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Society is going through a change to be more sustainable, and one big step in that process is to convert the power grid from convectional power generation to increased part of renewable energy sources. Renewable energy sources often require power electronics such as converters to connect to the power grid, and power electronics can cause interference in the grid. This development in Sweden and rest of the Nordic countries is driven by the large increase of load based on power electronics. To maintain a stable power grid, it is essential to detect disturbances through measurement techniques adapted to the challenges that may arise.   The measurement techniques in the Swedish power grid have historically been based on power quality meters and RMS-based measurements, and this thesis focuses on the disturbances that RMS-based measurements may fail to detect. The objective is to compare the RMS-based measurements techniques available in the power grid with waveform measurement techniques developed to see how they could detect disturbances in the power grid. The first research question pertains to the characteristic frequency bandwidths within which a power system typically operates, and what frequency bandwidths a system could have with a significant amount of power electronics installed. The second research question concerns the measurement techniques.   This work consists of four main parts: bandwidth analysis of control systems for voltage source converter, RMS vs waveform detection techniques, interaction between converter and voltage perturbation, and realistic phenomena studies. The bandwidth analysis aims to determine the frequency range expected in future power systems, which in turn informs the minimum detection capabilities required for measurement techniques. This was achieved through calculations involving the control loops of converters, including the inner current control loop, outer control loop, and phase locked loop. Bode diagrams were generated for each control loop, with variables manipulated, and the short circuit ratio adjusted to determine the bandwidth of the control loop.   The RMS vs waveform detection techniques  phase was central to the study, involving simulations imitating various phenomena that could occur in the power grid. This was accomplished using two ideal sources and examining their interactions. The simulations included frequency perturbations, amplitude perturbations, and added oscillations apparent at sub-synchronous, super-synchronous, and high super-synchronous frequencies. Simulation results were presented for both RMS and waveform based defection techniques, simulating different reporting rates to mimic real measurement tools.   The third and fourth parts involved validating the RMS vs waveform detection techniques  results using real-case simulations. An HVDC model was employed to simulate the effects of voltage perturbation and observe the coupling over frequency mechanism. The same HVDC model was also used to simulate phenomena occurring in weak grids. Additionally, a wind park model was utilized to simulate the induction generator effect phenomena.   The findings reveal that the bandwidth of a power system undergoes significant expansion as the proportion of power electronics increases in the grid. Specifically, analysis of converter indicates a shift from under 50 Hz to several kHz in systems dominated by synchronous generators versus those dominated by power electronics. To effectively detect higher frequency oscillations within the grid, waveform measurement tools become essential, as classical RMS measurement tools are inadequate for capturing oscillations originating from power electronics. As power systems evolve towards dominance by power electronics, it becomes imperative to develop measurement systems capable of accurately detecting high frequency oscillations.   The recommendation of this thesis is to invest in waveform measurement tools alongside the already existing RMS-based ones to enhance the detection of disturbances, particularly those with super synchronous frequencies, addressing future power grid challenges.

Characteristic modes (CMs) provide deep insight into the electromagnetic behaviour of any arbitrarily shaped conducting structure because the CMs are unique to the geometry of the object. We exploit this very fact by predicting a perhaps surprising number of important antenna metrics such as resonance frequency, radiation efficiency and antenna Q (bandwidth) without needing to specify a feeding location. In doing so, it is possible to define a collection of objective functions that can be used in an optimizer to shape-synthesize antennas without needing to define a feed location a priori. We denote this novel form of optimization “feedless” or “excitation-free” antenna shape synthesis. Fundamentally, we are allowing the electromagnetics to dictate how the antenna synthesis should proceed and are in no way imposing the physical constraints enforced by fixed feeding structures. This optimization technique is broadly applied to three major areas of antenna research: electrically small antennas, multi-band antennas and reflectarrays. Thus, the scope of applicability ranges from small antennas, to intermediate sizes and concludes with electrically large antenna designs, which is a testament to the broad applicability of characteristic mode theory. Another advantage of feedless electromagnetic shape synthesis is the ability to synthesize antennas whose desirable properties approach the fundamental limits imposed by electromagnetics. As an additional benefit, the feedless optimization technique is shown to have greater computational efficiency than traditional antenna optimization techniques.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), WLAN (2400-2500 MHz and 5000-5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated.

