Wireless Power Transfer Applications Research Articles

Numerical demonstration of a dispersion engineered metallic metasurface assisted mm-wave wireless sensor

In this paper, a metasurface-assisted multiport wireless power sensor is proposed and numerically verified for wireless power transfer (WPT) applications at mm-wave frequency band. A fully metallic 2D Luneburg lens constructed using glide symmetric unit cells, with a maximum gain of 18 dBi, acts as the radiating structure to receive the input RF power with a wide angular coverage range of ±70°. A set of optimized class F rectifiers are integrated with this multiport lens using waveguide to microstrip transitions to obtain high power conversion efficiency over a wide angular space. These rectifying circuits are further connected for DC power combining, and a maximum power conversion efficiency of 72% is obtained at an input power level of 15.8 dBm.

Compact and Free-Positioning Omnidirectional Wireless Power Transfer System for Unmanned Aerial Vehicle Charging Applications

Compact design in receiver and misalignment tolerance are two basic considerations for practical applications of wireless power transfer (WPT) in unmanned aerial vehicles (UAVs). To balance these two requirements, a novel magnetic design with the composite interval-acted parallel- & vertical-flux throw, orthogonal two-dimensional flux pick-up, and power-flow summed output is proposed in this letter. The resulting magnetic structure includes a target-shaped transmitter and two quadrature receivers, and the transmitter consists of four annular-type coils which are magnetized in a bipolar mode, making it possible to form a magnetic field with a parallel- and vertical-flux complementary distribution. Moreover, by integrating two orthogonal receiving coils into one receiver, a stable summed output current can supply the UAV onboard load with only a small size receiver. A UAV WPT prototype is established based on the proposal. The results show that the prototype can deliver 325 W with a system efficiency of 86%, and especially the variation of the output current is within ±0.76 A for different landing positions and directions. The overall system efficiency is from 87.3% down to 83.1%.

A Fast-Speed GMPPT Method for PV Array Under Gaussian Laser Beam Condition in Wireless Power Transfer Application

The laser power transfer system is one of the most promising systems in the long-range wireless power transfer field. However, the low efficiency at photovoltaic (PV) receiver limits the performance of an implemented system due to the Gaussian laser beam. Since the irradiance profile of the Gaussian laser beam is not uniform, the PV array exhibits complex output characteristics with multiple peaks, leading that the conventional maximum power point tracking (MPPT) method is not acceptable either on tracking accuracy or on tracking speed. In this article, a simple and rapid voltage-location global MPPT (VL-GMPPT) method is proposed for PV array under Gaussian laser beam condition (GLBC) in terms of reducing the voltage searching range. In order to do so, the mathematical model of PV array's global maximum power point (GMPP) is developed under GLBC. Then, the VL-GMPPT method incorporates voltage-location mechanism to directly move the operating point to the vicinity of GMPP and employs IncCond method to accurately find the GMPP. The experimental and simulation results are shown to verify the proposed GMPPT method. It was found that the proposed method can reduce 90% of tracking time that is consumed by the conventional global searching method.

Output-Voltage Adaptive of Omnidirectional Wireless Power Transfer Based on Receivers With Digital Coils

Omnidirectional wireless power transfer (WPT) can provide power for multiple loads at any position in space. The voltage required for different loads is unavoidably various, and the characteristics of load may also change at different stages of power replenishment (e.g., battery impedance). WPT needs to adjust the supply voltage and power in real time to meet the needs of different loads and diverse working conditions. This article presents a receiver composed of digital receiving coil (DRC) with voltage adaptive regulation. The layers of DRC are changed to adjust the coupling state of magnetic coupling mechanism (MCM). The voltage of DRC is actively adjusted to maintain continuous stability of power supply, or to meet the specific requirements for different stages. The proposed design can achieve the peak-to-peak voltage of DRC stabilized in the range of 8.5–14 V with the transmitting distance varying from 28 to 47 cm, 18–26 V with the load of 3–100 <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> , and 8–13.5 V with the input dc voltage changing from 11.5 to 46 V. When the layers of DRC are adjusted, different voltages can be obtained with fixed distance, load, and input DC voltage. The designed receiver with DRC is less sensitive to load, transmission distance, rotation angle, and other factors, and meet the differential voltage requirements of space multiload. The proposed system can reduce the design difficulty and requirements of the converter, and will promote the application of WPT in the field of power supply for Internet of Things (IoT) equipment.

