Dissertations / Theses on the topic 'Wireless Power Transfer, Electric Vehicle, Power Electronics'

Wireless power transfer is a method of transferring electric power from a transmitter to a receiver without requiring any physical connection between the two. Dynamic Wireless Power Transfer (DWPT) entails having the transmitters buried under the roadway and the receiver unit being installed on the Electric Vehicle (EV). In this method, EVs are charged while driving over the transmitters as they receive bursts of electric energy at the time of significant alignment between transmitters and receivers. Compared to the stationary charging method which involves parking the EV for long hours for a full charge, the dynamic charging method (i.e., DWPT) offers convenience as the vehicle gets charged while driving. It also facilitates extended driving range of EVs. Despite offering these advantages, DWPT causes a few significant issues. DWPT charging results in a transient power profile both at grid side and EV side, which not only hampers grid-side regulation but also affects EV-battery longevity. To address these two issues, both grid-side and EV-side energy management are needed to be employed to protect the grid and the vehicle from sudden exposure to harmful power transients. In this dissertation, the grid-side and EV-side energy management methods have been investigated. Firstly, a detection system to safely detect the vehicle on charging lane is proposed. This detection system is used to facilitate safe and efficient operation of DWPT chargers on EV roadways. Secondly, A novel DWPT system is proposed, which reduces the grid-side power transients with minimal additional hardware requirements. Finally, an EV-side energy management system is proposed which reduces the exposure of EV batteries to pulsating DPWT-power, thereby helping batteries to last longer.

Contactless Electric Vehicle (EV) charging based on magnetic resonant induction is an emerging technology that can revolutionize the future of the EV industry and transportation systems by enabling an automated and convenient charging process. However, in order to make this technology an acceptable alternative for conventional plug-in charging systems it needs to be optimized for different design measures. Specifically, the efficiency of an inductive EV charging system is of a great importance and should be comparable to the efficiency of conventional plug-in EV chargers. The aim of this study is to develop solutions that contribute to the design enhancement of inductive EV charging systems. Specifically, generalized physics-based design optimization methods that address the trade-off problem between several key objectives including efficiency, power density, misalignment tolerance, and cost efficiency considering critical constraints are developed. Using the developed design methodology, a 3.7kW inductive charging system with square magnetic structures is investigated as a case study and a prototype is built to validate the optimization results. The developed prototype achieves 93.65% efficiency (DC-to-DC) and a power density of 1.65kW/dm3. Also, self-tuning power transfer control methods with resonance frequency tracking capability and bidirectional power transfer control are presented. The proposed control methods enhance the efficiency of power converters and reduce the Electromagnetic Interference (EMI) by enabling soft-switching operations. Several simplified digital controllers are developed and experimentally implemented. The controllers are implemented without the use of DSP/FPGA solutions. Experimental tests show that of the developed simplified controllers can effectively regulate the power transfer around the desired value. Moreover, the experiments show that compared to conventional converters, the developed converters can achieve 4% higher efficiency at low power levels. Moreover, enhanced matrix converter topologies that can achieve bidirectional power transfer and high efficiency with a reduced number of switching elements are introduced. The self-tuning controllers are utilized to design and develop control schemes for bidirectional power transfer regulation. The simulation analyses and experimental results show that the developed matrix converters can effectively establish bidirectional power transfer at the desired power levels with soft-switching operations and resonance frequency tracking capability. Specifically, a direct three-phase AC-AC matrix converter with a reduced number of switches (only seven) is developed and built. It is shown that the developed converters can achieve efficiencies as high as 98.54% at high power levels and outperform conventional two-stage converters.

As electric vehicles (EVs) become more popular, the utility companies are forced to increase power generations in the grid. However, these EVs are capable of providing power to the grid to deliver different grid ancillary services in a concept known as vehicle-to-grid (V2G) and grid-to-vehicle (G2V), in which the EV can serve as a load or source at the same time. These services can provide more benefits when they are integrated with Photovoltaic (PV) generation. The proper modeling, design and control for the power conversion systems that provide the optimum integration among the EVs, PV generations and grid are investigated in this thesis. The coupling between the PV generation and integration bus is accomplished through a unidirectional converter. Precise dynamic and small-signal models for the grid-connected PV power system are developed and utilized to predict the system’s performance during the different operating conditions. An advanced intelligent maximum power point tracker based on fuzzy logic control is developed and designed using a mix between the analytical model and genetic algorithm optimization. The EV is connected to the integration bus through a bidirectional inductive wireless power transfer system (BIWPTS), which allows the EV to be charged and discharged wirelessly during the long-term parking, transient stops and movement. Accurate analytical and physics-based models for the BIWPTS are developed and utilized to forecast its performance, and novel practical limitations for the active and reactive power-flow during G2V and V2G operations are stated. A comparative and assessment analysis for the different compensation topologies in the symmetrical BIWPTS was performed based on analytical, simulation and experimental data. Also, a magnetic design optimization for the double-D power pad based on finite-element analysis is achieved. The nonlinearities in the BIWPTS due to the magnetic material and the high-frequency components are investigated rely on a physics-based co-simulation platform. Also, a novel two-layer predictive power-flow controller that manages the bidirectional power-flow between the EV and grid is developed, implemented and tested. In addition, the feasibility of deploying the quasi-dynamic wireless power transfer technology on the road to charge the EV during the transient stops at the traffic signals is proven.