當大型災害來臨，通訊系統對救災效益具有不可或缺的重要性。然而，一般公眾通訊系統，如行動通訊網路等，常因各種不同因素導致系統攤瘓，使得協調大批非組織的救災志工，顯得異常困難。現存多個緊急通訊系統的佈建，需仰頼良好的交通運輸。不幸的是，部分道路和橋樑常因大型災害而斷裂或變型，導致災區對外交通運輸中斷，無法快速的將緊急通訊系統的網路元件，運送至災區佈建。我們提出應急行動通訊系統(Contingency Cellular Network, CCN) 以提供災區救災工作的緊急通訊。部分行動基地台雖然結構完整，但因失去與核心網路連線能力或電力供應，而無法提供服務，成為孤立基地台。應急行動通訊網路(CCN) 搭配無線通訊與衛星通訊技術建置一多重跳接無線網路，以恢復孤立基地台與核心網路連線能力；並配備發電機，提供電力，使孤立基地台可提供有限的服務。救災志工和災民無需使用特殊手持設備或額外的訓練，只需使用原有的手機，即可使用CCN的應急通訊服務。CCN可於第一時間，提供大批救災志工和災民通訊服務，以提高救災效益，因而拯救更多寶貴的生命。 本論文主要聚焦在應急行動通訊系統設計所衍生出的相關議題，如 應急網路需求分析、系統架構設計、網路拓樸規劃、網路頻寬規劃、佈署行程規劃等議題。本論文針對網路拓樸規劃、網路頻寬規劃、佈署行程規劃問題以數學模式進行塑模並證明這些問題為NP-Hard問題。因網路拓樸規劃、網路頻寬規劃、佈署行程規劃需緊急完成，我們也提出啟發式算法快速解決這些規劃問題。實驗結果顯示，這些啟發式算法均具良好的效能。 / Communication system is crucial to the efficiency of disaster response operation in the large-scale disaster. However, communication systems, such as cellular networks, usually crashed due to various causes making coordination among disorganized disaster responders extremely difficult. Unfortunately, rapid deployment of many existing emergency communication systems relies on a good transportation system, which is usually not available in a catastrophic natural disaster. We proposed a Contingency Cellular Network (CCN) for emergency communication by connecting disconnected base stations together with wireless links to construct a wireless multi-hop cellular network. CCN can support existing mobile phone users with reduced capability. Such a system can support a large number of disaster responders in the early hours of a catastrophic natural disaster, thus save many lives. Our research addresses the design issues of the network topology of CCN, such as network topology planning, bandwidth management, deployment scheduling and etc., and we take the degree of emergency and population of each stricken area as the priority measure as well as the available resources as the constraint to determine the network topology. Mathematical models of these design issues are proposed and proved as NP-Hard problems. Since the network topology, bandwidth management, deployment scheduling are needed in urgent, we propose heuristic algorithms to solve these problems quickly. Finally, we evaluated the proposed algorithms by simulation. A significant improvement in resiliency is reached.

Au cours des deux dernières décennies, les signaux chaotiques ont été de plusen plus pris en compte dans les télécommunications, traitement du signal ou transmissionssécurisées. De nombreux articles ont été publiés qui étudient la densitéspectrale de puissance (DSP) des signaux générés par des transformations spécifiques.La concentration sur la DSP est due à l’importance de la fréquence dans lestélécommunications et la transmission sécurisée. Grâce au grand nombre de systèmessans fil, la disponibilité des fréquences de transmission et de réception est de plus enplus rare pour les communications sans fil. Aussi, les médias guidés ont des limitationsliées à la bande passante du signal. Dans cette thèse, nous étudions certainespropriétés associées à la bifurcation collision de frontière pour une transformationunidimensionnelle linéaire par morceaux avec trois pentes et deux paramètres. Nouscalculons les expressions analytiques de l’autocorrélation et de la densité spectralede puissance des signaux chaotiques générés par les transformations linéaires parmorceaux. Nous montrons l’existence d’une forte relation entre les différents typesde densité spectrale de puissance (passe-bas, passe-haut ou coupe-bande) et les paramètresde bifurcation. Nous notons également en évidence une relation entre le typede spectre et l’ordre des cycles attractifs. Le type du spectre dépend de l’existencedes orbites périodiques au-delà de la bifurcation de collision de frontière qui a donnénaissance au chaos. Nous utilisons ensuite les transformations chaotiques pour étudierla fonction d’ambiguïté. Nous combinons quelques transformations chaotiquesbien déterminées pour obtenir un spectre large bande avec une bonne fonction d’ambiguïtéqui peut être utilisée en système radar / During the two last decades, chaotic signals have been increasingly consideredin telecommunications, signal processing or secure transmissions. Many papers haveappeared which study the power spectral density (PSD) of signals issued from somespecific maps. This interest in the PSD is due to the importance of frequency in thetelecommunications and transmission security. With the large number of wirelesssystems, the availability of frequencies for transmission and reception is increasinglyuncommon for wireless communications. Also, guided media have limitations relatedto the bandwidth of a signal. In this thesis, we investigate some properties associatedto the border-collision bifurcations in a one-dimensional piecewise-linear map withthree slopes and two parameters. We derive analytical expressions for the autocorrelationsequence, power spectral density of chaotic signals generated by our piecewiselinearmap. We prove the existence of strong relation between different types of thepower spectral density (low-pass, high-pass or band-stop) and the parameters. Wealso find a relation between the type of spectrum and the order of attractive cycleswhich are located after the border collision bifurcation between chaos and cycles.We use the chaotic transformations to study the ambiguity function. We combinesome chaotic transformations well determined to obtain a broadband spectrum witha good ambiguity function that can be used in radar systems

