Efficiency Of Wireless Power Transfer System Research Articles

Asymmetrical Coils for High Efficiency Wireless Power Transfer System Under Various Angular Misalignments

Asymmetrical Coils for High Efficiency Wireless Power Transfer System Under Various Angular Misalignments

Performance Improvement of Wireless Power Transfer System for Sustainable EV Charging Using Dead-Time Integrated Pulse Density Modulation Approach

The recent developments in electric vehicle (EV) necessities the requirement of a human intervention free charging system for safe and reliable operation. Wireless power transfer (WPT) technology shows promising options to automate the charging process with user convenience. However, the operation of the WPT system is designed to operate at a high-frequency (HF) range, which requires proper control and modulation technique to improve the performance of power electronic modules. This paper proposes a dead-time (DT) integrated Pulse Density Modulation (PDM) technique to provide better control with minimal voltage and current ripples at the switches. The proposed technique is investigated using a LCC-LCL compensated WPT system, which predominantly affects the high-frequency voltage and current ripples. The performance analysis is studied at different density conditions to explore the impact of the integrated PDM approach. Moreover, the PDM technique gives better control over the power transfer at different levels of load requirement. The simulation and experimental analysis was performed for a 3.7 kW WPT prototype test system under different modes of operation of the high-frequency power converters. Both the simulated and experimental results demonstrate that the proposed PDM technique effectively enhances the efficiency of the HF inverter while significantly reducing output current ripples, power dissipation and improving the overall WPT system efficiency to 92%, and leading to a reduction in the power loss in the range of 10% to 20%. This leads to improved overall system control and performance.

An efficient wireless power transfer system planar turn based for implantable medical devices applications

A wireless power transfer system based on inductive coupling for powering implantable medical devices of diverse application is proposed. The system is composed of two resonators based with circular spiral printed on a dielectric substrate. With operation corresponding to the frequency range of medical applications in implants of 403 MHz, and an RF power transfer efficiency (PTE) greater than 50.0 % is obtained with a total reach of 8.0 mm into living tissue. Numerical studies and analyses are carried out in order to investigate the influence of tissues on the frequency response and efficiency of the presented resonators. Through simulations it is possible to establish the maximum input power limit of 120.0 mW of the model to comply with the safety limits of the specific absorption rate (SAR) below 2.0 W/kg. In general, the simulated and measured results demonstrate a good level of agreement. Comparative analyses and conclusions are presented and discussed.

Wireless power transfer efficiency enhancement based on a negative permeability double‐helix metamaterial structure

SummaryIn wireless power transfer (WPT) systems, extended transmission distances significantly impede efficiency, posing a major challenge to their practical application. This paper presents a novel ortho‐octagonal double‐helix metamaterial that can effectively enhance the transmission efficiency of WPT systems. It has theoretically derived and experimentally verified the enhancement of evanescent wave transmission by this metamaterial dielectric plate. A WPT simulation system operating at 10.78 MHz is constructed by HFSS software, and the effects of adding passive relay coils and different shapes of metamaterials on the transmission efficiency are comparatively investigated. Simulated data converge to indicate that integrating variously shaped metamaterials at the transceiver's end distinctly elevates the WPT system's transmission efficiency. When the transceiver coil spacing of the WPT system is greater than 22 cm, the effect of metamaterials on the system transmission efficiency enhancement shows an increasing and then decreasing trend as the distance increases. The positive octagonal metamaterial improves 12% over the circular metamaterial in the mid‐range transmission distance due to its better magnetic coupling effect. When the transceiver coil spacing is 22 cm, the open‐circuit voltage of the receiving coil after loading the metamaterial is stabilized to be enhanced by nearly five times, and it has the best effect at 30 cm, and the transmission efficiency is enhanced from 30% to 60%, which verifies the effective enhancement of the metamaterial on the transmission efficiency of the WPT system.

