Recent progress in mid-range wireless power transfer

This is a review paper describing recent progress of mid-range applications of wireless power transfer. Starting from Tesla's principles of wireless power transfer a century ago, it outlines magneto-inductive research activities in the last decade on wireless power transfer with the transmission distance in the order of or greater than the coil dimension. It covers the basic characteristics of 2-coil systems, 4-coil systems, systems with relay resonators and the wireless domino-resonator systems. © 2012 IEEE.published_or_final_versio

Pregled stanja u području bezkontaktnog prijenosa električne energije: primjene, izazovi i trendovi

Methods of contactless electrical power transfer technologies have been surveyed and results are presented here. In this among, the inductive based contactless electrical power transfer systems are investigated in more detail. The principles, structures and operations of the systems as well as their methods presented in the literature are reviewed and their applications are explored. Also, current challenges and opportunities and future trends are noted. An effective index is proposed to compare different contactless power transfer systems describing their present statuses and the future trends. Finally, some remarks and recommendations regarding future studies are proposed.U radu je dan prikaz različitih tehnologija u području bezkontaktnog prijenosa električne energije. U radu je naglasak na indukcijom baziranim sustavima bezkontaktnog prijenosa električne energije. Pregledom literature utvrðeni su koncepti, strukture i način rada pojedinih sustava bezkonaktnog prijenosa kao i njihove primjene. Također, zabilježeni su trenutni izazovi, prilike i trendovi. Predložen je efektivni indeks za vrednovanje sustava bezkontaktnog prijenosa električne energije s ciljem komparativne analize različitih sustava opisanih trenutnim statusom i trendovima. Konačno, dan je kritički osvrt i predložene su preporuke za buduće studije

A critical review of recent progress in mid-range wireless power transfer

Starting from Tesla’s principles of wireless power transfer a century ago, this critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into (i) the maximum power transfer and (ii) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the 2-coil systems, the 4-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the 2-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the 4-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (< 50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load.published_or_final_versio

Analysis, design and implementation of a residential inductive contactless energy transfer system with multiple mobile clamps

This study presents the analysis, design and implementation of a simple and cost-effective residential inductive contactless energy transfer system with multiple mobile clamps. The topology is based on the cascaded connection of a buck converter and a high-frequency resonant inverter loaded by several output passive rectifiers. The proposed system includes a sliding transformer to supply the mobile loads, leading to a safe and flexible location of loads. The theoretical analysis and design of the proposed system is based on a mathematical model derived using the first harmonic approximation. Selected experimental results are included to verify the system features. In comparison with conventional topology, the proposed system significantly improves efficiency, complexity and cost.Peer ReviewedPostprint (author's final draft

Enhancement algorithm for reverse loop technique on planar reverse loop antenna

Finding a trade-off balance between wireless transfer efficiency (WTE) and distance is a key issue in wireless energy transfer (WET). This paper presents a method of reducing the radical alteration in WTE versus distance, by using a reverse loop technique on planar reverse loop antenna (PRLA). The design focuses on 13.56 MHz Near Field Communication (NFC). The first stage uses mathematical modelling, based on an analytical approach, to determine the size of the reverse loop using Matlab. The proposed model predicts the size of the reverse loop to stabilize the WTE at a closer distance. Next, full-wave electromagnetic simulations are applied, using the computer simulation technology (CST) MICROWAVE STUDIO®, to determine the WTE effect with distance changes with mismatch condition. Planar loop antennas (PLAs) are fabricated on glass-reinforced epoxy laminated sheets (FR4). A validation of the simulation result in a real test scenario, using these PLAs and PRLA, confirms a stability enhancement in WTE at closer distance using the reverse loop technique, compared to conventional designs