O problema estudado relaciona-se ao planejamento de redes ópticas de acesso TWDM (Time and Wavelength Division Multiplexing), tendo como meta prover meios para atender ao consumo crescente de banda e, ao mesmo tempo, associar o mesmo ao menor consumo de energia possível e disponibilizar serviços de qualidade aos usuários da rede. Neste contexto, após a apresentação de uma revisão bibliográfica, alguns trabalhos foram selecionados como referências base para o estudo. Neste, foram analisadas técnicas de gerenciamento do comprimento de onda numa possível migração tecnológica dos equipamentos de acesso à rede pelo lado do usuário, as unidades de rede óptica (ONUs), considerando ser possível aproveitar de forma eficiente a distribuição de ONUs em cada par de comprimentos de onda, e como resultado, desligar interfaces de gerenciamento para economia de energia. Em paralelo a este objetivo, foram agregados métodos de \"registro adaptativo\" para melhorar o desempenho das ONUs que estão migrando e/ou entrando na rede, evitando colisões entre seus sinais e aumentando as chances de registro no terminal de linha óptico (OLT). Além do mais, o trabalho aborda o cumprimento do contrato de serviços (SLA) por parte das operadoras de telecomunicações, bem como oferece meios de estruturar uma rede óptica passiva (PON) para oferecer serviços com garantia de métricas de qualidade (QoS). Diferentes cenários foram tratados ao variar a porcentagem de usuários ativos na rede, e percebeu-se que, quando a PON opera com baixo índice de atividade (média 10% de ONUs ativas), foi possível economizar mais de 80% de energia em interfaces de gerenciamento. Por outro lado, ao envolver cenários mais realistas em redes ópticas (média de 50% de ONUs ativas), o TWDM-PON economizou quase 50% de energia nestas interfaces ao ser configurado com baixo período de migração (5 minutos). Além disso, alcançou um SLA de aproximadamente 100%, um valor considerado acima do usual quando se trata de cumprimento de serviços. Como uma tecnologia emergente, o TWDM-PON destaca-se num cenário que deve ser planejado para ser compatível com tecnologias implantadas, e além de disso, superar o legado de redes PON na economia de energia e qualidade de serviços oferecidos. / The problem studied is related to the planning of optical access networks TWDM (Time and Wavelength Division Multiplexing), aiming to provide means to meet the increasing bandwidth consumption and, at the same time, associating it to the lowest possible power consumption and providing quality services to the network users. In this context, following the presentation of a literature review, some studies were selected as a reference basis for the study. In this, some wavelength management techniques were analyzed aiming a possible technological migration of the network access equipment at the user side, the optical network units (ONU), whereas it is possible to use efficiently the ONUs distribution in each pair of wavelength. As a result, it becomes possible to switch off some management interfaces thus assuring a degree of power consumption save. In parallel, methods for providing an \"adaptive record\" of ONUs have been aggregated to improve the performance of those ONUs that are migrating and/or entering the network, avoiding collisions between their signals and increasing the chance of their registration in the optical line terminal (OLT). Furthermore, this work deals with the fulfillment of the service agreement (SLA) signed by telecommunications operators and proposes ways to design a passive optical network (PON) in order to offer services with quality metrics assurance (QoS). Different scenarios were treated to vary the percentage of active users on the network, and it was noticed that when the PON operates with low rate of activity (average 10% of active ONUs), it was possible to save over 80% energy in the management interfaces. Moreover, by involving more realistic scenarios in optical networks (50%, in average, of active ONUs), the TWDM-PON saved almost 50% of energy at the interfaces to be configured with low migration period (5 minutes). Additionally, it reached an SLA of approximately 100%, a value considered above the usual when it comes to compliance services. As an emerging technology, TWDM-PON stands out in a scenario that should be designed to be compatible with deployed technologies, and beyond that, to overcome the legacy of PON networks in energy saving and quality of services offered.

