High Power Transfer Research Articles

Review Map of Comparative Designs for Wireless High-Power Transfer Systems in EV Applications: Maximum Efficiency, ZPA, and CC/CV Modes at Fixed Resonance Frequency Independent From Coupling Coefficient

This article proposes a review map for comparative designs of wireless high-power transfer (WHPT) systems using single- and double-resonance blocks. In-depth analyses and key guidelines are provided to design high-efficiency WHPT systems while keeping zero-phase-angle/unity-power-factor and constant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</i> current/voltage supply to the load. Basic single- and double-resonance blocks based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC-</i> resonant circuits are analyzed. Then, resonant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T-</i> blocks are recommended as the best transmission blocks for competitive designs. The proposed approach is applied to map recent developments on the wireless charging technologies for electric vehicles (EVs), especially for weak-coupling systems and dynamic-charging technologies. The proposed design approach offers a systematic and effective methodology to quickly evaluate current technologies and solutions for WHPTs in EVs applications. In extension, this article indicates different control strategies for WHPTs, especially for optimal-efficiency tracking. Design guidelines and control strategies are provided to achieve the maximum efficiency at a standard resonance frequency against variations from loads and coupling coefficients in operation which can easily map to recent research works and future research directions. Experimental verifications of dominant designs are also presented to validate the proposed approach. The map for comparative designs and control structures presented in this article aims to serve as a guideline and to ease the initial steps for other researchers in this area.

Design of a Flexible T-Matched Feed UHF RFID Tag Antenna

Abstract A flexible radio frequency identification (RFID) tag antenna with a T-match feeder is proposed in this paper. The T-match feed acts as the conjugate network matching of the tag antenna and 0.99 of power transfer coefficient was achieved. By incorporating a meander line and capacitive tip loading technique, the compact size is realized with a wide bandwidth of 44MHz that can cover the RFID spectrum allocated for the Malaysia region, from 919 to 923 MHz. The proposed antenna is printed on the flexible polyethene terephthalate (PET) substrate with a dimension of 90mm × 24mm × 0.143mm. By employing 4W EIRP power, the detection distance of 29.15m in free space. The proposed meandered line and capacitive tip loading tag antenna with T-match feed line is beneficial to be part of the RFID systems because of their compactness, wide bandwidth and high-power transfer coefficient.

Metamaterial-enhanced near-field readout platform for passive microsensor tags

Radiofrequency identification (RFID), particularly passive RFID, is extensively employed in industrial applications to track and trace products, assets, and material flows. The ongoing trend toward increasingly miniaturized RFID sensor tags is likely to continue as technology advances, although miniaturization presents a challenge with regard to the communication coverage area. Recently, efforts in applying metamaterials in RFID technology to increase power transfer efficiency through their unique capacity for electromagnetic wave manipulation have been reported. In particular, metamaterials are being increasingly applied in far-field RFID system applications. Here, we report the development of a magnetic metamaterial and local field enhancement package enabling a marked boost in near-field magnetic strength, ultimately yielding a dramatic increase in the power transfer efficiency between reader and tag antennas. The application of the proposed magnetic metamaterial and local field enhancement package to near-field RFID technology, by offering high power transfer efficiency and a larger communication coverage area, yields new opportunities in the rapidly emerging Internet of Things (IoT) era.

Wireless power transfer and energy harvesting in distributed sensor networks: Survey, opportunities, and challenges

Distributed sensor networks have emerged as part of the advancements in sensing and wireless technologies and currently support several applications, including continuous environmental monitoring, surveillance, tracking, and so on which are running in wireless sensor network environments, and large-scale wireless sensor network multimedia applications that require large amounts of data transmission to an access point. However, these applications are often hampered because sensor nodes are energy-constrained, low-powered, with limited operational lifetime and low processing and limited power-storage capabilities. Current research shows that sensors deployed for distributed sensor network applications are low-power and low-cost devices characterized with multifunctional abilities. This contributes to their quick battery drainage, if they are to operate for long time durations. Owing to the associated cost implications and mode of deployments of the sensor nodes, battery recharging/replacements have significant disadvantages. Energy harvesting and wireless power transfer have therefore become very critical for applications running for longer time durations. This survey focuses on presenting a comprehensive review of the current literature on several wireless power transfer and energy harvesting technologies and highlights their opportunities and challenges in distributed sensor networks. This review highlights updated studies which are specific to wireless power transfer and energy harvesting technologies, including their opportunities, potential applications, limitations and challenges, classifications and comparisons. The final section presents some practical considerations and real-time implementation of a radio frequency–based energy harvesting wireless power transfer technique using Powercast™ power harvesters, and performance analysis of the two radio frequency–based power harvesters is discussed. Experimental results show both short-range and long-range applications of the two radio frequency–based energy harvesters with high power transfer efficiency.

