significant conclusions to be drawn. The main results include the optimal number of substations for typical urban and rural LV, HV and EHV distribution systems, network costs (investment, purchasing and maintenance) and losses as well as the sensitivity of optimal network design to future energy prices and cost of equipment. The impact of the increasing amount of microgeneration on networks has not been fully addressed to date. There have not been clustering problems in existing networks as a result of customers choosing to install microgenerators, either as a new device or as a replacement of a previous heating system. The operation of microgeneration connected to the distribution network can cause statutory voltage limits, recommended voltage unbalance levels and switchgear fault ratings to be exceeded. However, there are a range of distribution network designs and operating practices and thus the impact will vary accordingly. The operation of distribution networks is approached considering the existence of single or three-phase loads and microgeneration. This would however cause the network to be unbalanced and hence, traditional methods that consider a three-phase balanced system would provide misleading results. Every residential daily load’s behaviour shows rapid shifts from “load valleys” to high peaks due to the random and frequent “switch on/off” of appliances. Modelling each load individually will reveal problematic operating conditions which were not considered when using a smooth load profile. Thus, each and every domestic load was represented by a different load profile and the impact on losses was evaluated. Relating losses, voltages, currents and load unbalance ratio leads to conclusions about the way how to optimise the network with DG. The aim was to investigate and develop methodology for evaluation of the long-term loss-inclusive optimal network design strategies and to determine the effect of the penetration of microgeneration, such as CHP and PV, in realistic distribution networks and optimal network planning. The need for reinforcement of network components will depend on the level of generation and on the extent to which reverse power flows occurs. In most parts of the network, microgeneration exports will not be sufficient to result in any need for network investment. However, if the network was to be planned accounting with DG, capital investment scenarios are presented and compared to existing networks trying to accommodate clusters of microgeneration.

The increasing penetration of distributed energy resources (DERs) in distribution systems may result in a number of technical problems such as over-voltage, overloading, maloperation of protection systems and power quality issues. One approach to address the above-mentioned issues is upgrading the distribution network, which is quite costly. The second approach is to limit the penetration of DERs to the hosting capacity (HC), which is defined as the maximum DER capacity that can be installed in a system without violating the operational constraints. Understanding this concept can assist utilities to ensure the reliable operation of the system. There have been different studies to identify the HC in a system. Nevertheless, the uncertainties associated with the DERs and loads have not been addressed properly in such studies. Besides, it is very difficult to quantify the findings of those studies and make general conclusions, as they were often based on specific networks, while their methods is time consuming in a big distribution network. Furthermore, the impact of voltage control schemes and emerging technologies, such as electric vehicles (EVs) and battery energy storage systems (BESSs) on the HC have not been studied, adequately. Thus, in this thesis, we propose a suitable HC assessment framework, as well as utilize some of the conventional and emerging resources to increase the HC.

The purpose of a water distribution system (WDS) is to deliver the required amount of water to the customer under the desired pressure and quality. However, demand change and component failure result in low pressures at customer taps and make it difficult to achieve the goal. To mitigate the impact of the disturbances, system performance measure such as robustness and resilience can be considered in the WDS design and operation. Robustness is generally defined as an ability of the systems to maintain its function under a defined set of disturbance. On the other hand, Resilience is a system's ability to prepare and recover from a failure. The goal of this dissertation is to develop methodologies to enhance WDS robustness and resilience. In robustness-based design, reliability has been considered. Reliability is generally defined as the system's ability to provide an adequate service to customers under uncertain system condition and measured by the probability that stochastic nodal pressures are greater than or equal to a prescribed minimum pressure. However, although improving reliability will improve system robustness, the question is how the reliability index will improve system robustness. Robustness incorporates the variation of system performance; an additional aspect of system performance that reliability does not encompass. Pipe bursts are the most common failure in WDS. Therefore, promptly detecting and locating bursts will decrease the failure duration and increase system resilience. While many burst detection methods are available, identifying the method with the highest detectability is important to system owners/operators. However, to date, no cross comparisons of these methods have been completed for burst detection using a common data set. In addition, most traditional burst detection methods do not have a mechanism to include system operational changes. This dissertation is composed of three journal manuscripts that address these three key issues on WDS robustness and resilience. For WDS robustness improvement, a new robustness index is developed and used for multi-objective robustness-based design. The robustness-based design is compared to conventional reliability-based design. For WDS resilience improvement, the best method among six Statistical Process Control (SPC) methods is identified in terms of detection effectiveness and efficiency. Finally, a burst detection method applicable under system operational condition change is posed.

