Stability analysis of a grid-connected VSC controlled by SPC

In the near future a large part of traditional generation based on conventional synchronous machines (SM) will be replaced by renewable generation based on voltage source converters (VSC). In this sense, power system operators have begun to demand VSC-based power plants be able to participate in the frequency and voltage regulation, and are also interested in services like inertia emulation and damping of power oscillation, functions that today are carried out by large synchronous generators. Therefore, several studies have suggested new ways to control voltage source converters, that try to emulate the behavior of synchronous generators and are known generically as Virtual Synchronous Machines. The synchronous power controller (SPC) is a flexible solution that emulates the classical swing equation of a synchronous machine and improves its response. The SPC inherits the advantages of conventional synchronous generators, while it fixes many of its drawbacks. In this work, a sensitivity analysis of a VSC connected to the grid and controlled by SPC is performed. In this sense, a non-linear mathematical model of the system is first developed. This non-linear model is then linearized, obtaining a linear model from which the eigenvalues and sensitivities of the system to some relevant parameters are calculated. Finally, time-domain simulations are performed to confirm the results of the sensitivity analysis.Postprint (author's final draft

Virtual digital libraries

Digital libraries represent the meeting places for knowledge providers and knowledge consumers supporting and enhancing the process through which knowledge is created, used, and discovered. The demand for digital libraries is worldwide strong. These complex systems can offer a richer set of functionality than that initially expected and are able to transform the way in which joint research is conducted, thus responding to the requirements of a great number of research communities. In fact, nowadays research is a collaborative and multidisciplinary effort conducted by virtual research organisations whose components are spread worldwide. Despite this large and innovative demand the current digital library development models remain unchanged and so they are not able to match the emerging requirements. In this dissertation we propose a novel approach based on virtual digital libraries, i. e. digital libraries built by dynamically aggregating and appropriately presenting the pool of shared resources needed to fulfil the requirements of digital library communities. To support such an approach we introduced (i ) a reference model for understanding significant relationships among the components of digital libraries and for developing consistent services that support them and (ii ) a set of approaches and services able to provide virtual views over the heterogeneous information space resulting from reusing shared information sources. In particular, three approaches to information space virtualization are presented that provide profitable usage of the shared resources: information objects virtualization, collections virtualization, and distributed semantic search

A workflow language for research e-infrastructures

AbstractResearch e-infrastructures are "systems of systems," patchworks of resources such as tools and services, which change over time to address the evolving needs of the scientific process. In such environments, researchers carry out their scientific process in terms of sequences of actions that mainly include invocation of web services, user interaction with web applications, user download and use of shared software libraries/tools. The resulting workflows are intended to generate new research products (articles, datasets, methods, etc.) out of existing ones. Sharing a digital and executable representation of such workflows with other scientists would enforce Open Science publishing principles of "reproducibility of science" and "transparent assessment of science." This work presents HyWare, a language and execution platform capable of representing scientific processes in highly heterogeneous research e-infrastructures in terms of so-called hybrid workflows. Hybrid workflows can express sequences of "manually executable actions," i.e., formal descriptions guiding users to repeat a reasoning, protocol or manual procedure, and "machine-executable actions," i.e., encoding of the automated execution of one (or more) web services. An HyWare execution platform enables scientists to (i) create and share workflows out of a given action set (as defined by the users to match e-infrastructure needs) and (ii) execute hybrid workflows making sure input/output of the actions flow properly across manual and automated actions. The HyWare language and platform can be implemented as an extension of well-known workflow languages and platforms

Influence of the ICFF decoupling technique on the stability of the current control loop of a grid-tied VSC

