Sviluppi del trasferimento di energia elettrica mediante risonatori piani a spirale

The aim of this thesis is to develop a depth analysis of the inductive power transfer (or wireless power transfer, WPT) along a metamaterial composed of cells arranged in a planar configuration, in order to deliver power to a receiver sliding on them. In this way, the problem of the efficiency strongly affected by the weak coupling between emitter and receiver can be obviated, and the distance of transmission can significantly be increased. This study is made using a circuital approach and the magnetoinductive wave (MIW) theory, in order to simply explain the behavior of the transmission coefficient and efficiency from the circuital and experimental point of view. Moreover, flat spiral resonators are used as metamaterial cells, particularly indicated in literature for WPT metamaterials operating at MHz frequencies (5-30 MHz). Finally, this thesis presents a complete electrical characterization of multilayer and multiturn flat spiral resonators and, in particular, it proposes a new approach for the resistance calculation through finite element simulations, in order to consider all the high frequency parasitic effects. Multilayer and multiturn flat spiral resonators are studied in order to decrease the operating frequency down to kHz, maintaining small external dimensions and allowing the metamaterials to be supplied by electronic power converters (resonant inverters)

A fast and precise tool for multi-layer planar coil self-inductance calculation

An open-source tool that allows for a fast and precise analytical calculation of multi-layer planar coils self-inductance, without any geometry limitation is proposed here. The process of designing and simulating planar coils to achieve reliable results is commonly limited on accuracy and or geometry, or are too time-consuming and expensive, thus a tool to speed up this design process is desired. The model is based on Grover equations, valid for any geometry. The validation of the tool was performed through the comparison with experimental measurements, Finite Element Model (FEM) simulations, and the main analytical methods usually used in literature, with errors registered to be below 2.5%, when compared to standard FEM simulations, and when compared to experimental measurements they are below 10% in the case of the 1-layer coils, and below 5% in the 2-layer coils (without taking into consideration the coil connectors). The proposed model offers a new approach to the calculation of the self-inductance of planar coils of several layers that combines precision, speed, independence of geometry, easy interaction, and no need for extra resources.This work is supported by: European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project nº 037902; Funding Reference: POCI-01-0247-FEDER-037902]. The work of Andreia Faria was funded by FCT—Fundação para a Ciência e Tecnologia under Grant PD/BD/128142/2016. The work of Carlos Ferreira was supported by the Fundação para a Ciência e Tecnologia (FCT) under Grant PD/BDE/135102/2017

Dual-Band Resonator Designs for Near-Field Wireless Energy Transfer Applications

Dual-band near-field wireless energy transfer (WET) designs outweigh single-band system with regard to either concurrent energy and data transfer or multiple wireless charging standard functionalities. There are two major approaches in resonator designs, namely, multi-coil and single-coil. This chapter presents a review on design constraints for each design approach and rectification techniques available in counteracting impediments of dual-band near-field WET systems. Challenges pertinent to link design are discussed primarily followed by methods implemented to mitigate detrimental impact on performance metrics. Front-end dual-band resonator design methods are accentuated in this chapter in lieu of end-to-end WET system. This is envisioned to offer insights for designers contemplating on design modes or developing ways to facilitate a boost in rectification options currently available