A Load-Independent Output Current Method for Wireless Power Transfer Systems with Optimal Parameter Tuning

In current study, a method for achieving a load-independent output current with the ability to optimize the parameter tuning, which is applied to wireless power transfer (WPT) systems, is analyzed. The proposed technique is based on the immittance property in a passive resonant network (PRN) with the purpose of transforming a voltage/current resource into a current/voltage resource. This study determines an immittance conditions-qualified family of PRN, which is associated with a more appropriate topological description in WPT applications. Considering the resource and sink type, a comprehensive specification of the coupling coefficient-based design condition and operating point is carried out. Moreover, the parameters of each proposed topology are reconfigured by adjusting the proportion of active power to reactive power ratios as an index to optimize the topology size as well as a reduction of voltage/current stresses on their elements without changing the specified system-level parameters, such as the loosely coupled transformer operating frequency, and specified constant current outputs. The sample topology selection is also carried out with respect to the absorption of the parasitic components and achieving the inherent dc-blocked transformer. Zero-voltage-switching (ZVS) operation of the switches, minimum conduction losses of the rectifier diodes within an extensive variety of load variations, and capability of consistent generation of stable load-regulated current are also achieved. Analytical results show that the proposed compensation has the minimum output current fluctuation versus variations of the coupling coefficient and other parameters. Finally, the effectiveness of the proposed methodology is evaluated through simulations, and practical experiments, and compared with the conventional design method.

Analysis and Design of Single-Ended Resonant Converter for Wireless Power Transfer Systems.

Single-ended resonant converters such as Class-E inverters have been widely considered as a potential topology for small- and medium-power wireless power transfer (WPT) applications, which feature compact circuits, low switching losses, and cost benefits, as they only use a low-side switch with a simple gate driver. However, there remains a practical challenge in the design of voltage stress, efficiency, and power density. In this paper, a single-ended resonant converter with a primary parallel resonant-matching network is investigated to absorb the bulky input-choke inductors of the Class-E inverters into the coil inductance. The analytical expressions for all the converter parameters are derived based on time-domain resonant waveforms, including: (1) analysis of critical zero-voltage switching (ZVS) conditions and (2) power transfer capabilities under the given maximum switch voltage stress. Furthermore, this paper elaborates on the design methodology of the proposed single-ended resonant converters, and an optimal operating point is chosen to ensure soft-switching operation and rated power. Finally, the accuracy of the proposed model is verified by simulation and experimental results.

Self-Tuning Omnidirectional Wireless Power Transfer Using Double-Toroidal Helix Coils

In this article, we suggest and study a novel omnidirectional wireless power transfer (WPT) system based on unusual double-toroidal helix coils. The suggested antenna is a double-helix coil wounded around a torus. It creates two mutually orthogonal magnetic fields. One is toroidal and confined inside the torus, and another one is poloidal and is distributed outside it. The intensities of these two fields can be independently tuned via the geometry of the turns. The coupling coefficients are tailored to ensure high efficiency regardless of the receiver position and orientation, without active circuitry for tuning or control. This topology provides self-tuning functionality which is achieved when the coupling between the transmitter and receiver is minimized while the coupling in the pairs transmitter–repeater and repeater–receiver is strong. The system consists of three transmitter–repeater pairs orthogonal to each other, ensuring omnidirectional functionality. Experimental results confirm self-tunability and high efficiency for any position and orientation of receivers. The proposed double-helix antenna is applicable to different WPT applications where the coupling/decoupling between coils can be freely controlled.

