Wireless Power Transfer Technology Research Articles

Resource Allocation for a Secure SWIPT Network Based on a Quantitative Energy Harvesting Mechanism.

Simultaneous wireless information and power transfer (SWIPT) technology can effectively extend the lifecycle of energy-constrained networks. In order to improve the energy harvesting (EH) efficiency and network performance in secure SWIPT networks, this paper studies the resource allocation problem based on the quantitative EH mechanism in the secure SWIPT network. Based on a quantitative EH mechanism and nonlinear EH model, a quantified power-splitting (QPS) receiver architecture is designed. This architecture is applied in the multiuser multi-input single-output secure SWIPT network. With the goal of maximizing the network throughput, the optimization problem model is established under the conditions of meeting the legal user's signal-to-interference-plus-noise ratio (SINR), EH requirements, the total transmit power of the base station, and the security SINR threshold constraints. Due to the coupling of variables, the problem is a nonconvex optimization problem. To deal with the nonconvex optimization problem, a hierarchical optimization method is adopted. Firstly, an optimization algorithm based on the optimal received power of EH circuit is proposed, and a power mapping table is constructed through the optimization algorithm, from which the optimal power ratio to meet the user's EH requirements is obtained; then, the nonconvex problem is transformed into a convex problem by using variable substitution, semidefinite relaxation, dichotomous optimization, etc. The simulation results show that compared with the power splitting receiver architecture, the input power threshold range of the QPS receiver architecture is larger, which can avoid the EH circuit falling into the saturated working area and maintain high network throughput.

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.

Wireless Power Transfer to Electrothermal Liquid Crystal Elastomer Actuators.

Wireless actuation of electrically driven soft actuators is of paramount importance for the development of bioinspired soft robotics without physical connection or on-board batteries. Here, we demonstrate untethered electrothermal liquid crystal elastomer (LCE) actuators based on emerging wireless power transfer (WPT) technology. We first design and fabricate electrothermal LCE-based soft actuators that consist of an active LCE layer, a conductive liquid metal-filled polyacrylic acid (LM-PA) layer, and a passive polyimide layer. LM can function not only as an electrothermal transducer to endow resulting soft actuators with electrothermal responsiveness but also as an embedded sensor to track the resistance changes. Various shape-morphing and locomotive modes such as directional bending, chiral helical deformation, and inchworm-inspired crawling can be facilely obtained through appropriately controlling the molecular alignment direction of monodomain LCEs, and the reversible shape-deformation behaviors of resulting soft actuators can be monitored in real-time through resistance changes. Interestingly, untethered electrothermal LCE-based soft actuators have been achieved by designing a closed conductive LM circuit within the actuators and combining it with inductive-coupling WPT technology. When the resulting soft actuator approaches a commercially available wireless power supply system, an induced electromotive force can be generated within the closed LM circuit, which results in Joule heating and wireless actuation. As proof-of-concept illustrations, wirelessly driven soft actuators that can exhibit programmable shape-morphing behaviors are demonstrated. The research disclosed herein can provide insights into the development of bioinspired somatosensory soft actuators, battery-free wireless soft robots, and beyond.

Principles and applications of wireless energy transmission

In this day and age, people's lives are inextricably linked to electricity, which is being used more and more in everyday life. The traditional transmission of electrical energy usually uses materials such as metal wires and cables as the transmission medium, and the losses and potential damage (line deterioration, tip discharges) caused by this transmission medium are inevitable. The introduction of radio has been very effective in reducing this situation, and the development of Wireless Power Transfer (WPT) technology has seen three major developments since then, with Tesla lighting a phosphorescent lamp at the Colombian World's Fair in 1893, igniting hopes for WPT. This new way of transmitting electrical energy has expanded the imagination of people in terms of power supply methods by making it possible to provide more freedom in situations where cable charging is not suitable.The working theory, fundamental design, and potential applications of wireless energy transmission technology are covered in this study. By doing this, it offers insight into the development and use of wireless energy transmission technology as it is now. In the end, it is envisaged that the market will adopt wireless energy transfer technology extensively.