Wireless Power Transfer (WPT) systems transfer electric energy from a source to a load without any wired connection. WPTs are attractive for many industrial applications because of their advantages compared to the wired counterpart, such as no exposed wires, ease of charging, and fearless transmission of power in adverse environmental conditions. Adoption of WPTs to charge the on-board batteries of an electric vehicle (EV) has got attention from some companies, and efforts are being made for development and improvement of the various associated topologies. WPT is achieved through the affordable inductive coupling between two coils termed as transmitter and receiver coil. In EV charging applications, transmitter coils are buried in the road and receiver coils are placed in the vehicle. Inductive WPT of resonant type is commonly used for medium-high power transfer applications like EV charging because it exhibits a greater efficiency. This thesis refers to a WPT system to charge the on-board batteries of an electric city-car considered as a study case. The electric city-car uses four series connected 12V, 100A•h VRLA batteries and two in-wheel motors fitted in the rear wheels, each of them able to develop a peak power of 4 kW to propel the car. The work done has been carried out mainly in three different stages; at first an overview on the wired EV battery chargers and the charging methodologies was carried out. Afterwards, background of different WPT technologies are discussed; a full set of Figures of Merit (FOM) have been defined and are used to characterize the resonant WPTs to the variations in resistive load and coupling coefficient. In the second stage, the WPT system for the study case has been designed. In the third stage, a prototypal of the WPT system has been developed and tested. Design of the WPT system is started by assessing the parameters of the various sections and by estimating the impact of the parameters of the system on its performance. The design process of the coil-coupling has come after an analysis of different structures for the windings, namely helix and spiral, and different shapes for the magnetic core; further to the preliminary results that have shown the advantages of the spiral structure, a more detailed analysis has then been executed on this structure. The coil design has encompassed the determination of the inductive parameters of the two-coil coupling as a function of the coil distance and axial misalignment. Both the analysis and the design was assisted by a FEM-approach based on the COMSOL code. Design of the power supply stages of the WPT system has consisted of the assessment of values and ratings of a) the capacitors that make resonant the coil-coupling, b) the power devices of the PFC rectifier and of the high frequency inverter (HF) that feeds the transmitting coil, c) the power devices of the converters supplied by the receiver coil: the rectifier diode and the in-cascade chopper that feeds the battery in a controlled way. For the converters that operate at high frequency (inverter and the rectifier in the receiver section), power electronic devices of the latest generation (the so-called Wide Band Gap (WBG) devices) have been used in order to maximize the efficiency of the WPT system. A prototypal WPT battery charger was arranged by using available cards with the power and signal circuits. Relevant experimental activities were: a) measurement of the parameters of the coils, b) desk assembling of the prototype, and c) conducting tests to verify proper operation of the prototype. The thesis work includes also a brief overview of i) emerging topics on WPT systems such as on-line electric vehicle (OLEV), ii) shielding of the magnetic fields produced by a WPT system, and iii) standards on WPT operation. These three issues play a significant role in the advancement of the WPT technology. The thesis work has been carried out at the Laboratory of “Electric systems for automation and automotive” headed by Prof. Giuseppe Buja. The laboratory belongs to the Department of Industrial Engineering of the University of Padova, Italy.<br>I sistemi per il trasferimento di potenza wireless (WPT) trasferiscono energia elettrica da una sorgente ad un carico senza alcuna connessione via cavo. I sistemi WPT sono attraenti per molte applicazioni industriali grazie ai loro vantaggi rispetto alla controparte cablata, come l’assenza di conduttori esposti, la facilità di ricarica e la trasmissione senza rischi della potenza in condizioni ambientali avverse. L’adozione di sistemi WPT per la carica delle batterie di bordo di un veicolo elettrico (EV) ha ricevuto l'attenzione di alcune aziende, e sforzi sono stati fatti per lo sviluppo e il miglioramento delle varie topologie ad essi associate. Il WPT è ottenuto tramite l'accoppiamento induttivo tra due bobine, definite bobina trasmittente e bobina ricevente. Nelle applicazioni per la carica delle batterie, le bobine trasmittenti sono installate sotto il manto stradale mentre le bobine riceventi sono poste a bordo del veicolo. Il WPT induttivo di tipo risonante è comunemente utilizzato nelle applicazioni per il trasferimento di potenze medio-alte, come la carica degli EV, perché presenta una maggiore efficienza. Questa tesi tratta un sistema WPT per caricare le batterie di bordo di una city-car elettrica considerato come caso di studio. La city-car elettrica utilizza quattro batterie da 12V, 100A•h VRLA collegate in serie e due motori-ruota montati sull’assale posteriore, ognuno in grado di sviluppare una potenza di picco di 4 kW per la propulsione del veicolo. Il lavoro svolto è stato effettuato principalmente in tre fasi diverse; in un primo momento è stata effettuata una panoramica sui caricabatteria cablati per EV e sulle metodologie di ricarica. Successivamente, sono stati discussi i principi base di diverse tecnologie WPT; è stato definito un insieme di figure di merito (FOM) che sono state utilizzate per caratterizzare il comportamento dei WPT risonanti rispetto alle variazioni di carico resistivo e al coefficiente di accoppiamento. Nella seconda fase, è stato progettato il sistema WPT per il caso di studio. Nella terza fase, è stato sviluppato e sperimentato un prototipo del sistema WPT. La progettazione del sistema WPT è stata iniziata con una valutazione dei parametri delle varie sezioni e stimando l'impatto dei parametri del sistema sulle sue prestazioni. La progettazione della bobina di accoppiamento è stata effettuata dopo l'analisi di avvolgimenti con strutture diverse, ovvero elica e spirale, e con forme differenti del nucleo magnetico; a seguito dei risultati preliminari che hanno mostrato i vantaggi della struttura a spirale, è stata poi eseguita un'analisi più dettagliata su questa struttura. Il progetto della bobina ha compreso la determinazione dei parametri induttivi dell’accoppiamento in funzione della distanza e del disallineamento assiale delle bobine. Sia l'analisi che la progettazione sono state assistite da un approccio FEM basato sul codice COMSOL. La progettazione degli stadi di alimentazione del sistema WPT è consistita nella valutazione dei valori e dei dati di targa di a) i condensatori che rendono risonante l’accoppiamento tra le bobine, b) i dispositivi di potenza del raddrizzatore PFC e dell'inverter ad alta frequenza (HF) che alimenta la bobina di trasmissione, c) i dispositivi di potenza dei convertitori alimentati dalla bobina ricevente, segnatamente il raddrizzatore a diodi e il chopper collegato a valle che carica la batteria in modo controllato. Per i convertitori che operano ad alta frequenza (l’invertitore e il raddrizzatore della sezione ricevente), sono stati utilizzati dispositivi elettronici di potenza di ultima generazione (i cosiddetti dispositivi Wide Band Gap (WBG)) al fine di massimizzare l'efficienza del sistema WPT. E’ stato realizzato un caricabatteria WPT prototipale utilizzando schede elettroniche disponibili in Laboratorio con i circuiti di potenza e di segnale. Le relative attività sperimentali sono state: a) misurazione dei parametri delle bobine, b) assemblaggio a banco del prototipo, e c) esecuzione di prove sperimentali per verificare il corretto funzionamento del prototipo. Il lavoro di tesi comprende anche una breve panoramica su temi emergenti in materia di sistemi WPT come i) IL WPT dinamico, chiamato anche “on-line electric vehicle” (OLEV), ii) la schermatura dei campi magnetici prodotti da un sistema WPT, e iii) la normativa sui sistemi WPT. Questi tre temi svolgono un ruolo significativo nello sviluppo della tecnologia WPT. Il lavoro di tesi è stato effettuato presso il Laboratorio di “Sistemi elettrici per l'automazione e la veicolistica” diretto dal Prof. Giuseppe Buja. Il Laboratorio fa parte del Dipartimento di Ingegneria Industriale dell'Università degli Studi di Padova, Italia.

