Robust nonlinear distributed controller design for active and reactive power sharing in islanded microgrids

This paper presents a robust nonlinear distributed controller design for islanded operation of microgrids in order to maintain active and reactive power balance. In this paper, microgrids are considered as inverter-dominated networks integrated with renewable energy sources (RESs) and battery energy storage systems (BESSs), where solar photovoltaic generators act as RESs and plug-in hybrid electric vehicles as BESSs to supply power into the grid. The proposed controller is designed by using partial feedback linearization and the robustness of this control scheme is ensured by considering structured uncertainties within the RESs and BESSs. An approach for modeling the uncertainties through the satisfaction of matching conditions is also provided in this paper. The proposed distributed control scheme requires information from local and neighboring generators to communicate with each other and the communication among RESs, BESSs, and control centers is developed by using the concept of the graph theory. Finally, the performance of the proposed robust controller is demonstrated on a test microgrid and simulation results indicate the superiority of the proposed scheme under different operating conditions as compared to a linear-quadratic-regulator-based controller.

After Charlie: free speech and the political economy of communication

Three significant events at the start of 2015 have put freedom of speech firmly on the global agenda. The first was the carry-over from the December 2014 illegal entry to the Sony Corporation’s file servers by anonymous hackers, believed to be linked to the North Korean regime. The second was the horrible attack on journalists, editors, and cartoonists at the French satirical magazine, Charlie Hebdo on 7 January. The third was the election of leftwing anti-austerity party Syrzia in Greece on 25 January.While each event is different in scope and size, they are important to scholars of the political economy of communication because they all speak to ongoing debates about freedom of expression, freedom of speech and freedom of the press. I name each of these concepts separately because, despite popular confusion, they are not the same thing (Patching and Hirst, 2014) . Freedom of expression is the right to individual self-expression through any means; it is an inalienable human right. Freedom of speech refers to the right (and the physical ability) to utter political speech, to say what others wish to repress and to demand a voice with which to express a range of social and political thoughts. Freedom of the press is a very particular version of freedom of expression that is intimately bound with the political economy of speech and of the printing press. Freedom of the press is impossible without the press and, despite its theoretical availability to all of us, this principle is impossible to articulate without the material means (usually money) to actually deploy a printing press (or the electronic means of broadcasting and publishing).Freedom of expression is immutable; freedom of speech subject to legal, ethical and ideological restriction (for better, or worse) and freedom of the press is peculiar to bourgeois society in that it entails the freedom to own and operate a press, not the right to say or publish on a level playing field. Access to freedom of the press is determined in the marketplace and is subject to the unequal power relationships that such determination implies.It is fitting to start with the Charlie Hebdo massacre because the loss of 17 lives makes this the most chilling of the three events and demands that it be given prominence in any analysis. No lives have been lost yet because Sony’s computers were hacked and the election of Syriza has not (yet) led to mass deaths in Greece.

On optimally reducing power loss in micro-grids with power storage devices

Smart micro-grids can produce 'renewable' energy and store them in power storage devices. Power loss, however, is a significant problem in power exchange among the micro-grids and between the macro-station and individual micro-grids. To optimally reduce the total power losses in such a power grid system, in this paper, a greedy coalition formation algorithm is proposed, which allows the macro-station to coordinate mutual power exchange among the micro-grids and between each micro-grid and the macro-station. Our algorithm optimizes the total power losses across the entire power grid, including the cost of charging and discharging power storage devices and power losses due to power transfers. The algorithm creates exchange pairs among the micro-grids, giving priority to pairs with higher power loss reduction per exchanged power unit. Through computer-based simulations, we demonstrate that the proposed approach significantly reduces the average power loss compared with the conventional noncooperative method. The simulations also demonstrate that the communications overhead of our proposal (due to negotiations aimed at forming coalitions) does not significantly affect the available communication resource. © 2014 IEEE.

A novel distributed algorithm for power loss minimizing in Smart Grid

Because power generation of renewable resources are unstable and demands of the customers are time-varying, the supply power and demands of the customers are always unequal. To meet the demands of the customers, power is transmitted from primary power generation to secondary power generation. It will cause high power loss. To solve this problem, a distributed algorithm is proposed in this paper. By using the algorithm, the micro-grids are able to exchange power with their neighbors so as to minimize the total power losses of the smart grid. Moreover, communication overhead (bandwidth) is reduced, comparing with centralized algorithm. Through computer simulations, we demonstrate that the proposed algorithm can lead to near-optimal result for alleviating the average power loss per micro-grid and reduce the communication overhead significantly in contrast with the centralized approach.