Analysis of transmission performance on wireless power transfer system with metamaterial

Abstract In order to solve the problems of low power transfer efficiency (PTE) and limited distance in magnetic coupling resonant wireless power transfer (MCR-WPT) technology. In this paper, based on the magnetic field control ability of metamaterials (MMs), the way to improve the performance of MCR-WPT systems is studied. First, the influence of MMs on the coupling of MCR-WPT system is theoretically analyzed by establishing an equivalent circuit model. Through a series of simulations and experiments, the relationships between the PTE and the array and placement of the MM slab are investigated. The results demonstrate that when one MM slab is placed in the middle, near the Tx coil or the Rx coil, the optimal PTE can be obtained by inserting one slab with $6 \times 6$ , $1 \times 1$ , and $6 \times 6$ arrays, respectively. Moreover, the systems with multilayer MM slabs are also studied. The measured PTEs on one, two, and three layers of MM slabs can increase by 20.6%, 29.3%, and 22.6%, respectively. The efficiency improvement capability of one MM slab is better than three slabs but worse than two slabs. This paper discusses the application of MMs in MCR-WPT systems, which has a certain reference significance.

Review of Wireless Charging System: Magnetic Materials, Coil Configurations, Challenges, and Future Perspectives

Electric transportation will assist in lowering emissions of greenhouse gases and mitigating the impact of rising petrol prices. To promote the widespread adoption of electric transportation, a diverse range of charging stations must be established in an atmosphere that is friendly to users. Wireless electric vehicle charging systems are a viable alternative technology that can charge electric vehicles (EVs) without any plug-in issues. Wireless power transfer (WPT), which involves the transmission of electricity via an electromagnetic field despite the presence of an intervening area, holds out the possibility of new prospects for EVs to increase environmentally responsible mobility. This review article examines the WPT technology and how it might be applied to electric vehicles from both a technical and safety standpoint. The prime aim of this review is (1) to illustrate the current state of the art in terms of technological advances as well as research limitations in the field of WPT development and use within the field of transportation; (2) to organise the experimental the deployment of WPT EV systems in the actual world; and (3) to analyse the results over a sustainable period and to identify limitations as well as chances for growth. From a technical point of view, the progress that has been made on the selection of material for designing coils, different types of coils with a specific focus on the overall performance of the system. As a result, this study aims to provide an extensive overview focusing on the magnetic materials and the architectures of the transmitter and receiver pads.

Intelligent computing for WPT–MEC-aided multi-source data stream

Due to its low latency and energy consumption, edge computing technology is essential in processing multi-source data streams from intelligent devices. This article investigates a mobile edge computing network aided by wireless power transfer (WPT) for multi-source data streams, where the wireless channel parameters and the characteristic of the data stream are varied. Moreover, we consider a practical communication scenario, where the devices with limited battery capacity cannot support the executing and transmitting of computational data streams under a given latency. Thus, WPT technology is adopted for this considered network to enable the devices to harvest energy from the power beacon. In further, by considering the device’s energy consumption and latency constraints, we propose an optimization problem under energy constraints. To solve this problem, we design a customized particle swarm optimization-based algorithm, which aims at minimizing the latency of the device processing computational data stream by jointly optimizing the charging and offloading strategies. Furthermore, simulation results illustrate that the proposed method outperforms other benchmark schemes in minimizing latency, which shows the proposed method’s superiority in processing the multi-source data stream.

Design of Wireless Power Transfer System Based on LCC-S

Recently, wireless power transfer (WPT) technology has become a research hot spot due to its benefit of contactless power transfer. Firstly, for the sake of solving the problem of the small coupling coefficient of traditional orbital wireless power transfer systems, a new structure and control strategy of transceiver coil was proposed, and then the optimal parameters of system transmission efficiency were found out by comprehensive analysis of the LCC-S compensation circuit structure and equivalent circuit, and the correctness of the parameters was verified in MATLAB/Simulink simulation. Finally, an experimental prototype was built, and the experimental findings show that the wireless power transfer system based on LCC-S can realize voltage regulation control, the coupling coefficient is increased by 0.4 compared with the traditional orbital structure, and the transmission efficiency of this system is more than 80%.

Composite Control to Suppress Output Fluctuation for Receiver Side of Dynamic Wireless Power Transfer System

Mobile device charging is made possible by the dynamic wireless power transfer technology and it's developing towards higher power levels. The output power fluctuates significantly with the movement of the device due to the discontinuous coil switching and the peculiarities of the dynamic magnetic coupler, which has an impact on charging effectiveness and battery life. In this paper, a three-level Buck (Buck TL) is used as a DC-DC converter at the receiver side and a composite control aiming to suppress output power fluctuations is proposed. The minimum effective suppression range for the frequency of the coupling fluctuation and the control performance in the transient state are analyzed theoretically. Compared with PI control, the simulation is built, and the 2.6 kW experiment results showed that the composite control could reduce the system output voltage ripple from 13% to 4.4% with resistive load and the output charging current ripple from 22% to 9% with battery load without impacting the efficiency of the Buck TL system, which verified the effectiveness of the proposed composite control strategy.