Guest Editorial Advances in Wireless Power Transfer Technologies

Recently, application of wireless (contactless) power transfer (WPT) technology in electric transportation, smart e-mobility, and future smart cities has gained wider attention. This is evident from the use of WPT technology in electric cars and heavy-duty mass transit, unmanned aerial vehicles (UAVs/drones), sea/undersea vehicles (ships/submarines), utility vehicles (forklifts/golf carts), micromobility devices (scooters/e-bikes), and smart cities, offices, and buildings. WPT can be achieved either via electromagnetic inductive power transfer (IPT) or via electrostatic capacitive power transfer (CPT). This special section (SS) received contributions from papers that focus on the latest advances in WPT technology in the previous applications. This SS received a large number of submissions from across Asia/Pacific, Europe, Africa, South America, as well as North America. Keeping space limitations in mind, about 30% of the papers were accepted for inclusion in this special section.

Reconfigurable Resonant Topology Linking Two-, Three-, and Four-Coil Modes for WPT With Large Coupling Range and Fixed Frequency

In wireless power transfer (WPT) applications, it is usually desired to transfer full power from the transmitter to the receiver in a position range as large as possible. However, the full-power operation range of a WPT system is typically designed for a small position range. This article proposes a reconfigurable resonant topology adopting the splitting coil structure in both the primary and secondary sides. The proposed reconfigurable resonant topology can output high power when the air gap varies in a wide range. Simulation and experimental results are provided to demonstrate that the proposed reconfigurable resonant topology can output full power in a large coupling range without significantly increasing the VA rating of the system. The measured dc–dc efficiency of the 3.3-kW prototype in an air gap range of 95–215 mm is 92%–95%.

Design and Analysis of Polarization-Independent, Wide-Angle, Broadband Metasurface Absorber Using Resistor-Loaded Split-Ring Resonators

Metasurface (MS) absorbers with polarization-insensitivity and wide-angle reception features have attracted much attention due to their unique absorption property. A polarization-insensitive broadband MS absorber structure, having wide-angle reception based on square split-ring resonators (SSRRs) and loaded with lumped resistors, is proposed in this paper. The proposed MS unit cell consists of a fixed-thickness FR4 dielectric substrate and a variable air-thickness substrate. The simulation results show that the proposed MS absorber is stable across a wide angular range for both normal and oblique incidences. Furthermore, the simulated results show that some parameters, such as unit-cell geometry and lumped resistors, can be varied to improve the performance of the MS absorber. The experimental results indicate that the proposed MS absorber can be achieved an absorption higher than 90% across the frequency range from 1.89 GHz to 6.85 GHz with a relative bandwidth of 113%, which is in agreement with simulation results. Thus, the proposed MS absorber can be more suitable in RF energy harvesting or wireless power transfer applications.

Anti-offset performance optimization of coupling coils in wireless power transfer system based on genetic algorithm

With the popularity of electric vehicles (EVs), the application of wireless power transfer (WPT) in EVs has attracted more and more attention. The coupling coil is the key component to realize the stable transmission of electric energy, but in the process of wireless charging, the position of the primary and secondary coils may be misaligned, resulting in the change of mutual inductance and the instability of output current and power. Therefore, the study of the structure of the coupling coil is helpful to improve the transmission performance of WPT. In order to improve the anti-offset ability of the coupling coil, a DS (Double tangent semicircle) coil model based on the DD (Double D) coil is proposed in this paper, which can improve the pick-up ability and anti-offset ability of the receiver coil. Through theoretical analysis, genetic algorithm (GA) optimization, simulation analysis and experiments, it is verified that DS coil is better than DD coil in horizontal offset state and rotary offset state. At the same time, the experiments show when the rotation angle is in the range of −45° to 45° and 135° to 225°, that the current at the receiving end remains stable, and the maximum change rate is only 0.3%. This paper is of great significance to the optimal design of WPT coupling coil.

