Thesis (D.Tech (Engineering Electrical)) - Central University of Technology, Free State, 2005 / When Thomas Edison invented his carbon filament lamp in 1879, gas shares fell overnight. A committee of inquiry was set up to examine the future possibilities of the new method of lighting, and had reached the conclusion that electric light in the home was fanciful and absurd. Today electric light burns in practically every house in the civilised world, with many great advances in the production and use of electricity and electric power supplied by various utilities. The objective of the electric utility to deliver pure sinusoidal voltage at fairly constant magnitude throughout their system is complicated by the fact that there are currently loads on the system that produce harmonic voltages, which result in distorted voltages and currents that can adversely impact on the system performance in different ways. Because the numbers of harmonic producing loads have increased over the years, it has become necessary to address their influence, when making any additions or changes to an installation. Quality of supply measurements have long been used to characterise non-linearity on the power system, and have traditionally been measured with expensive portable analysers. A potentially faster, more integrated, and more flexible solution to measure the harmonics with a Supervisory System is accomplished by this research. Any script which aspired to cover in full detail the whole field of a subject so enormous as techniques to measure the quality of electricity supply on a SCADA system, would hardly be practical in less than a few volumes. The pretensions of this research are both modest and of a more immediate value to the reader.

Contemporary young women would appear to enjoy greater freedoms to consume alcohol and socialise in bars, pubs and clubs than their predecessors. However, concern about women’s level of alcohol consumption, drink spiking and drug-assisted sexual assault have contributed to a renewed focus on safety advice for young women in these social settings. This thesis examines the views, experiences and behaviours of 35 young women in relation to their safety in bars, pubs and clubs using qualitative data from interviews and focus groups with young women (18-25 years) in Scotland. Exploring the divergent claims made within feminist structural and poststructural perspectives, this thesis develops a nuanced understanding of young women’s safety in bars, pubs and clubs by drawing upon the theoretical concepts of power, resistance and social control. Constraints on women’s leisure imposed by patriarchal structures, safety concerns and notions of ‘appropriate femininity’, formed a significant focus of early feminist theorising in this area. More recently, however, poststuctural feminist theorists have highlighted the opportunities that leisure experiences may offer women for liberation by providing a means to resist conventional cultural discourses around feminine identities. To a certain extent, the findings from this study challenge the conventional construction of consuming alcohol and socialising in bars, pubs and clubs as a masculine leisure pursuit, by identifying this leisure activity as a central aspect of young women’s social lives. However, young women’s experiences and behaviours within bars, pubs and clubs remain significantly structured by gender and young women perceive the risks that they experience in these settings to have increased over time. The continuing salience of gender is evident in the way that women access bars, pubs and clubs, their safety concerns and experiences, and ultimately their behaviour within these venues. Young women’s safety concerns in this context are overwhelmingly related to the fear and reality of sexual violence, lending credence to social control theories espoused by radical feminists. These concerns and the individualising discourse embodied within safety literature results in women normalising and taking individual responsibility for preventing sexual assault. This reflects the positioning of sexual violence as an inevitable fixed reality, thus evading the need to question the behaviour of men who choose to sexually assault and harass women in bars, pubs and clubs. Safety behaviours adopted by young women in bars, pubs and clubs are complex and contradictory in that they simultaneously adopt, resist and transgress those advocated within safety literature. Since these safety behaviours are inextricably linked to normative femininity and gendered expectations of women’s behaviour in bars, pubs and clubs, they are more adequately theorised as ‘accommodating techniques’ than ‘resistant practices’. These findings pose significant difficulties for locating women’s experiences of consuming alcohol in bars, pubs and clubs within a poststructuralist framework of liberation and freedom; in some respects, it would appear that women’s behaviour within these social spaces is subject to heightened regulation and control. While poststructural theorising about power and resistance is of some assistance in illuminating the process of how safety concerns regulate women’s behaviour, alongside the possibility of resistance, understanding young women’s safety is best served by an appreciation of feminist structural perspectives which highlight the salience of gender, and in particular the power of gendered norms and taboos which continue to operate with regard to women’s sexuality. Ultimately, bars, pubs and clubs remain a social space infused with gendered expectations and risks.