Silver was evaluated as disinfectant to maintain water quality in water distribution system. It was used to inhibit growth of two opportunistic bacteria in planktonik form and in biofilm formation in Robbins devices with stainless steel and PVC surfaces. The results of this work show that silver is a potential secondary disinfectant to be used in water distribution systems

The changes occurring in electrical systems, due to technical and economic reasons, and the requirements of a reliable and efficient delivery of the power supply to the customers demand a smarter management of the current grids at all the levels. In particular, the distribution level, until now managed without a detailed monitoring of its operating conditions, requires significant reinforcements, in terms of both measurement infrastructure and control functionalities, to deal with the changes in a t. In this context, Distribution System State Estimation tools play a key role, sin e they allow the estimation of the operating conditions of the distribution grid, representing the essential link between the measurements gathered from the field and the control functions envisaged in future Distribution Management Systems. In this thesis, the focus has been on the development of appropriate procedures to accurately perform DSSE. Several goals have been pursued. First of all, a DSSE algorithm specifically on conceived for the distribution systems and tailored to the features of these networks has been designed. The proposed estimator allows the proper processing of all the types of measurement, in luding both conventional measurements and new generation synchrophasors provided by Phasor Measurement Units. Particular attention has been paid to the measurement model to be used within the DSSE algorithm, since its implementation an strongly a e t the a ura y a hiev- able in the estimation results. Moreover, a simple method to handle the equality constraints, well suited to the proposed estimator, has been presented to improve its computational efficency. The proposed estimator has been riti ally analyzed and compared to other approaches available in the literature, in order to highlight strengths and weaknesses of the on eived solution. In the second part of the thesis, the problem of DSSE has been analyzed from a wider perspective, aiming at highlighting the impact of different measurement as- pe ts on the estimation results. The impact of measurement type and placement on the estimation a ura y of the different electrical quantities has been deeply investigated, supporting the empiric cal results through a detailed mathematical analysis. Such study an provide important guidelines for the choice of the measurement infrastructure to be deployed in future distribution systems in order to a achieve spe i a ura y targets for the estimation of the different electrical quantities. The possibility to enhan e the estimation a ura y by properly considering the measurement correlations has also been investigated. Developed analysis shows that different sources of correlation an exist in the measurements used as input to the DSSE algorithm. Performed simulations prove that the in lusion of these orrelations in the DSSE model an lead to significant benefits on the estimation a ura y. Finally, a possible de entralized multi-area ar hite ture, designed to handle large distribution networks, has been proposed. Su h a solution has been on eived duly taking into a ount the opposite requirements of a ura y, computational e ien y and low communication costs desirable in realistic scenarios. Even in this case, particular attention has been fo used on the proper modeling of the measurements in order to a hieve estimation results as a urate as possible. To this purpose, a mathematical analysis has been developed to assess the correlations arising in the proposed multi-area approach. Test results on rm the validity of the developed analysis and, above all, prove the importance of a proper consideration of all the measurement aspects for enhacing the a ura y of the estimations. In conclusion, in this thesis, the problem of state estimation in future distribution system has been deeply analyzed, focusing in particular on the issues related to the measurement modeling and processing. The analysis and the results presented in this thesis shows how the achievement of a really smart management and control of future distribution grids (as expected in the Smart Grid scenario) is strictly dependent on the smart deployment, processing and management of the measurements in the network.

