This dissertation studies the model reduction and distributed control problems for interconnected systems, i.e., systems that consist of multiple interacting agents/subsystems. The study of the analysis and synthesis problems for interconnected systems is motivated by the multiple applications that can benefit from the design and implementation of distributed controllers. These applications include automated highway systems and formation flight of unmanned aircraft systems. The systems of interest are modeled using arbitrary directed graphs, where the subsystems correspond to the nodes, and the interconnections between the subsystems are described using the directed edges. In addition to the states of the subsystems, the adopted frameworks also model the interconnections between the subsystems as spatial states. Each agent/subsystem is assumed to have its own actuating and sensing capabilities. These capabilities are leveraged in order to design a controller subsystem for each plant subsystem. In the distributed control paradigm, the controller subsystems interact over the same interconnection structure as the plant subsystems. The models assumed for the subsystems are linear time-varying or linear parameter-varying. Linear time-varying models are useful for describing nonlinear equations that are linearized about prespecified trajectories, and linear parameter-varying models allow for capturing the nonlinearities of the agents, while still being amenable to control using linear techniques. It is clear from the above description that the size of the model for an interconnected system increases with the number of subsystems and the complexity of the interconnection structure. This motivates the development of model reduction techniques to rigorously reduce the size of the given model. In particular, this dissertation presents structure-preserving techniques for model reduction, i.e., techniques that guarantee that the interpretation of each state is retained in the reduced order system. Namely, the sought reduced order system is an interconnected system formed by reduced order subsystems that are interconnected over the same interconnection structure as that of the full order system. Model reduction is important for reducing the computational complexity of the system analysis and control synthesis problems. In this dissertation, interior point methods are extensively used for solving the semidefinite programming problems that arise in analysis and synthesis. / Ph. D. / The work in this dissertation is motivated by the numerous applications in which multiple agents interact and cooperate to perform a coordinated task. Examples of such applications include automated highway systems and formation flight of unmanned aircraft systems. For instance, one can think of the hazardous conditions created by a fire in a building and the benefits of using multiple interacting multirotors to deal with this emergency situation and reduce the risks on humans. This dissertation develops mathematical tools for studying and dealing with these complex systems. Namely, it is shown how controllers can be designed to ensure that such systems perform in the desired way, and how the models that describe the systems of interest can be systematically simplified to facilitate performing the tasks of mathematical analysis and control design.

Numerous power electronics building blocks (PEBB) based power conversion systems have been developed to explore modular design, scalable voltage and current ratings, low-cost operations, etc. This paper further extends the modular concept from the power stage to the control system. The communication network in SiC-based modular power converters is becoming significant for distributed control architecture, with the requirements of tight synchronization and low latency. The influence of the synchronization accuracy on harmonics under the phase-shifted carrier pulse width modulation (PSC-PWM) is evaluated. When the synchronization is accurate, the influence of an increase in harmonics can be ignored. Thus, a synchronous distributed control and communication protocol with well-performed synchronization of 25 ns accuracy is proposed and verified for a 120 kHz SiC-based impedance measurement unit (IMU) with cascaded H-bridge PEBBs. An improved synchronization method with additional analog circuits is further implemented and verified with sub-ns synchronization accuracy. / The power electronics building block (PEBB) concept is proposed for medium-voltage converter applications in order to realize the modular design of the power stage. Traditionally, the central control architecture is popular in converter systems. The voltage and current are sensed and then processed in one central controller. The control hardware interfaces and software have to be customized for a specified number of power cells, and the scalability of controller is lost. In stead, in the distributed control architecture, a local controller in each PEBB can communicate with the sensors, gate drivers, etc. A high-level controller collects the information from each PEBB and conducts the control algorithm. In this way, the design can be more modular, and the local controller can share the computation burden with the high-level controller, which is good for scalability. In such distributed control architecture, a synchronous communication system is required to transmit data and command between the high-level controller and local controllers. A power converter always requires a highly synchronized operation to turn on or turn off the devices. In this work, a synchronous communication protocol is proposed and experimentally validated on a SiC-based modular power converter.