Study on the Coil Position Adaptive Adjustment Control Scheme of Wireless Power Transfer System

Wireless power transfer (WPT) technology can completely isolate the equipment from the power supply, and has been widely used. However, the transmission efficiency of WPT system is optimal only as the transmitting coil was completely aligned with the receiving coil. But in practical applications, the mobile devices are all dynamic system, and perfectly alignment of the coils is a very demanding condition. In order to solve this problem, the paper proposed a coil position adaptive adjustment control scheme of WPT system with lateral misalignment or angular misalignment. Firstly, the relationship between transmission efficiency and lateral misalignment and angular misalignment was analyzed. And the research results show that if there is a lateral misalignment between the coils, the transmission efficiency can be optimized by adjusting the angular misalignment. Secondly, based on the hill climbing algorithm, a coil position adaptive adjustment control method was proposed. Finally, a coil position adaptive adjustment WPT system experimental platform was built, and the experimental researches are carried on. The results of the experiment show that as the transfer distance is 0.10 m and the lateral misalignment is 0.12 m, the transfer efficiency can be increased from 38.38% to 55.61% through the proposed control scheme. And the results verify the feasibility and effectiveness of control scheme proposed in the paper. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Metamaterial integrated highly efficient wireless power transfer system for implantable medical devices

In this article, a novel and highly efficient metamaterial (MTM) integrated approach is presented for the development of a wireless power transfer system (WPT) specifically tailored for implantable medical devices. The system is designed by using a biocompatible implantable ring slot antenna constructed on a flexible dielectric, functioning as a receiving (Rx) antenna. Additionally, a conventional patch antenna is modelled for the use in free space, serving as an external transmitting (Tx) element. By exploiting the unique characteristics of MTMs, the power transfer efficiency (PTE) of the introduced system is effectively improved. To ensure the system’s performance stability in real-time application scenario, the effects of misalignment (lateral and angular) and the flexibility of the implantable antenna are meticulously performed. The prototypes of the Tx, Rx, and MTM structures are fabricated, and comprehensive measurements are performed in human-equivalent tissue models, such as skin-mimicking gel and minced pork. Both the simulated and measured results established the proposed methodology, showcasing marked improvements in PTE due to the use of MTMs. The efficiency of the pioneering MTM-integrated WPT system increases from 0.19% to 3.07% in skin-mimicking gel and from 0.24% to 3.26% in minced pork, respectively. This study highlights the potential of MTM-integrated WPT systems in advancing the field of implantable medical devices and expanding their practical applicability.

WIRELESS POWER TRANSFER FOR UNDERWATER VEHICLES

Wireless power transfer (WPT) through magnetic resonance coupling (MRC) offers a safe and simple solution for underwater (UV) vehicles without being affected by water conductivity. Due to its ease of control in WPT systems, the most suitable topology is Serial-Serial (SS). In this study, square transmitting and receiving coils with dimensions of 40 cm - 40 cm were designed for 3.3 kW power transmission at 85 kHz. The design was studied in the air, pure water, and seawater environments. Three different cases were analyzed with ANSYS Maxwell 3D. The WPT system responded similarly in air and pure water environments. However, it was determined that the eddy current loss increased, the mutual inductance decreased, the coupling factor weakened, and the critical air gap decreased by about 0.2 cm in the seawater environment. The results showed that the WPT system's efficiency was similar for air and pure water but tolerably lower in the marine environment. Further, the health effects of the WPT design were examined through the ANSYS HFSS, in line with the IEEE standard and ICNIRP guidelines.

An Efficiency Optimization Method Based on Double Side Impedance Angle Design for Wireless Power Transfer System

Wireless power transfer (WPT) system has already been applied to battery charging occasions, and the charging process can be roughly divided into two stages: constant current mode (CCM) and constant voltage mode (CVM). In CVM, researchers always focus on the effect of the primary phase angle (PPA) on the system efficiency but rarely pay attention to secondary phase angle (SPA). A large SPA will also lead to a decrease of system efficiency, which should be worth more attention and consideration when designing the system parameter. The double-sided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensation topology can not only achieve constant current or constant voltage output at different frequencies but also has the advantage of high parameter design freedom, so it is very suitable for battery charging scenarios. Considering the influence of the PPA and SPA on the system efficiency, a novel parameter design method based on double-sided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensation topology is proposed in this article. By changing the system operating frequency, the switching between CCM and quasi-constant voltage mode (QCVM) is realized. In order to verify the feasibility and practical effect of the parameter design method, an experimental prototype based on a planar square coil was established and three groups of comparative experiments were conducted. The experimental results show that the optimized WPT system efficiency is significantly improved under the same power level. The maximum output power of the system is 620 W. When the optimized system works in CCM and QCVM, the maximum efficiency is about 95%.