Thesis: M. Eng. in Logistics, Massachusetts Institute of Technology, Engineering Systems Division, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages [72]-[74]).
The handicraft sector in Morocco represents more than 9% of the nation's GDP and employs 2.3 million people. However, despite their talent and expertise, Morocco's artisans are struggling to reach markets other than local regional or national markets. The main distribution model used so far has been the classic retail distribution model, which does not add value to the artisans' work, with most downstream actors playing the role of the middlemen. Other Ecommerce models such as the marketplace model or the crowdfunding model did not solve all the issues faced by artisans and customers. This paper provides the framework for a new distribution channel for Moroccan artisans to improve the efficiency of the value chain linking them to the American consumer by eliminating all unnecessary steps, overhead, and overall inefficiencies of the current distribution models. We first identify the models that are currently used to bring the artisans' crafts to the end consumer in developed markets: the market place (used by the platform Etsy), the crowdfunding model and the classic retail distribution model involving middlemen. We assessed the benefits of all the models by developing a new framework allowing to score each one of them. We then switched our focus to a hybrid model: a crowdfunding platform where the company partners with the artisans to align the different stakeholders' interests. To the extent of our knowledge, this model has not been used yet. It was found that our methodology could help artisans access international markets more efficiently. We finished by determining the optimal strategy using social media to market this platform and engage more efficiently potential customers. Keywords: handicraft, supply chain, crowdfunding, retail, social network marketing.
by Zyad El Jebbari.
M. Eng. in Logistics

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2004.
Includes bibliographical references (p. 70-73).
This thesis' fundamental research question is to evaluate the structure of the hydrogen production, distribution, and dispensing infrastructure under various scenarios and to discover if any trends become apparent after sensitivity analysis. After reviewing the literature regarding the production, distribution, and dispensing of hydrogen fuel, a hybrid product pathway and network flow model is created and solved. In the literature review, an extensive analysis is performed of the forthcoming findings of the National Academy of Engineering Board on Energy and Environmental Systems (BEES). Additional considerations from operations research literature and general supply chain theory are applied to the problem under consideration. The second section develops a general model for understanding hydrogen production, distribution, and dispensing systems based on the findings of the BEES committee. The second chapter also frames the analysis that the thesis will review using the model. In the problem formulation chapter, the details of the analytic model at examined at length and heuristics solution methods are proposed. Three heuristic methodologies are described and implemented. An in-depth discussion of the final model solution method is described. In the fourth chapter, the model uses the state of California as a test case for hydrogen consumption in order to generate preliminary results for the model The results of the MIP solutions for certain market penetration scenarios and the heuristic solutions for each scenario are shown and sensitivity analysis is performed. The final chapter summarizes the results of the model, compares the performance of heuristics, and indicates further areas for research, both in terms of developing strong lower bounds
(cont.) for the heuristics, better optimization techniques, and expanded models for consideration.
by Jon R. Pulido.
M.Eng.in Logistics

In each hospital, the priority to ensure a patient's live is high. Therefore, a health department strives to build best medical facilities and hire superior staff to meet patient's needs. The Saudi Ministry of Health has the highest budget's portion among other ministries, yet, there are many projects that need to be implemented as soon as possible in order to save the most lives. Blood availability is considered to be one of the top needs at each hospital; however, blood banks in Saudi Arabia collect only 40% of the blood while 60% is collected by patients' families. To increase the blood availability, this paper presents a holistic project to support the trend toward 100% voluntary blood donations. By applying System Engineering discipline, the project aims to ensure communication and distribution between blood banks in the city of Riyadh and also connects thirty-four hospitals of different sectors, them being public, private, and military. Since blood availability is a national duty, the Ministry of Health will be responsible for launching and operating the project. So, blood banks will work together under the umbrella of the General Department of Laboratories and Blood Banks to achieve the system's objective.