In this thesis, we develop scalable frameworks to (re)design a class of large-scale network systems with built-in control mechanisms, including electric power systems and the Internet, in order to improve their economic efficiency and performance while guaranteeing their stability and robustness. After a detailed introduction relating to power system control and optimization, as well as network congestion control, we turn our attention to merging primary and secondary frequency control for the power grid. We present modifications in the conventional generation control using a consensus design approach while considering the participation of controllable loads. The optimality, stability and delay robustness of the redesigned system are studied. Moreover, we extend the proposed control scheme to (i) networks with more complexity and (ii) the case where controllable loads are involved in the optimization. As a result, our controllers can balance power flow and drive the system to an economically optimal operating point in the steady state. We then study a real-time control framework that merges primary, secondary and tertiary frequency control in power systems. In particular, we consider a transmission level network with tree topology. A distributed dynamic feedback controller is designed via a primal-dual decomposition approach and the stability of the overall system is studied. In addition, we introduce extra dynamics to improve system performance and emphasize the trade-off when choosing the gains of the extra dynamics. As a result, the proposed controller can balance supply and demand in the presence of disturbances, and achieve optimal power flow in the steady state. Furthermore, after introducing the extra dynamics, the transient performance of the system significantly improves. A redesign framework for network congestion control is developed next. Motivated by the augmented Lagrangian method, we introduce extra terms to the Lagrangian, which is used to redesign the primal-dual, primal and dual algorithms. We investigate how the gains resulting from the extra dynamics influence the stability and robustness of the system. Moreover, we show that the overall system can achieve added robustness to communication delays by appropriately tuning these gains. Also, the meaning of these extra dynamics is investigated and a distributed proportional-integral-derivative controller for solving network congestion control problems is further developed. Finally, we concentrate on a reverse- and forward-engineering framework for distributed control of a class of linear network systems to achieve optimal steady-state performance. As a typical illustration, we use the proposed framework to solve the real-time economic dispatch problem in the power grid. On the other hand, we provide a general procedure to modify control schemes for a special class of dynamic systems. In order to investigate how general the reverse- and forward-engineering framework is, we develop necessary and sufficient conditions under which an linear time-invariant system can be reverse-engineered as a gradient algorithm to solve an optimization problem. These conditions are characterized using properties of system matrices and relevant linear matrix inequalities. We conclude this thesis with an account for future research.

Recent issues such as priority access of renewable resources recommended by European energy directives and increase the electricity trading among countries lead to new requirements on the operation and expansion of transmission grids. Since AC grid expansions are limited by legislative issues and long distance transmission capacity, there is a considerable attention drawn to application of HVDC transmission grids on top of, or in complement to, existing AC power systems. The secure operation of HVDC grids requires a hierarchical control system. In HVDC grids, the primary control action to deal with power or DC voltage deviations is communication-free and local. In addition to primary control, the higher supervisory control actions are needed to guarantee the optimal operation of HVDC grids. However, the implementation of supervisory control functions is linked to the arrangement of system operators; i.e. an individual HVDC operator (central structure) or sharing tasks among AC system operators (distributed structure). This thesis presents distributed control of an HVDC grid. To this end, three possible supervisory functions are investigated; coordination of power injection set-points, DC slack bus selection and network topology identification. In this thesis, all three functions are first studied for the central structure. For the distributed solution, two algorithms based on Alternating Direction Method of Multipliers (ADMM) and Auxiliary Problem Principle (APP) are adopted to solve the coordination of power injection. For distributed selection of DC slack bus, the choice of parameters for quantitative ranking of converters is important. These parameters should be calculated based on local measurements if distributed decision is desired. To this end, the short circuit capacity of connected AC grid and power margin of converters are considered. To estimate the short circuit capacity as one of the required selection parameters, the result shows that the recursive least square algorithm can be very efficiently used. Besides, it is possible to intelligently use a naturally occurring droop response in HVDC grids as a local measurement for this estimation algorithm. Regarding the network topology, a two-stage distributed algorithm is introduced to use the abstract information about the neighbouring substation topology to determine the grid connectivity. / <p>QC 20170306</p>