O presente trabalho se propõe a elaborar algoritmos para controle robusto de sistemas de potência. O modelo de sistema de potência multimáquinas utilizado é o de pequenas perturbações, e o objetivo principal é aumentar o amortecimento dos autovalores críticos do sistema, garantindo sua estabilidade e desempenho em diversas condições operativas. Para isso, são utilizadas as Desigualdades Matriciais Lineares (ou LMI\'s), muito adequadas ao tratamento de problemas de controle robusto por sua flexibilidade e possibilidade de agrupamento de diversos requisitos de desempenho. São propostos, entre outros, três algoritmos fundamentais para controle robusto: dois estão relacionados ao controle descentralizado e com controladores de estrutura fixa, o que é muito comum na indústria de potência atualmente, e o outro está relacionado ao controle hierarquizado, que consiste na integração de várias camadas de controle utilizando sinais remotos. Os algoritmos de controle descentralizado propostos são inovadores, pois ambos os métodos permitem a utilização de controladores de estrutura fixa (qualquer que seja ela), e o algoritmo de controle hierarquizado propõe uma estrutura de controle inédita que utiliza aproximações de Padé de diversas ordens para representar os atrasos de comunicação no sistema. Durante a fase de projeto, pode-se escolher o atraso de comunicação, bem como a ordem da aproximação de Padé desejada. Nos algoritmos de controle robusto descentralizado, realizamos uma minimização da norma da matriz de ganhos estáticos do controlador, o que impede que o resultado do algoritmo sejam parâmetros de valores muito elevados e infactíveis para os controladores. A técnica utilizada para os três controladores propostos é o posicionamento de pólos, o que garante que os autovalores do sistema de potência em malha fechada estejam numa dada região do plano complexo, relacionada ao amortecimento mínimo desejado para os autovalores do sistema. Os testes e simulações realizados para validação dos algoritmos de controle robusto foram feitos em ambiente MATLAB, e foram utilizados diversos sistemas de potência: sistema New England de 39 barras e 9 geradores, sistema New England de 69 barras e 16 geradores e sistema New England de 39 barras utilizando modelos de termogeradores. Os testes sugerem que as técnicas propostas são eficazes, pois todas elas garantem boas taxas de amortecimento para os sistemas de potência utilizados. Ao final, simulações não-lineares comprovam a eficácia e a eficiência de um dos controladores projetados para o sistema New England de 39 barras. / The aim of this work is to elaborate robust control algorithms to power systems. The mathematical model employed to describe the multimachine power system is that used in small signal studies, and the main goal is to increase the damping of the critical eigenvalues of the system, guaranteeing its stability and performance in various operating conditions. To do this, we apply the Linear Matrix Inequalities (or simply LMI\'s), suitable to deal with robust control problems due to its flexibility and possibility to group many performance requisites. We propose three robust control algorithms: two of them are related to decentralized control with controllers of predefined structure, which are commonly used in the power industry, and the other one is related to the hierarchized control, which consists on the integration of various controllers layers using remote signals. The decentralized robust control algorithms proposed are novel, because both methods make possible the development of controllers of pre-defined structure, and the hierarchized control algorithm suggests a novel control structure that uses Padé approximations of different orders to represent the communication delays in the system. During the design, we can choose the communication delay, as well as the order of the Padé approximation desired. The decentralized robust control algorithms solve minimization problems over the controller gain matrix norm, which guarantees that the final values of the controller\'s parameters will not be much high and impracticable. The technique employed for the three types of controllers proposed is the pole placement, which ensures that the eigenvalues of the closed loop power system will be in a certain region of the complex plane, related to the minimum damping required for the system. Tests and simulations are done in MATLAB to validate the robust control algorithms, and we apply these algorithms to various power systems: 39-bus 9-machine New England power system, 69-bus 16-machine New England power systems and 39-bus New England power system with thermo machine models. The tests suggest that the proposed techniques work well, once all of them guarantee good damping rates to the power systems considered. To complete the tests round, nonlinear simulations proof the efficiency of the controllers designed for the 39-bus New England power system.