Superconducting wireless power transfer for electric vehicles

Electric vehicles (EVs) are an important pillar for the transition towards a cleaner and more sustainable future as renewable energy can penetrate into the transportation section and act as energy storage to cope with the intermittent supply of such energy sources. EVs have recently been significantly developed in terms of both performance and drive range. Various models are already commercially available, and the number of EVs on roads increases rapidly. Rather than being limited by physical cable connections, the wireless (inductive) link creates the opportunity of dynamic charging – charging while driving. Once realised, EVs will no longer be limited by their achievable range and the requirement for battery capacity will be greatly reduced. However, wireless charging systems are limited in their transfer distance and power density. Such drawbacks can be alleviated through high-temperature superconductors (HTS) and their increased current carrying capacity, which can substitute conventionally used copper coils in the charging pads. This thesis investigates the effectiveness of wireless power transfer (WPT) systems as a whole and when HTS coils are used as well as HTS performance at operating frequencies commonly used in WPT-systems. Initially, the fundamentals of superconductivity are outlined to give some background on how such conductors can help tackle problems occurring in WPT-systems and how their behaviour can be simulated. Subsequently, key technical components of wireless charging are summarised and compared, such as compensation topologies, coil design and communication. In addition, health and safety concerns regarding wireless charging are addressed, as well as their relevant standards. Economically, the costs of a wide range of wireless charging systems has also been summarised and compared. To explore the benefits of WPT-system for EVs, a force-based vehicle model is coupled with an extended battery model to simulate the impact of wireless charging on the state of charge of the accumulator sub-system. In total, three different scenarios, i.e. urban, highway and combined driving are presented. The trade-off between having a standalone charging option versus combined dynamic (or on-road charging) and quasi-dynamic (stationary charging in a dynamic environment) wireless charging is outlined and minimum system requirements, such as charging power levels and road coverage, for unlimited range are established. Furthermore, the effects of external factors such as ambient temperature, battery age and wireless transfer efficiency are investigated. It is shown that employing combined charging at medium power levels is sufficient to achieve unlimited range compared to high power requirements for standalone charging. HTS coils show great potential to enhance the WPT-system performance with high current-carrying capability and extremely low losses under certain conditions. However, HTS coils exhibit highly nonlinear loss characteristics, especially at high frequencies (above 1 kHz), which negatively influence the overall system performance. To investigate the improvements, copper, HTS and hybrid wireless charging systems in the frequency range of 11-85 kHz are experimentally tested. Results are compared with finite element analysis (FEA) simulations, which have been combined with electrical circuit models for performance analysis. The measurements and modelling results show good agreement for the WPT-system and HTS charging systems have a much higher transfer efficiency than copper at frequencies below 50 kHz. As the operating frequency increases towards 100 kHz, the performance of HTS systems deteriorates and becomes comparable to copper systems. Similar results are obtained from hybrid systems with a mixture of HTS and copper coils, either as transmitting or receiving coils. Nevertheless, it has been demonstrated that HTS significantly improves the transfer efficiency of wireless charging within a certain range of frequencies. The AC losses occurring in HTS coils, particularly transport current loss, magnetisation loss and combined loss, at high frequencies are studied further. A multilayer 2D axisymmetric coil model based on H-formulation is proposed and validated by experimental results as the HTS film layer is inapplicable at such frequencies. Three of the most commonly employed coil configurations, namely: double pancake, solenoid and circular spiral are examined. While spiral coils experience the highest transport current loss, solenoid coils are subject to the highest magnetisation loss due to the overall distribution of the turns. Furthermore, a transition frequency is defined for each coil when losses in the copper layer exceed the HTS losses. It is much lower for coils due to the interactions between the different turns compared to single HTS tapes. At higher frequencies, the range of magnetic field densities, causing a shift where the highest losses occur, decreases until losses in the copper stabilisers always dominate. In addition, case studies investigating the suitability of HTS-WPT are proposed. Lastly, methods to reduce AC losses of HTS coils are investigated with particular focus on flux diverters, which have been used for low frequency superconducting applications but their effectiveness at high frequencies is unexplored. Therefore, the impact of flux diverters on HTS double pancake coils operating at high frequencies up to 85 kHz is researched. Various geometric characteristics of the flux diverter are investigated such as air gap between diverter and coil, width and thickness. An FEA-model was used to examine the coil and diverter losses at such frequencies and different load factors between 0.1 and 0.8. It is demonstrated that flux diverters are a viable option to reduce the coil losses even at high frequencies and the width of the coil has the biggest impact on the loss reduction. In general, flux diverters are more suitable for applications using high load factors. Lastly, the impact of the diverter in terms of magnetic field distribution above the coil and overall loss distribution in the HTS coil was examined

Underwater Inductive Power Transfer with Wireless Charging Applications

Underwater wireless power transfer (UWPT) has become an area of great interest due to the advancement of autonomous underwater vehicles (AUVs) and electic boats. This paper seeks to investigate the variation of the coupling coefficient and power transfer in air versus in seawater. The design is based on a class E converter as it can achieve soft-switching inherently. I made the transmitter and receiver coils then measured self-inductance and parasitic resistance in air and in water. I noted that self-inductance increases when they are placed in water but the mutual inductance is lower. I then calculated the component values for the class E converter based on inductor values (140 μH and 105 μH) and simulated the circuit on LTspice. The power at the output was 74W which is lower than the required value. However, I noted that reducing the coils inductance values while maintaining the value of the other passive components increased the efficiency and power at the output upto four times (311W). The final value chosen for making the inductors was 115 μH and 75 μH as these values gave the maximum power at the output while achieving ZVS. I then designed the transmitter and receiver circuits on Altium and printed the PCBs. All the components were then soldered onto the board and the tests done