The Design and Fabrication of Multiple-Transmitter Coils and Single-Receiver Coils for a Wireless Power Transfer System to Charge a 3s LiPo Drone’s Battery

Recent research has shown an increasing interest in wireless power transfer (WPT) technology for drone batteries. The inconvenience of wired charging, especially for drones, is a huge obstacle. In this research project, a WPT platform was proposed by applying four transmitting coils and a single receiving coil. To meet the industrial standards required for transmitter Tx and receiver Rx, a calculation of the parameters was implemented. An H-bridge MOSFET was used as a DC–AC inverter, a bridge diode was used as an AC–DC rectifier, and a Pi low pass filter was added to the receiver circuit design to filter the high-frequency noise. Experimental investigations were conducted to study the maximum power and power efficiency of the coil’s alignment. The focus of this article was to design and fabricate workable multiple-transmitter coils and a single-receiver coil for a wireless power transfer system, in order to charge a 3S LiPo drone’s battery. It not only covers an overview of wireless power transfer but also includes the method for charging a 3S LiPo drone’s battery, a misalignment study on the X and Y axes of the wireless charging system, and a stable charging of the battery that does not exceed the maximum current of 1.26 A for healthy charging. An efficiency of 58.29% was achieved at a power of 14.924 W and the minimum value was found to be 0.008 W. The efficiency of the typical coil design and the proposed coil design were 55.04% and 12.06%, respectively. The charging current obtained was 1.27 A, which gives an estimated charging time of 3.31 h based on the calculation. The actual charging time of the 3s 4200 mAh 11.1 V LiPo battery was 2 h.

A New Transmitting Coil for Powering Endoscopic Capsules Using Wireless Power Transfer

This study focuses on using wireless power transfer (WPT) technology based on magnetic resonant coupling (MRC) to supply electric power to an endoscopic capsule to be used for the direct feeding of specific functions or for battery charging. One of the main limitations of the diffusion of endoscopic capsules is the limited autonomy of the internal battery. The aim of the paper is to present an innovative system to wirelessly power capsules using inductive coupling. Here, a new transmitting coil architecture is proposed to allow the wireless charging of the capsule equipped with a monoaxial receiving coil for any possible geometric position and orientation. The new wearable transmitting coil consists of four rectangular coils with independent excitations, and it is capable of producing a magnetic field in any direction. The obtained results in terms of electrical performance of the proposed WPT system and in terms of in situ electromagnetic physical quantities are compared with the basic restrictions of electromagnetic field (EMF) safety guidelines. The results obtained are very promising, as the proposed WPT configuration can transfer at least 250 mW in a capsule that travels along the entire gastrointestinal tract.

Joint Resource Allocation in a Two-Way Relaying Simultaneous Wireless Information and Power Transfer System

Simultaneous wireless information and power transfer (SWIPT) technology provides an efficient solution to energy-limited communication terminals in a wireless network. However, in the current application scenario of SWIPT technology, relays use all the collected energy forwarding to assist communication between source nodes, while ignoring the fact that relays can accumulate and store energy. This is of great practical significance in collaborative communication. By using a transmission scheme of a time-division broadcast for the direct transmission link, improvement of the system diversity gain through combining the technology at the receiver can be realized. Based on the above, we propose a two-way relay energy accumulation communication system, which is extended from a single relay system to a multi-relay system. The instantaneous transmission rate of the system link and the system equivalent profit are optimized by jointly optimizing the relay selection, time slot allocation factor, power splitting factor and relay transmit power. Compared with the comparison algorithm, the proposed algorithm shows a significant improvement in the performance of the system.

Constant output voltage and non-communication-based maximum efficiency tracking for wireless power transfer systems: Single current control of primary-side

Wireless power transfer (WPT) technology is a novel power transmission technology using electromagnetic field as the transmission medium. It uses the advantages of electromagnetic coupling in the near field to realize contactless transmission of electric energy on the basis of resonance theory. This mode has the advantages of stability, flexibility, efficiency and safety. WPT is mainly used for non-contact charging of electrical equipment without electrical connection. It can safely, flexibly and quickly charge the electrical equipment, which makes up for the shortcomings of the traditional charging mode. Due to the change of the load or the transmission coil position in WPT system, the transmission efficiency will drop sharply. It is of great significance to maintain the maximum efficiency transmission. This paper proposes a novel maximum efficiency transmission method. This method can achieve the maximum efficiency transmission with constant voltage output by controlling the primary-side current without communication feedback between the primary-side and the-secondary side. The Buck-Boost converter with constant output voltage is introduced at the load-side to equivalent the actual load. By adjusting the duty ratio of the Buck converter on the primary side and detecting the minimum input current, the maximum transmission efficiency could be tracked. The theoretical conditions of the method are analyzed and experimental verification is performed. The experimental results of variable relative position load show that the transmission efficiency of the proposed method can still reach 83%.