Adoption of social media as a communication medium : a study of theoretical foundations

The continuing popularity and adoption of social media by the general public and the realisation of its potential customer engagement power by business, is highlighting the importance of social media to ongoing business activities and strategies. However, current research that is more focused around the potential power of social media generates little debate of the adoption factors driving public use of social media as a communication medium. Even though businesses have an opportunity to broaden their reach by adding social media to the communication strategic-mix, the dearth of informed discussions relating to theoretical underpinnings associated with the public adaptation of social media as a communication medium fails to clearly inform strategic business decisions regarding adoption decision-making. This research study conducted in the Australian context queries established theoretical frameworks by asking the question; what theoretical foundations do influence the social media adoption by the intended audience of communication?

The construction of power in family medicine bedside teaching: a video observation study

INTRODUCTION: Bedside teaching is essential for helping students develop skills, reasoning and professionalism, and involves the learning triad of student, patient and clinical teacher. Although current rhetoric espouses the sharing of power, the medical workplace is imbued with power asymmetries. Power is context-specific and although previous research has explored some elements of the enactment and resistance of power within bedside teaching, this exploration has been conducted within hospital rather than general practice settings. Furthermore, previous research has employed audio-recorded rather than video-recorded observation and has therefore focused on language and para-language at the expense of non-verbal communication and human-material interaction. METHODS: A qualitative design was adopted employing video- and audio-recorded observations of seven bedside teaching encounters (BTEs), followed by short individual interviews with students, patients and clinical teachers. Thematic and discourse analyses of BTEs were conducted. RESULTS: Power is constructed by students, patients and clinical teachers throughout different BTE activities through the use of linguistic, para-linguistic and non-verbal communication. In terms of language, participants construct power through the use of questions, orders, advice, pronouns and medical/health belief talk. With reference to para-language, participants construct power through the use of interruption and laughter. In terms of non-verbal communication, participants construct power through physical positioning and the possession or control of medical materials such as the stethoscope. CONCLUSIONS: Using this paper as a trigger for discussion, we encourage students and clinical teachers to reflect critically on how their verbal and non-verbal communication constructs power in bedside teaching. Students and clinical teachers need to develop their awareness of what power is, how it can be constructed and shared, and what it means for the student-patient-doctor relationship within bedside teaching.

The monologic, power and mental illness

 This thesis considers the issue of the ‘Monologic, Power and Mental Illness’. Bakhtin’s concept of ‘Heteroglossia’, Foucault’s concept of ‘Subjectivation’, and the work of other writers in relation to mental illness are covered both in the Exegesis and throughout the creative component comprising excerpts from Kemp’s novella entitled, Haven.

Organizações culturais e (re)configuração do espaço: o caso do Istituto Europeo di Design, na cidade do Rio de Janeiro

O presente estudo tem como objetivo investigar de que maneira a possibilidade de instalação do Istituto Europeo di Design (IED) no bairro da Urca, na cidade do Rio de Janeiro, interfere na (re)configuração do espaço. Para o estudo desse processo adotou-se o conceito de espaço definido por Milton Santos, que o caracteriza como um conjunto indissociável de sistemas de objetos e ações, considerando necessária sua análise numa perspectiva histórica. Para ampliação das considerações sobre poder, identificação e caracterização dos atores sociais e das relações entre eles estabelecidas foram utilizados conceitos propostos por Carlos Matus para a análise da realidade social. A pesquisa de campo, de natureza qualitativa, coletou dados secundários a partir de notícias sobre o processo de revitalização do antigo Cassino da Urca e instalação do Istituto Europeo di Design no local, publicadas em jornais e revistas impressos, jornais on line e blogs, assim como dados primários, a partir de observação não estruturada das instalações ao redor do prédio do antigo Cassino da Urca, participação em reuniões da associação de bairro e entrevistas semi-estruturadas com representantes de organizações envolvidas no processo. Para o tratamento dos dados coletados, realizou-se análise argumentativa e interpretativa a partir da teoria utilizada. Com base nas notícias e documentos consultados, foi definido o período de análise, desde a cessão do prédio do antigo Cassino da Urca ao IED, em agosto de 2006, até o anúncio de parceria com outra organização, pelo instituto, em maio de 2012. O estudo permitiu identificar que a instalação do IED na Urca interferiu na configuração do espaço, principalmente no que se refere à formação e à atuação da associação de moradores do bairro, à instalação de novos empreendimentos comerciais no entorno do prédio já restaurado e, por consequência, na paisagem do bairro. Destaca-se também que a instalação do IED gerou mudanças que extrapolam os limites territoriais do bairro. Com base nos dados analisados, destaca-se que a relação de cooperação entre a Prefeitura Municipal do Rio de Janeiro e o IED foi estabelecida em torno da valorização por parte da Prefeitura do domínio de uma capacidade técnica pelo IED, nas áreas de atuação da organização, que são o ensino, pesquisa e consultoria nas áreas de arquitetura, design, moda e comunicação, o que reforça o argumento da valorização atual de organizações culturais no processo de (re)configuração do espaço urbano, quanto aos aspectos econômicos, simbólicos e sociais.