Submitted by Marlene Aparecida de Souza Cardozo (mcardozo@pucsp.br) on 2016-12-19T11:13:47Z No. of bitstreams: 1 Adolfo Tanzi Neto.pdf: 342018725 bytes, checksum: f404f3c1ab5393d069d1a7529f53dcca (MD5) / Made available in DSpace on 2016-12-19T11:13:47Z (GMT). No. of bitstreams: 1 Adolfo Tanzi Neto.pdf: 342018725 bytes, checksum: f404f3c1ab5393d069d1a7529f53dcca (MD5) Previous issue date: 2016-06-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This doctoral thesis, situated in the field of Applied Linguistics, seeks to address the role of language in different school settings. Through the study of three distinct schools of the Brazilian public education, a more traditional one, another full-time with experimental involvement projects with students and the last one with democratic principles without walls, classes, grading or classification. The present research pursues to answer how the relations of power and control in social positions and discursive mediation artefacts constitute a specific school space and thus, influence the conscience formation of its participants. The research also investigates how a school space, and its relationship with a distinct physical space, contributes to different possibilities of social positions of psychological tools and discursive artefacts. Therefore, based on a socio historical cultural research, exploring the concept of mediation [oposredovanie] Vygotsky (1978, 1981, 1987, 2009 [1934]), we seek to understand how the human cultural development is being performed and how participants of this culture are mutually shaped, for being social, cultural and institutionally situated. From the reflections of Bakhtin (2010 [1924]) and Bernstein (2003 [1990], 1996, 1999, 2000) other aspects are analysed. The first author bolsters this research with studies on the architectonic form, aesthetic and genre, in which we attempt to understand the verbal-visual mass of an architectonic whole and thus, understand their interdependencies, its dialogical and axiological positions in architectonic form that governs the construction of a verbal-visual mass. The second contributed with studies on the relations of power and control within an institution that tend to govern the forms of communication or open spaces for different forms of communication to be materialised. This research indicated that it is possible to break the boundaries of power and control, discourses and regulatory practices of more traditional physical and social school spaces and therefore, break the invisible barriers, offering a more horizontal space of social positions, exchange, identities and voices of its participants. In this sense, we believe that it is possible to reconfigure the architectonic form of any physical and social space in order to propose different relationships between agents, hierarchical rules etc. To this end, we note the importance of the verbal-visual productions in different school spaces, which favoured the voice of the student, reconfiguring their dialogic and axiological positions in the architectonic form of the school social space. Thus, even in a more traditional organizational and pedagogical space context, we found that the social basis, the voice and identity of students, when privileged, generated a school closer to students, which engendered feelings of belonging and school recognition relationship as a change agent for achievement of future dreams / Esta tese de doutorado, situada no campo da Linguística Aplicada, nasce da necessidade de discutirmos o papel da linguagem em diferentes contextos escolares. Por meio do estudo de três escolas distintas da rede pública brasileira de ensino, uma mais tradicional, outra com projetos experimentais de envolvimento dos alunos e período integral e outra com princípios democráticos sem paredes, aulas, seriação ou classificação, a pesquisa busca responder como as relações de poder e controle nos posicionamentos sociais e nos artefatos discursivos de mediação constituem-se em um espaço escolar específico e, assim, influenciam na formação da consciência dos seus envolvidos. A pesquisa investiga, também, como um espaço escolar e sua relação com um espaço físico distinto contribuem para diferentes possibilidades de posicionamentos sociais, de ferramentas psicológicas e de artefatos discursivos. Para tanto, embasados em uma pesquisa de cunho sócio, histórico e cultural, explorando o conceito de mediação [oposredovanie] de Vygotsky (1978, 1981, 1987, 2009 [1934]), buscamos a compreensão de como se dá o desenvolvimento cultural humano e como os participantes dessas culturas são mutuamente modelados, por estarem social, cultural e institucionalmente situados. A partir das reflexões de Bakhtin (2010 [1924]) e de Bernstein (2003 [1990], 1996, 1999, 2000) outros aspectos são analisados. O primeiro autor ampara esta pesquisa com os estudos sobre forma arquitetônica, estética e gênero, nos quais buscamos entender a massa verbo-visual de um todo arquitetônico e, assim, compreender as suas interdependências, suas posições dialógicas e axiológicas na forma arquitetônica que governa a construção de uma massa verbo-visual. O segundo contribui com os estudos sobre as relações de poder e controle dentro de uma instituição, que tendem a governar as formas de comunicação ou a abrir espaços para que diferentes formas de comunicação insurjam. Esta pesquisa apontou para o fato de que é possível quebrar as fronteiras de controle e poder, de discursos e práticas reguladoras de espaços físicos e sociais escolares mais tradicionais e, assim, romper com as barreiras invisíveis, oferecendo um espaço de posicionamentos sociais mais horizontal, de troca, de identidades e vozes de seus participantes. Nesse sentido, entendemos que é possível reconfigurar a forma arquitetônica de qualquer espaço físico e social, de modo a propor diferentes relações entre agentes, regras hierárquicas etc. Para tanto, notamos a importância das produções verbo-visuais, nos diferentes espaços escolares, que privilegiavam a voz do aluno, reconfigurando suas posições dialógicas e axiológicas na forma arquitetônica do espaço social escolar. Assim, mesmo em um contexto de organização de espaços e orientação pedagógica mais tradicional, constatamos que a base social, a voz e a identidade dos alunos, quando privilegiadas, geram uma relação mais próxima de pertencimento escolar e de reconhecimento da escola como agente de mudança para conquista de sonhos futuros