As redes ópticas estão passando por mudanças significativas, impulsionadas pelo crescimento exponencial do tráfego, principalmente advindo de serviços multimídia e armazenamento em nuvem. Esta demanda exigirá aumento da capacidade da taxa de transmissão para padrões como 400 Gb/s e 1 Tb/s. Nesse contexto, foi proposta uma arquitetura de rede com grade de frequências granular flexível chamada elastic optical network (EON). A EON divide o espectro de frequências em fatias (slots) de tamanho fixo e aloca grupos de slots contíguos estritamente de acordo com os requisitos de banda das demandas de conexão, implicando eficiência de uso do espectro. Com o aumento significativo da taxa de transmissão, acentuou-se a preocupação em manter a sobrevivência da rede, já que pouco tempo de queda no serviço pode acarretar uma imensa perda de dados. Neste trabalho, investigamos esquemas de proteção baseados em caminhos compartilhados (shared-path protection, SPP) e esquemas de restauração de tráfego. Avaliamos esquemas divulgados na literatura como o dynamic load balancing shared-path protection (DLBSPP) e esquemas de restauração como o traffic aware restoration (TAR) e bandwidth squeezed restoration (BSR). Avaliamos também uma heurística de alocação de slots chamada inverted dual stack (IDS). O DLBSPP utiliza balanceamento dinâmico de carga para computar os caminhos primários e de proteção compartilhados. O TAR executa a restauração dinâmica ordenando as conexões por granularidade de banda. O BSR utiliza a capacidade de contração de banda do EON para restaurar conexões por meio da política de melhor esforço ou de banda garantida, dependendo do acordo de níveis de serviço do cliente. O esquema IDS concentra o maior número possível de slots compartilhados em uma região do espectro. As medidas de desempenho dos algoritmos são avaliadas segundo as métricas: probabilidade de bloqueio, taxa de utilização do espectro, número médio de hops e taxa de restauração falha. As simulações computacionais mostram o bom desempenho da utilização do esquema IDS com DLBSPP. / Optical networks are undergoing significant changes driven by the exponentially growing traffic, especially coming from multimedia and cloud storage services. This demand will require increasing of the transmission rate capacity as high as 400 Gb/s and 1 Tb/s. Within this context, it was proposed the elastic optical network (EON), which is a network architecture with flexible granular frequency grid. EON divides the frequency spectrum into slices (slots) of fixed size and allocates groups of contiguous slots strictly according to the bandwidth requirement of the connection demands, providing high spectrum use efficiency. The significant increase in transmission rate put emphasis on the need to maintain the survival of the network, since the occurrence of faults in the network nodes or links can cause huge loss of data. In this work, we investigate protection schemes based on shared-path protection (SPP) and traffic restoration schemes. We evaluate schemes related in the literature, such as the dynamic load balancing shared-path protection (DLBSPP), and restoration schemes such as the traffic aware restoration (TAR) and the bandwidth squeezed restoration (BSR). The DLBP scheme uses dynamic load balancing to compute primary and shared protection paths. The TAR performs dynamic restoration ordering the connections based on band granularity. The BSR uses EON\'s band squeezing feature to restore connections by means of the best effort or guaranteed bandwidth strategy, depending on the customer\'s service level agreement. IDS scheme concentrates the maximum possible number of shared slots in a given region of the spectrum. Performance of the algorithms are evaluated according to metrics: blocking probability, spectrum utilization rate, average number of hops and failure restoration rate. Computer simulations show that the use of the IDS scheme improves the performance of the investigated algorithms.