Doctor of Philosophy
Department of Computing and Information Sciences
Scott A. DeLoach
Coalition formation is a key cooperative behavior of a system of multiple autonomous agents. When the capabilities of individual agents are not su fficient for the improvement of well-being of the individual agents or of the entire system, the agents can bene t by joining forces together in coalitions. Coalition formation is a technique for finding coalitions that are best fi tted to achieve individual or group goals. This is a computationally expensive task because often all combinations of agents have to be considered in order to find the best assignments of agents to coalitions. Previous research has therefore focused mainly on small-scale or otherwise restricted systems. In this thesis we study coalition formation in large-scale multi-agent systems. We propose an approach for coalition formation based on multi-agent simulation. This approach allows us to find coalitions in systems with thousands of agents. It also lets us modify behaviors of individual agents in order to better match a specific coalition formation application. Finally, our approach can consider both social welfare of the multi-agent system and well-being of individual self-interested agents. Power distribution systems are used to deliver electric energy from the transmission system to households. Because of the increased availability of distributed generation using renewable resources, push towards higher use of renewable energy, and increasing use of electric vehicles, the power distribution systems are undergoing signi ficant changes towards active consumers who participate in both supply and demand sides of the electricity market and the underlying power grid. In this thesis we address the ongoing change in power distribution systems by studying how the use of renewable energy can be increased with the help of coalition formation. We propose an approach that lets renewable generators, which face uncertainty in generation prediction, to form coalitions with energy stores, which on the other hand are always able to deliver the committed power. These coalitions help decrease the uncertainty of the power generation of renewable generators, consequently allowing the generators to increase their use of renewable energy while at the same time increasing their pro fits. Energy stores also bene t from participating in coalitions with renewable generators, because they receive payments from the generators for the availability of their power at speci fic time slots. We first study this problem assuming no physical constraints of the underlying power grid. Then we analyze how coalition formation of renewable generators and energy stores in a power grid with physical constraints impacts the state of the grid, and we propose agent behavior that leads to increase in use of renewable energy as well as maintains stability of the grid.

Majority of electricity networks have growing number of ageing elements. Critical network components, such as ageing underground cables, are very expensive to install and disruptive to replace. On the other hand, global climate changes have made connection of new low carbon technologies (LCT) into the grids increasingly necessary. These factors are contributing to the increasing complexity of the planning and management of power systems. Numerous techniques published on this subject tend to ignore the impact of LCT integration and the anchoring ꞌSmartꞌ solutions on ageing network assets, such as underground cables and transformers. This thesis presents the development procedures of an ageing underground cable reliability model (IEC-Arrhenius-Weibull model) and cable ranking models for replacement based on system wide effects and thermal loss-of-life metrics. In addition, a new concept of LCT integration and distribution network management was proposed using two optimization models. The first optimizes connection of new wind sources by minimizing the connection cost and the cost of cable thermal loss-of-lives in the planning period. In the second stage, the network is optimally reconfigured in such a way to minimize thermal-loss-of-life of ageing cable. Both optimization models are formulated as mixed integer non-linear programming (MINLP) problems applicable to radially operated medium voltage networks. To quantify the reliability benefits of the proposed approach, Sequential Monte Carlo Simulation (SMCS) procedure was formulated. Some of the main features of the SMCS procedure are the IEC-Arrhenius-Weibull model for ageing cable, optimal network reconfiguration, wind generation modelling using ARMA models and real time thermal ratings. The final outputs are reliability metrics, cable ranking lists for replacement, savings due to 'non-spend' cable thermal lives, etc. These studies have proven to be important in formulating an effective strategy for extending the lives of network cables, managing overall network reliability and planning cables replacement in power distribution networks.

The purpose of this research has been to develop an agent based protection and reconfiguration scheme for power electronic building block based (PEBB) DC distribution systems. One of the foremost applications would be in the new zonal DC distribution on naval ships. The research involves the design of an agent based protection scheme which uses the PEBBs for current limiting and circuit breaking purposes. Considerations are given to reduce the system downtime under fault conditions, allow proper coordination and provide backup protection. The research also involves the design of a reconfiguration management scheme based on collaborative agents. The collaboration ensures that the reconfiguration is achieved at a global level, enhancing the system survivability under the conditions of multiple faults and damages. The coordination ensures that only the faulted part of the system is isolated and the reconfiguration makes sure that the power to the healthy part of the system is supplied continuously. The reconfiguration management also performs load shedding if the generation does not meet the load demand of the reconfigured system due to a fault or damage in the generator.

