Wireless Power Transfer Applications Research Articles

Graded-Index-Fiber-Inspired 3-D Printed Surface Focusing Porous Dielectric Structure With GaAs MMIC Rectenna Toward Millimeter-Wave Wireless Power Transfer Application

Graded-Index-Fiber-Inspired 3-D Printed Surface Focusing Porous Dielectric Structure With GaAs MMIC Rectenna Toward Millimeter-Wave Wireless Power Transfer Application

Advantages and Disadvantages of Computational Dosimetry Strategies in the Low mmW Range: Comparison Between Multilayer Slab and Anthropomorphic Models

Wireless technologies spanning at the higher bands of microwave range (i.e., Ka-band) are gaining increasing importance in everyday life. Most recent wireless power transfer (WPT) applications work in the microwave and millimeter wave (mmW) frequencies, overlapping with the new frequency bands of the fifth-generation (5G) mobile technology. The spread of such novel electromagnetic (EM) sources raised the need to investigate their possible effects on population’s health. Numerical dosimetry is fundamental to assess the exposure of the human body. In the range 24–28 GHz, i.e., the low-band spectrum of the mmW, and bridge between microwaves and mmW, there is poor consensus on the best strategy to model the human body. This article proposes a comparison between the two numerical methodologies typically adopted for this frequency range: the use of multilayer planar slabs and realistic anthropomorphic numerical models. The aim is to highlight the advantages and limits of each method, by comparing EM exposure results obtained on the Virtual Population (ViP) model Duke with several multilayer planar slabs. The differences between the two methods are non-negligible, suggesting the need of further studies and the necessity of improving both modeling approaches, depending on the frequency of work and the investigated application.

New Printed-Circuit-Board Resonators With High Quality Factor and Transmission Efficiency for Mega-Hertz Wireless Power Transfer Applications

New Printed-Circuit-Board Resonators With High Quality Factor and Transmission Efficiency for Mega-Hertz Wireless Power Transfer Applications

Model-Based Optimization of Spiral Coils for Improving Wireless Power Transfer

Inductive wireless power transfer is a promising technology for powering smart wearable devices. The spiral coil shape is widely used in wireless power transfer applications. Nevertheless, during the coil design process, there are many challenges to overcome considering all the design constraints. The most important is to determine the optimal coil parameters (internal radius, external radius, spacing, wire width, and conductive wire) with the aim of obtaining the highest coil quality factor. Coil modeling is very important for the wireless power transfer system’s efficiency. Indeed, it is challenging because it requires a high computational effort and has convergence problems. In this paper, we propose a new approach for the approximation of spiral coils through concentric circular turns to reduce the computational effort. The mathematical model determines the optimal coil parameters to obtain the highest coil quality factor. We have chosen the smart textile as an application. The system operates at a frequency of 100 Khz considering the Qi guidelines. To validate this approach, we compared the approximated circular coil model with the spiral coil model through a finite element method simulation using the COMSOL software. The obtained results show that the proposed approximation reduces the complexity of the coil design process and performs well compared to the model corresponding to the spiral shape, without significantly modifying the coil inductance. For a wire width smaller than 1 mm, the total deviation is around 4% in terms of the coil quality factor in a predetermined domain of its parameters.

Benchmarking of cutting-edge wireless power transfer for electric vehicles

Wireless power transfer (WPT), which can transfer energy though magnetic field, electronic field, laser beam, microwave and other methods without wire, provide electric vehicles (EVs) a better prospect. Compared to cars with internal combustion engines, Electric vehicles are more environmental-friendly, and do not need any fossil fuel, which is a ideal transportation in the future, however, for electric vehicles, battery technology is the major barrier: high cost, low energy density and large weight, which make electric vehicles very expensive and difficult to improve the endurance mileage, by applying wireless power transfer technology, using dynamic wireless charging can solve these problems perfectly. This paper reviews basic information of wireless power transfer technologies: four basic classification of WPT, basic compensation networks for inductive wireless power transfer, coil designs to improve the transferring efficiency, and wireless power transfer applications on EV charging, additionally, challenges and potential solutions for wireless power transfer of EV are presented.

