The load reliant power transfer of the series-to-series inductive resonant wireless power transfer

In this paper, the effect of the output impedance to the power transfer efficiency of the series-to-series inductive resonant wireless power transfer at the resonance frequency is reviewed in details. The analysis is carried out by utilizing the theoretical inductive resonance wireless power transfer model using the MATLAB ® package. In this paper, the experiment is designed to confirm the highest power transfer efficiency is obtained at the resonance frequency for the given value of the coupling coefficient. Besides that, the experiment is also conducted to find the optimum load impedance for all given value of coupling coefficient. The analysis shows that the maximum wireless power transfer efficiency for series-to-series inductive resonant wireless power transfer is at the maximum peak when operational at the resonance frequency. In addition, the power transfer efficiency is improved by working at the optimum load impedance. The experimental set up is presented and the analytical results are reported

Frequency splitting elimination and cross-coupling rejection of wireless power transfer to multiple dynamic receivers

Simultaneous power transfer to multiple receiver (Rx) system is one of the key advantages of wireless power transfer (WPT) system using magnetic resonance. However, determining the optimal condition to uniformly transfer the power to a selected Rx at high efficiency is the challenging task under the dynamic environment. The cross-coupling and frequency splitting are the dominant issues present in the multiple Rx dynamic WPT system. The existing analysis is performed by considering any one issue present in the system; on the other hand, the cross coupling and frequency splitting issues are interrelated in dynamic Rx’s, which requires a comprehensive design strategy by considering both the problems. This paper proposes an optimal design of multiple Rx WPT system, which can eliminate cross coupling, frequency splitting issues and increase the power transfer efficiency (PTE) of selected Rx. The cross-coupling rejection, uniform power transfer is performed by adding an additional relay coil and independent resonance frequency tuning with capacitive compensation to each Rx unit. The frequency splitting phenomena are eliminated using non-identical transmitter (Tx) and Rx coil structure which can maintain the coupling between the coil under the critical coupling limit. The mathematical analysis of the compensation capacitance calculation and optimal Tx coil size identification is performed for the four Rx WPT system. Finite element analysis and experimental investigation are carried out for the proposed design in static and dynamic conditions

Prédiction et gestion de l’énergie dans un réseau de capteurs sans fil récolteurs d’énergie vibratoire pour les applications industrielles de l’internet des objets

La question de l’autonomie énergétique des capteurs sans fil (WS pour Wireless Sensor), indispensables pour l’automatisation de nombreux procédés industriels, est aujourd’hui une limite fondamentale dans l’atteinte des objectifs de l’industrie 4.0. Pour surmonter cette limite, la piste de solution la plus prometteuse est celle de la récolte de l’énergie ambiante (EH pour Energy Harvesting). L’EH consiste à identifier une source d’énergie primaire (soleil, vibrations, ondes radiofréquences, chaleur, etc.), disponible dans l’environnement immédiat du capteur et de la transformer en énergie électrique pour son alimentation. Cette thèse est une contribution dans ce domaine de recherche en pleine expansion, pour des applications dans l’environnement industriel. Les vibrations qui abondent dans la plupart des procédés industriels sont considérées comme source d’alimentation des WS capables de remplacer les capteurs filés actuellement utilisés. Prenant en considération le caractère aléatoire de la quantité d’énergie récoltable, deux contributions majeures sont proposées dans cette thèse à savoir la conception d’un Prédicteur de l’Énergie Récoltable des vibrations (PERV) et la mise en place d’une solution permettant de gérer efficacement l’énergie récoltée à travers un Protocole Hiérarchique à Équilibrage d’Énergie (PHEE). La conception du PERV est basée sur des données de vibrations enregistrées à 12 emplacements différents, et ce pendant un mois, sur le processus de concassage des minerais par un broyeur semiautogène. La périodicité observée dans les signaux est exploitée pour minimiser la quantité de données devant être stockées pour l’estimation de la puissance à un instant donné. Les performances du PERV sont ensuite comparées à un prédicteur de l’état de l’art le EWMA (Exponentially Weighted Moving-Average qui utilise l’historique des données d’énergie pour estimer les quantités d’énergie récoltable dans le futur) et il est obtenu que l’erreur quadratique moyenne pour les 12 points de mesure subie des améliorations allant de 10 % à 90.5 % comparé au prédicteur EWMA. Le PERV permet ainsi d’augmenter la précision dans la prédiction tout en réduisant la quantité des données devant être stockées. Sous la base de l’énergie prédite, le PHEE est conçu avec pour objectif d’optimiser à la fois la Qualité de Service individuelle de chacun des noeuds, mais aussi celle du réseau en entier. De façon plus spécifique, sous la base de l’énergie prédite, les noeuds capteurs contrôlant le procédé sont capables d'opérer de façon perpétuelle lorsque le coût énergétique par cycle de mesure est inférieur à 160

