1,720,966 research outputs found
Advanced Primary Controllers for Inverter Based Power Sources: Microgrids and Wind Power Plants
No full textThe aim of this doctoral thesis is to present the research activity fulfilled during the Ph.D. studies.
The research project of the candidate was focused on two main cores.
The first core is centred in the microgrid area; in particular in islanded microgrid modelling and control. Firstly, the model was compared with experimental results collected in some facilities available at University of Genoa. Then traditional controllers for islanded microgrid are analysed and explored, proposing a new stability estimation procedure for droop controlled microgrid. Finally, a new control strategy based on Model Predictive Control (MPC) is proposed in order to collect many functionalities in just one control layer. MPC is widely used in MG environment, but just for power and energy management at tertiary level; instead here it is here proposed with an inedited use. Some experimental validations about this new methodology are obtained during a research period in Serbia and Denmark.
The second core is related with synthetic inertia for wind turbine connected to the main grid, i.e. frequency support during under-frequency transients. This aspect is very important today because it represents a way to increase grid stability in low inertia power systems. The importance of this feature is shared by all the most important Transmitter System Operators (TSO) all over the world
Measurement campaign and experimental results of an islanded microgrid
No full textMicrogrids (MGs) represent surely the most challenging topic in electrical engineering, promising the decreasing of carbonization, the totally integration of different renewable sources and a cheap solution for those rural areas where electric distribution is economically unsustainable. The most important feature of a MG is represented by the possibility to work in islanded configuration in order to satisfy its own load without the support of the main grid. Literature is poor of experimental results on islanded MG and the research has focused on theoretical approaches on several topics, such as frequency, voltage stability, modeling, software simulations and energy management systems. The purpose of this article is to provide some experimental results such as power supply, voltage and frequency measurement during islanded operation. This test campaign was performed in the Smart Polygeneration Microgrid, a test tool of University of Genova created for experimental validation for grid-connected and islanded MG operation
A new method to evaluate the stability of a droop controlled micro grid
No full textThe increasing interest in Microgrids (MGs) leads to the research of more efficient control methods and claims for new methods to assess the obtained working points stability. As the majority of renewable sources are connected to the MG by means of power electronic converters, it is often impossible to replicate some of the concepts, tools and control philosophies commonly used in traditional networks. One of the more frequent control methods in literature is the droop philosophy, whose stability issues have been deeply investigated. In order to evaluate the stability of a droop controlled MG, the present paper presents a new method, whose main advantage is the reduction of the computational effort that reflects in benefits for PLC and control hardware implementation. Simulation tests for validating the suggested technique are provided highlighting its good performances
A simplified first harmonic model for the Savona Campus Smart Polygeneration Microgrid
No full textMicrogrids (MGs) may represent a new answer to many old problems in energy and electric world, such as pollution, high reliability, efficiency and so on. The MG rapid increase implies a fast transformation of the electric power systems that are now characterized by new energy sources requiring dedicated control architectures and simulation tools. Unfortunately, the majority of such new sources are connected to the MG by means of power electronic converters that often make it impossible to replicate some of the concepts, tools and control philosophies commonly used in traditional networks. For this reason, there is a strong need of developing models for MG structures that can be reliable but sufficiently simple to be used for the control system design. In this framework, this paper presents a simplified first harmonic model for the Smart Polygeneration Microgrid (SPM) located in the Savona Campus of the University of Genoa that allows the interface with many controllers. The developed simplified model is validated comparing it with a complete simulation performed in the PSCAD-EMTDC environment that allows to represent each component with a high level of detail
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Habitat ecological integrity and environmental impact assessment of anthropic activities: A GIS-based fuzzy logic model for sites of high biodiversity conservation interest
No full textIn literature, an effective method enabling the classification, based on a single indicator, of habitats that need a priority protection intervention has not been identified yet. Moreover, the excessive number of landscape metrics, used to quantify integrity of habitats, can cause confusion, often providing redundant and inconsistent results. The aim of this work is to develop a method for evaluating the ecological vulnerability of the habitats in sites of high biodiversity conservation interest. In the first phase, we selected and analyzed, by using principal component analysis (PCA) and fuzzy logic, the landscape metrics, in order to obtain the map of the intrinsic ecological vulnerability index. In the second step, the result of this intrinsic vulnerability was connected, through another fuzzy model, to anthropogenic impacts, obtaining the integrated ecological vulnerability index. We developed specific spatial indicators (landscape metrics), which can examine the mutual position and morphology of the habitats present, along with indicators of human pressure, related to the type and intensity of use of the anthropic territory, with reference to the habitat itself as well as to the areas immediately adjacent. The developed fuzzy models are innovative, compared to the current ecological studies, and examine landscape metrics as well as the impact of human activities. The case study is the "Val Basento-Ferrandina Scalo" Site of Community Importance, Ferrandina-SCI (Basilicata Region, Southern Italy). The results allowed us to build a rank of the habitats based on their intrinsic and integrated ecological vulnerability. Moreover, the results show that, in the Ferrandina-SCI, the most important source of concern is not human activities, but rather the inherent risk of ecological fragility caused by geographical and landscape features of the different patches of habitats themselves. This model aims to be a tool for decision support in sustainable landscape management. It is easy to use and to apply on other regions, although it should always be accompanied by a sensitivity analysis to reduce the subjectivity
ITER Fast Discharging Units: A Black Box Model Approach for Circuital Simulations
No full textNuclear fusion represents in the current century one of the most important challenges in the energy field. Achieving such an important goal will completely change the energy scenario and it will reduce the current dependency on fossil fuels with a sustainable alternative. In this framework, ITER project represents the most advanced project for nuclear fusion all over the world. However, challenges related to the physics of the plasma and many others related to various fields of engineering need to be faced in order to accomplish the ITER project development. In particular, one is the need for the
definition of suitable discharging units able to de-energise the superconductive coil power supply when necessary. This paper deals with the application of arc models available in the literature to support the definition of a suitable layout for the previously mentioned Fast Discharging Units. This can be achieved firstly by defining a procedure to identify the optimal parameters of the so-called “Black Box Arc Models” in order to fit the experimental
oscillograms provided by circuit breakers producers and secondly by implementing it on a circuital simulator in order to define the compliance of the discharging unit with the coil insulation limits
Wastewater reuse for irrigation of energy crops: CO2 balance in simplified treatment schemes
No full textThe objective of this study was the assessment of environmental sustainability of urban wastewater reuse for irrigation of energy crops, by carrying out the balance of CO2 emissions in biological wastewater treatment plants (WWTPs). The proposed innovative scheme is able to
remove pathogens and dangerous components for the environment, but it is able to release nutrients useful for fertigation of energy crops. Moreover, it has a significant operational flexibility, which is guaranteed by the possibility of gradually changing the plant configuration
passing from the configuration for irrigation of energy crops to that for discharge into receiving water bodies. The innovative feature of this research is the assessment of the budget of climatechanging
greenhouse gas emissions (GHG) caused by the simplified treatment for controlled release and reuse of reclaimed wastewater. Numerical simulations were carried out by implementing the ASM1 model. The stoichiometric matrix of the ASM1 model was modified, in order to obtain equivalent emissions of greenhouse gases directly from the mass balance equations.
The developed model is able to perform a continuous monitoring of equivalent CO2 emissions from WWTPs. The aim is to assess the evolution of GHG due to changes of possible adopted
treatment schemes, and to estimate the amount of emissions. The new controlled-release scheme produces wastewater with high concentrations of fertilizers and nutrients, such as stabilized
nitrogen and organic matter, but, at the same time, it minimizes risks for the environment, by reducing the total emissions of equivalent CO2
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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