Comparison of One-Way and Two-Way Coupled Simulation for Thermal Investigation of Vehicular Wireless Power Transfer Modules

The thermal management of the vehicular module is key to the design of efficient wireless power transfer systems. In order to predict the thermal behavior by simulation, the mutual interaction of the electromagnetic and thermal fields must be taken into account. This multiphysical coupling leads to extensive computational effort. One approach to reduce the complexity by limiting the interdependencies between the domains is one-way coupling. This paper examined the applicability of one-way and two-way coupling for the prediction of the thermal management of an exemplary vehicular wireless power transfer module. The electromagnetic–thermal behavior of the proposed module was systematically studied by experiments and simulations on the component and module level. The performed studies showed that both simulation approaches accurately capture the transient thermal behavior of the coil and ferrites on the component level, whereas the one-way coupled simulation underpredicts the power losses caused by shielding by more than 20%, leading to a steady-state temperature difference of 15 K. As a result, on the module level, the two-way coupled simulation model provides a more accurate representation of the electromagnetic–thermal behavior of the proposed car pad module. Therefore, the authors recommend using a two-way coupling approach for the thermal dimensioning of wireless power transfer modules for electric vehicles.

Long‐distance and anti‐disturbance wireless power transfer based on concentric three‐coil resonator and inhomogeneous electromagnetic metamaterials

SummaryFor wireless power transfer system (WPTS), the deflection of the resonant coil and the increase of the transmission distance will cause a sharp decline in transmission efficiency. This paper presents a novel long‐distance and anti‐deflection wireless power transfer based on concentric three‐coil resonator and inhomogeneous electromagnetic metamaterials (IEM). First, the effective receiving area of the resonator is analyzed, and the anti‐disturbance concentric three‐coil resonator is designed quantitatively. Considering the magnetic field distribution generated by the transmitting coil, this paper proposes and designs IEM with three kinds of effective permeability, which is applied in different design area, respectively. Meanwhile, the finite‐element‐method simulation proves an improvement in magnetic field modulation and flux leakage control when WPTS with IEM is used. The experimental results show that, compared with the traditional one‐coil to one‐coil, the WPTS designed in this paper achieves an increase of 43% in the efficiency at a 90° deflection. Furthermore, the efficiency of WPTS with IEM is 17% and 7% higher than that of WPTS with homogeneous electromagnetic metamaterials (HEM) and without electromagnetic metamaterials. As a result, the design method in this paper can improve the anti‐disturbance capability and increase the transmission distance and efficiency.

Analysis, Design, and Optimization of the IPT System With LC Filter Rectifier Featuring High Efficiency

Passive diode bridge rectifier with LC filter is widely used in wireless power transfer (WPT) system due to its simple structure and uncontrolled characteristics. However, as the load resistance decreases, its input phase angle will also decrease rapidly until it shows obvious capacitive. Therefore, a novel rectifier topology with an input-series inductor (hereafter called ISIR) is proposed in this article to solve this problem. What is more, the ISIR can avoid the duty cycle loss and improve the dc–dc efficiency. First, the mechanism of ISIR is analyzed in detail combined with the operating status of topology. Then, the inductance and compensation parameters are determined based on theoretical calculation and simulation results. Finally, a prototype with a maximum load of 7 Ω is built to validate the feasibility and effectiveness of ISIR, and 88% efficiency is achieved under this condition. Compared with the traditional method, it has increased by 1.05%. The maximum efficiency of WPT system is as high as 91.14% with the proposed ISIR.

Wireless Powering and Telemetry of Deep-Body Ingestible Bioelectronic Capsule

In this article, a complete and efficient wireless power transfer (WPT) system, consisting of a full-duplex antenna, a half-wave rectifier, and a WPT transmitter (Tx), is designed and validated for deep-body ingestible biomedical capsules. A two-port full-duplex antenna is adopted to perform seamless telemetry and to act as a receiver for WPT Tx without using a multiplexer circuit. The full-duplex implantable antenna operates at 915 MHz (Port 1) and 1300 MHz (Port 2) and occupies compact dimensions of 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 0.13 mm 3. It maintains high isolation of >30 dB and peak realized gains of −19.3 dBi at 915 MHz and −17.7 dBi at 1300 MHz. The miniaturization of this antenna is achieved using semicircular slots on the patch and circular slots on the ground plane while mutual coupling between the ports is reduced by a series of metallic vias. Moreover, a low-profile and efficient rectifier is designed at 1300 MHz and integrated with port 2 of the antenna. The suggested rectifier achieves a radio frequency (RF) to direct current (dc) conversion efficiency of 80.4% at an input power of 1 dBm. Furthermore, a patterned patch antenna is designed that acts as a WPT Tx for the biomedical capsule. After examining the individual performance of the antenna, rectifier, and WPT Tx, the overall WPT system is then validated by placing the capsule (rectifier integrated antenna) inside minced pork meat and powered by the WPT Tx. This WPT system is suitable for modern capsule devices due to its features, such as compact size, high gains, high RF-dc conversion efficiency, simultaneous wireless powering and telemetry, and high-power transfer efficiency (PTE).