The corporate internal information distribution system is designed using the systems engineering model. This system enhances the internal distribution of documents within Lockheed Martin. This distribution system is much timelier and more cost effective than the current means of distribution. Although unable to totally replace the current distribution systems, this system does save Lockheed Martin a considerable amount of money in distribution costs as a complementary system. The definition of need sets the stage for the design of this system. Advanced system planning provides operational requirements and a conceptual design. Function analysis helps to identify system components and facilitates requirements allocation. The detail design specifies the individual components, which make up the total system, and sets forth an implementation plan as well as a plan for test and evaluation of the integrated system.
Master of Science

The increasing integration of renewable energy installations at the distribution grid level has led to a strong increase in grid reinforcement measures in recent years. Since the costs are being passed on to the general public via the grid user charges, it is necessary to investigate and evaluate alternatives. As part of the project, that is investigated in this thesis, a large-scale vanadium redox flow battery storage system was integrated into the power grid of a German distribution grid operator for the first time. The battery system is a prototype and its inverter and battery have been developed specifically for the analysed project. The main objective of the project was to quantify the extent to which grid expansion measures can be avoided by the use of batteries and to what extent the balancing act between an economic and grid supportive operation is possible. Finally, the battery application was compared technically and economically with other flexibility options for a pilot region. A preliminary analysis of possible business cases for large battery systems shows that the application of batteries in the primary control power market is by far the most lucrative application in the current German framework. It is followed by an application for cost reduction where self-consumption of PV power is favoured over grid power. Both business cases are analysed in further detail. The thesis is mainly focused on the grid supportive primary control application. The grid supportive behaviour of the analysed battery has been ensured by regulating the voltage in the low voltage grid via a reactive power control and thus increasing the grid capacity. The developed battery system was tested in the field during a one-year field test. The battery prototype and the grid of the pilot region was modelled based on measurement data. Furthermore, a method to derive an optimal operating strategy for electricity storage was developed and implemented. The strategy was developed with the aim to identify a self-sufficient operation mode, which ensured the highest possible profit and validated in a field test. Albeit being the most lucrative battery application in Germany today, economic calculations have shown that the average cost of vanadium redox batteries would have to fall by about 60% to achieve profitable operation. Nonetheless, since this is a new technology, both the expectations and potential for cost reduction are high. The second most promising application, the maximization of self-consumption, is also analysed through the means of a simulation for the pilot region, but without a implementation in the field. For this purpose, a battery model for a vanadium redox flow battery based on measurement data is applied. To ensure grid supportive behaviour, an autonomous reactive power control based on a Q(V)-characteristic and peak shaving is implemented. The technical and economic assessment of this operation strategy is compared with a lithium-ion battery providing the same service. It is shown that this business case could already be profitable, with a more favorable legal framework in place. However, at present the investment costs of the vanadium redox flow battery has to fall by at least 77% to break even for this operation strategy. Nonetheless, it could be demonstrated that it has almost no negative economic impacts if the battery storage system is operated in a grid supportive way in addition to its primary purpose. Finally, a technical and economic assessment of the impact of the two large scale battery applications on distribution grid planning is conducted. Additional flexibility options such as a cos'φ(P) and Q(V)-control of PV systems and the use of residential storages are considered as well. For this purpose, a future PV expansion pathway was developed for the pilot region, as well as an automatic (traditional) grid expansion without flexibility option as a reference scenario. The PV expansion pathway is based on the identification of suitable roof areas for PV systems using aerial photographs. It has been shown that the hosting capacity for renewable energy installations increases in all cases compared to the scenario without flexibility options, sometimes by up to 45 %. In addition, it was found that from the perspective of grid operators it is more profitable to apply the presented flexibility option instead of a traditional grid expansion