This thesis is devoted to the development of new approaches for control coordination of PSSs (power system stabilisers) and FACTS (flexible alternating current transmission system) devices for achieving and enhancing small-disturbance stability in multi-machine power systems. The key objectives of the research reported in the thesis are, through optimal control coordination of PSSs and/or FACTS devices, those of maintaining satisfactory power oscillation damping and secure system operation when the power system is subject to persisting disturbances in the form of load demand fluctuations and switching control. Although occurring less frequently, fault disturbances are also considered in the assessment of the control coordination performance. Based on the constrained optimisation method in which the eigenvalue-based objective function is minimised to identify the optimal parameters of power system damping controllers, the thesis first develops a procedure for designing the control coordination of PSSs and FACTS devices controllers. The eigenvalue-eigenvector equations associated with the selected electromechanical modes form a set of equality constraints in the optimisation. The key advance of the procedure is that there is no need for any special software system for eigenvalue calculations, and the use of sparse Jacobian matrix for forming the eigenvalue-eigenvector equations leads to the sparsity formulation which is essential for large power systems. Inequality constraints include those for imposing bounds on the controller parameters. Constraints which guarantee that the modes are distinct ones are derived and incorporated in the control coordination formulation, using the property that eigenvectors associated with distinct modes are linearly independent. The robustness of the controllers is achieved very directly through extending the sets of equality constraints and inequality constraints in relation to selected eigenvalues and eigenvectors associated with the state matrices of power systems with loading conditions and/or network configurations different from that of the base case. On recognising that the fixed-parameter controllers, even when designed with optimal control coordination, have an inherent limitation which precludes optimal system damping for each and every possible system operating condition, the second part of ii the research has a focus on adaptive control techniques and their applications to power system controllers. In this context, the thesis reports the development of a new design procedure for online control coordination which leads to adaptive PSSs and/or supplementary damping controllers (SDCs) of FACTS devices for enhancing the stability of the electromechanical modes in a multi-machine power system. The controller parameters are adaptive to the changes in system operating condition and/or configuration. Central to the design is the use of a neural network synthesised to give in its output layer the optimal controller parameters adaptive to system operating condition and configuration. A novel feature of the neural adaptive controller is that of representing the system configuration by a reduced nodal impedance matrix which is input to the neural network.

Current trends in electric power consumption indicate an increasing use of dc in end-user equipment, such as computers and other electronic appliances used in households and offices. With a dc power system, ac/dc conversion within these loads can be avoided, and losses reduced. AC/DC conversion is instead centralized, and by using efficient, fully controllable power-electronic interfaces, high power quality for both ac and dc systems during steady state and ac grid disturbances can be obtained. Connection of back-up energy storage and small-size generation is also easier to realize in a dc power system. To facilitate practical application, it is important that the shift from ac to dc can be implemented with minimal changes. Results from measurements carried out on common household appliances show that most loads are able to operate with dc supply without any modifications. Furthermore, simple, and yet sufficiently accurate, load models have been derived using the measurement results. The models have been used for further analysis of the dc system, both in steady state and during transients. AC microgrids have gained research interest during the last years. A microgrid is a part of power systems which can operate both connected to the ac grid, and autonomously in island mode when the loads are supplied from locally distributed resources. A low-voltage dc microgrid can be used to supply sensitive electronic loads, since it combines the advantages of using a dc supply for electronic loads, and using local generation to supply sensitive loads. An example of a commercial power system which can benefit from using a dc microgrid is data center. The lower losses due to fewer power conversion steps results in less heat which need to be cooled, and therefore the operation costs are lowered. To ensure reliable operation of a low-voltage dc microgrid, well-designed control and protection systems are needed. An adaptive controller is required to coordinate the different resources based on the load-generation balance in the microgrid, and status of the ac grid. The performance of the developed controller has been studied and evaluated through simulations. The results show that it is possible to extend use of the data center dc microgrid to also support a limited amount of ac loads close to the data center, for example an office building. A protection-system design for low-voltage dc microgrids has been proposed, and different protection devices and grounding methods have been presented. Moreover, different fault types and their impact on the system have been analyzed. The type of protection that can be used depends on the sensitivity of the components in the microgrid. Detection methods for different components have been suggested in order to achieve a fast and accurate fault clearing. An experimental small-scale dc power system has been used to supply different loads, both during normal and fault conditions. A three-phase two-level voltage source converter in series with a Buck converter was used to interconnect the ac and the dc power systems. Together the converters have large controllability, high power quality performance, and allow bi-directional power flow. This topology can preferably be used together with energy storage. The tests confirm the feasibility of using a dc power system to supply sensitive electronic loads. / QC 20100908

