Design of Ancillary Services for Battery Energy Storage Systems to Mitigate Voltage Unbalance in Power Distribution Networks

power system, voltage unbalance issues are expected to exacerbate. Single{phase connectedphotovoltaic (PV) panels may cause unequal three{phase power ows, resultingin unbalanced grid currents and voltages. In addition, the random charging behaviour ofPlug{in Hybrid Electric Vehicles (PHEVs) equipped with single{phase on{board chargersis expected to further contribute to voltage unbalance rise as the number of thesedevices grows. If voltage unbalance increases to unacceptable levels, it may have adverseeects on power system operation and on the equipment connected to it. Traditionally,the phase swapping technique has been deployed by distribution system operators forvoltage unbalance mitigation, while other mitigating techniques include the deploymentof power electronics-based devices. The majority of the devices reported in the literatureare based on three-phase congurations, including series and parallel active power lters,unied power quality conditioners (UPQCs), static synchronous compensators (STATCOMs)and, more recently, three-phase distributed generation (DG) inverters.This research proposes the use of single-phase battery energy storage systems (BESSs)for the provision of phase balancing services, which has been considered only in a few literatureworks, with most of these research papers focusing on three-phase BESSs. In thisthesis, a novel control strategy is proposed for single-phase BESS units to compensatevoltage unbalance by injecting both active and reactive power simultaneously. The proposedapproach is based on the coordinated operation of three independent single-phaseBESS inverters using local voltage and current measurements.Initially, a comprehensive literature review is performed with the following aims: arobust classication of the ancillary services currently oered by BESSs, harmonisation ofthe notation found in the literature for ancillary services, and identication of potentialfuture applications of BESSs to power grids with large number of Low Carbon Technologies(LCTs). Then, the eectiveness of the proposed voltage unbalance compensationmethod is validated in the simulation environment, where two realistic models of distributionsystems are developed. Next, the impact of increasing PV and EV penetrationlevels on voltage unbalance for a typical UK distribution system is assessed based on adeterministic approach. The control strategy is validated experimentally by carrying outHardware-In-The-Loop (HIL) tests. Finally, an equivalent model of the distribution systemand BESS inverter is derived, which allows to carry out a preliminary probabilisticstudy to cater for the uncertainties related to the location and size of the PVs and EVs,and to evaluate the voltage unbalance levels without and with the BESSs controlled toprovide voltage unbalance compensation.It is concluded that the proposed BESS control system may eectively reduce thevoltage unbalance levels under various loading and generating conditions

Cyclotomic Factors and LRS-Degeneracy

We present three new, practical algorithms for polynomials in $\mathbb{Z}[x]$: one to test if a polynomial is cyclotomic, one to determine which cyclotomic polynomials are factors, and one to determine whether the given polynomial is LRS-degenerate. A polynomial is ``LRS-degenerate'' iff it has two distinct roots $\alpha, \beta$ such that $\beta = \zeta \alpha$ for some root of unity $\zeta$. All three algorithms are based on ``intelligent brute force''. The first two produce the indexes of the cyclotomic polynomials; the third produces a list of degeneracy orders. The algorithms are implemented in CoCoALib

Battery Energy Storage Systems in the United Kingdom: A Review of Current State-of-the-Art and Future Applications

The number of battery energy storage systems (BESSs) installed in the United Kingdom and worldwide is growing rapidly due to a variety of factors, including technological improvements, reduced costs and the ability to provide various ancillary services. The aim of this paper is to carry out a comprehensive literature review on this technology, its applications in power systems and to identify potential future developments. At first, the main BESSs projects in the UK are presented and classified. The parameters provided for each project include rated power, battery technology and ancillary services provided, if any. In the next section, the most commonly deployed ancillary services are classified and described. At the same time, the nomenclature found in the literature is explained and harmonised. The second part of the paper focuses on future developments and research gaps: ancillary services that currently are not common but that are likely to be deployed more widely in the future will be described, and more general research topics related to the development of BESSs for power system applications will be outlined

Voltage Unbalance Mitigation by Novel Control of BESS Single–phase Inverters

A voltage unbalance compensation method usingthree single–phase battery energy storage systems (BESSs) isproposed in this paper. A novel control strategy based on orthogonalsignal generation is presented to regulate active and reactivepower injection from the BESS inverters. A modified version ofthe ’IEEE 13 node’ benchmark three–phase distribution system isbuilt in MATLAB / Simulink and three case studies are illustratedto verify the effectiveness of the proposed compensation method

CERN

As a team, we decided to elaborate on the CERN center for scientific research. We are going to refer to topics such as; the history of the institute, the countries that have participated in the foundation of CERN, the main projects that take place there and lastly the contribution of our country, Greece,  in the scientific research taking place there.

Optoelectronic properties of InAs GaAs columnar quantum dot laser diodes

In this thesis results are described with the aim of examining the optoelectronic properties of InAs/GaAs columnar quantum-dots and comparing them with those of more conventional self-assembled quantum-dots. The polarisation properties of a set of columnar quantum-dot samples — of varied aspect ratio and In compositional contrast between the rod-shaped dot and the surrounding 2-D layer — are studied. For this investigation a new method to obtain the ratio of the fundamental TE/TM optical response using edge photo-absorption spectroscopy is proposed, which corrects for the polarisation-dependent features of the experimental set-up. The method is verified by application to compressive and tensile strained InGaP quantum well structures, where the results are in agreement with known ratios of the band-edge matrix elements. When applied to columnar quantum-dot samples it is shown that the TE/TM optical response depends on the dot aspect ratio and the In compositional contrast. A polarisation-independent photo-absorption is illustrated for a columnar quantum-dot of an aspect ratio (dot's height over diameter) 3.51:1, which is desired for use in semiconductor optical amplifiers. For the columnar dot of an extremely high aspect ratio, 7.5:1, a room temperature TM-dominant polarisation lasing emission is observed. By studying the Quantum-Confined Stark Effect, a dramatic enhancement of the Stark shift amplitude is shown for columnar quantum-dot samples of an increased dot aspect ratio from 0.63:1 up to 1.12:1, which may have application in optical modulation/switching. For a higher aspect ratio columnar quantum-dot the shift of the band edge of the photo-absorption spectra is reduced dramatically and this has been attributed to an overall effect where the observable shift becomes the result of higher energy transitions, where their oscillator strength change very rapidly within the studied range of field. For the highest aspect ratio dot, i.e. of aspect ratio 10:1, there is no any observable shift.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

