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Dynamic Wireless Charging of Electric Vehicles
Full text linkThis thesis deals with the Wireless Power Transfer (WPT) for the dynamic charging of Electric Vehicles (EVs). Dynamic WPT is an emerging technology that can accelerate the transition from conventional to electrical mobility. Dynamic Wireless Power Transfer Systems (WPTSs) exploit the principle of electromagnetic induction to power EVs during their motion without the need for a galvanic contact between the vehicles and a stationary supplying system. Since a portion of the power required by the EVs for the charging and for the propulsion is provided by an external grid, the size of the on-board batteries can be shrunk with the consequent benefits in terms of cost and weight of the EVs. An infrastructure of widespread public dynamic WPTSs can contribute to maintain the EVs always charged thus providing them with an ideal infinite range.
After a detailed introduction of the fundamental principles that govern the WPT technology and after a thorough description of a general WPTS, the focus of the thesis moves to dynamic WPTSs. The variations of the magnetic parameters caused by the EV movement make the study, the design, and the control of dynamic WPTSs very challenging. In the thesis, various dynamic WPTSs are studied under steady-state condition. This analysis shows that the LC compensation in the track side is particularly suited for such systems since it provides the track with the current source capability. This feature greatly simplifies the control and the power transfer regulation of dynamic WPTSs.
The attention of this thesis is focused mainly on the modeling and on the control of dynamic WPTSs. As regards the modeling, a novel method called Modulated Variable Laplace Transform (MVLT) is proposed. The method is used for the base band modeling of systems, such as dynamic WPTSs, where modulated quantities are involved. The accuracy of the MVLT is verified through the application of the method for the study of the dynamic of various circuits. In particular, MVLT method is adopted to find the dynamic model of an LC-compensated dynamic WPTS. With the aid of the obtained model the regulator that controls the track current of the system is designed. The performance of the regulator is tested by simulations, obtaining results in good agreement with the expected ones.
The thesis investigates also the dc/dc converter installed on-board the EVs responsible for the battery charging control. The operation of this converter is analyzed in conjunction with the type of compensating network used for the pickup. A novel topology for the pickup circuitry is proposed together with a new control strategy for the switch of the dc/dc converter. This topology allows for the pickup size reduction and it shows high performance in terms of efficiency.Questa tesi si occupa della tecnologia del trasferimento wireless di potenza (dall'inglese Wireless Power Transfer - WPT) per la ricarica dinamica dei Veicoli Elettrici (VE). Il trasferimento dinamico di potenza è una tecnologia innovativa che può accelerare la transizione da una mobilità convenzionale, basata su veicoli azionati da motore a combustione interna, verso una mobilità elettrica incentrata sui VE. I sistemi per il trasferimento wireless dinamico di potenza (dall'inglese Dynamic Wireless Power Transfer systems - DWPT systems) sfruttano il principio dell'induzione elettromagnetica per alimentare i VE mentre sono in movimento, senza la necessità di utilizzare un contatto galvanico tra i veicoli e un sistema di alimentazione stazionario. Poiché parte della potenza richiesta dai VE per la ricarica e per la propulsione è fornita da una rete elettrica esterna, le dimensioni delle batterie a bordo dei veicoli possono essere ridotte con i conseguenti benefici in termini di costo e peso dei VE. Una estesa infrastruttura di sistemi DWPT può contribuire a mantenere le batterie dei VE sempre cariche, consentendogli di avere un'autonomia idealmente illimitata.
Dopo una dettagliata introduzione dei principi fondamentali che governano la tecnologia WPT e dopo un'accurata descrizione di un sistema WPT generico, il fulcro della tesi si sposta verso i sistemi DWPT. Le variazioni dei parametri magnetici causate dal movimento dei VE rendono lo studio, il dimensionamento e il controllo dei sistemi DWPT molto impegnativo. In questa tesi, vari sistemi DWPT sono studiati in condizione di regime stazionario. Questa analisi mostra che la compensazione del track fatta con una rete LC è particolarmente adatta per tali sistemi poiché essa conferisce al track la caratteristica di generatore di corrente. Questa proprietà semplifica di molto il controllo e la regolazione della potenza nei sistemi DWPT.
L'attenzione di questa tesi è focalizzata principalmente sulla modellizzazione e sul controllo dei sistemi DWPT. Per quanto riguarda la modellizzazione, un nuovo metodo chiamato Modulated Variable Laplace Transform (MVLT) è presentato in questo lavoro. Questo metodo è usato per la modellizzazione dei sistemi, come ad esempio i sistemi DWPT, in cui sono coinvolte grandezze modulate. L'accuratezza del metodo MVLT è verificata attraverso la sua applicazione nello studio della dinamica di diversi circuiti. In particolare, il metodo MVLT è utilizzato per trovare il modello dinamico di un sistema DWPT in cui il track è compensato con una rete LC. Con l'ausilio del modello ottenuto viene progettato il regolatore che controlla la corrente del track del sistema. Le prestazioni di questo regolatore sono testate attraverso delle simulazioni, ottenendo risultati molto prossimi a quelli attesi.
Nella tesi è studiato anche il convertitore dc/dc installato a bordo dei VE responsabile del controllo del processo di ricarica. Il funzionamento di questo convertitore è analizzato in modo congiunto con il tipo di compensazione del pickup. Una nuova topologia di circuito per il pickup è proposta assieme ad una nuova strategia di controllo per il convertitore dc/dc. Questa topologia permette una riduzione delle dimensioni del pickup e mostra elevate prestazioni in termini di efficienza
A modified LCC-compensated pickup topology for dynamic wireless power transfer systems
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Modeling of the dynamics of a resonant wireless power transfer circuit
No full textThis paper deals with the modeling of the voltage and current dynamics in a resonant Wireless Power Transfer (WPT)
circuit in the view of their control. The high-frequency operation of the circuit calls for the selection of appropriate quantities to be
considered and for the development of specific methods to be used for describing their dynamics. In the paper, three methods
developed for this purpose are presented and discussed. They are the Generalized State-Space Averaging (GSSA), Laplace Phasor
Transform (LPT) and Modulated Variable Laplace Transform (MVLT) methods, where the latter one is here proposed.
Afterwards, the receiving circuit of a series-resonant WPT charger of an electric vehicle is picked up as a study case, and the
model of its dynamics is worked out by the three methods. At last, the accuracy of the resulting models is evaluated by checking their
step response against that of the study case as obtained by simulation
Optimization of the compensation networks for WPT systems
Full text linkPerformance of wireless power transfer systems are greatly influenced by the topology and the sizing of the compensation networks connected to the coils and number of design procedures have been proposed to optimize one or the other characteristic of the system acting on their parameters. This paper introduces a method base on an optimization algorithm to design the compensation networks with the objective of optimizing the power transfer efficiency and the amount of transferred power for a given supply voltage amplitude. The soundness of the method has been checked comparing the obtained results with those achieved analytically in the case of the simple SS compensation topology, and checking by means of amplitude Bode diagrams the outcomes relevant to more complex topologies
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
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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