Research on coil identification algorithm of wireless power transmission system based on deep learning

In the practical application of wireless power transfer (WPT) technology, the identification of uncertain secondary side coil is of great significance to the interoperability of the WPT system. Whether the secondary coil can be accurately identified to realize the ideal match of the primary coil and the secondary coil is one of the keys to achieve efficient power transmission. Based on the characteristics of magnetic field image, this paper combines the convolutional neural network (CNN) to realize the recognition of the coil type, and establishes a 4-layer and 6-layer neural network respectively, and the recognition accuracy is as high as 98%. Compared with the existing visual geometry group (VGG) 16 neural network algorithm, the proposed algorithm has lower complexity and is more suitable for the WPT application field.

LitzImp: A Fast Impedance Extraction Algorithm for Litz Wire Coil

Litz wire coil (LWC) is an electronic component commonly used in wireless power transfer (WPT) and heating applications. However, due to its complex twisting structure with turns, existing calculation methods such as analytical methods and finite element method (FEM) cannot extract the impedance of LWC efficiently. This paper proposes an efficient numerical calculation algorithm named LitzImp for fast impedance extraction of LWC. LitzImp provides different simplification schemes for different coil structures, reducing the resource consumption in the repeated calculation for the same structures and improving efficiency while maintaining high accuracy. Experiments with nine manufactured coils, including circular coils (CC) and rectangular coils (RC), from simple to complex, are adopted to verify the performance of LitzImp. The comparative verification compared with FEM and the analytical method shows the advantages of LitzImp in terms of efficiency and accuracy. Through the analysis of the time consumption, the proposed method is 45 times faster than the similar numerical method for a given coil structure. For highly complex coils (500 strands), the impedance is obtained in less than 5.5 hours with good agreement with the measurement. LitzImp will be a powerful tool for the optimal design of LWC due to its high efficiency.

2.4 GHz Rectifier Antenna for Radiofrequency-based Wireless Power Transfer: Recent Developments, Opportunities, and Challenges

The use of radio frequency (RF) energy for wireless power transfer (WPT) has gained significant attention in recent years due to its potential for powering electronic devices without the need for wires or batteries. A key component of RF-based WPT systems is the rectenna, which converts RF energy into usable DC power. This article provides an overview of recent developments, opportunities, and challenges in the design of 2.4 GHz rectennas for RF-based WPT applications. We have searched major online libraries extensively for studies regarding the 2.4 GHz rectenna. As a result, 35 high-quality studies published between 2010 and 2023 were gathered. In the discussion section, we begin by presenting the basic principles of rectenna design and the key parameters that affect its performance, such as the antenna characteristics, rectifier capabilities, and nonlinearity properties of the rectifier. We then highlighted recent advancements in rectenna design, including novel approaches for improving efficiency and power transfer capability, such as the involvement of hybrid solar cell-rectenna structures, transistor-based rectifiers, and bridge rectifiers. Finally, the article concludes by identifying future opportunities, research directions, and open challenges in the design and optimization of rectennas for RF-based WPT, including the development of compact, low-cost, and high-performance rectennas for a wide range of applications. Overall, this article provides a comprehensive overview of the state-of-the-art of 2.4 GHz rectenna design for RF-based WPT and highlights the exciting opportunities and challenges for this rapidly growing field.

Distance Extension of S-PS Wireless Power Transfer System Based on Parity-Time Symmetry

The application of wireless power transfer (WPT) has become more and more extensive, and the parity-time (PT) symmetric principle has been proved to significantly improve the degree of freedom of the WPT system without increasing the control complexity. However, the PT-symmetric region of the original WPT system with series-series (SS) compensation is limited. To overcome this drawback, a novel PT-symmetric WPT system with series-parallel-series (S-PS) compensation is proposed in this paper. The PS compensation network is converted to the S compensation network by equivalent circuit method. Then a mathematical model of the proposed system is established by circuit theory. It is found that the critical coupling coefficient of the proposed system are much smaller than the original PT-symmetric system. Furthermore, the proposed system has a compromise between transmission distance and transfer efficiency by setting the capacitance distribution ratio. A 26W prototype is built to verify the feasibility of the proposed method. Experimental results demonstrate that the proposed method doubles the transmission distance and improves the output power.