O rápido avanço tecnológico nestes últimos anos, principalmente dos recursos computacionais e de comunicação, permite que os sistemas produtivos (SP) evoluam tanto no seu aspecto estrutural quanto no comportamental para que atendam às necessidades crescentes do mercado. Os elementos integrantes dos SP vêm incorporando estes avanços, atingindo maior autonomia e flexibilidade p ara cumprir suas funcionalidades. Além disso, a tendência dos dispositivos de controle de incorporar a capacidade de atuação em ambientes distribuídos onde a interação ocorre através de redes de comunicação, verificada na evolução das normas aplicadas a sistemas de controle, reflete a necessidade de aderência dos sistemas de controle a essa realidade. A necessidade de se manter competitivo no mercado impõe aos atuais SP situações em que emergem novos desafios para realização do controle dos seus processos globais, uma vez que estes assumem múltiplos objetivos, envolvendo diferentes naturezas de indeterminismo, assincronismo e variância no tempo, provocando um nível de complexidade inédito no que se refere ao controle destes sistemas. Este trabalho propõe inicialmente uma nova abstração para modelar-se os SP baseada no conceito de decomposição multidimensional e em múltiplas faces, distribuindo o controle através dos componentes colaborativos. Feito isto, são propostos procedimentos e técnicas para modelagem de sistemas de controle distribuídos e colaborativos (SCDC) de SP. Considera-se para isso, primeiro, uma arquitetura lógica de controle que contemple os múltiplos domínios semânticos presentes em SP, que são provenientes das especificidades dos elementos integrantes. Segundo, a multiplicidade de habilidades necessárias para garantir a execução das estratégias de controle pertinentes a cada domínio. Terceiro, o fluxo de informações heterogêneas provenientes das interações colaborativas entre os domínios. / Recent technological advances, mainly of computer and communication systems, allow the production systems (SP) to evolve in structural aspect as well as in behavioral aspect. The SP resources have achieved enhanced autonomy and flexibility with embedded computer and communication capability. Latest trends of control devices, as seen in the evolution of standards related to control systems, focus on the use of these devices in a distributed environment, where interaction occur through a communication network Thus, the SP control system and its design methods have to fit to this reality. In a competitive scenario, the SP are challenged to keep control of the global processes, considering the multiple goals of these processes and the involvement of different aspect of indeterminism, lack of synchronisms and time variance, generating a inedited complexity level for control of this systems. This work proposes a new abstraction for modeling the control systems of SP, based on the concept of multidimensional decompositions. Based on this, it introduces the procedures and techniques for modeling the distributed and collaborative control systems (SCDC) of the production systems. First, it considers the logic architecture of the control that support many semantic domains presented in this type of SP. Then, the diversity of skills related to each domain necessary to accomplish the control strategies. And then, the heterogeneous information flow through the domains boundaries, derived from the collaborative interaction between the control components.

Muitos são os motivos para a realização de pesquisas que envolvam o setor de saneamento básico no Brasil, entre estes motivos estão algumas características muito peculiares relacionadas a este setor, características que vão desde a sua concepção e a sua forma de organização até sua susceptibilidade à externalidades como influências naturais, políticas e sociais. Este trabalho oferece uma visão prática sobre a aplicação de tecnologias de automação em sistemas de saneamento e tem como objetivo expor um conjunto de soluções voltadas à automação de sistemas de abastecimento hídrico. Os sistemas automatizados caracterizam-se principalmente pela necessidade de aquisição e envio de informações de um ou mais centros de controle operacionais a estações remotas situadas nas mais diversas localizações como: centros densamente urbanizados, áreas não urbanas, locais de acesso restrito, áreas costeiras, áreas portuárias, localidades subterrâneas e localidades de topografia elevada. Esta diversidade de características demanda um conjunto de soluções de automação, supervisão e gerenciamento de informações para o controle e a gestão do sistema de abastecimento de forma integrada e eficiente. Neste trabalho são descritas algumas destas soluções, aqui denominadas referenciais de análise, com o objetivo de delinear um modelo de automação para sistemas de abastecimento hídrico que possa oferecer subsídios para o desenvolvimento destes sistemas em regiões que ainda não os possuam plenamente automatizados. / Many are the reasons to carry out researches whom involves the sector of basic sanitation in Brazil, among these reasons are some very peculiar characteristics related to this section, characteristics that goes from its conception and organization to its susceptibility to the to external factors as natural, politics and social influences. This work offers a practical vision about the application of automation technologies in systems of sanitation and has as objective to expose a group of solutions oriented to the automation of hydric supply systems. That automated systems are characterized mainly by the necessity of acquisition and information sending of one or more operational control centers to remote stations located in the most several locations as: densely urbanized centers, non urban areas, restricted access places, coastal areas, port areas, underground places and high topography places. This diversity of characteristics demands a group of automation, supervision and administration of information solutions to the control and the administration of the supply system in an integrated and efficient way. In this work some of these solutions are described, here denominated analysis referentials, with the objective of delineating an automation model for hydric supply systems that could offer subsidies for the development of these systems in areas that still don\'t possess them fully automated.