In the years 1884-1889, after Nicola Tesla invented "Tesla Coil", wireless power transfer (WPT) technology is in front of the world. WPT technologies can be categorized into three groups: inductive based WPT, magnetic resonate coupling (MRC) based WPT and electromagnetic radiation based WPT. MRC-WPT is advantageous with respect to its high safety and long transmission distance. Thus it plays an important role in the design of wireless electric vehicle (EV) charging systems. The most significant drawback of all WPT systems is the low efficiency of the energy transferred. Most losses happen during the transfer from coil to coil. This thesis proposes a novel coil design and adaptive hardware to improve power transfer efficiency (PTE) in magnetic resonant coupling WPT and mitigate coil misalignment, a crucial roadblock to the acceptance of WPT for EV. In addition, I do some analysis of multiple segmented transmitters design for dynamic wireless EVs charging and propose an adaptive renewable (wind) energy-powered dynamic wireless charging system for EV.

Wireless charging of electric vehicle (EV) batteries by inductive power transfer (IPT) offers unique advantages compared to conventional conductive chargers. Due to the absence of a galvanic connection, the charging process requires no user interaction and no moving of mechanical components. For public transport systems, e.g., public buses or tramways, this makes possible a fully automated opportunity charging at bus stations, taxicab stands, or traffic lights. The schematic of wireless battery charger (WBC) is made of two stages, one is transmitter stage and another one is receiver stage. Both the stages include coils and capacitors to resonate at the supply frequency along with power conversion circuits. The transmitter coil is buried in the ground while receiving coil is situated in the vehicle. Based on the connection of resonating capacitors four topologies are possible which can be divided into two arrangements i) transmitter capacitor in series while receiver capacitor is in either series or in parallel, giving rise to SS and SP topologies, ii) transmitting capacitor in parallel while receiving capacitor is in either series or in parallel, giving rise to PS and PP topologies. In the thesis, these topologies have been studied in detail in terms of efficiency, power sizing of supply inverter and resonating coils, behavior under the extreme condition of open and short circuit of the receiver. Power conversion circuitry of a WBC system includes a diode rectifier to supply the load with a direct voltage and resorts to different solutions for charging the battery. The two most used solutions are either in a straightforward manner through the diode rectifier or through a chopper in cascade to the diode rectifier. These two arrangements have been discussed and compared in terms of efficiency and power sizing of supply inverter and transmitting and receiving coil, including the selection of the optimum chopper input voltage. Due to aging and thermal effect, the parameters of the reactive components of a WBC system may change and this can deviates the resonance frequency from the supply frequency. In this thesis the impact of such mismatch on efficiency and supply inverter power sizing factor of WBC with SS topology has been studied. Three supply frequency updating techniques to keep in resonance either the transmitter stage or the receiver stage or the impedance seen from power supply have been investigated. The thesis continues with the study of high power WBC systems which includes power supply architecture, core material and coil geometry. A review of different power supply architectures such as single phase with two stage and parallel topologies including their merits and demerits have been presented. Reviewing some paper on coil geometry, DD coil is found to be suitable for high power application. Using JMAG simulation tool, a transmitter track of three DD coils and a receiver with one DD coil has been analyzed when receiver is moving on the transmitting track. Due to disfavor of ferrite as a core material for high-power WBC system, a varieties of different powdered magnetic materials have been considered here and compared in terms of saturated value of the magnetic flux density, magnetic properties -like dependency of their permeability on temperature, magnetic field strength and frequency-, power losses and cost. At last, two methods to model the WPT system have been considered. The methods model the system by considering the envelop of the signals.<br>La ricarica wireless delle batterie a bordo dei veicoli elettrici, ottenuta utilizzando il trasferimento di potenza induttivo, offre vantaggi unici rispetto ai caricabatterie tradizionali. A causa dell'assenza di una connessione galvanica, il processo di ricarica non richiede alcuna interazione dell'utente né alcuna movimentazione di un componente meccanico. Per i sistemi di trasporto pubblico, ad esempio autobus o tram, questo rende possibile la cosiddetta carica di opportunità completamente automatizzata presso i depositi degli autobus, le corsie dei taxi, o ai semafori. I caricabatterie wireless sono costituiti da due stadi: uno stadio trasmittente e uno stadio di ricezione. Entrambi gli stadi includono bobine e condensatori, dimensionati per risuonare alla frequenza di alimentazione, e convertitori statici di potenza. La bobina del trasmettitore è interrata nel manto stradale, mentre la bobina ricevente è situata a bordo del veicolo. Sulla base della connessione dei condensatori risonanti sono possibili quattro topologie circuitali diverse che possono essere raggruppate in due principali: i) un condensatore in serie con la bobina di trasmissione con il condensatore lato ricevitore in serie o in parallelo costituisce le topologie SS e SP, rispettivamente, e ii) un condensatore in parallelo alla bobina di trasmissione con il condensatore della sezione ricevente in serie o in parallelo costituisce le topologie PS e PP, rispettivamente. Nella tesi queste topologie sono state studiate dettagliatamente in termini di efficienza, dimensionamento dell'invertitore di alimentazione e progetto delle bobine risonanti, e di comportamento nelle condizioni estreme di circuito aperto e di cortocircuito del ricevitore. Il circuito di conversione di potenza di un sistema per la ricarica wireless induttiva di un veicolo elettrico include un raddrizzatore a diodi nello stadio di ricezione per ottenere un bus di tensione in continua e utilizza differenti modi per caricare la batteria del veicolo. Le due soluzioni più diffuse eseguono la carica o direttamente attraverso il raddrizzatore a diodi oppure attraverso un chopper collegato in cascata ad esso. Queste due modalità sono state discusse e confrontate in termini di efficienza, di dimensionamento sia dell'invertitore di alimentazione, che delle bobine di trasmissione e ricezione, includendo nell’analisi la scelta della tensione ottima in ingresso al chopper. A causa dell'invecchiamento e dell'effetto termico, i parametri dei componenti reattivi di un circuito di ricarica wireless possono variare e questo fa sì che la frequenza di risonanza e la frequenza di alimentazione non siano perfettamente identiche. In questa tesi è stato studiato l'impatto che tale deviazione ha sull'efficienza e sul dimensionamento dell’invertitore in un sistema di ricarica wireless con topologia SS. Sono state studiate tre tecniche di adattamento della frequenza di alimentazione per mantenere in risonanza o lo stadio trasmittente o quello di ricezione oppure l’impedenza vista dall’alimentazione. La tesi prosegue con lo studio dei sistemi di ricarica wireless per elevate potenze che richiedono una specifica architettura di alimentazione, particolari materiali per la costruzione del nucleo magnetico, oltre ad una peculiare geometria delle bobine. E’ stata presentata una panoramica di diverse architetture di alimentazione come, ad esempio, le topologie monofase a due stadi e in parallelo, inclusi i loro pregi e svantaggi. Sulla base di un’accurata revisione della letteratura della geometria delle bobine, la geometria DD si è rivelata essere la più conveniente per le applicazioni di alta potenza. Utilizzando il codice agli elementi finiti JMAG, è stato simulato il comportamento di un sistema di ricarica wireless costituito da tre bobine di trasmissione e una bobina di ricezione, tutte di tipo DD. Poiché, date le sue caratteristiche, le ferriti non si prestano bene per sistemi ad alta potenza, sono state considerate altre tipologie di materiali magnetici. Sono state analizzate e confrontate diverse leghe amorfe in base all’induzione magnetica di saturazione, alle proprietà magnetiche, come la dipendenza della permeabilità dalla temperatura, dal campo magnetico applicato e dalla frequenza, alle perdite di potenza e al costo. Infine, sono stati considerati due metodi per modellizzare il WPT. I metodi modellizzano il sistema considerando l'inviluppo dei segnali.