Security analysis of a power system requires a process called contingency analysis that analyzes results from all possible single contingencies (i.e. outages) in the system. The process of contingency analysis requires the definition of a parameter that is used to monitor a certain aspect of the system, which is called a performance index. The performance index definitions used traditionally have been highly nonlinear, and the results have not accurately predicted the outcome of the performance index in some cases. These incorrect results are referred to as misrankings since the contingency results are usually placed in order of severity so that the most severe cases are evident. This thesis considers a new definition of contingency ranking using a more linearized definition of the performance index. The construction of both the new, proposed definition and the classic definition both consider the current loading of circuits in the system as compared to their rated values. Specifically, the parameter measured by the proposed definition measures the difference, while the more nonlinear definition uses a ratio of the two quantities, which is then raised to a higher power. A small, four bus test system is used to demonstrate the benefits of the new, more linearized definition. The average percent error for all single line contingencies of the system decreased by over 9.5% using the proposed definition as compared to the previous one. This decrease in error allows this performance index to monitor a similar parameter (comparing current loading and current rating of the lines) and achieve a higher degree of accuracy. Further linearization of this proposed definition also shows a reduction in the average percent error by an additional 22% so that when compared to the original, highly nonlinear definition, the average error is reduced by almost 30%. By linearizing the definition of the performance index, the results are more accurate and misrankings are less likely to occur from the security analysis process.

VJ表演隱藏著一種矛盾性。VJ表演之觀眾特徵，較常表現出非主流的品味，傾向於追求與眾不同的體驗，與對於自主權的掌握展現較高的積極性。然而享受音樂表演意味著某種程度的沈浸與忘我，在觀賞表演時需暫時捨棄自身的自主權與主體性方有可能真正享受其中，這之間便產生了控制與被控制的矛盾。當互動科技的元素介入到VJ表演時，這種矛盾性就會更加明顯，甚至被揭露與強調。互動科技的加入旨在過程中使人們能夠參與，讓人們擁有做決定或影響表演的權力。故互動的VJ表演具有控制權矛盾之特徵，而這樣的矛盾性應當被表演設計者所發現並探索。本研究希望透過理論爬梳與作品實踐，探索互動加入在VJ表演時如何提高觀眾的參與感。於是如何盡量減少互動所造成的干擾性以完成一場互動表演，便成為本研究關心的一項重點。 　　在內容主題上，台灣民間信仰是關於控制與被控制一個很好的轉喻。故此計畫將設計一個以台灣民間信仰為主題的互動VJ表演，並利用台灣民間信仰來反映觀眾主體性矛盾與控制權矛盾的不同面相。

M. Tech. Electrical Engineering. / Discusses the practical management of electrical networks, no perfect monitoring of an electrical power system state is available, either because it is expensive or technically unfeasible due to the poor quality of the available measurements in the control centre. To have a stable network, the control centre must receive the network information to be able to provide a proper security in unforeseen situation. As a power system network is a complex and a non-linear system, it is important to use more advanced methods for its analysis and control in a real time environment. The aim of this research work is therefore, to apply several state estimation algorithms using artificial intelligence by developing their mathematical models for the purpose of comparing their performances in estimating the state variable of the power system. The three types of state estimation algorithms investigated for this research work are: the Particle Swarm Optimisation (PSO), the Genetic Algorithm (GA) and the Newton method for state estimation (NSE).

Research in the field of random access protocols for narrow-band systems started as early as the 1970s with the introduction of the ALOHA protocol. From the research done in slotted narrow-band systems, it is well known that contention results in all the packets involved in the contention being unsuccessful. However, it has been shown that in the presence of unequal power levels, ore of the contending packets may be successful. Ibis is a phenomenon called capture. Packet capture has been shown to improve the performance of slotted narrow-band systems. Recently, much work has been done in the analysis of spread-spectrum ALOHA type code-division multiple access (CDMA) protocols. The issue of designing power control techniques to improve the performance of CDMA systems by reducing multiple access interference (MAl) has been a subject of much research. It has been shown that in the presence of power control schemes, the performance of spread-ALOHA CDMA systems is improved. However, it is also widely documented that the design of power control schemes capable of the ideal of compensation of radio propagation techniques is not possible for various reasons, and hence the imperfections in power control. None of the research known to the author has looked at capture in spread-ALOHA systems, and to a greater extent, looked at expressions for the performance of spreadALOHA systems in the presence of capture. In this thesis we introduce spread-ALOHA systems with capture as a manifestation of the imperfections in power control. We propose novel expressions for the computation of the perfonnance ofspread-ALOHA systems with capture. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.