Sistemas de controle distribuídos cujas malhas são fechadas através de uma rede de comunicação são chamados de sistemas de controle distribuídos em redes de comunicação (NCS - Networked Control System). Este tipo de arquitetura permite a divisão do sistema de controle em módulos interconectados através da rede de comunicação, proporcionando a divisão do processamento, a redução de custo e de peso, além de facilitar o diagnóstico e manutenção do sistema e de aumentar a sua exibilidade e agilidade; e por isso seu emprego na indústria está se tornando comum (e.g., y-by-wire e drive-by-wire). Porém, a distribuição do processamento e a inserção de uma rede de comunicação aumenta a complexidade da análise e do projeto deste tipo de sistema. Um dos fatores que contribui para esse aumento da complexidade é a presença de atrasos aleatórios nos sinais de controle, causados pela dinâmica do sistema computacional (conjunto de hardware e software) que serve como plataforma para implementação do sistema de controle digital. Este trabalho faz um estudo sobre este tipo de sistema sob a perspectiva destes sinais com atrasos. Para isso, faz-se uso dos toolboxes para MATLAB: TrueTime e Jitterbug. Através destas ferramentas, mostra-se a existência de uma relação de compromisso entre o desempenho do controle e o desempenho do sistema computacional. Através deste estudo, é proposto uma solução de um sistema de controle do tipo NCS para um ROV (do inglês Remotely Operated Vehicle), modelado através de 6 equações diferenciais desacopladas não-lineares. Este tipo de veículo tem uma relevância econômica significativa para o Brasil, visto que é utilizado em operações de manutenção e instalação de plataformas de extração do petróleo que está depositado em profundidades que variam de mil a 2 mil metros. Para este NCS proposto, são utilizados controladores do tipo PI com estrutura feedback-feedfoward cujos parâmetros de projeto são obtidos em função dos atrasos inseridos pelo sistema computacional. / Distributed control systems wherein the control loops are closed through a communication network are called Networked Control Systems (NCSs). This type of architecture allows the control systems division into modules interconnected through the communication network, providing the processing division, reduction of cost and weight, and facilitates the systems diagnosis and maintenance, and increases their exibility and agility. Therefore its use in industry is becoming common (eg, y-by-wire and drive-by-wire). However, the processing distribution and the communication network insertion increase the system analysis and design complexity. One of the factors that contributes to this increased complexity is the presence of random time delays, caused by the dynamics of the computer system (set of hardware and software) used as a platform for digital control system implementation. This work deals with the networked control systems under these random time delays view. For this, it is used two MATLAB toolboxes: Jitterbug and TrueTime. With these tools, it is shown the existence of a relationship between the performance of control and performance of computer system. With this study, it proposed a solution of a NCS for a ROV (Vehicle Operated Remotely), modeled by 6 differential nonlinear decoupled equations. This type of vehicle has a significant economic relevance for Brazil, as it is used in maintenance and installation of platforms for oil extraction deposited at depths ranging from thousand to 2 thousand meters. For this proposed NCS are adopted PI controllers with feedfoward-feedback structure whose parameters design are given in terms of delay inserted by the computer system.

Frente a abrangente presença da internet no ambiente acadêmico e residencial, a literatura relata, na última década, um número crescente de experiências de ensino a distância na área de automação e controle industrial, nas quais desde procedimentos teóricos até aulas práticas podem ser realizados através de acesso remoto. Neste contexto, este trabalho apresenta o estado da arte sobre as experiências acadêmicas no emprego de laboratórios on-line relacionados à teoria de controle e introduz uma nova proposta de arquitetura de acesso remoto, que será aplicada ao ensino de sistemas de controle distribuídos via rede de campo no protocolo FOUNDATION Fieldbus em ambiente simulado. / Due to the increasing presence of the internet in the academic and residential environment, the literature shows an increasing number of experiences of distance learning in the automation and industrial control area in the last decade, in which theoretical procedures as well as practical lessons can be carried out through remote access. In this context, this dissertation presents a brief survey on the academic experiences in the application of on-line laboratories and introduces a new proposal of remote access architecture that will be applied on a distance learning experience in the networked control systems area based on the FOUNDATION Fieldbus protocol using a simulated environment.