Electronic contact lens: a platform for wireless health monitoring applications

Electronic contact lenses can be used for non‐invasively monitoring vital human signs and medical parameters. However, maintaining a secure communications connection and a self‐sustainable power source are still looming challenges. This paper demonstrates a proof of concept electronic contact lens that includes a spiral antenna with its wireless circuit unit for data telemetry, a rectifier circuit for power conditioning and a micro light emitting diode (µLED) as a load. The spiral antenna with its rectifying circuit was designed considering operation in the Industrial, Scientific and Medical (ISM) band of 2.4 GHz. The spiral coil with an inner diameter of 10 mm, an outer diameter of 12 mm and a wire width of 0.2 mm was fabricated on a donut‐shaped flexible polyimide substarte. For biocompatibility purposes, Polyimide was used as the contact lens substrate and polydimethylsiloxane (PDMS) was used for encapsulation. A 3D‐printed eye model was developed for accurately shaping the curvature of the PDMS‐encapsulated contact lens. The reflection coefficient (S11) of the fabricated antenna was tested in different conditions and on an eye model to mimic the liquid condition of the human eye. In a wide range of conditions, a minimum of ‐20 dB reflection coefficient (S11) was obtained. The maximum antenna gain was ‐28 dBi and the contact lens satisfied the electromagnetic exposure safety limit of 1.6 W/kg for 1 g of tissue mass. We also determined the wavelength dependence of the electronic contact lens on different lens thicknesses. Our results showed that the lens is transmissive in the visible part of the spectrum

Doctor of Philosophy

dissertationMore than a century ago, in his labs in Colorado Springs and New York, Nikola Tesla started experimenting with wireless power transfer (WPT). His ideas were ahead of his time, but they fell into obscurity shortly after his death. Nowadays, WPT is no longer thought of as science fiction: neural prostheses, wearables, cellphones, and even electric vehicles can be powered through WPT. In its most common implementation, WPT leverages the magnetic coupling between resonant transmitter and receiver coils to exchange energy. Considerable work is devoted to the design and optimization of WPT antennas; efficiently transmitting the required amount of power can only be accomplished when the coil coupling is in the right range. In this work, we explore the use of spatial filters in WPT systems. Spatial filters are capable of controlling the harmonic content of an incident wave: subwavelength focal spots, perfect lensing, and diffractionless beams are some of their uses. In the first part of this dissertation, the focus is on the analysis and design of a compact negative permeability metamaterial slab. Compared to other works in the literature, this slab is an extremely small fraction of the wavelength, and works at a low operating frequency. Analysis and experimental validation demonstrate that the resulting metamaterial sample can be used in a 2-coil WPT system to achieve large range and efficiency enhancements. In the second part of this dissertation, the analysis and implementation of holographic screens is presented. A method to reduce the fabrication complexity of the desired holographic screen while maintaining the fidelity of the prescribed field distribution is presented. We demonstrate our method through the analysis, design, and experimental validation of a nondiffractive beam launcher with a Bessel field distribution. Finally, we utilize the analysis and methods presented in this work to design an antenna capable of prescribing a uniform field distribution. Because of this property, this WPT antenna is capable of transmitting near constant power with near constant efficiency to the target receiver load, without the need of an adaptive compensation system

Wireless Power Transfer Technology for Electric Vehicle Charging

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

Compact Multi-Coil Inductive Power Transfer System with a Dynamic Receiver Position Estimation

Inductive power transfer (IPT) systems with tolerance to the lateral misalignment are advantageous for enhancing the transmitted power, usability and security of the system. In this thesis, a misalignment tolerant multi-coil design is proposed to supply stationary and dynamic battery-free wireless devices. A compact architecture composed of individually switchable 3 layers of printed coils arranged with overlap for excellent surface coverage. A hybrid architecture based on three compact AC supply modules reduces the supply circuit complexity on the sending Seite 2 von 4side. It detects the position of the receiver coil quickly, controls the activation of the transmitting coils and estimates the next receiver position. The proposed architecture reduces the circuit footprint by a factor of 62% compared to common architectures. A transmitter coil activation strategy is proposed based on the detection of the transmitting coils voltage and communication between sending side and receiving side to detect devices to supply nature and position and to differentiate them from other conductive objects in the sending area to the supplying security. The experimental results prove that the proposed architecture has a good performance for different trajectories when the device speed does not exceed 15 mm/s. Besides, the maximum detection time for the initial device position is about 1.6 s. The maximal time interval to check the transmitter coils is around 0.7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOKInduktive Energieübertragungssysteme (IPT) mit Toleranz gegenüber seitlichem Versatz sind vorteilhaft, um die übertragene Leistung, die Nutzbarkeit und die Sicherheit des Systems zu verbessern. In dieser Arbeit wird ein versatztolerantes Multispulen-Design vorgeschlagen, um stationäre und dynamische batterielose drahtlose Geräte zu versorgen. Die kompakte Architektur besteht aus 3 einzeln schaltbaren Schichten gedruckter Spulen, die überlappend angeordnet sind, um eine hervorragende Oberflächenabdeckung zu gewährleisten. Eine hybride Architektur, die auf drei kompakten AC-Versorgungsmodulen basiert, reduziert die Komplexität der Versorgungsschaltung auf der Senderseite. Sie erkennt die Position der Empfängerspule schnell, steuert die Aktivierung der Sendespulen und schätzt die nächste Empfängerposition. Die vorgeschlagene Architektur reduziert den Platzbedarf der Schaltung um einen Faktor von 62 % im Vergleich zu herkömmlichen Architekturen. Es wird eine Aktivierungsstrategie für die Sendespulen vorgeschlagen, die auf der Erkennung der Spannung der Sendespulen und der Kommunikation zwischen Sende- und Empfangsseite basiert, um die Art und Position der zu versorgenden Geräte zu erkennen und sie von anderen leitfähigen Objekten im Sendebereich zu unterscheiden. Die experimentellen Ergebnisse zeigen, dass die vorgeschlagene Architektur eine gute Leistung für verschiedene Trajektorien hat, wenn die Geschwindigkeit der Geräte 15 mm/s nicht überschreitet. Außerdem beträgt die maximale Erkennungszeit für die anfängliche Geräteposition etwa 1,6 s. Das maximale Zeitintervall für die Überprüfung der Senderspulen beträgt etwa 0,7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOO

Printed Spiral Coil Design, Implementation, And Optimization For 13.56 MHz Near-Field Wireless Resistive Analog Passive (WRAP) Sensors

Noroozi, Babak. Ph.D. The University of Memphis. June 2020. Printed Spiral Coil Design, Implementation, and Optimization for 13.56 MHz Near-Field Wireless Resistive Analog Passive (WRAP) Sensors. Major Professor: Dr. Bashir I. Morshed.Monitoring the bio-signals in the regular daily activities for a long time can embrace many benefits for the patients, caregivers, and healthcare system. Early diagnosis of diseases prior to the onset of serious symptoms gives more time to take some preventive action and to begin effective treatment with lower cost. These health and economy benefits are achievable with a user-friendly, low-cost, and unobtrusive wearable sensor that can easily be carried by a patient with no interference with the normal life. The easy application of such sensor brings the smart and connected community (SCC) idea to existence. The spread of a designated disease, like COVID-19, can be studied by collecting the physiological signals transmitted from the wearable sensors in conjunction with a mobile app interface. Moreover, such a comfortable wearable sensor can help to monitor the vital signals during fitness activities for workout concerns. The desire of such wearable sensor has been responded in many researches and commercial products such as smart watch and Fitbit. Wireless connection between the sensor on the body and the scanner is the key and common factor of all convenient wearables. This essential feature has been currently addressed by the costly techniques which is the main impediment to be widely applicable. The existing wireless methods including WiFi, Bluetooth, RFID, and NFC impose cost, complexity, weight, and extra maintenance including battery replacement or recharging, which drove us to propose a low-cost, convenient, and simple technique for wireless connection suitable for battery-less fully-passive sensors. Using a pair of coils connected by the near-field magnetic induction has been copiously used in wireless power transfer (WPT) for medical and industrial applications. However, near field RFID and NFC rely on this technique with active circuits. In contrast, we have proposed a wireless resistive analog passive (WRAP) sensor in which a resistive transducer at the secondary side, affects the primary quality factor (Q) through the inductive connection between a pair of square-shaped Printed Spiral Coils (PSC). The primary 13.56 MHz (ISM band) signal is modulated in response to the continuous change of bio-signal and the amount of response to the unit change in transducer resistance is defined as sensitivity. A higher sensitivity enables the system to respond to the smaller bio-signals and increases the coils maximum relative mobilities. The PSCs specifications and circuit components determine the sensitivity and its tolerance to the coils displacements. We first define and formulize the objective function for coil and components optimization to achieve the maximum sensitivity. Although the optimization methods do not show much different results, due to the speed and simplicity, the Genetic Algorithm (GA) technique is chosen as an advanced method. Then in second optimization stage, the axial and lateral distances that affect the mutual inductance are introduced to the optimization process. The results as a pair of PSCs profiles and the associated circuit components are obtained and fabricated that produced the maximum sensitivity and misalignment tolerance. For the sake of patient comfort, the secondary coil size is fixed at 20 mm and the primary coil is optimized at 60 mm with the maximum (normalized) sensitivity 1.3 m for 16 mm axial distance. If the Read-Zone is defined as the space in which the center of secondary coil can move and the sensitivity keeps at least half of its maximum value, the best Read-Zone has a conical shape with the base radius 22.5 mm and height 14 mm. The analytical results are verified by the measurement results on the fabricated coils and circuits