Wireless battery charging (WBC) is an attracting solution to promote electric vehicles (EVs) in the market, which may provide superior charging infrastructure and unlimited driving range. The most suitable technique to implement WBC is inductive power transfer (IPT) with a coupling established between two distant coils, one buried into the road and another installed in EV, and the power transferred from the buried coil to that onboard EV through a high-frequency oscillating magnetic flux. WBC can be carried out with EV that is either standing (while parked) or moving (on the road); the two WBC modes are termed static wireless charging (SWC) and dynamic wireless charging (DWC), respectively. However, this thesis focusses on the DWC, where an IPT track is buried into the road whilst the coil onboard EV, commonly termed pickup, remains coupled with the track to get power while moving on the road. The in-moving vehicle charging has been researched and demonstrated by some institutes across the world using two possible track arrangements: stretched and lumped coil track. The former one is composed of a single elongated coil, much longer than the pickup size, and the later one is an arrangement of multiple coils placed one next to the other, the length of them being comparable to the pickup size. A lumped track permits activation/deactivation only of the coil interacting with a pickup. This ability is called segmentation and is very important for DWC to reduce the losses and to avoid exposing the people to electromagnetic radiations; therefore, a lumped track has been dealt with in this thesis. The contactless power transfer at large airgap is possible with high frequency (in kHz) and high-magnitude current supply of the track coils; as increasing supply frequency improves power transfer efficiency. Apart from the supply characteristics and the coil dimensions, power transfer capabilities of a the system depend upon the coupling properties of the coil pairs, thus a pair polarized coils (also called DD coils) has been found more suitable for DWC due to its coupling merits at misalignment. Considering a lumped track composed of equally distant several DD coils, power and energy transfer to an EV moving on the track have been analyzed. Based on that, lumped track layout and its design procedure have been discussed in detail with an example of an EV. Segmentation of a DWC track is very important function, as mentioned above, which can be obtained by various methods and one of them is using the impedance reflected into a track coil from the coupled pickup. In this way, four compensation topologies have been discussed to investigate their reflexive properties (resistance and reactance) when they are deployed in a pickup circuit. Summarizing the outcomes and comparing their behavior, two topologies have been found useful for the track segmentation. Considering them, further analysis has been done to obtain and discuss their performance figures. This thesis also discusses about the power converters in both track side and pickup side circuit. The track side power converters include rectifier, power factor correction circuit and inverter, which extract power from the supply grid and transform into the appropriate form to realize efficient WBC. Converter arrangement in the pickup circuit includes rectifier and chopper to charger a battery using the received power.<br>La ricarica della batteria senza fili (dall’inglese Wireless Battery Charging - WBC) è una soluzione attraente per la possibile diffusione dei Veicoli Elettrici (VE) nel mercato. Essa può fornire infrastrutture di ricarica migliori e un’ autonomia del veicolo praticamente illimitata. La tecnica più adatta per attuare il WBC è il trasferimento di potenza induttivo (Inductive Power Transfer - IPT), il quale sfrutta l’accoppiamento magnetico tra due bobine, una posizionata sotto il manto stradale e l’altra installata a bordo di un veicolo elettrico, e la potenza viene trasferita dalla bobina interrata a quella di bordo attraverso un flusso magnetico oscillante alta frequenza. Il WBC può essere effettuato con un VE fermo (parcheggiato) o in movimento sulla strada; le due modalità di WBC sono chiamate ricarica senza fili statica (Static Wireless Charging - SWC) e ricarica senza fili dinamica (Dynamic Wireless Charging - DWC), rispettivamente. Tuttavia, questa tesi si concentra sulla DWC, dove una bobina trasmittente, chiamata track, è interrata sotto la strada, mentre la bobina a bordo del VE, comunemente chiamata pickup, rimane accoppiata con il track per ricevere la potenza mentre il VE è in movimento. La ricarica di un VE in movimento è stata studiata e dimostrata da alcuni istituti di tutto il mondo i quali hanno adottato due differenti strutture di bobina trasmittente: track allungato e track concentrato. La prima struttura è formata da una singola bobina allungata, molto più lunga del pickup, mentre la seconda struttura è una disposizione di più bobine posizionate una dopo l’altra, la cui lunghezza è paragonabile alle dimensioni pickup. La struttura con track concentrato consente l'attivazione/disattivazione della sola bobina interagente con il pickup. Questa capacità è chiamata segmentazione ed è molto importante per DWC perché consente di ridurre le perdite e di evitare l'esposizione delle persone a radiazioni elettromagnetiche; di conseguenza, in questa tesi è stata trattata la soluzione con track concentrato. Il trasferimento della potenza senza fili con un elevato traferro è possibile solo con un’alta frequenza (dell’ordine dei kHz) ed un’alta intensità della corrente di alimentazione delle bobine del track; poiché l'aumento della frequenza di alimentazione migliora l'efficienza di trasferimento della potenza. Oltre alle caratteristiche di alimentazione e le dimensioni delle bobine, le capacità di trasferimento di potenza di un sistema dipendono dalle proprietà di accoppiamento delle bobine stesse, così una coppia di bobine polarizzate (chiamate anche bobine DD) è stata trovata essere la soluzione più adatta per il DWC grazie al suo elevato valore di accoppiamento quando track e pickup sono disallineati. Considerando un track concentrato composto da diverse bobine DD equamente distribuite, sono state analizzate la potenza e l’energia trasferite al VE in movimento. Sulla base di questo, la struttura del track concentrato e la sua procedura di progettazione sono stati discussi in dettaglio per un particolare caso di studio. Come detto precedentemente, la segmentazione del track è una funzione molto importante. Essa può essere ottenuta con vari metodi e uno di questi utilizza l'impedenza riflessa del pickup in una bobina del track. Così, quattro topologie di compensazione del circuito di pickup sono state investigate per studiarne le differenti impedenze riflesse. Riassumendo i risultati e confrontando il loro comportamento, solo due topologie sono state trovate utili per la segmentazione del track. Considerando quest’ultime, ulteriori analisi sono state fatte per ottenere e discutere le loro prestazioni. Questa tesi tratta anche i convertitori di potenza utilizzati sia nel track che nel pickup. I convertitori di potenza del track includono un raddrizzatore, un circuito di correzione del fattore di potenza (PFC) e un inverter, i quali sfruttano l’energia prodotta dalla rete di alimentazione e la convertono nella forma più appropriata per realizzare efficienti WBC. Nella bobina di pickup il circuito di condizionamento è formato dalla cascata di un raddrizzatore e un chopper che permettono di ricaricare la batteria di bordo utilizzando la potenza ricevuta.

