Wireless Power Transfer Applications Research Articles

Wireless Power Transfer System Model Reduction with Split Frequency Matching

Reduced-order dynamic models of wireless power transfer (WPT) systems are desired to simplify the analysis and design of power control, phase synchronization, and maximum efficiency tracking. The reduced-order dynamic phasor model is a good choice because of its straightforward physical meaning and concise mathematical formula. However, the model relies on the assumption of loose coupling and loses accuracy when the coupling becomes stronger. In this paper, a model reduction method with split frequency matching is proposed to improve model accuracy under relatively strong coupling conditions, which is suitable for most short-distance WPT applications, such as wireless electrical vehicle charging. Split frequency matching is achieved through a pair of conjugate equivalent mutual inductances, which are derived from the asymmetry characteristics of the full-order dynamic phasor model in the positive and negative frequency domains. The proposed model retains the advantages of the existing model while significantly improving the accuracy under strong coupling conditions. Its characteristics are verified by comparing the experimental results and model predictions under both large step changes and small-signal perturbations.

Design and optimization of a miniaturized dual band rectenna for wireless power transfer applications

This paper presents the design of a compact printed rectenna circuit suitable for wireless power transfer applications at frequencies 900 MHz and 1450 MHz. The rectenna circuit consists of a rectangular patch antenna measuring 17.7 x 8.85 mm2, printed on a Rogers RO4003 substrate. It also includes a voltage doubler (VD) circuit comprising Schottky diodes (SMS7631) and an impedance-matching circuit. The design and optimization of the antenna are performed using Ansys HFSS software, while the DC and RF features of the VD circuit are analyzed using the Advanced Design System (ADS) software. The circuit design is presented in two stages: one for single-frequency operation at 900 MHz and another for dual-band operation at 900 and 1450 MHz. The design of single-stage and double-stage VD for dual-band operation is also discussed in this paper. The rectenna's Power Conversion Efficiency (PCE) is evaluated under various load and input power conditions. The maximum DC output voltage measured is 5.318 V at 900 MHz and 5.52 V at 1450 MHz. Furthermore, the maximum PCE achieved is 53% and 54% for 900 MHz and 1450 MHz respectively. These values are obtained with a RF input power level of 20 dBm and a load resistance of 10 KΩ.

Evaluation of Additive Manufacturing for Wireless Power Transfer Applications

Additive Manufacturing (AM) has emerged as an economical and feasible technology for creating industrial components. This paper evaluates the use of AM for inductive Wireless Power Transfer (WPT) systems. In particular, the innovative use of metal 3D printing is proposed as a manufacturing process for the coils. For this reason, the recent improvement of metal AM is proposed as a suitable solution to increase design opportunities, reduce costs and production time while improving transmission efficiency. In fact, the WPT coil current distribution can be preliminarily studied through Finite Element Analysis (FEA) to optimize its cross-section and geometry. In this work, a general design procedure for WPT coils using metal AM is presented and this technology is compared with traditional solutions (i.e. hollow and litz wire) through extensive experimental measurements. The analysis shows that AM allows to reduce the parasitic resistance, costs and weight while increasing the transmission efficiency. Thus, the obtained results confirm the potential of AM for producing WPT coils, nominating this technology as a flexible, sustainable, and rapid solution for custom WPT coils production.

A multi‐receiver adaptive design of variable magnetic coupled structure for omnidirectional WPT system

SummaryOmnidirectional Wireless Power Transfer (OWPT) system can provide power to multiple loads in space. The different loads have different requirements for current and power levels under various operating conditions. This paper proposes a Variable Receiving Coil (VRC) structure and its control strategy. Active regulation of the output current is achieved by adjusting the geometric size of the receiving coil. Meets the power supply needs of equipment in different scenarios. This design allows the effective value of the VRC current to remain stable within the range of 1.01–1.62A (transmission distance of 22–27 cm). By adjusting the geometric transformation state of the VRC, different output currents can be obtained under fixed positions, loads, and input voltages. The designed receiver can meet the differential current requirements of multiple spatial loads, and is insensitive to factors such as load, transmission distance, and rotation angle. This system can reduce the design complexity of charging and power supply systems and effectively promote the application of Wireless Power Transfer (WPT) in the field of Internet of Things devices.