James Joyce: Η μεταφυσική του Finnegans Wake

Αν το Finnegans Wake συγκαταλέγεται στα δυσκολότερα έργα της παγκόσμιας λογοτεχνίας, αυτό οφείλεται τόσο στη μορφή όσο και στο περιεχόμενό του, καθώς ο Joyce επιχειρεί να φέρει σε επαφή διαφορετικούς πολιτισμούς, διαφορετικές γλώσσες, επιστήμες, τέχνες και κοσμοθεωρίες, αποδεικνύοντας έμπρακτα ότι η λογοτεχνία αποτελεί τον κατεξοχήν τόπο της ιεροποίησης της συνάντησης. Η παρούσα μελέτη επιθυμεί να υπογραμμίσει την επιτυχία του εγχειρήματος του Joyce, μέσω ενός δοκιμίου, το οποίο λαμβάνει υπόψιν του και συζητά τις θεμελιώδεις μεταφυσικές ιδέες του έργου, αναζητώντας ταυτοχρόνως τις ηθικές του προεκτάσεις, εντός ενός πλαισίου που δεν αγνοεί τις σύγχρονες συζητήσεις σε επιστήμες όπως είναι για παράδειγμα η θεωρία της λογοτεχνίας, η φιλοσοφία, η ιστορία, η φυσική και η βιολογία. Ως εκ τούτου, από τις μεταφυσικές προϋποθέσεις του Finnegans Wake, δηλαδή από τον Ηράκλειτο ως τον Vico, τον Bruno, τον Cusanus, τον Nietzsche και την κβαντική φυσική, θα οδηγηθούμε στις μορφές ζωής του Wittgenstein και τον είρωνα του Rorty, συνεπικουρούμενοι από στοχαστές και επιστήμονες σαν τον Barthes, τον Planck, τον Bergson τον Levinas και τον Adorno, για να διαπιστώσουμε ότι το επιχειρούμενο άνοιγμα εκ μέρους του Joyce, απαιτεί από τους αναγνώστες ένα παρόμοιο άνοιγμα και μια δημιουργικότητα του όντος που κατοικεί ποιητικά και που αναλαμβάνει την ευθύνη έναντι του άλλου και του εαυτού του.If Finnegans Wake is one of the toughest works of world literature, this is due both to its form and to its content, as Joyce attempts to bring together different cultures, different languages, sciences, arts and worldviews, proving in fact that literature is the place of the sacrament of the meeting. This study wishes to highlight the success of Joyce's project through an essay that takes into account and discusses the fundamental metaphysical ideas of the project while seeking its moral extensions within a context that does not ignore the contemporary discussions in sciences such as for example the theory of literature, philosophy, history, physics and biology. Therefore, from Finnegans Wake's metaphysical preconditions, from Heraclitus to Vico, Bruno, Cusanus, Nietzsche and quantum physics, we will lead to Wittgenstein's forms of life and Rorty's quipster, assisted by thinkers and scientists like Barthes, Planck, Bergson, Levinas, and Adorno to see that the attempted opening on Joyce's behalf requires readers to have a similar opening and a creativity of the entity that lives poetically and takes the responsibility over the other and himself

Optoelectronic properties of InAs GaAs columnar quantum dot laser diodes

In this thesis results are described with the aim of examining the optoelectronic properties of InAs/GaAs columnar quantum-dots and comparing them with those of more conventional self-assembled quantum-dots. The polarisation properties of a set of columnar quantum-dot samples — of varied aspect ratio and In compositional contrast between the rod-shaped dot and the surrounding 2-D layer — are studied. For this investigation a new method to obtain the ratio of the fundamental TE/TM optical response using edge photo-absorption spectroscopy is proposed, which corrects for the polarisation-dependent features of the experimental set-up. The method is verified by application to compressive and tensile strained InGaP quantum well structures, where the results are in agreement with known ratios of the band-edge matrix elements. When applied to columnar quantum-dot samples it is shown that the TE/TM optical response depends on the dot aspect ratio and the In compositional contrast. A polarisation-independent photo-absorption is illustrated for a columnar quantum-dot of an aspect ratio (dot's height over diameter) 3.51:1, which is desired for use in semiconductor optical amplifiers. For the columnar dot of an extremely high aspect ratio, 7.5:1, a room temperature TM-dominant polarisation lasing emission is observed. By studying the Quantum-Confined Stark Effect, a dramatic enhancement of the Stark shift amplitude is shown for columnar quantum-dot samples of an increased dot aspect ratio from 0.63:1 up to 1.12:1, which may have application in optical modulation/switching. For a higher aspect ratio columnar quantum-dot the shift of the band edge of the photo-absorption spectra is reduced dramatically and this has been attributed to an overall effect where the observable shift becomes the result of higher energy transitions, where their oscillator strength change very rapidly within the studied range of field. For the highest aspect ratio dot, i.e. of aspect ratio 10:1, there is no any observable shift