This thesis is the result of the research work carried out as part of the PhD course in Energy and Information Technology between November 2019 and January 2023 at the University of Palermo jointly with the University of Lisbon. The research project has been focused on wireless charging systems for electric vehicles. A wide-ranging analysis was conducted on the topic, with a particular focus on the design aspects of these systems. This thesis, a summary of the work carried out over the previous three years, is organized into two parts, identifying the macro research activities into which the project was been divided. The first part is focused on the design approach of the Wireless Power Transfer systems, the second one on the energy storage system characterization and design. In each chapter, a basic overview of the subject matter has been firstly provided, resulting from the bibliographical analysis conducted in each phase of the project, followed by a more in-depth discussion of each topic. The majority of the conducted studies have an experimental nature; for this reason, together with the theoretical analysis carried out, the experimental results of the conducted research have been presented. In Chapter 1, the fundamentals of wireless power transmission are provided through the description of different technologies available in literature. In Chapter 2, resonant magnetic power transfer systems for electric vehicles charging are discussed. In particular, each element of such systems is analyzed in detail and the experimental results of the work carried out are shown after the statement of the models employed for the study. In Chapter 3, an analysis of dynamic wireless charging systems is provided with a focus on their configurations and control. In Chapter 4, the main energy storage systems for automotive applications are extensively described, with a focus on lithium batteries, supercapacitors and hybrid storage systems. Finally, Chapter 5 takes the form of a summary, presenting di erent practical application of the the investigated systems, treated in the previous chapters.

This research investigates how to draw energy from a distant emanating and alternating (i.e., AC) magnetic source and deliver it to a battery (i.e., DC). The objective is to develop, design, simulate, build, test, and evaluate a CMOS charger integrated circuit (IC) that wirelessly charges the battery of a microsystem. A fundamental challenge here is that a tiny receiver coil only produces mV's of AC voltage, which is difficult to convert into DC form. Although LC-boosted diode-bridge rectifiers in the literature today extract energy from similar AC sources, they can do so only when AC voltages are higher than what miniaturized coils can produce, unless tuned off-chip capacitors are available, which counters the aim of integration. Therefore, rather than rectify the AC voltage, this research proposes to rectify the current that the AC voltage induces in the coil. This way, the system can still draw power from voltages that fall below the inherent threshold limit of diode-bridge rectifiers. Still, output power is low because, with these low currents, small coils can only extract a diminutive fraction of the magnetic energy available, which is why investing battery energy is also part of this research. Ultimately, the significance of increasing the power that miniaturized platforms can output is higher integration and functionality of micro-devices, like wireless microsensors and biomedical implants.

This 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.<br>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.