Joint design of electric bus transit service and wireless charging facilities

Cities worldwide are deploying electric buses rapidly to enhance eco-friendly public transportation. Most existing electric transit systems rely solely on stationary charging at terminals and have to equip buses with large-sized batteries to maintain operation in networks. Consequently, the stationary-charging electric bus (SE-Bus) systems are subject to high battery costs, limited range per charge, long charging time (layover time), etc. These limitations may be addressed by integrating the new wireless power transfer technology, which provides contactless charging to the operating buses without extra delays. To guide wireless-charging electric bus (WE-Bus) designs in corridors, this paper proposes an optimization model to jointly optimize (i) the electric supply system and (ii) the transit service that are interdependent.Specifically, we construct parsimonious models for system metrics using five design variables/functions, i.e., battery size, the number of wireless power transfer (WPT) pads, stationary charging rate, service headways, and stop densities. Accordingly, we formulate the optimal design problem to minimize the generalized system cost as the sum of the transit agency’s and patrons’ costs. The problem is attacked by first decomposing into two sub-problems regarding (i) electric supply system design and (ii) transit service design and then solving them iteratively. The (i) sub-problem is converted to a linear programming problem by linearization, and the (ii) sub-problem is analyzed with optimal conditions. Numerical tests show the proposed solution approach produces accurate results.Extensive numerical experiments unveil several findings. First, the WE-Bus systems outperform the SE-Bus in various scenarios except when wireless charging facilities are too costly. Second, the optimized WE-Bus designs can reduce costs not only to the agency (with smaller-sized bus battery and reduced fleet cost) but also to patrons (who enjoy improved services with shorter headways). Additional parameter analyses also investigate the impacts of demand levels, wireless charging rates, depths of discharge, etc. Lastly, a case study in Chengdu (China) illustrates the application of the proposed model.

State of the Art Wireless Charging Technology for Electric Vehicles

Wireless charging technology for EV (electric vehicles) is a trend in the car of the future Because it is a bit significant, such as driving with no emissions at all. When decelerating, the energy can be repeated in life. Noise and vibration are low. The core technology of electric vehicles lies in the "three electric" system, namely electric drive system, battery system and electric control system, these three systems constitute the key technology of electric vehicle. The advantage of wireless power transfer technology is that the weight and volume of the power system are significantly reduced, and the versatility and reliability are high. In this paper, wireless charging technology is divided into magnetic induction transmission and electric field coupling transmission. The research status and focus of this technology are summarized from the aspects of transmission coil, compensation network, power electronic converter and its control method. Finally, the compelling places and future directions of wireless charging technology are discussed Introduction.

A Comprehensive Review on Wireless Power Transfer Systems for Charging Portable Electronics

Wireless power transfer (WPT) for portable electronic applications has been gaining a lot of interest over the past few decades. This study provides a comprehensive review of the recent advancements in WPT technology, along with the challenges faced in its practical implementation. The modeling and design of WPT systems, including the effect of cross-coupling in multiple receivers, have been discussed and the techniques for efficiency improvement have been highlighted. The challenges of coil design, EMI shielding, and foreign object detection have been pointed out and various cutting-edge solutions have been presented. With improvements in wide bandgap technology, there is a push to operate WPT systems at mega-hertz frequencies. The reason for this is twofold: the miniaturization of the system and the ability to achieve a better magnetic link efficiency. However, with higher frequency comes the challenge of operating the power electronic components efficiently by using soft-switching techniques. Hence, an in-depth discussion on soft-switched topologies such as the Class D and Class E converters and their variations has been provided. Finally, the effects of magnetic field exposure on humans along with safety standards have been discussed.