Performance Analysis of Different Shielding Material for A 100W Wireless Power Transfer System

To improve the efficiency and performance of the wireless power transfer system (WPT), the core material or the coil shielding material must be selected appropriately due to its significant factors to the system. This paper discusses the importance of using coil shielding and the types of material that is suitable to increase the performance of WPT system. The simulation was carried out using 3D finite element analysis called JMAG-Designer. The purpose of using shielding material in a coil is to redirect the magnetic field generated from the primary to the secondary coil. The result and analysis shows that soft magnetic material (ferrite core) used as core shielding is suitable for WPT application. It increases the power transferred and performance efficiency of the system. Compared to the other shield materials, the usage of ferrite core is found to increase the WPT efficiency up to 92%.

High-Efficiency Omnidirectional Wireless Power Transfer System

To achieve omnidirectional wireless power transfer (WPT), it is crucial to tune the direction of the total magnetic field from the transmitter (Tx) coils toward the receiver coil (Rx) that can be placed at different positions with respect to Tx. Several methods, such as amplitude modulation, phase-shifting, and frequency modulation, have been proposed to vary the Tx currents, depending on the angular position of Rx, but complex sensing and feedback control systems are required. In this article, we propose an efficient omnidirectional WPT system that is capable of self-tuning the power flow without any feedback from the Rx-side. It only requires a simple Tx current switching rather than complex feedback control system for detecting the Rx position. The proposed system consists of three orthogonal transmitter–repeater (Tx-Rp) channels that deliver power to Rx. In this configuration, the Tx currents are proportional to the mutual coupling between the Rp and Rx in the same channel, which ensures the self-tuning of the optimal power flow through channels. Both theoretical and experimental studies are performed to validate the proposed method. The prototype of the proposed approach enables the Rx to harvest power with almost uniform high efficiency (about 90%) regardless of its angular position.

Design and Control of Cost Effective Wireless Power Transfer Systems of AC Motor Drives with Efficiency Maximization

Abstract-Motor drives supplied through wireless power transfer (WPT) systems require a high frequency inverter in primary side, a rectifier and low frequency inverter in secondary side of the system. Due to this arrangement, reliability and efficiency are reduced whereas the cost and complexity of the system are increased. In this paper, a single inverter in the primary side drives an induction motor by removing rectifier and inverter and replacing it with AC/AC chopper in the secondary side. In this way, the desirable ac power can be injected into the motor effectively and also the WPT system efficiency is improved because of reduced power conversions. The performance of proposed wireless ac motor drive under a closed-loop V/f control system is verified by simulation using MATLAB/SIMULINK. KEYWORDS-AC/AC converters, electric vehicles, wirelessmotordrives, wireless powertransfer.

Unified Coil and Compensation Network Design for Improving Wireless Power Transfer Efficiency Over Wide Output Load Variation Ranges

It is shown that compensation network and coil design collectively affect wireless power transfer efficiency. Based on this fact, a novel design approach of wireless power transfer (WPT) systems is proposed. Unlike majority of existing designs which aim at enhancing power transfer efficiency (PTE) at one rated operating point, the proposed design enhances the overall system PTE. This feature is essential for variable output loads such as batteries, where their internal impedance varies during charging period. To achieve this goal, improving time-weighted average efficiency of WPT system is set as the design criterion. Experimental studies of a 1.2 kW WPT system supplying constant resistive loads and battery loads verify that the proposed design enhances PTE both at rated output load and under wide output load variations.

