Wireless Power Transfer System

Abstract

This paper presents a survey of recent wireless power transfer systems. The issue of wireless power transfer is to achieve a highly efficient system with small positioning errors of the facilities setting. Several theories have been presented to obtain precise system design. This paper presents a summary of design theory for short range power transfer systems and detailed formulations based on a circuit model and an array of infinitesimal dipoles. In addition to these theories, this paper introduces a coil array scheme for improving the efficiency for off axis coils. In the microwave range, tightly coupled resonators provide a highly efficient power transfer system. This paper present sanoverlay resonator array consisting of half wavelength microstrip line resonators on the substrate with electromagnetically coupled parasitic elements placed above the bottom resonators. The tight couplings between the waveguide and the load resonator give strong power transmission and achieve a highly efficient system, and enables a contact-less power transfer railroad. Its basic theory and a demonstration of a toy vehicle operating with this system are presented. In the last topic of this paper, harmonic suppression from the rectenna is discussed with respect to acircular microstrip antenna with slits and stubs. Ⅰ. IntroductionSeveral solutions have been proposed for wireless power transfer using electromagnetic (EM) waves. For example, Felica utilizes electromagnetically inductive coils [1] over a very short distance. One of the hottest issues is non-radiative mid-range energy transfer [2]. This has weak tolerance for positioning and the coverage area is limited near the coil, however, it is a good candidate for high power transfer for fixed to fixed point applications. After its demonstration by the MIT group, many researchers carried out further studies and presented design methods. This is sometimes referred toas "magnetic field resonance"; however, it is simply understood as the strong coupling between two resonators. Its transfer efficiencydepends heavily on the distance between coils and is around 90 % at 1 m and 40 % at 2 m [2]. Although substantial electric power transmission is expected to charge an electric vehicle, a standard of small power less than 5 W was provided by the consortium [3]. In order to charge mobile devices, the detection of the device position is a key issue. The movement of coupling coils and the coil array are major schemes for free positioning of the device to be charged. Several applications using these methods are already on the market as cell phone chargers.A basic theory for coil coupling is given by circuit theory [2], [4], and is also explained by a filter theory [5] and others. This paper presents a simple circuit theory based one lectromagnetism to find the coupling efficiency between coils. In practical power transfer applications, the efficiency is a very important factor. To improve the transfer efficiency, an parameter optimization of the coil [6] and a coil array approach ha...

Sensor Coil System for Misalignment Detection and Information Transfer in Dynamic Wireless Power Transfer of Electric Vehicle

“…Wireless power transfer (WPT) is currently applied in various fields because of its convenience, safety, and aesthetics [1][2][3][4][5]. WPT technology is essential in the medical field for operations of human-implantable medical devices such as artificial organs.…”

Wireless Torque and Power Transfer Using Multiple Coils with LCC-S Topology for Implantable Medical Drug Pump

“…WPT system can increase the degree of freedom of devices that have been supplied with power through the wire, and can solve both the inconvenience and the safety problem of the wire at the same time. WPT technologies ranging from low-power such as mobile phones and medical devices to large-power such as electric vehicles and industrial robots are being developed and in progress [1,2].…”

Magnetic Resonant Wireless Power Transfer with L-Shape Arranged Resonators for Laptop Computer

“…In indirect-fed MR-WPT systems, the Tx part consists of the source loop and the Tx coil, while the Rx part consists of the load loop and the Rx coil. Most user experiences indicate that in practical applications, it is difficult to use strongly-coupled magnetic resonance wireless charging system [2,3]. This is mainly because of the large volume of the Rx part and the spatial restrictions of the Tx and Rx coils.…”