Heterogeneous Computation and Resource Allocation for Wireless Powered Federated Edge Learning Systems

Federated learning (FL) is a popular edge learning approach that utilizes local data and computing resources of network edge devices to train machine learning (ML) models while preserving users’ privacy. Nevertheless, performing efficient learning tasks on the devices and achieving longer battery life are primary challenges faced by federated learning. In this paper, we are the first to study the application of heterogeneous computing (HC) and wireless power transfer (WPT) to federated learning to address these challenges. Especially, we propose a heterogeneous computation and resource allocation framework based on a heterogeneous mobile architecture to achieve effective implementation of FL. To minimize the energy consumption of smart devices and maximize their harvesting energy simultaneously, we formulate an optimization problem featuring multidimensional control, which jointly considers time splitting for WPT, dataset size allocation, transmit power allocation and subcarrier assignment during communications, and processor frequency of processing units (central processing unit (CPU) and graphics processing unit (GPU)). However, the major obstacle is how to design a proper algorithm to solve this optimization problem efficiently. For this purpose, we decouple the optimization variables so as to achieve high efficiency in deriving its solution. Particularly, we first compute the optimal processor frequency and dataset size allocation via employing the Lagrangian dual method, followed by finding the closed-form solution to the optimal time splitting allocation, and finally attain the optimal subcarrier assignment as well as transmit power for transmissions through an iteration algorithm. To evaluate the performance of our proposed scheme, we set up four baseline schemes as comparison, and simulation results show that the proposed scheme converges quite fast and better enhance the energy efficiency of the wireless powered FL system compared with the baseline schemes.

A Wireless Power Transfer System With Inverse Coupled Current Doubler Rectifier for High-Output Current Applications

In this paper, a series-series wireless power transfer (WPT) system combined with an inverse coupled current-doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high current low voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with diode rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10kW 400V/48V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 Vdc and 55 Vdc, and the rated output current is 200A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220W energy saving with respect to the traditional diode-rectifier system, when 9.5kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high power WPT applications.

New Magnetic Coupling Pad with Circular Geometry for Wireless Power Transfer Applications

In Resonant Inductive wireless power transfer systems (RIPT), the magnetic coupler plays a fundamental role. That assists in passing of power without wires. In wireless power transfer systems (WPT), couplers are designed to achieve various parameters such as power transfer efficiency, high power density, transferrable distance, and tolerant towards misalignment. In addition, minimizing leakage flux, low weight, less cost, and space occupied. To achieve these parameters, researchers proposed different types of coils with different shapes. Those circular coils are more popular due to their unique features. Compared to other coils, these coils lack in power transfer distance. In this paper, a distinct magnetic coupler with circular geometry proposed to preserve some extent of its features. In proposed, a circular quadrature coil added with two circular coils shaped to the circular coil. Proposed topology analyzed using ANSYS Maxwell Finite Element Analysis 3D simulation and compared with different combinations chosen better performing combination.

WIRELESS POWER TRANSFER

This paper depicts an original idea to remove the hazardous usage of electrical wires which involve lot of confusion in particularly organizing them and it also involves lot of wear, aging and produced electric spark etc, also transferring power in some areas like high mountains and several ocean region may be difficult, wireless power transfer can play a major role in such areas .Therefore, wireless power transfer technology has made people to look towards it also increasing the developments in the field .So this paper introduces the applications of Wireless Power transfer anywhere in the world also we look into the current developments and the basic problems faced.

A Planar Distributed Multicoil Antenna to Generate 3-D Ellipsoidally Polarized H-Field for Angular Misalignment Tolerant WPT System

This article presents 3-D polarized magnetic-field forming using a planar multicoil transmitter antenna for wireless power transfer (WPT) applications. Three orthogonal <inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula>-field components resulting in optimized 3-D ellipsoidal polarization are generated to mitigate the angular misalignment problem by the proposed antenna. The analytical optimization of the 3-D polarized <inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula>-field is presented, and its effect on induced voltage in the receiver coil is investigated. To achieve unconstrained induced voltage in the receiver independent of its angular movement, an optimized planar multicoil design is proposed for a maximum S21 between the transmitter and the receiver coil antennas. Unlike the 3-D transmitter designs available in the literature, the proposed antenna is a 2-D planar printed circuit board (PCB) design, therefore, represents a cost-effective solution and is suitable for various practical WPT applications. The analytical results of the design are verified experimentally. The result proves that the proposed antenna is able to completely mitigate the angular misalignment problem, which represents a potential planar antenna solution for orientation-insensitive WPT applications.