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

Design optimization of contactless power transfer systems for electric vehicles using electromagnetic resonant coupling

Contactless power transfer (CPT) systems have been gaining considerable attention and have achieved tremendous technology advancements across a wide variety of utilizations in the past decade. CPT technologies offer promising advantages and open up new avenues for development of numerous real-world applications. Of particular importance is the implementation of CPT systems on the charging of electric vehicles (EV), which are considered as a sustainable alternative that will effectively address global fossil energy scarcity and climate change issues in the future. The overarching aim of this thesis is to investigate and improve the operation performance of CPT systems for contactless EV charging. Optimized high-performance CPT systems are expected to be the ultimate goal for EV wireless charging in the following century. In the CPT applications, some certain characteristic outputs and parameters such as overall system efficiency, RMS power transfer, air gap and resonant frequency are considered as key performance metrics to be addressed. These crucial metrics and properties have been emphasized throughout this thesis. The electromagnetic resonant coupling technique has been put forward and adopted for most designed prototypes in this thesis in order to optimize the overall performance of CPT systems. The research methodology development, model designs, implementations and results analysis of the thesis are undertaken from the perspective of both power electronics and electromagnetics towards achieving the main objectives of the research. With focuses on overall system efficiency, real transfer power to load, air gap, frequency, magnetic coupler design, shielding materials, inner shielding distance and misalignment characteristics, a range of studies have been conducted in the thesis based on the proposed methodology, enhanced simulation models and laboratory prototypes. A number of important contributions have been made by the thesis. The four most significant contributions are: Firstly, the originally developed methodology for the CPT research of the thesis – the research flowchart system based on the preliminary natural resonant frequency probe and anticipation method. This uniquely proposed method for this thesis has been used to effectively probe, track and narrow down the most appropriate resonant frequency range to be chosen for CPT systems to perform with, towards reaching an optimized status of electromagnetic resonant coupling in terms of CPT technology-based EV charging. Secondly, the magnetic coupler modular-based CPT designs for investigating overall system performance optimization. As a result, in the thesis, a novel small-sized CPT prototype that is based on a geometrically improved H-shaped magnetic coupler, with ferromagnetic cores, passive aluminium shielding, an SS compensation topology and electromagnetic resonant coupling, has been proposed as an optimal design solution. Thirdly, approximating a CPT system to operate in close proximity to its calculated natural resonant frequency point by tuning and controlling system operating frequency could effectively lead to an overall system performance optimization most of the time in practical applications using electromagnetic resonant coupling, whereas setting the system operating frequency exactly at its calculated natural resonant frequency to make the system maximally operate at an extreme state of magnetic resonance may only produce a partial optimization from perspective of the system parameters and outputs. Fourthly, reasonable trade-offs between performance metrics are required to be considered and evaluated in order to achieve a feasible overall CPT system optimization. Through the detailed analysis of the results, model outcome comparisons, explanations on findings, limitation discussions and holistic system evaluations, this thesis is devoted to report and provide a series of newly proposed solutions and innovatively designed CPT systems. These solutions are supported by empirical findings, conclusions and contributions, which may encourage further pursuits of system performance optimizations for high-power high-frequency CPT charging technologies applied for future EV, despite methodological limitations, experiment restrictions and external uncertainties