El objetivo principal de la tesis es cuantificar hasta qué punto las medidas de expansión de la red pueden evitarse mediante el uso de baterías y en qué medida es posible el equilibrio entre una operación económica y la de apoyo a la red. Como parte del proyecto, que se investiga en esta tesis, un sistema prototipo de batería de vanadio redox flow a gran escala se integró por primera vez en la red eléctrica de un operador del sistema de distribución en Alemania. Un análisis preliminar de posibles modelos de negocio para grandes sistemas de baterías muestra que la aplicación de baterías en el mercado de energía de control primario es, con mucho, la aplicación más lucrativa en el marco alemán actual. Le sigue el uso de autoconsumo de energía fotovoltaica para reducir costes. Ambos casos comerciales se analizan en detalle. La tesis se centra en la aplicación de control primario de apoyo a la red. El apoyo de la red por parte de la batería se asegura a través de la regulación de la tensión en la red de baja tensión a través de un control de potencia reactiva. El sistema de batería desarrollado fue probado en la región piloto durante un periodo de un año. Ese prototipo y la red de la región piloto se modelaron en base a los datos medidos ese periodo. Además, se desarrolló e implementó un método para derivar una estrategia operativa óptima para el almacenamiento de electricidad. Esa estrategia tiene el objetivo de identificar un modo de operación autosuficiente que garantice el mayor beneficio posible y fue validada en una prueba en la región piloto. A pesar de ser la aplicación de baterías más lucrativa en Alemania hoy en día, los cálculos económicos han demostrado que el costo promedio de las baterías vanadio redox flow tendría que disminuir aproximadamente un 60% para lograr una operación rentable. No obstante, dado que esta es una nueva tecnología, tanto las expectativas como el potencial de reducción de costos son altos. La segunda aplicación más prometedora, la maximización del autoconsumo, también se analiza a través de una simulación para la región piloto, pero sin una implementación en el campo. Para este propósito, se aplica un modelo de batería vanadio redox flow basada en datos medidos del prototipo. Para garantizar el comportamiento de soporte de la red, se implementa un control de potencia reactiva autónomo basado en una característica Q (V) y una amortiguación de la generación máxima. La evaluación técnica y económica de esta estrategia de operación fue comparada con una batería de iones de litio que proporciona el mismo servicio. Fue demostrado que este caso comercial ya podría ser rentable, con un marco legal más favorable. Sin embargo, en la actualidad los costos de i baterías vanadio redox flow tienen que caer al menos en un 77% para obtener beneficios económicos. Sin embargo, se podía demostrar que los impactos económicos negativos son mínimos si la batería se opera en una forma de soporte de red además de su propósito principal. Finalmente, se llevó a cabo una evaluación técnica y económica del impacto de las dos aplicaciones de la batería a gran escala en la planificación de la red de distribución. Otras opciones de flexibilidad, como el control cos’φ (P) y Q (V) de los sistemas FV y el uso de baterías residenciales también fueron consideradas. Para este propósito, un escenario de expansión fotovoltaica para la región piloto fue desarrollado basado en la identificación de áreas de techo adecuadas para sistemas fotovoltaicos utilizando fotografías aéreas. Para cuantificar los costes para la expansión de la red eléctrica una metodología fue desarrollada para expandir la red de una forma automática y sistemática basado en directrices de planificación creados por los operadores del sistema de distribución en Alemania. Se demostró que desde la perspectiva de los operadores de red es más rentable aplicar la opción de flexibilidad presentada en lugar de una expansión de red tradicional.

The main topic of this licentiate thesis is fast faultdetection. The thesis summaries the work performed in theproject“Fast fault detection for distributionsystems”.

In the first chapters of the thesis the term“fast”is used in a general manner. The term is laterdefined based upon considerations and conclusions made in thefirst chapters and then related to a specific time.

To be able to understand and appreciate why fast faultdetection is necessary, power system faults and theirconsequences are briefly discussed. The consequences of a faultare dependent of a number of different factors, one of thefactors being the duration of the fault.