Gyrator-Gain Variable WPT Topology for MC-Unconstrained CC Output Customization Using Simplified Capacitance Tuning

Load-independent constant current (CC) outputs are desirable in many applications of wireless power transfer (WPT). Yet the WPT gain of a conventional system is normally dependent on the magnetic components (MCs) such as coils or inductors, making it difficult to customize the output for interoperability. This paper presents a gain variable WPT topology for CC output customization, which only employs capacitance tuning to provide sufficient freedom in gain regulation. To break the gain limitation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-S</i> compensation, which is the simplest with gyrator characteristics for CC output, a capacitive or inductive component is paralleled to the coil as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SP-S</i> or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-PS</i> compensation. A thorough analysis based on the Y-Δ transform indicates that the gain is restrictively variable with the parallel component. An <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-CLC</i> -compensated topology without an independent inductor is further proposed to avoid those restrictions with as few additional components as possible. The inductor in the topology, coupled with the transmitter coil and integrated into the receiver coil, extends the gain variable range. A complete design process of the topology is presented to realize efficient WPT and CC output customization with a wide variable-gain range and misalignment tolerance. Analytical and simulation results confirm the effectiveness of the gyrator-gain variation by capacitance tuning. Finally, the performance of the WPT topology is evaluated by experimental results on a scaled-down prototype.

4×4 UWB Phased Array Antenna With &gt;51° Far-Field Scanning Range for Wireless Power Transfer Application

4×4 UWB Phased Array Antenna With &gt;51° Far-Field Scanning Range for Wireless Power Transfer Application

A Novel Impedance Matching of Class DE Inverter for High Efficiency, Wide Impedance WPT System

In high-frequency wireless power transfer (WPT) applications, Class D, E, and F inverters are most widely used. Class DE inverters combine the respective advantages of Class D and Class E inverters. However, the Class DE inverter is sensitive to changes in impedance, which can easily lead to the loss of soft switching characteristics, thereby reducing efficiency. In this paper, an impedance-matching compensation design method is proposed to expand the high-efficiency region of the Class DE inverter by matching impedance and parameters. The effect of the method on the zero-voltage switching (ZVS) characteristic of Class DE inverters is analyzed in detail. The proposed WPT system maintains a constant voltage and zero phase angle by employing PS/PS compensation topology. Theoretical analysis shows that the impedance can be compressed for the design of resonant network impedance, and the method can expand the high-efficiency region with a reasonable choice of parameters to match the phase. Finally, a 500 kHz, 1 kW WPT prototype was constructed with a coupling factor of 0.25–0.4 and a load range of 30–80 Ω. The inverter’s efficiency exceeds 95%, with optimal efficiency reaching 97.3%. The system efficiency is greater than 87%.

A Simultaneous Power and Data Transfer Technology Using Dual-Resonance-Band Circuits for Domino-Resonator WPT Systems

The integrated transmission of power and data is a promising technology in various wireless power transfer (WPT) application scenarios. In this work, a novel simultaneous power and data transfer (SPDT) technology for domino-resonator WPT systems is proposed. The frequency shift keying (FSK) power modulation method is adopted in dual-resonance-band circuits to maintain high system transfer efficiency at two different frequencies. Considering the cross-coupling between nonadjacent resonators, the system operating frequencies shift slightly away from the circuit resonant frequencies, and the same constant output voltage (CV) characteristics can be always guaranteed with different data sequences. Subsequently, a compact coil structure is developed to accommodate the tight space constraint inside the insulator. Finally, aiming at the 35-kV suspension composite insulator with five embedded domino resonators, a 15W experimental prototype is built to realize simultaneous power and data transfer and constant voltage output. The experimental results show that the fluctuation of output voltage is less than 5%, and the overall system transfer efficiency is higher than 75%.

Wireless Power Transfer Technologies, Applications, and Future Trends: A Review

Wireless Power Transfer Technologies, Applications, and Future Trends: A Review

A Novel Design of a Microstrip Antenna Array for Wireless Power Transfer Applications

A Novel Design of a Microstrip Antenna Array for Wireless Power Transfer Applications

Analysis and Design of Multiple Regulatable Output Rectifier Integrated Buck Converter for Wireless Power Transfer Application

Analysis and Design of Multiple Regulatable Output Rectifier Integrated Buck Converter for Wireless Power Transfer Application

Analysis and Design of an Active Rectifier for Wireless Power Transfer in 90 nm CMOS Technology

In this paper, an analysis and design of a new active rectifier used for wireless power transfer applications using 90 nm CMOS technology are presented. The proposed architecture of the active rectifier has mainly been chosen to improve the VCE and the PCE and also to eliminate the need for large on-chip capacitors. The proposed circuits eliminate the drop needed for conduction by replacing diode-connected nMOS devices with others controlled by an active circuit. The new architecture of the active rectifier has been designed, simulated, and laid out by Cadence Virtuoso using TSMC 90nm technology. The input range is 0–5 V, and the output voltage is 2.14 V, with the VCE and the PCE values of 82.9% and 86.2%, respectively. The layout utilizes a compact space of 0.0597 mm2 within the TSMC CMOS 90 nm technology.