Optimum transmitter receiver ratio for maximum wireless energy transfer

Due to high demand of using cordless mobile device, the interest in wireless energy transfer (WET) has been growth intensively. This paper presented a method to obtained optimum transmitter receiver ratio for maximum performance of WET system using different initial antenna size at various distance. An optimized algorithm has been developed to determine the optimum ratios that yield the highest wireless transfer efficiency (WTE) at near field communication (NFC) frequency, 13.56MHz. 30mm × 30mm single square loop antenna is used as initial size of both transmitter and receiver using FR4 with operating distance = 50mm. Operating distance and initial size of the antenna will be varied and the effect to the WTE will be studied using Matlab, verified using Microsoft Studio CST. At distance = 50mm and initial size of the antenna = 30mm × 30mm, optimum transmitter to receiver ratio equal to 1:3 is obtained. The pattern of optimum transmitter receiver ratio between Matlab and CST has met an agreement. This research limited to integer transmitter receiver ratio used only and no decimal number being involved in magnify the transmitter size

AN INDUCTIVE POWER TRANSFER SYSTEM WITH A HIGH-Q RESONANT TANK FOR PORTABLE DEVICE CHARGING

Master'sMASTER OF ENGINEERIN

A systematic optimization procedure of antenna miniaturization for efficient wireless energy transfer

This paper presents a systematic optimization procedure to determine the reduced antenna size aimed at obtaining the best efficiency or at least equal performance with the initial large antenna design in a wireless energy transfer (WET) system. A low-cost, square-shaped planar loop antenna designed on each side of FR4 substrate is used as both the miniature transmitter and receiver antennas operating at 13.56 MHz for the near-field communication (NFC) band. The effect of distance and antenna size on the link parameters such as inductance, resistance and mutual coupling is studied, prior to the study of their effects on WTE. The accuracy of the procedure is cross-validated using two methods; analytically and using full wave simulations. The simulation then is verified using lab measurement setup at real scene environment. Trends of the resulting curves using both methods indicated good agreements, and optimal miniature antenna for the best wireless transfer efficiency (WTE) is able to be quickly determined. A miniature antenna is able to achieve 4% wireless transfer efficiency improvement with 47% antenna size reduction. Such method can be applied to efficiently estimate a low-cost WTE system setup, besides enabling the integration of self-tuning or reconfigurability features in such systems for a known initial antenna size to mitigate changes to its operating distance

Range-Adaptive Wireless Power Transfer Based on Differential Coupling using Multiple Bi-directional Coils

Wireless power transfer systems using coupled magnetic resonances are susceptible to transfer position variation between the transmitter (Tx) and receiver (Rx). This is due to that the coupling between Tx and Rx is highly position-dependent. Once the transfer position deviates from the optimum one, the coupling will be either excessive or weak which results in power transfer efficiency (PTE) degradation. This paper presents a Tx structure consisting of multiple sub-coils oriented in opposite directions to keep the coupling relatively constant over an extensive range of transfer positions. The proposed design was able to achieve a PTE of 88% - 70% with transfer distance varying from 0 mm to 70 mm and a PTE of 85% - 60% with a misalignment of 0 mm – 80 mm at a 40 mm transfer distance. The radius of the Tx and Rx are 84.6 mm and 45.1 mm respectively. The measured PTE of the proposed design can be kept better than 70% with a 0 mm to 50 mm transfer distance while the misalignment changing from 0 mm to 50 mm. The performance of the system is much less sensitive to the transfer position, demonstrating a great potential in wireless charging applications

Wireless energy transfer between anisotropic metamaterials shells

The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated.This work was supported by the Spanish Ministry of Economy and Competitiveness under Grants TEC 2010-19751 and Consolider CSD2008-00066. The authors acknowledge Daniel Torrent for useful discussions.Diaz Rubio, A.; Carbonell Olivares, J.; Sánchez-Dehesa Moreno-Cid, J. (2014). Wireless energy transfer between anisotropic metamaterials shells. Annals of Physics. 345:55-62. doi:10.1016/j.aop.2014.03.005S556234