The importance of the speed of the fault detection dependson the type of equipment used to clear the fault. A circuitbreaker which interrupt currents only when they pass through anatural zero crossing might be less dependent on the speed ofthe fault detection than a fault current limiter which limitsthe fault current before it has reached its first prospectivecurrent peak.

In order to be able to detect a fault in a power system, thepower system must be observed, i.e., measurements of relevantquantities must be performed so that the fault detectionequipment can obtain information of the state of the system.The fault detection equipment and some general methods of faultdetection are briefly described.

Some algorithms and their possible adaptation to fast faultdetection are described. A common principle of many algorithmsare that they assume that either a signal or the power systemobject can be described by a model. Sampled data values arethen fitted to the model so that an estimate of relevantparameters needed for fault detection is obtained. An algorithmwhich do not fit samples to a model but use instantaneouscurrent values for fault detection is also described andevaluated.

Since the exact state of a power system never is known dueto variations in power production and load, a model of thepower system or of the signal can never be perfect, i.e., theestimated parameter can never be truly correct. Furthermore,errors from the data acquisition system contribute to the totalerror of the estimated parameter.

Two case studies are used to study the performance of the(modified) algorithms. For those studies it has been shown thatthe algorithms can detect a fault within approximately 1msafter fault inception and that one of the algorithms candiscriminate between a fault and two types of common powersystem transients (capacitor and transformer energization).

The second case study introduced a system with two sourceswhich required a directional algorithm to discriminate betweenfaults inside or outside the protection zone.

It is concluded that under certain assumptions it ispossible to detect power system faults within approximately 1msand that it is possible to discriminate a power system faultfrom power system transient that regularly occurs within powersystems but which not are faults.

To date, closed form optimal solutions for stocking levels in arborescent multiechelon inventory systems have not been obtained. These problems exhibit the joint difficulties of requiring an allocation policy as well as a stocking policy, and the multidimensional nature of their state space makes dynamic programming formulations impractical. In this dissertation, we introduce procedures that approximate multiechelon networks with sets of single installation problems. We first use this technique to solve for base-stock levels in a distribution network with asymmetric retailers. Second, we use this technique to analyze delayed differentiation production processes and provide guidance as to when the strategy is most warranted. Third, we modify the technique to account for inventory that exhibits perishability and solve for stocking policies for distribution systems when the inventory has a fixed shelf life.

Maintaining water quality in distribution systems has become a prominent issue in the study of water networks. This thesis concentrates on disinfectant and particle counts as two important indicators of water quality. The models discussed in this work are based on data collected by the author. The experimental set-up and procedure are described and observations of particle counts, particle counter size distributions, monochloramine as disinfectant, temperature, heterotrophic plate counts and epifluorescence microscopy counts are reported. A model of the response of particle counts to an increase in flow is developed. This model is obtained from specification derived from the data and assumptions, and is validated by its interpretability and its fit to data. A local shear-off density and an initial biofilm shedding profile were introduced and thus a linear model for this part of the water quality dynamics could be obtained. A procedure for the identification of the parameters of the local shear-off function and for the determination of the biofilm shedding profile is presented. This profile can be used to provide information about the status of the distribution system in terms of shear-off from the biofilm on the pipe walls. Monochloramine decay dynamics are investigated. The chlorine meter data is preprocessed with the help of titration data to correct meter drift. The data is then used in calibrating two different possible chlorine models: a model with a single decay coefficient and a model with bulk decay coefficient and wall demand (as used in Epanet). Important difficulties in identifying these parameters that come about because of the structure of the models are highlighted. Identified decay coefficients are compared and tested for flow, inlet chlorine and temperature dependence. The merits and limits of the approach to modelling taken in this work and a possible generalisation are discussed. The water industry perspective and an outlook are provided.