O rápido avanço tecnológico nestes últimos anos, principalmente dos recursos computacionais e de comunicação, permite que os sistemas produtivos (SP) evoluam tanto no seu aspecto estrutural quanto no comportamental para que atendam às necessidades crescentes do mercado. Os elementos integrantes dos SP vêm incorporando estes avanços, atingindo maior autonomia e flexibilidade p ara cumprir suas funcionalidades. Além disso, a tendência dos dispositivos de controle de incorporar a capacidade de atuação em ambientes distribuídos onde a interação ocorre através de redes de comunicação, verificada na evolução das normas aplicadas a sistemas de controle, reflete a necessidade de aderência dos sistemas de controle a essa realidade. A necessidade de se manter competitivo no mercado impõe aos atuais SP situações em que emergem novos desafios para realização do controle dos seus processos globais, uma vez que estes assumem múltiplos objetivos, envolvendo diferentes naturezas de indeterminismo, assincronismo e variância no tempo, provocando um nível de complexidade inédito no que se refere ao controle destes sistemas. Este trabalho propõe inicialmente uma nova abstração para modelar-se os SP baseada no conceito de decomposição multidimensional e em múltiplas faces, distribuindo o controle através dos componentes colaborativos. Feito isto, são propostos procedimentos e técnicas para modelagem de sistemas de controle distribuídos e colaborativos (SCDC) de SP. Considera-se para isso, primeiro, uma arquitetura lógica de controle que contemple os múltiplos domínios semânticos presentes em SP, que são provenientes das especificidades dos elementos integrantes. Segundo, a multiplicidade de habilidades necessárias para garantir a execução das estratégias de controle pertinentes a cada domínio. Terceiro, o fluxo de informações heterogêneas provenientes das interações colaborativas entre os domínios. / Recent technological advances, mainly of computer and communication systems, allow the production systems (SP) to evolve in structural aspect as well as in behavioral aspect. The SP resources have achieved enhanced autonomy and flexibility with embedded computer and communication capability. Latest trends of control devices, as seen in the evolution of standards related to control systems, focus on the use of these devices in a distributed environment, where interaction occur through a communication network Thus, the SP control system and its design methods have to fit to this reality. In a competitive scenario, the SP are challenged to keep control of the global processes, considering the multiple goals of these processes and the involvement of different aspect of indeterminism, lack of synchronisms and time variance, generating a inedited complexity level for control of this systems. This work proposes a new abstraction for modeling the control systems of SP, based on the concept of multidimensional decompositions. Based on this, it introduces the procedures and techniques for modeling the distributed and collaborative control systems (SCDC) of the production systems. First, it considers the logic architecture of the control that support many semantic domains presented in this type of SP. Then, the diversity of skills related to each domain necessary to accomplish the control strategies. And then, the heterogeneous information flow through the domains boundaries, derived from the collaborative interaction between the control components.

Muitos são os motivos para a realização de pesquisas que envolvam o setor de saneamento básico no Brasil, entre estes motivos estão algumas características muito peculiares relacionadas a este setor, características que vão desde a sua concepção e a sua forma de organização até sua susceptibilidade à externalidades como influências naturais, políticas e sociais. Este trabalho oferece uma visão prática sobre a aplicação de tecnologias de automação em sistemas de saneamento e tem como objetivo expor um conjunto de soluções voltadas à automação de sistemas de abastecimento hídrico. Os sistemas automatizados caracterizam-se principalmente pela necessidade de aquisição e envio de informações de um ou mais centros de controle operacionais a estações remotas situadas nas mais diversas localizações como: centros densamente urbanizados, áreas não urbanas, locais de acesso restrito, áreas costeiras, áreas portuárias, localidades subterrâneas e localidades de topografia elevada. Esta diversidade de características demanda um conjunto de soluções de automação, supervisão e gerenciamento de informações para o controle e a gestão do sistema de abastecimento de forma integrada e eficiente. Neste trabalho são descritas algumas destas soluções, aqui denominadas referenciais de análise, com o objetivo de delinear um modelo de automação para sistemas de abastecimento hídrico que possa oferecer subsídios para o desenvolvimento destes sistemas em regiões que ainda não os possuam plenamente automatizados. / Many are the reasons to carry out researches whom involves the sector of basic sanitation in Brazil, among these reasons are some very peculiar characteristics related to this section, characteristics that goes from its conception and organization to its susceptibility to the to external factors as natural, politics and social influences. This work offers a practical vision about the application of automation technologies in systems of sanitation and has as objective to expose a group of solutions oriented to the automation of hydric supply systems. That automated systems are characterized mainly by the necessity of acquisition and information sending of one or more operational control centers to remote stations located in the most several locations as: densely urbanized centers, non urban areas, restricted access places, coastal areas, port areas, underground places and high topography places. This diversity of characteristics demands a group of automation, supervision and administration of information solutions to the control and the administration of the supply system in an integrated and efficient way. In this work some of these solutions are described, here denominated analysis referentials, with the objective of delineating an automation model for hydric supply systems that could offer subsidies for the development of these systems in areas that still don\'t possess them fully automated.