Analytical Modeling of Self- and Mutual Inductances of DD Coils in Wireless Power Transfer Applications

Self- and mutual inductances are major design parameters for wireless power transfer (WPT) systems. To optimize a WPT system and estimate its performance in terms of received power and efficiency, it is essential to obtain a simple, fast, and accurate calculation of these two parameters. The polarized double-D (DD) coils were selected due to their simplicity of structure, high efficiency, and low sensitivity to misalignment conditions. This paper presents analytical calculations of self- and mutual inductance using the Biot-Savart law for DD coils. The results of the analytical calculations of mutual inductance in different distances between coils were investigated, and the results of the calculations were verified using experimental and finite element method (FEM) simulation results. This paper also presents analytical and FEM-based optimization guidelines for the coupling coefficient of the transmitter coil.

Resonant Inductive Coupling for Wireless Power Transmission

Wireless power transmission (WPT) is the method that transferring electrical energy from power source to electrical without any physical contact and it can be used to transfer power to electricity dependent systems or devices. In WPT, electromagnetic energy is produced to transmit the energy from power source (transmitter) to the load (receiver) via resonant inductive coupling. This article focuses on the design of a resonant inductive coupling using parallel-T topology in coupling WTR and combined of single transmitter with multiple receivers. In addition, principle of magnetic wave between the transmitter and receiver with related parameters is utilized to develop in WPT. A parallel-T topology that consists of T-matching network for secondary side is proposed as it is more suitable for weak coupling wireless power transfer applications. Besides that, three circuits are designed to show the resonant inductive coupling for WTP which including the circuit with and without matching network and the circuit of single transmitter with multiple receivers. The simulation of output voltage and output current are observed to relate the effects of frequency on the circuit. The graph of output voltage and power are plotted to show the pattern on effect of the frequencies to the resonant inductive coupling circuit.

Dual-Polarized Dipole Antenna for Wireless Data and Microwave Power Transfer

This manuscript presents a broadband high-efficiency dual-polarized dipole antenna for wireless power and data transfer. The proposed antenna mainly consists of cross-dipole patches, matching baluns, and a ground plane. The dual-polarized radiation mode was achieved by using two linear-polarization matching baluns to feed the cross-dipole patches orthogonally. The proposed dual-polarized dipole antenna realizes a bandwidth with S11 less than −10 dB (4.28 GHz–5.92 GHz) and a high radiation efficiency of about 95%. An independent rectifying circuit was designed, and a microwave energy transmission experiment was carried out. The final measured conversion efficiency for the two polarized ports at 5.8 GHz was about 77.6% and 76.4%, respectively. Simulation and measurement results showed that the proposed antenna is suitable for both wireless power and wireless data transfer applications.

Single-phase bidirectional AC-AC converter with H-bridge energy buffer for wireless power transfer applications

This paper introduces a single-phase bidirectional AC-AC Matrix type converter for wireless power transfer (WPT) applications. The proposed converter converts mains 50 Hz alternating current (AC) directly to high frequency 85 kHz AC without an intermediate direct current (DC) conversion stage. A minimum cost realization of only two bidirectional AC switches comprised each of two semiconductor device and one gate drive signal is employed. The converter operation modes are quantum energy injection and circulating self-oscillation. Elimination of the DC link introduces a sag in the power transfer during the zero crossing of input AC mains, which is well documented in literature. A novel H-bridge buffer structure is introduced which eliminates the power sag by storing energy during mains peak and delivering energy during the zero-crossing period. The converter operates with inherent zero current switching, thus achieving a low switching loss and electro-magnetic interference. The control feature ensures that the converter can be used for both static and dynamic wireless charging applications. The bidirectional power transfer capability ensures that the system can operate in both grid to vehicle (G2V) and vehicle to grid (V2G) power transfer modes. The proposed converter design is analyzed analytically and verified through thorough simulation study.