The U.S. transportation sector represented about 28% of all energy consumption in 2018. Petroleum products accounted for 92% of this total energy. Light-duty vehicles are the largest energy consumers in the transportation sector. The high amount of petroleum used by light-duty vehicles creates significant economic and environmental challenges. Electric Vehicles (EVs) have a higher fuel economy and can be emission-free; they are therefore an alternative solution for minimizing the negative environmental impact of internal combustion engine vehicles. However, the adoption of EVs has been limited by their limited driving range, long recharging time, and comparatively higher price. Dynamic wireless charging technology allows for charging the EV battery in motion. Charging pads are embedded in the road and the EV battery is charged while the vehicle is passing over them. This technology not only extends the EV range but also results in a considerable reduction in battery size and capacity. Therefore, dynamic wireless charging solves one of the major issues of EVs, leading to their large-scale adoption. In the first part of this dissertation, a pad optimization methodology is presented to minimize system cost and losses. Using this method, two pads are optimized, built and tested for charging the EV. In the next section, two methods are presented to estimate how much the EV is laterally misaligned with respect to the center of the charging pads. This helps to increase system efficiency and power transfer capability. Finally, new concrete-based material is presented and studied to reduce the charging pad cost and increase their durability.

Les travaux de recherche de cette thèse sont menés dans le cadre d’une collaboration entre le laboratoire GeePs et l’institut VEDECOM.Le coût, le volume et le poids des batteries électrochimiques représentent encore un frein important au déploiement des véhicules électriques (VE). Une des solutions envisagées pour prolonger l’autonomie des VE sans augmenter démesurément la capacité des batteries, consiste à utiliser des systèmes de transfert d’énergie électrique sans contact pour les alimenter pendant leurs déplacements. Cette thèse porte sur une de ces techniques et plus particulièrement sur le transfert d’énergie inductif résonant. Les problématiques liées à ce mode de transfert d’énergie sont principalement liées au rendement énergétique, à l’encombrement contraint du fait de la nécessité d’intégration dans le véhicule et dans la route ainsi qu'au respect des normes d’émissions électromagnétiques.L’efficacité énergétique du transfert d’énergie est au premier ordre lié au couplage des deux bobines (coupleur magnétique). Une comparaison des coefficients de couplage pour différentes géométries de coupleurs et différentes configurations de désalignement fait l’objet d’une première partie du travail réalisé. Dans la seconde partie une approche à base de sources équivalentes est proposée pour le prédimensionnement analytique d’une plaque de blindage destinée à limiter le rayonnement du coupleur dans le véhicule et en dehors de celui-ci. Dans le dernier axe de la thèse, l’étude est dédiée aux techniques de détection de la présence du véhicule et au séquencement de l’alimentation des bobines au sol. Une solution originale, permettant de répondre à cette problématique est proposée. Le bilan des travaux ainsi que les perspectives envisagées, viennent clôturer ce manuscrit<br>This thesis is carried out in collaboration between the GeePs laboratory and the VEDECOM institute. The cost, volume and weight of electrochemical batteries still represent a major obstacle to the deployment of electric vehicles (EVs). One of the solutions being considered to extend the range of EVs without excessively increasing the capacity of the batteries, is to use contactless electrical energy transfer systems to power them while they are on the move. This thesis focuses on one of these techniques which is the resonant inductive energy transfer. The problems associated with this mode of energy transfer are mainly related to energy efficiency, the size constrained due to the need for integration into the vehicle and the road as well as compliance with electromagnetic emissionstandards. The efficiency is directly linked to the coupling of the two coils (magnetic coupler). A comparison of the coupling coefficients for different coupler geometries and different misalignment configurations is the subject of the first part of this work. In the second part, an approach based on equivalent sources is suggested for the analytical pre-dimensioning of shielding plate intended to limit the magnetic emissions in and outside the vehicle. In the last axis of the thesis, the study is dedicated to techniques for detecting the presence of the vehicle and the sequencing of the different ground coils. A conclusion giving an assessment of the work and perspectives that open up from this work, close this manuscript

In the last decades, Wireless Power Transfer (WPT) has attracted increasing interest from industry and academic research because of its possible applications. In this thesis, the application of WPT to the Electric Vehicle (EV) charging is studied. This project was born thanks to the collaboration with MARELLI EUROPE S.p.A., and it has as objective the creation of an on-board vehicle converter able to provide a desired current charging profile to the battery and simultaneously maximize the transmission efficiency. Based on the standards concerning the static wireless charging, the power charging level has been set to Po=3.7kW.

<div>Electric vehicles (EVs) face a major issue before becoming the norm of society, that is, their lack of range when it comes to long trips. Fast charging stations are a good step forward to help make it simpler for EVs, but it is still not as convenient when compared to vehicles with an internal combustion engine (ICE). Plenty of infrastructure changes have been proposed in the literature attempting to tackle this issue, but they typically tend to be either an expensive solution or a difficult practical implementation.</div><div> </div><div> This dissertation presents two solutions to help increase the range of EVs: a novel wireless charging method and a multi-motor architecture for EVs. The first proposed solution involves the ability for EVs to charge while en route from another vehicle, which will be referred to from here on as vehicle-to-vehicle recharging (VVR). The aim of this system is to bring an innovative way for EVs to charge their battery without getting off route on a highway. The electric vehicle can request such a service from a designated charger vehicle on demand and receive electric power wirelessly while en route. The vehicles that provide energy (charger vehicles) through wireless power transfer (WPT) only need to be semi-autonomous in order to ``engage'' or ``disengage'' during a trip. Also, a novel method for wireless power transfer will be presented, where the emitter (TX) or receiver (RX) pads can change angles to improve the efficiency of power transmission. This type of WPT system would be suitable for the VVR system presented in this dissertation, along with other applications.</div><div> </div><div> The second solution presented here will be an architecture for EVs with three or more different electric motors to help prolong the state of charge (SOC) of the battery. The key here is to use motors with different high efficiency regions. The proposed control algorithm optimizes the use of the motors on-board to keep them running in their most efficient regions. With this architecture, the powertrain would see a combined efficiency map that incorporates the best operating points of the motors. Therefore, the proposed architecture will allow the EV to operate with a higher range for a given battery capacity.</div><div> </div><div> The state-of-the-art is divided into four subsections relevant to the proposed solutions and where most of the innovations to reduce the burden of charging EVs can be found: (1) infrastructure changes, (2) device level innovations, (3) autonomous vehicles, and (4) electric vehicle architectures. The infrastructure changes highlight some of the proposed systems that aim to help EVs become a convenient solution to the public. Device level innovations covers some of the literature on technology that addresses EVs in terms of WPT. The autonomous vehicle subsection covers the importance of such technology in terms of safety and reliability, that could be implemented on the VVR system. Finally, the EV architectures covers the current typologies used in EVs. Furthermore, modeling, analysis, and simulation is presented to validate the feasibility of the proposed VVR system, the WPT system, and the multi-motor architecture for EVs.</div>