Newer technologies like Electric Vehicles (EVs) and Distributed Generation (DG) are being viewed as potential harmonic distortion threats for the distribution systems which are already facing increased harmonic stress due to the increased use of the non-linear home appliances in the recent years. Therefore, it is necessary to evaluate and analyze the harmonic distortion due to the various non-linear home appliances, EV battery chargers and DG inverters to give a clear picture of the future scenario. So that future technologies can be accommodated in the distribution systems while the existing harmonic distortion threats are dealt with. This research work investigates the harmonic spectrums of various non-linear residential loads, battery chargers and DG inverters which are then deployed to perform various simulations of the distribution systems, using Electrical Transient Analyzer Program (ET AP), considering several different scenarios. A high penetration level of non-linear residential loads is considered to simulate the current scenario. The results show high level of harmonic distortion at the Point of Common Coupling (PCC). The investigation is then extended to simulate the future scenarios by considering advent of the EV s and DG. The results indicate a significant increase in the Total Harmonic Distortion in the Voltage (THDv) in the presence of EVs and DG, at the PCC. Currently, Demand Side Management (DSM) strategies are primarily being designed based upon the daily load profile only. This research work gives a different perspective for the DSM based upon "Daily Harmonic Profile" developed by combining the experimental and simulation results. The results indicate that throughout the day, the THDv has a value of more than 1.5 % with per hour average THDv being equal to 3.25 %. The-situation worsens if the increased winter loading is considered to investigate the daily harmonic profile. This research work also explores the potential impacts of the developed profile on the DSM schemes to control the harmonic distortion in the future distribution systems.

The new framework of random polynomials developed by R. Pemantle, I. Rivin and the late O. Schramm has been studied in this thesis. The strong Pemantle-Rivin conjecture asks whether for random polynomials with independent and identically distributed zeros with a common probability distribution μon the complex plane, the empirical measures of their critical points would converge weakly to μ almost surely. This convergence question has connection with geometry of polynomials. S. D. Subramanian confirmed the conjecture whenμis a non-uniform distribution supported in the unit circle ∂D. In this thesis, the conjecture has been extended to considering not only the critical points of the random polynomials, but also the zeros of their higher order, polar and Sz.-Nagy's generalized derivatives. The case thatμ(uniform or not) is supported in ∂D has been studied, where the derivative of each order has been proved to satisfy the conjecture. Subramanian's work has thereby been completed plus generalization. The same almost sure weak convergence has also been shown for polar and Sz.-Nagy's generalized derivatives, under some mild conditions. In particular, the result on polar derivative is the crux of filling up Subramanian's missing case of uniform μ. Meanwhile, the original Pemantle{Rivin conjecture asks about convergence in probability instead of the aforesaid stronger almost sure convergence. Z. Kabluchko fully solved this conjecture. In this thesis, his methodologies have been adapted to prove the analogous conjecture for random finite Blaschke products. More precisely, for random finite Blaschke products with independent and identically distributed zeros with a common probability distributionμon the unit disc, the empirical measures of their critical points have been shown to converge weakly toμin probability. Consequently, this work contributes the very first probabilistic result to T. W. Ng and C. Y. Tsang's polynomial-finite-Blaschke-product dictionary. While the above works address probabilistic problems about zero distribution of polynomials and finite Blaschke products (regarded as non-euclidean polynomials by J. L. Walsh), the other part of this thesis is an application of the BKK theory in deterministic polynomial systems. The numbers of various configurations for vortex dynamics in an ideal plane fluid without background flow had been investigated by many researchers for decades. In this thesis, fixed equilibria have been studied in the presence of a steady, incompressible and irrotational background flow. A more physically significant definition of a fixed equilibrium configuration has been suggested. Under this new definition, an attainable generic upper bound for their number has been found (in terms of the degree of the non-constant polynomial that determines the background flow and of the sizes of vortex species). Our result is established by transforming the rational function system arisen from fixed equilibria into a polynomial system, whose form is good enough to apply the aforesaid BKK theory (named after D. N. Bernshtein, A. G. Khovanskii and A. G. Kushnirenko) to show the finiteness of its number of solutions. Having this finiteness, the required bound follows from Bézout's theorem.
published_or_final_version
Mathematics
Doctoral
Doctor of Philosophy