A New Simplified Method and Design Guidelines for the Optimization of Push–Pull Class $\Phi _{2}$ Converters for Wireless Power Transfer Applications

The complicated resonant operations of class <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\Phi} _{2}$</tex-math></inline-formula> topology bring challenges for accurate design and performance optimization, hindering the full utilization potential of converters. Considering the narrow design freedom in traditional methods with almost fixed duty cycle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$D$</tex-math></inline-formula> , this article widens the design options of push–pull class <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\Phi} _{2}$</tex-math></inline-formula> converters through frequency-harmonic analysis. A full selection freedom of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$D\in (0,0.5)$</tex-math></inline-formula> is discussed analytically, providing ample space for optimization based on any required performance indices. From 1.98E5 analytical results, we found six numerical equations that fully decouple the interconnected relations between each circuit parameter and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$D$</tex-math></inline-formula> . The proposed numerical method allows rapid circuit design and component selection with a high accuracy regardless of the system power or load voltage. Parasitic effects are discussed and incorporated into the design approach as correction steps. Finally, we introduce performance analysis based on an example wireless power transfer (WPT) system, providing in-depth studies on the optimization regarding efficiency, power output capability, and component selection. Experimental results validate the accuracy and efficiency of the proposed design method based on a 100-W WPT system at 6.78 MHz frequency. Both inverter and rectifier present load-independent soft-switching operations, with converter efficiency over 93%. The system provides 83% dc–dc efficiency at full load.

Design of Compact and Superdirective Metamaterial-Inspired Two- and Three-Elements Antenna Arrays

This paper presents the development of a miniature antenna array in a small space in order to achieve superdirectivity for long-range communication. The proposed structures consist of a superdirective metamaterial-inspired array based on a capacitively loaded loop (CLL) driven by an electrically small monopole antenna. This elementary antenna is then used in two- and three-array configurations separated by a fixed interelement distance of 0.1λ to achieve a higher directivity and compact size (with λ the wavelength calculated at the operation frequency 1.850 GHz). The design of the elementary antenna, its simulated radiation performances, as well as those of the parasitic array are also reported. The results of the optimization of two- and three-antenna arrays are discussed. For this study, three corresponding prototypes were fabricated and tested. The measured impedance mismatch and radiation pattern results are presented and shown to be in good agreement with their simulated values. The maximum measured directivity is equal to 5.9 dBi and 4.75 dBi in the case of the two- and three- elements, respectively. The proposed antenna arrays can serve for the realization of point-to-point wireless links and can have a significant impact on compact and high-directive radiofrequency front-ends of a wireless system and for wireless power transfer applications.

Design of a 2.4 &amp; 5.8 GHz Efficient Circularly Polarized Rectenna for Wireless Power Transfer Applications

In this paper, we proposed a novel dual-band circularly polarized rectifier antenna for collecting environmental electromagnetic energy at 2.4 and 5.8 GHz. The receiving antenna is a circularly polarized microstrip slot antenna that achieves circular polarization in the low-frequency band (2.4 GHz) and high-frequency band (5.8 GHz) through the use of the “U” slot of the ground and the “L” branch of the upper patch, respectively. The antenna exhibits impedance bandwidths of 320 MHz (2.18–2.50 GHz) and 3.73 GHz (5.33–9.06 GHz) in the 2.4 GHz and 5.8 GHz bands, respectively, while the 3 dB axis specific bandwidths are 260 MHz (2.32–2.58 GHz) and 420 MHz (5.66–6.08 GHz), respectively. The antenna gains are 3.5 dBi and 6.2 dBi at 2.4 GHz and 5.8 GHz, respectively. Furthermore, a dual-frequency voltage doubling rectifier circuit was designed to operate with the antenna. A dual-branch matching circuit was used to achieve impedance matching between the antenna and the rectifier circuit, and the output was optimized to suppress high-order harmonics through sector branches to improve the rectification efficiency. The simulation results show that the maximum rectification efficiency of the circuit is more than 80%, with a measured efficiency of over 60%. This 2.4–5.8 GHz dual-band circularly polarized rectifier antenna has the potential to self-power low-power devices in the Internet of Things, making it a valuable contribution to the field of wireless energy harvesting.

A 5.8 GHz 1.8 V +20 dBm 32.5% PAE Power Amplifier for a Short-Range Over-the-Air WPT Application.