Dissertação de mestrado em Engenharia Eletrónica Industrial e de Computadores<br>A aposta nos veículos elétricos (VEs) tem vindo a aumentar e, como tal, surgem novos desafios a nível da integração da mobilidade elétrica e das redes elétricas. Do ponto de vista da mobilidade elétrica, o tempo de carregamento de um VE e a autonomia continuam a ser os principais inconvenientes associados a estes veículos. Para mitigar estes problemas têm surgido vários sistemas inovadores, nomeadamente: sistemas de carregamento cada vez mais potentes que permitem diminuir o tempo de carregamento; novas tecnologias de sistemas de armazenamento de energia (maioritariamente baterias); e sistemas de gestão das baterias mais avançados e eficientes. Do ponto de vista da rede elétrica, a integração do VE apresenta também um conjunto significativo de vantagens, especialmente, quando os mesmos empregam sistemas de carregamento bidirecionais. Assim, além do modo de operação grid-to-vehicle (G2V), os sistemas bidirecionais permitem também outros modos de operação como o vehicle-to-grid (V2G) e o vehicle-for-grid (V4G). Com o objetivo de simplificar a interface entre o VE e o utilizador, assim como acompanhar as tendências do mercado, surge a necessidade de sistemas de carregamento sem fios. Atualmente, existem diversos sistemas de carregamento sem fios a operar de forma unidirecional com resultados que superaram as expectativas, tanto a nível da potência de carregamento, como de eficiência. Nesta dissertação foi implementado em ambiente de simulação o sistema completo para um carregamento por WPT para mobilidade elétrica. Onde foi validada as topologias dos conversores e os algoritmos de controlo dos mesmo, mais especificamente a interface com a rede elétrica, a transferência de energia bidirecional e o carregamento e descarregamento das baterias. O protótipo desenvolvido na presente dissertação foi dimensionado para uma potência de carregamento de 3,6 kW e realiza a interface entre a rede elétrica e o primário do sistema WPT. O protótipo é composto por uma única Placa de Circuito Impresso (PCB) onde se encontra o conversor CA-CC, o conversor CC-CA de alta frequência, o condicionamento de sinal e o microcontrolador. O sistema desenvolvido permite operar em três modos: G2V, V2G e V4G. Por fim, foram obtidos os resultados experimentais do protótipo que validam os três modos de operação.<br>The focus on electric vehicles (EVs) has been increasing, and new challenges arise regarding the integration of electric mobility and electric networks. According to electric mobility, an EV and autonomy charging time continues to be the main drawbacks associated with these vehicles. Several innovative systems have emerged to mitigate these problems: increasingly powerful charging systems that reduce charging times; new technologies for energy storage systems (mainly batteries); and more advanced and efficient battery management systems. According to the electricity grid, EV integration also presents a significant set of advantages, especially when using bidirectional charging systems. Thus, in addition to the grid to a vehicle (G2V) operating mode, bidirectional systems also allow for other operating modes such as vehicle to grid (V2G) and vehicle for-grid (V4G). To simplify the interface between the EV and the user and follow market trends, the need for wireless charging systems arises. Currently, wireless charging systems operate unidirectionally with results that surpass expectations, both in charging power and efficiency. In this dissertation, the complete system for a WPT charge for electric mobility was implemented in a simulation environment. Furthermore, the topologies of the converters and their control algorithms were validated, specifically the interface with the electrical network, the bidirectional energy transfer, and the charging and discharging of batteries. The prototype developed was dimensioned for a charging power of 3.6 kW and performed the interface between the electrical network and the primary of the WPT system. The prototype consists of a single Printed Circuit Board (PCB) where the AC-DC converter, the high-frequency DC-AC converter, the signal conditioning, and the microcontroller are located. The developed system allows operating in three modes: G2V, V2G, and V4G. Finally, the experimental results of the prototype that validate the three modes of operation were obtained.<br>Este trabalho de dissertação está enquadrado no projeto de IC&DT “newERA4GRIDs – New Generation of Unified Power Conditioner with Advanced Control, Integrating Electric Mobility, Renewables, and Active Filtering Capabilities for the Power Grid Improvement”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEIEEE/30283/2017.<br>Este trabalho de dissertação está enquadrado no projeto de IC&DT “DAIPESEV – Development of Advanced Integrated Power Electronic Systems for Electric Vehicles”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEIEEE/30382/2017.

The present work addresses the optimization of a power transfer system to achieve wireless power link in underwater conditions. Underwater wireless power transfer (WPT) in ocean is critically limited by the energy dissipated in salt water. This conductive medium is responsible for most of the power losses, significantly increasing with the distance between power transmitter (Tx) and receiver (Rx). The system comprises a power transmitter (Tx), coupling coils and a receiver (Rx). A careful design of the coil pair with proper geometry and adequate choice of materials can effectively help in reducing these losses, but only up to some degree. The main goal of this thesis is to optimize the underwater power transmitter (Tx), with special focus on the development of a power inverter, specically designed for energy transfer by means of magnetic resonant coupling, having salt water as the transmission medium. Series capacitors are used both at the primary and secondary sides of the coupled coils, but with the operating frequency defined above resonance. The design makes use of the impedance of load and resonant coupling coils to establish class-DE conditions in a full-bridge inverter.

碩士<br>國立成功大學<br>電機工程學系<br>103<br>In this thesis, we investigate the efficiency of inductive wireless power transfer (WTP) systems for electric vehicles in terms of frequency response analysis and the design method. Up to present, most relevant WPT studies were about designing system circuit parameters and designing coupled structures of induction coils. Research on the efficiency of the power conversion from compensation topology composed of induction coils and compensational capacitors is lacking. Study on design methods to increase the efficiency within the operational frequency band range is nonexistent. However, through the equivalent circuit model of compensation topology, this study has derived a conversion efficiency formula for a non-resonant point frequency band in a system. With reference to the inductive charging specification and recommendation in SAE standard J2954 in the frequency band range between 81.38 kHz to 90 kHz, a design process for optimal compensation capacitors was proposed for raising system conversion efficiency, increasing actual operable range, and for system safety consideration. To verify the enhanced method for system conversion efficiency proposed in this article, some collocating peripheral circuits and an inductively coupled contactless energy transfer platform with a 20 cm air gap were used. The experimental data showed that when the operating frequency is 86 kHz, input power is 468.98 W, output power is 434.47 W, and the system power transfer efficiency is 92.64 %. When the operating frequency is adjusted to 90 kHz, the system efficiency increased to 93.65 %. When the operating frequency is 81 kHz, the system efficiency is 91.46 %. This new method is both practical and informative.

