Analysis and guidelines for inductive power transfer links design
- Autores: Alberto Delgado Expósito
- Directores de la Tesis: Jesús Ángel Oliver Ramirez (dir. tes.)
- Lectura: En la Universidad Politécnica de Madrid ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: José Antonio Cobos Marquez (presid.), Pedro Alou Cervera (secret.), Jesús Acero Acero (voc.), Antonio Maffucci (voc.), Cristina Fernández Herrero (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Eléctrica y Electrónica por la Universidad de Oviedo y la Universidad Politécnica de Madrid
- Materias:
- Enlaces
- Tesis en acceso abierto en: Archivo Digital UPM
- Resumen
Wireless energy transfer systems are becoming a revolutionary and fundamental tool for the development of the modern world. This term refers to any system without wires capable of sending energy over a certain distance through acoustic waves, mechanical vibrations, laser, electromagnetic conversion, etc. This thesis is based on the last one, specifically on electromagnetic induction systems. More than 100 years ago, Nikola Tesla left his demonstration to the world of the possibility of making such systems. Back in the 1960s, his technology began to be used for medical devices. Since then, these transfer systems utilizing magnetic induction have been increasing their complexity and usefulness over the years. It is due to its most significant benefits such as: - The reduction of batteries and increase of their useful life, such as in the inductive charging of electric vehicles. It is not only spoken of a technological key point as they are the batteries, but also of the possibility of making that the consumer charges his vehicle without the necessity to lower the same one. It is possibly the comfort of the strong points of these systems that makes it in height in investigations, as much in the universities, as in the industries. Not only in applications such as electric vehicles where the power is around 3-20kW but also in applications such as wearables and personal electronic devices that are around tens of watts. - The elimination of wires connecting the power source to the load: we are talking about medical implants: from hearing enhancement devices, pacemakers, to devices that keep the heart beating, such as Left Ventricular Assist Devices (LVADs). - The possibility of automating and modernizing systems without human supervision and intervention, as, for example, in the robotization of industry, allowing the loading of autonomous vehicles for transporting goods in warehouses at wireless stations, the clear example being Amazon. They make these systems attractive both to industry and its marketing and to universities and their research. Although these systems are not new, where for example we can find these systems in their most basic mode as in induction cookers where the powers are relatively low, and their complexity equally does not mean a tremendous technological challenge today due to its long history in the industry (Fagor as a clear example in Spain), its study, both in high power ranges as in low, has occupied a large part of congresses and magazines during the last years where it has come to more. The increase of patents on these systems is evident, reaching between 2018 and 2019 to add more than 20 thousand. However, there is an evident absence in the state of the art of design methodologies for the coils that play the fundamental role of transferring energy through a non-magnetic medium. Also noteworthy is the scarcity in the current literature of a comprehensive study of the behavior of inductive links depending on the configuration used to perform the resonance. Therefore, we can say that the apparent absence of design methodologies makes the realization of a wireless energy transfer system not trivial. Although this is not all if we think about how an inductive link is formed: a primary coil, emitter, and at some distance a secondary coil, receiver, we can understand that it is a transformer where the air gap it presents is huge, comparable even sometimes with the size of the same coil. It means that the fundamental equations we have so far are not useful. That is to say, trying to carry out an analysis of an inductive link using, for example, the Schwarz-Christoffel equation to model the air gap, will make the results obtained very far from the final result, making it practically impossible to obtain the proper couplings and inductances, very necessary for the design of these systems. Therefore, finite element simulation for the design of these systems is becoming one of the fundamental tools. However, this does not solve the problem. Due to the large size of these coils and the type of conductors in some cases (Litz wire), the mesh required to perform such simulations is so large that it requires either supercomputers or excessively high time of computation and analysis. Even in the case of Litz wire, it can make it impossible to perform. Once again, there is a lack, in this case, models that simplify the meshing required in the finite element tools to be able to simulate these coils with these conductors in a fast, effective way and, above all, in a conventional computer found in any laboratory. This doctoral thesis has two main objectives very clear directed to the behavioral analysis and electromagnetic modeling of the inductive links and their ways of resonating. Firstly, the behavioral analysis and modeling of the resonance forms will allow the reader to identify the advantages and disadvantages of each of the forms to choose one that best suits their specifications. This analysis is based firstly on the study of the behavior of the topology, in other words, whether it behaves as: a) a source of voltage, that is, that the voltage at the output of the resonant stage is independent of the load as long as the resonance is maintained; b) a source of current, in other words, that the current at its output, as in the previous case, will remain constant, even if the load varies. The other analysis is based on examining the input impedance presented by the topologies, and, above all, on their phase. It is essential because of its effect on the losses in the circuit's electronic devices that precedes it (the inverter). This investigation in the phase allows, in turn, to obtain specific design methodologies so that the user can carry out his design. The second major milestone of this doctoral thesis is the contribution to the state of the art of analytical and empirical models that allow rapid 3D finite element simulations of inductive links, both of new materials that allow lightening the weight of the system, and the conductors: either standard solid wire or Litz wire. These equations are based on simplifying the structures of the 3D inductive link's coils introduced in the finite element tools so that the mesh required for the computation and analysis of the problem is drastically reduced, but obtaining equivalent results. This has been one of the significant milestones since it allows the design and simulation in an ordinary computer without a supercomputer's need. At the same time, this Ph.D. Thesis also proposes several design methodologies for inductive links employing rapid simulations by finite elements based on these models, which will allow the reader to come up with an optimal design for its application quickly. Likewise, several practical designs are proposed where the design methodology followed is explained in a practical and applied way, in order to consolidate the knowledge exposed in the previous chapters. As a summary, the main contributions of the thesis are - A comprehensive analysis of the behavior and frequency response of inductive link resonant topologies. - Modeling of the integral components of inductive links to perform 3D finite element simulations quickly and effectively. - Exhaustive study of the geometrical parameters that affect the coils and obtain behavior graphs allow the designer to carry out his prototype through simulations in a fast and effective way. - To explain through numerous experimental case studies, some methodologies can be applied to designs of certain topologies and specifications. All this has given the IEC a key position in the implementation of wireless energy transfer projects with many companies.