Multifunctional coil technique for alignment-agnostic and Rx coil size-insensitive efficiency enhancement for wireless power transfer applications

This paper presents a multifunctional coil technique to enhance the transfer efficiency of an inductively-coupled wireless power transfer (WPT) system, regardless of the alignment condition and size ratio between the transmitter (Tx) and receiver (Rx) coils. The technique incorporates an auxiliary coil on the Tx side, where current is induced through coupling from the primary coil. Since the Tx coil consists of two coils, transmission to the Rx occurs through the coil with the higher coupling coefficient, determined by the misalignment state. Additionally, by controlling this current using a varactor placed on the auxiliary coil, an optimal magnetic flux is generated based on the alignment condition and/or the size of the Rx coil. In perfect alignment, the auxiliary coil focuses the flux from the Tx to the Rx coil, maximizing transfer efficiency. In misalignment scenarios, the current on the auxiliary coil is adjusted to shift the effective center of the Tx coil, achieving the strongest alignment of the magnetic flux traversing the Rx coil. This adjustment, which can be controlled adaptively based not only on the degree of misalignment but also on the size of the Rx coil, enables virtually null-free operation across varying misalignment conditions and for different Rx sizes. Furthermore, as this multifunctionality of the proposed system is achieved with a minimal number of additional components-just a single auxiliary coil and a single varactor-the impact on the overall quality factor (Q) of the system is minimized, contributing to the higher efficiency. In a size-symmetric system, where the Tx and Rx coils have the same size, the efficiency reaches 98.1% in perfect alignment and remains above 60% with up to 135% misalignment relative to the largest coil dimension. In a size-asymmetric system, with the Rx coil reduced to a quarter of the Tx coil, the efficiency is 96.1% in perfect alignment and remains above 60% up to 95% misalignment. Despite its enhanced practicality through a simple structure featuring only one auxiliary coil and an asymmetric configuration integrated solely on the Tx side, the proposed technique surpasses previous methods by delivering significantly superior performance. Moreover, it demonstrates unprecedented tolerance to both misalignment and smaller Rx coil sizes, which is frequently encountered in practical applications.

Machine Learning Based Foreign Object Detection in Wireless Power Transfer Systems

As power electronics continue to drive advancement in electronic devices by managing the system's energy flow, it is advantageous to examine all areas of energy transfer. Wireless power transfer is one section seeing increased adoption in consumer, industrial, and healthcare applications. This consequently increases the concern for safety, reliability, and efficiency. Power transmission to any unintended load is a primary safety issue in high-power wireless power transfer applications, such as unmanned aircraft systems. Foreign object detection is utilized to selectively transmit power to only the intended target to mitigate this issue. This paper seeks to demonstrate a novel alternative method of using machine learning and artificial intelligence techniques for performing foreign object detection solely on the transmitter portion of the system by only monitoring the TX coil current. This method is first evaluated in SPICE simulation software. Then by transitioning to a closed-loop hardware-based testbed designed to be deployed in unmanned aircraft systems. During the test process for the novel FOD method, the aggregate detection accuracy achieved was 83%, including worst-case misalignment conditions with the RX coil. When the outlying worst-case conditions are excluded, the detection accuracy improves to 97%. To measure the FOD effectiveness in preventing temperature rise in a metallic object, the metallic object was placed at the peak power draw location on the transmitter coil. When the metallic object is left at this location for extended periods, the novel FOD method lowers the maximum temperature reached by 86.8°C when compared to no FOD being active. The primary advantage to this novel method is the simplistic hardware additions, which only require minimal alterations to a WPTS without any FOD implemented. Along with this, implementing this foreign object detection method in the transmitter would mitigate the need for a direct communication link between the receiver and transmitter. As a result, the entire system complexity would decrease, thus increasing the UAS power density while maintaining a safe, effective, and reliable wireless power transmission method.

Tunable Dual-Band High-Impedance Coil for Wireless Power Transfer Applications

Tunable Dual-Band High-Impedance Coil for Wireless Power Transfer Applications

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.