<p>Presently, internal combustion engines provide power to move the majority of vehicles on the roadway. While battery-powered electric vehicles provide an alternative, their widespread acceptance is hindered by range anxiety and longer charging/refueling times. Dynamic wireless power transfer (DWPT) has been proposed as a means to reduce both range anxiety and charging/refueling times. In DWPT, power is provided to a vehicle in motion using electromagnetic fields transmitted by a transmitter embedded within the roadway to a receiver at the underside of the vehicle. For commercial vehicles, DWPT often requires transferring hundreds of kW through a relatively large airgap (> 20 cm). This requires a high-power DC-AC converter at the transmitting end and a DC-AC converter within the vehicle. </p> In this research, a focus is on the development of models that can be used to support the design of DWPT systems. These include finite element-based models of the transmitter/receiver that are used to predict power transfer, coil loss, and core loss in DWPT systems. The transmitter/receiver models are coupled to behavioral models of power electronic converters to predict converter efficiency, mass, and volume based upon switching frequency, transmitter/receiver currents, and source voltage. To date, these models have been used to explore alternative designs for a DWPT intended to power Class 8-9 vehicles on IN interstates. Specifically, the models have been embedded within a genetic algorithm-based multi-objective optimization in which the objectives include minimizing system mass and minimizing loss. Several designs from the optimization are evaluated to consider practicality of the proposed designs.

The purpose of the present study is to determine the thermal feasibility of an air-cooled power inverter. The inverter circuitry layout is designed in tandem with the thermal management of the devices. The cylindrical configuration of the air-cooled inverter concept accommodates a collinear axial air blower and a cylindrical capacitor with inverter cards oriented radially between them. Cooling air flows from the axial fan around the inverter cards and through the center hole of the cylindrical capacitor. The present study is a continuation of the thermal feasibility study conducted in fiscal year 2009 for the Oak Ridge National Laboratory to design a power inverter with a radial inflow cylindrical configuration. Results in the present study are obtained by modeling the inverter concept in computer simulations using the finite element method. Air flow rate, ambient air temperature, voltage, and device switching frequency are studied parametrically. Inlet air temperature was 50°C for all the results reported. Transient and steady-state simulations are based on inverter current that represents the US06 supplemental federal test procedure from the US EPA. The source of heat to the system comes from the power dissipated in the form of heat from the switches and diodes and is modeled as a function of the voltage, switching frequency, current, and device temperature. Since the device temperature is a result as well as an input variable, the steady-state and transient solution are iterative on this parameter. The results demonstrate the thermal feasibility of using air to cool an axial-flow power inverter. This axial inflow configuration decreases the pressure drop through the system by 63% over the radial inflow configuration, and the ideal blower power input for an inlet air flow rate of 540 cfm is reduced from 936 W to 312 W for the whole inverter. When the model is subject to one or multiple current cycles, the maximum device temperature does not exceed 164°F (327°F) for an inlet flow rate of 270 cfm, ambient temperature of 120°C, voltage of 650 V, and switching frequency of 20 kHz. Although the maximum temperature in one cycle is most sensitive to ambient temperature, the ambient temperature affect decays after approximately half the duration of one cycle. Of the parametric variables considered in the transient simulations, the system is most sensitive to inlet air flow rate.

With the increasing demand of water and underwater exploration, more and more electric unmanned surface vehicles (USV) are put into use in recent years. However, because of the present battery technology limits, these devices require to be recharged frequently that is a challenging problem taking into account the complex water environment where these equipments are acting. To improve safety and convenience of USV charging a wireless power transfer (WPT) system is proposed in this dissertation. In this case, the boat can be controlled to go to the charging facilities. During charging by the implemented WPT system, the state of charging can be remotely monitored by host computer. The moving control is based on embedded system. The relative position between transmitting coil and receiving coil is supposed to be sensed by magnetic sensor, since the relative position has great impact on transmission efficiency. The remote monitoring software was implemented in the host computer and was developed in LABVIEW. A graphical user interface was developed to control the boat moving and collect the data from the WPT and the boat sensors. The effectiveness of the proposed system was tested for instance in the laboratory environment and in-field tests are also planned in the near future.<br>Com a crescente procura da exploração em ambientes aquáticos e subaquáticos , os veículos elétricos de superfície não tripulados ("electric unmanned surface vehicle" -USV) têm sido cada vez mais utilizados nestes últimos anos. No entanto, devido aos limites atuais relacionados com a tecnologia utilizada nas baterias, os dispositivos precisam de ser recarregados com frequência para poderem operar num ambiente aquático complexo. Para melhorar a segurança e a conveniência do carregamento da bateria de um USV, um sistema para recarregamento da bateria de um barco não tripulado através de transferência de energia sem fios("wireless power transfer" - WPT) é proposto nesta dissertação. Neste caso de estudo, o barco tem a capacidade de ser controlado para chegar a um ponto de recarregamento da bateria, que se encontra fixado por uma doca mecânica. Enquanto o sistema WPT érecarregado, os dados associados ao processo de recarregamento da bateria podem ser monitorizados por um computador host. O controlo da movimentação do barco é baseado num sistema embebido. A posição relativa entre a bobina transmissora e a bobina receptora deve ser detectada pelo sensor magnético, uma vez que a posição relativa tem um grande impacto na eficiência da transmissão. Em termos do computador host, foi utilizado o software LABVIEW para programar a interface que permite controlar o movimento do barco e recolher os dados. Finalmente, a eficácia do sistema proposto foi experimentada e testada num ambiente de laboratório.