Compact and Efficient WPT System to Embedded Receiver in Biological Tissues Using Cooperative DGS Resonators

This brief presents a compact and efficient resonance-shift insensitive wireless power transfer (WPT) system. This is possible by using a small electrical length defected ground structure (DGS) resonator, which is found effective against the resonance-shift phenomenon resulted from the higher permittivity of the tissue. Tissue has two undesired effects on a WPT system: (i) reduced coupled quality factor, and (ii) self-resonance shifting that leads to mismatch loss. So, the efficiency of a WPT system degrades in a tissue environment. Then, using the small electrical length DGS, we build a WPT transmitter (TX) using three cooperative DGS resonators to mitigate both issues. The fabricated prototype operates at 49 MHz in the air and tissue. This shows no change in operating frequency when the same receiver (Rx) is kept in the air or embedded inside tissues, which proves the effectiveness of the proposed cooperative DGS-WPT system against the resonance shift. The measured efficiency is 62% when the RX is embedded inside the tissue and is 68% in the air.

Coil material and magnetic shielding methods for efficient wireless power transfer system for biomedical implant application

In this paper, a passive shielding method is presented to minimize the magnetic field around the transmitting (Tx) and receiving (Rx) coil of wireless power transfer (WPT) system for biomedical implant application. Different conductive materials for coil construction, as well as dielectric materials for shielding, are being considered to improve WPT performance. Several cases of WPT coils have been examined using the simulation approach at 800 kHz and 6.78 MHz in the existence of a pacemaker casing with and without a magnetic shield. According to simulated results, it is found that high conductivity coils and high permeability shield materials are excellent materials for increasing the WPT system's efficiency. The results of the simulation method and physical measurement in Lab are validated using an analytical method. The efficiency obtained by using simulation method is very close to that obtained using the analytical method. The voltage gain obtained using an analytical and a simulation method at 800 kHz and 6.78 MHz is very close to the actual measurement in the lab. It is found that the WPT efficiency at 6.78 MHz is higher as compare to 800 kHz.

Research on Constant Voltage/Current Output of LCC–S Envelope Modulation Wireless Power Transfer System

As a technology that makes power transfer more flexible, wireless power transfer (WPT) technology has become a hot research topic in recent years. However, most of the existing studies are based on a DC–DC WPT system. If applied to AC loads, the traditional system usually contains multiple energy conversion stages, which lead to a low transmission efficiency and therefore higher costs. Besides, the necessary large electrolytic capacitors make the system unreliable and bulky. The goal of this study is to design a reliable and efficient WPT system featuring constant current (CC) and constant voltage (CV) output for AC loads. In this work, an inductor–capacitor–capacitor series (LCC–S) enveloped modulation wireless power transfer (EM–WPT) system is proposed. The design of the proposed system is elaborated in this paper, including the working principle of the system’s power converters, the relationship between CC/CV output characteristics and the input current, and the control strategy of CC/CV output based on an AC–AC boost converter. Lastly, an experimental prototype is configured to verify the CC/CV characteristics. The measured overall efficiency of the system reaches 91% and the power factor of input power supply approaches 1.

Analysis of harmonic characteristics based on improved double-LCC compensation network structure

The article firstly analyzes the filtering characteristics of double-LCC circuit in wireless power transfer (WPT) system. By defining voltage interference ratio (VIR), the harmonic interference introduced by inverter output voltage square waveform is represented. The ability of suppressing harmonic voltage source interference with different frequency of each branch of compensation network is obtained by analyzing VIR. In order to further reduce the harmonic content of each branch of circuit and decrease the harmonic introduction from the input-side, the article adopts an LC-double-LCC topology circuit. That is, an LC resonant part is connected in series at the input-side of circuit. The VIR of both double-LCC and new structure are compared by building mathematical model, and it is proved that the new structure has better ability to restrain interference. The total harmonic distortion (THD) of input-side current is calculated and the relation between the values of LC part, coupling coefficient, load and THD is quantitatively expressed. The sensitivity analysis in detuning condition of two structures is conducted. When the frequency offset becomes larger, the new topology shows better effect on inhibiting the increase of capacitive and inductive degree of the input impedance angle. The efficiency of WPT system with LC-double-LCC structure is analyzed, and reactive power of input-side is expressed by the value of LC part. With the parameters selected in this article, the input reactive power decreases 55.6% and power factor increases 0.68% after adding LC part. The results of simulation and calculation show that the LC-double-LCC structure has higher efficiency and larger power factor. An experimental platform is built and the theoretical results are verified.