This paper presents a 5.8 GHz differential cascode power amplifier for an over-the-air wireless power transfer application. Over-the-air wireless power transfer provides a variety of benefits in several applications such as the Internet of Things and medical implantation applications. The proposed PA features two fully differentially active stages with a custom-designed transformer to provide a single-ended output. The custom-made transformer shows a high quality factor, as high as 11.6 and 11.2 for the primary and secondary sides at 5.8 GHz. Fabricated using a standard 180 nm CMOS process, the amplifier achieves input and output matching of -14.7 dB and -29.7 dB, respectively. To achieve a high power level and efficiency, accurate optimization through power matching, Power Added Efficiency (PAE), and the design of the transformer are carried out while the supply voltage is limited to 1.8 V. Measurement results show a 20 dBm output power with a PAE as high as 32.5%, which makes the PA suitable for application, and it can be implanted while arrayed with various antenna arrays. Finally, a FOM is introduced to compare the performance of the work with similar works in the literature.

Preface

Striving to achieve carbon peaking by 2030 and carbon neutrality by 2060 is a major strategic development decision for China at present. Among them, building a new power system with new energy as the main body is an important step to promote the clean and low-carbon energy transition and build a better China. To achieve the double carbon goal, energy, power and grid are all indispensable and important forces.Following this concept, the 2023 3rd International Conference on Power Grid Systems and Green Energy (PGSGE 2023) was held during January 6th to 8th, 2023 in Xiamen, China (virtual event). The conference aimed to encourage information exchange from the frontiers of energy grid research, connect the most advanced academic resources in China and the world, transform research results into industrial solutions, bring together talents, technologies and capital, and promote development.This volume contains the papers presented at PGSGE 2023. The papers cover various topics including Power Engineering, High Voltage Systems, Power System Reliability, Energy and Power Engineering, Energy Efficiency and Management, Heat and Mass Transfer Theory, etc. have been through rigorously reviewed by experts and meet the requirements of publication.The online conference attracted about 50 individuals, and four sophisticated professors performed their keynote speeches and shared with us their research experience and professional insights during the conference. The topics of keynote speech included: a): Advanced Predictive Control for Electric Energy Conversion Systems; b) Theory and Application of Wireless Power Transfer; c): Smart Energy Systems; d) Lithium-Ion Battery Simulation Models for Storage Systems in Renewable Power Generation. All the keynote speakers made brilliant speeches combing their own research domains and experiences, and interacted with the audience for the questions raised and better academic communication.On behalf of the Conference Organizing Committee, we would like to extend our sincere acknowledgement to all the keynote speakers, peer reviewers, and all the participants. Particularly, our heartfelt thanks and appreciation go to the Editors and Managers, Journal of Physics: Conference Series for their help and kind cooperation during the preparation of the proceedings. Hopefully, all participants and other interested readers can benefit significantly from the proceedings and find it rewarding.The Committee of PGSGE 2023List of Committee Member is available in this Pdf.

An Integrated Three-Phase AC–DC Wireless-Power-Transfer Converter With Active Power Factor Correction Using Three Transmitter Coils

Three-phase AC-DC converters are more commonly used for high-power applications compared to single-phase converters. For high-power wireless power transfer (WPT) applications, such as wireless electric vehicle chargers, usually a two-stage topology is applied, which consists of a three-phase AC-DC rectifier with power factor correction and a DC-DC converter for WPT. Recently, there are several studies on three-phase single-stage WPT solutions being proposed to reduce power conversion stages, and furtherly increase overall efficiency and reduce system cost. In this paper, an integrated three-phase AC-DC WPT converter topology with active power factor correction is proposed. The count of power semiconductor devices is significantly reduced compared to state-of-the-art three-phase single-stage topologies. Moreover, three transmitter coils are used to enhance the system power capacity. Topology description, operation analysis, control method, power loss analysis, and reference design guideline of the proposed topology are presented in detail. Finally, a laboratory prototype is built and evaluated. The functionalities, performances, and advantages are demonstrated by the corresponding experimental results.

A High-Power Capacity Transistor-Based Rectifier With Wide Input Power Range

This letter proposes a methodology for realizing the rectifier with a wide radio frequency (RF) input power range for large power capacity applications. The comprehensive analysis is given in this letter under the condition of class-F operation mode. The optimum conduction angle of the transistor corresponding to the maximum input power dynamic range is determined. Theoretical rectification efficiency of over 60% can be obtained in a 30 dB in-depth input power level. For validation, an RF-dc rectifier operating at 2.45 GHz is designed based on the GaN transistor. Measurements demonstrate that the rectification efficiency of between 60.4% and 82.1% is realized with a fixed dc load of 115 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $</tex-math> </inline-formula> when the RF input power is from 18 to 43 dBm. To the best of the authors’ knowledge, it is the first realization of a transistor-based RF-dc rectifier with a large input dynamic range of over 25 dB. The proposed rectifier shows great potential to be used in future high-power wireless power transfer (WPT) applications.