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The control scheme of grid-tied converters is often implemented in the dq-frame due to simplicity of design. However, with this transformation, there exists an inherent cross-coupling term between the d-and q-channels which is often compensated for by using a feed-forward term in the current-control loop. It is shown, by applying the generalized Nyquist criterion (GNC) to the dq-frame ac impedance of the converter, that the inclusion of this decoupling term, in fact, degrades the stability of the controller when increasing the bandwidth of the synchronous reference frame phase-locked loop (SRF-PLL). Harware-in-the-loop (HIL) experiments are also conducted and verify these results.Peer ReviewedPostprint (author's final draft

From research data repositories to virtual research environments: a case study from the Humanities

The difference in scholarly practices between the sciences and the mainstream humanities is highlighted in a study (Palmer et al., 2009), which investigated the types of information source materials used in different humanities disciplines, based on results contained in the US Research Libraries Group (RLG) reports. Structured data is relatively little used, except in some areas of historical research, and data as it is traditionally understood in the sciences, i.e. the results of measurements and the lowest level of abstraction for the generation of scientific knowledge, even less so. It is true that the study is partly outdated, containing results from the early 1990s, and that data in the traditional sense is becoming increasingly important in the humanities, particularly for disciplines such as linguistics and archaeology in which scientific techniques have been widely adopted. Nevertheless, it is clear that in general humanities research relies not on measurements as a source of authority, but rather on the provenance of sources and assessment by peers, and that what data repositories are for the sciences, archives are for the humanities. [...

From research data repositories to virtual research environments: a case study from the Humanities

The difference in scholarly practices between the sciences and the mainstream humanities is highlighted in a study (Palmer et al., 2009), which investigated the types of information source materials used in different humanities disciplines, based on results contained in the US Research Libraries Group (RLG) reports. Structured data is relatively little used, except in some areas of historical research, and data as it is traditionally understood in the sciences, i.e. the results of measurements and the lowest level of abstraction for the generation of scientific knowledge, even less so. It is true that the study is partly outdated, containing results from the early 1990s, and that data in the traditional sense is becoming increasingly important in the humanities, particularly for disciplines such as linguistics and archaeology in which scientific techniques have been widely adopted. Nevertheless, it is clear that in general humanities research relies not on measurements as a source of authority, but rather on the provenance of sources and assessment by peers, and that what data repositories are for the sciences, archives are for the humanities. [...

Evaluation and Management of Patients with Methomyl Poisoning – A Case Report

The Apulian Poison Centre (PC) of Foggia, Italy, annually manages numerous consultations concerning certain or suspected poisonings from pesticides, starting at the same time a careful activity related to the risk assessment phase. The management of the exposure to pesticides and to other chemicals, and the alerting of the “National center for chemicals, cosmetics and consumer protection” at the Istituto Superiore di Sanità (ISS), actively contributes to the improvement of products quality and safety. Thus, leading to a reduction in the number of intoxications - and therefore of the accesses to the emergency services - allows greater protection for workers, bystanders, residents and consumers. The reported case of methomyl poisoning has been of fundamental importance both from the medical point of view and for the management of the intoxicated patient, both for the risk assessment actions, and for cooperation with the competent authorities, generating discussion points on the regulations in force between PCs and National Competent Authority. It follows that the feedback of intoxication in an emergency can lead to improvements in the management and risk mitigation measures in order to reach a greater protection of human, animal, and environmental health. In addition, the regulatory feedback deriving from these reports is an input to the increase product quality improvement (mixtures, labels, packaging, and risk communication) leading to a greater protection of potential exposed subjects. The importance of creating an information and management network that allows the optimization of the flow of information deriving from PCs arises. The actions taken are therefore described, both relating to the management of the emergency, and relating to the subsequent information flow and to the measures for containing the consequent risks

DL.org Digital Library Conformance Checklist

This work has been partially supported by DL.org (December 2008-February 2011), a Coordination and support action, received funding from the Commission of the European Union (EC) under the 7th Framework Programme ICT Thematic Area “Digital libraries and technology-enhanced learning” through the EC’s Cultural Heritage and Technology Enhanced Learning Unit

Species distribution modeling in the cloud

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