Por trás de links, sempre existem pessoas: o anonimato como fator de pertencimento no uso de redes sociais on-line em projetos educacionais

The thesis investigated how social networks online that allows anonymous postings can be used by teachers and students to promote the meeting between the sexual education and the needs and expectations of young people face a crosscutting theme, remarkably a taboo. It needs teaching strategies more efficient than those traditionally defended. With this experience, found in a short course about sexuality and health, we sought to go beyond the use of social networks for social entertainment, showing they can be an field that favors the process of teaching and learning. The research was based on the convergence of the communication concepts from Paulo Frere and another from Jürgen Habermas, as well as the philosophical concepts of utopia, ideology and dialectic are interrelated not only among themselves, but also inside an education field. Methodologically in this thesis, we adopted the category of qualitative research; the method is a combination of case study with action research. The technique was the use of questionnaires, data collection was in attendance and the types of data were primary. Finally, we present, then, the idea the communication is not in the middle, but in the trusty relationship established between the interlocutors. In this way, we can think when a student has met their need to be able answer his questions about sex with their teacher through an online social network that allows anonymity and through which the student knows who responds is their teacher, but the teacher can not distinguish the identity of his students, this dialogic relationship serves to get claims of the validity that are characterized as potential communicative action

An Improved Parameterization Technique for the Continuation Power Flow

Continuation methods have been long used in P-V curve tracing due to their efficiency in the resolution of ill-conditioned cases, with close to singular Jacobian matrices, such as the maximum loading point of power systems. Several parameterization techniques have been proposed to avoid matrix singularity and successfully solve those cases. This paper presents a simple geometric parameterization technique to overcome the singularity of the Jacobian matrix by the addition of a line equations located at the plane determined by a bus voltage magnitude and the loading factor. This technique enlarges the set of voltage variables that can be used to whole P-V curve tracing, without ill-conditioning problems and no need of parameter changes. Simulation results, obtained for large realistic Brazilian and American power systems, show that the robustness and efficiency of the conventional power flow are not only preserved but also improved.

Improved geometric parameterisation techniques for continuation power flow

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Proposal of an alternative transmission line model for symmetrical and asymmetrical configurations

This article shows a transmission line model for simulation of fast and slow transients, applied to symmetrical or asymmetrical configurations. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents a practical procedure to model three-phase transmission lines directly in time domain, without the explicit or implicit use of inverse transforms. In three-phase representation, analysis modal techniques are applied to decouple the phases in their respective propagation modes, using a correction procedure to set a real and constant matrix for untransposed lines with or without vertical symmetry plane. The proposed methodology takes into account the frequency-dependent parameters of the line and in order to include this effect in the state matrices, a fitting procedure is applied. To verify the accuracy of the proposed state-space model in frequency domain, a simple methodology is described based on line distributed parameters and transfer function associated with input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust integration procedure to solve the state equations, enabling transient and steady-state simulations. The results obtained by the proposed methodology are compared with several established transmission line models in EMTP, taking into account an asymmetrical three-phase transmission line. The principal contribution of the proposed methodology is to handle a steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behavior, by a practical procedure applied directly in time domain for symmetrical or asymmetrical representations. (C) 2011 Elsevier Ltd. All rights reserved.

Proposal of a Transmission Line Model Based on Lumped Elements: An Analytic Solution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

GRAMMAR and COMMUNICATION IN PORTUGUESE AS A FOREIGN LANGUAGE A Study in the Context of Teletandem Interactions

This paper presents a study about the role of grammar in on-line interactions conducted in Portuguese and in English, between Brazilian and English-speaking interactants, with the aim of teaching Portuguese as a foreign language (PFL). The interactions occurred by means of chat and the MSN Messenger, and generated audio and video data for language analysis. Grammar is dealt with from two perspectives, an inductive and a deductive approach, so as to investigate the relevance of systematization of grammar rules in the process of learning PFL in teletandem interactions.