Non-radiative Wireless Power Transfer Research Articles

Scalability Analysis of SIMO Non-Radiative Resonant Wireless Power Transfer Systems Based on Circuit Models

Resonant inductive coupling wireless power transfer (RIC-WPT) is a leading field of research due to the growing number of applications that can benefit from this technology: from biomedical implants to consumer electronics, fractionated spacecraft, and electric vehicles, amongst others. However, applications are currently limited to point-to-point-links and do not target single input-multiple output (SIMO) scenarios. New challenges and applications of resonant non-radiative wireless power transfer emphasize the necessity to explore, predict, and assess the behavior of RIC-WPT in SIMO links. Moreover, new system-level metrics have to be derived to study the scalability of multi-point wireless power transfer applications and to provide design guidelines for these systems. In this article a single input-multiple output RIC-WPT system is modeled analytically from a circuit-centric point of view and validated using a finite element field solver. The analytical model and associated closed formulation is finally used to derive system-level metrics to predict the behavior and scalability of RIC SIMO systems, showcasing the results for an asymmetric SIMO scenario.

A Novel Phase-Control-Based Energy Beamforming Techniques in Nonradiative Wireless Power Transfer

Recent efforts to increase the energy transfer efficiency in magnetic resonant coupling-based wireless power transfer (WPT) systems, have been focused on improving quality factor, precision of impedance matching, and position alignment between the resonators. Although those approaches are effective to increase transfer efficiencies, the transferred energy can easily be wasted due to leakage flux of nondirectional fields. In this paper, we present a novel magnetic field shaping technology for improving the energy efficiency in a near-field WPT system. In this study, the beamforming techniques that have been used for radio frequency systems are efficiently exploited in a WPT system to improve the transfer efficiencies by minimizing unnecessary leakage flux. The optimal antenna structure for energy forming is first determined through mathematical analysis. Using the proposed crossed antennas, the phase-control method is effectively used to form magnetic fields in particular directions. The proposed energy forming-based WPT system using crossed antennas is implemented with the phase control of three-power stack transmitters. The experimental results matches well with the theoretical analysis, and the energy-forming approach for synthesizing the magnetic fields achieves average improvements of the transfer efficiency and transfer distance of up to 20.1% and 30%, respectively, over the conventional nonradiative energy transfer approach at 1 m distance.

Omnidirectional non-radiative wireless power transfer with rotating magnetic field and efficiency improvement by metamaterial

In this paper, omnidirectional wireless power transfer (OWPT) via magnetic resonant coupling is proposed based on rotating magnetic field. In contrast to conventional WPT, the proposed wireless power transmitter consists of two orthogonal loops with 90° feeding phase difference. Both theoretical analyses and numerical simulations show that such transmitter generates rotating magnetic field and can provide wireless power to multiple receivers moving around it. In addition, a cylindrical metamaterial slab with negative permeability is used to improve the efficiency of the OWPT system, for the unique property of enhancing evanescent wave of metamaterials. It is shown that the efficiency of the OWPT can be improved to more than five times of that of the original one by the metamaterial slab.

무선전력전송기술의 기술적 이론적 상호 관계

Wireless power transfer (WPT) system is very attractive because it removes power cables from home appliances, office equipments and battery chargers for electric vehicles. In this paper, non-radiative WPT systems studied recently are claimed to be technologically or theoretically identical in operation irrespective of the number of coils. Especially, 2-coil and 3-coil systems are compared in detail. It is also shown that multiplicity of coils does not increase power transfer capability.

Diversity Analysis of Multiple Transmitters in Wireless Power Transfer System

Nonradiative wireless power transfer is a popular technology that transfers energy over medium range via strongly coupled magnetic resonance. We investigated the effect of transmit diversity on power transfer efficiency under multiple transmitters. We derived closed-form equations for the power transfer efficiency and the optimal load from both coupled mode theory and equivalent circuit model analyses. We also showed that the analytical results obtained from the two types of analysis are basically the same, so they can be expressed as an equivalent equation that consists of a quality factor and coupling coefficient. In addition, we performed simulations using the Ansoft High Frequency Structure Simulator and the Agilent Advanced Design System to demonstrate the accuracy of our analysis. The results show that a multiple-transmitter wireless power-transfer system can improve power transfer efficiency over all regions in both an angular aligned scenario and an angular misaligned scenario, due to the diversity in the transfer of power.

A Study of Loosely Coupled Coils for Wireless Power Transfer

Nonradiative wireless power transfer using magnetically coupled coils is studied in order to transfer a predetermined amount of power at the maximum efficiency. Accordingly, a conceptual wireless power transfer system and a tuning method are presented. Such a study is essential for effectively exploiting the inherent ability of a given pair of coupled coils. With the equations for inductance and resistance calculations, the system performance is evaluated and verified with well-known experimental results and circuit simulations.