Precise Modeling and Design of Self-Resonant for High-Efficiency Mid-Range Wireless Power Transfer System

Transfer power and efficiency of wireless power transfer (WPT) systems are limited by the quality factor and coupling coefficient of the transmitting (Tx) coil and receiving (Rx) coil. Getting rid of compensation circuits, self-resonant coils have simple structure, high system reliability, high quality factor and high power level, making it a promising candidate for WPT applications. In modeling and computation of self-resonant coils, the results derived from the transmission line theory have obvious errors, and the finite element simulation takes a long computing time. For obtaining accurate results and achieving fast computation, a partial-element equivalent circuit (PEEC) method is applied to calculate the self-resonant frequency (SRF) and the current distribution of helical coils. To validate the accuracy of the proposed model, some prototypes were simulated and measured. The theoretical calculation predications are in great agreements with the simulation and measurement results. The magnetic coupling model between Tx and Rx is also established using PEEC method and a novel design guideline of self-resonant helical coils is proposed. Furthermore, a WPT system with 6.78MHz selfresonant helical coils was designed, fabricated and tested for a high-efficiency mid-range energy transfer. It was used to drive a 5W load wirelessly as a demonstration to validate the feasibility of the proposed system in practical applications.

Wireless Power Transfer: A Paradigm Shift for the Next Generation

The first generation of wireless power transfer (WPT) standard Qi, launched in 2010, contains a wide range of transmitter and receiver designs with the aim of maximizing compatibility to attract many manufacturers to share the same standard. Such compatibility feature (i.e., interoperability) has not only attracted over 400 company members in the Wireless Power Consortium (WPC), but also facilitated a fast-growing wireless power market for a decade. The WPC is now expanding the scope of WPT applications to mid-power and high-power applications up to several kilowatts while the Society for Automobile Engineers also set the SAE standard for wireless charging of electric vehicles (EVs) up to tens of kilowatts. Without compromising compatibility, the authors share in this paper their views on the need for a paradigm shift from compatibility to optimal performance in terms of maximum energy efficiency for the entire charging process and minimum charging time. This paradigm change is imminent and important in view of the increasing power of WPT applications. Several enabling technologies essential to the paradigm shift will be addressed.

An Overview of Technologies and Applications of Wireless Power Transfer

Wireless power transfer (WPT) is one of the most frequently discussed topics. Due to its straightforward implementations and designs, it is also one of the most commercialized. It is a technology that allows power to be transferred from one electrical transmitter to another electrical transmitter across an air gap. Inductive coupling, magnetic resonance coupling, and radio-frequency transfer are the three widely used wireless power transfer technologies, and this study provides a thorough summary of their respective histories. Latest implementations are also introduced. Current implementation of the technology in vogue are confronted with some challenges, which may be seen as future research trends, in hope of miniaturizing gadget complexity, enhancing device transmission duration and reducing costs.

Adaptive Wireless Power Transfer via Resonant Laser Beam Over Large Dynamic Range

Wireless power transfer (WPT) via resonant laser beam from a spatially-distributed laser resonator not only benefits the instinct safety, but also has important potential of adaptive operation without positioning and aiming when retroreflectors are used to enable the alignment-free operation of the laser. Despite the intense theoretical modeling and experimental efforts with different laser schemes, the adaptive resonant beam WPT across large dynamic range -including both working distance and field of view (FoV) -has never been demonstrated, due to the absence of true alignment-free laser. In this work, we summarized the requirements on the dynamic range and discussed the optimization criteria of dynamic range and laser safety, including the telescope in the laser resonator, the resonator stability, coupled-resonator scheme, and influences of the optical aberrations. The analysis indicated that loss induced by optical aberrations is the main issue limits the dynamic range. In the experiment, alignment-free laser with large dynamic range for WPT application was demonstrated with improved resonator design and optical design to compensate the aberrations. Efficient multiwatt optical output was obtained across a working distance of 1-5 m, a receiver FoV of ±30∘, and a transmitter FoV of 4.6∘; and over 1.3 W electrical output was obtained via an InGaAs photovoltaic cell, with DC-DC WPT efficiency being 4%. Our work proved the feasibility of large-dynamic-range alignment-free laser with distributed-resonator, which paves the way for practical resonant beam charging and communication applications based on it for the internet of things devices.