Integration of Wireless Power Transfer Technology With Hierarchical Multiwalled Carbon Nanotubes-Polydimethylsiloxane Piezo-Responsive Pressure Sensor for Remote Force Measurement

Integrating sensory devices with wireless power transfer technology for remote sensing (RS) requires the implementation of complex electronic circuitry and communication protocols. To overcome this challenge and remotely monitor mechanical force, we directly integrated piezo-responsive porous multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) nanocomposites with a near-field wireless power transfer system. The wireless system transfers power bidirectionally between the transmitter and the sensing receiver at the resonant frequency of 13.56 MHz. The detection principle is based on the mechanical force-induced impedance changes in the receiver circuit. The modulated impedance signal is detected wirelessly at the transmitter circuit via a full-bridge rectifier and a smoothing capacitor. Furthermore, we demonstrate the wireless monitoring of finger bending and applied force using our flexible and disposable sensor without using any energy storage devices. The results suggest a response and recovery time of 400 ± 50 ms, strain sensitivity of 24.73, and pressure sensitivity of 0.98. Our approach adds a new path for disposable haptic-based sensory applications that do not require complex communication protocols in medical, robotics, and other fields.

Optimal Control of Wireless Powered Edge Computing System for Balance Between Computation Rate and Energy Harvested

Wireless powered edge computing system (WPECS) enhances the computing power and extends the lifetime of wireless devices (WDs). This paper studies the WPECS with multiple WDs, in which the access point (AP) provides some transmission channels which differ from each other in the channel gain, and the WD powered through the wireless power transfer (WPT) technology has some indivisible tasks and adopts binary task-offloading actions. More energy harvested strengthens the WDs with more computing power, while corresponding to more energy consumption. Therefore, how to make the optimal tradeoff between computation rate and energy harvested arises as an interesting issue. To address this issue, this paper first formulates the switch process of transmission channel as a constrained Markov decision process (CMDP), and then proposed an effective algorithm to maximize the sum of computation rates of all WDs in terms of task data bits computed, within the required level of accumulative energy harvested. Theoretical analysis, simulations and field experiments jointly document and illustrate its performance. Note to Practitioners—This paper addresses the interesting tradeoff between computation rate and energy harvested in a wireless powered edge computing system that operates in the environments with limited available energy. It helps to improve the operation efficiency of the edge computing systems in the area of Internet of Things (IoT) or Cyber-Physical Systems (CPS) that employ wireless power transfer technology to power the wireless devices through the access point over the air to maximize the sum of computations rates of all WDs in terms of task data bits computed, while keeping the accumulative energy harvested within a range. Simulations and experimental investigations show that the solution proposed here outperforms existing solutions.

Dual-Frequency Modulation to Achieve Power Independent Regulation for Dual-Load Underwater Wireless Power Connector

The power supply of underwater devices can be realized by the nonelectrical contact wireless power transfer (WPT) technology. The diversity and flexibility of devices carried by the remotely operated vehicle (ROV) can be increased by the WPT which can achieve convenient and safe device switching. Power independent regulation is a key for the underwater wireless power connector (UWPC) with multiload, and a superimposed dual-frequency modulation (SDFM) method is proposed in this article to achieve the load power independent regulation. The equal-area rule is first applied to SDFM, which can use one inverter to generate SDFM current at the transmitter. The theory of decoupled power transfer is analyzed in detail for the SDFM UWPC with dual-load (DL). All the above analyses are verified in a DL UWPC system prototype. The experimental results show that the SDFM current is generated using one inverter, and the load power can be independently regulated by adjusting the output voltage of the inverter. Furthermore, the load power is still independent and controllable under the conditions of load switching and mutual inductances changing. The DL UWPC system power can reach 50 W and dc–dc efficiency is about 68.73%.

Software-Reconfigurable Multistage Constant Current Wireless Battery Charging Based on Multiharmonic Power Transmission

Wireless power transfer (WPT) technology has been widely applied in electric vehicle battery chargers because of its convenience, reliability, and safety. A typical battery charging profile consists of a constant current (CC) charging process followed by a constant voltage charging process. Recently, a multistage constant current (MSCC) charging profile is proposed to increase the charging speed, flexibility, and other performances. MSCC charging profile consists of multiple CC charging processes, which are applied to the battery in turn. This article proposes a low-cost software-reconfigurable MSCC charging technique for a typical single-stage dc–dc series–series compensated WPT converter using multiple high-order harmonics power transmission approach. Such a technique does not require any additional component and it can achieve inherent load-independent CC output and zero phase angle input characteristics. Moreover, it provides a precharge process for deeply discharged batteries to increase their lifetime. A scaled-down design example and the corresponding laboratory prototype are implemented to verify the proposed method.