High-Performance Multi-MHz Capacitive Wireless Power Transfer System for EV Charging Utilizing Interleaved-Foil Coupled Inductors

This article introduces a kilowatt-scale large air-gap capacitive wireless power transfer (WPT) system for electric vehicle (EV) charging that achieves high-power transfer density and high efficiency. High-power transfer density is achieved by operating at a multi-MHz frequency (13.56 MHz), and by utilizing innovatively designed matching networks that enable effective power transfer by providing gain and reactive compensation while absorbing the parasitics present in the EV charging environment. High efficiency is achieved through the use of new interleaved-foil air-core coupled inductors in the matching networks. Interleaved-foil inductors provide a better tradeoff between quality factor, size, and self-resonant frequency compared to conventional solenoidal inductors, making them suitable for compactly and efficiently processing kilowatt-scale power at multi-MHz frequencies. Two variants of the interleaved-foil concept are presented: a semi-toroidal interleaved foil (STIF) inductor and a toroidal interleaved-foil (TIF) inductor. The superior performance of interleaved-foil inductors is demonstrated using analytical formulations, which are validated through finite-element analysis and measurements. Compared to the highest-quality-factor solenoidal inductor, the STIF inductor is shown to achieve 32% smaller box volume while having only 3% lower measured quality factor, while the TIF inductor is shown to achieve an even better tradeoff with 27% smaller box volume and 30% higher measured quality factor. A 13.56-MHz, 12-cm air-gap prototype capacitive WPT system utilizing TIF inductors with a quality factor of 2055 in its matching networks is designed, built, and tested. This system achieves record-breaking performance for a capacitive EV charging system, with an efficiency of 94.7% while transferring 3.75 kW using 22-cm-diameter coupling plates, corresponding to a power transfer density of 49.4 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This TIF-inductor-based prototype is also shown to outperform a second high-performance prototype utilizing STIF inductors.

Conductive Electric Road Localization and Related Vehicle Power Control

Enabling vehicles to draw energy from an electric road system (ERS) significantly reduces the need for battery capacity on board the vehicle. It is not necessary, nor realistic, to cover every meter of every stretch of road with ERS. The question then arises how and where the ERS sections should be placed. One way of doing it is to place equally long sections of ERS with a certain separating distance. Another way is to place the sections where the highest amount of traction power of the vehicles is required. This paper presents a performance evaluation of both these methods from an energy consumption and battery degradation point of view. This study assumes a conductive ERS which allows for high power transfer. Being conductive, galvanic isolation between the energy source (the ERS) and the on board traction voltage system (TVS) is needed for electric safety reasons. In addition to the two alternative methods for location of ERS segments, three different powertrains, each with a different approach to galvanic isolation and charging, are evaluated. It is discovered that the method for location of the ERS can in fact affect both energy consumption and battery degradation depending on powertrain and driving scenario.

Guest Editorial: Special Issue on Advanced and Emerging Technologies of High Efficiency and Long-Distance Wireless Power Transfer Systems

Guest Editorial: Special Issue on Advanced and Emerging Technologies of High Efficiency and Long-Distance Wireless Power Transfer Systems

Scalable Architectures for High Frequency and Very High Frequency Wireless Power Transfer

Scalable Architectures for High Frequency and Very High Frequency Wireless Power Transfer

Novel Transformerless Multilevel Inductive Power Transfer System

Previous high power on-line inductive power transfer (IPT) systems use line-frequency (LF) transformers and high-frequency (HF) transformers to be compatible with the ratings of commercial power switches. However, LF and HF transformers make the IPT systems bulky and expensive. This study proposes a new transformerless multilevel on-line IPT system using multilevel rectifiers, inverters, and excitation coils. Instead of the LF transformers, a series-connected multilevel rectifier and inverter are used. Instead of the HF transformers, excitation coils, which have strong magnetic couplings with a transmitter coil, is connected to each of the output terminals of the multilevel inverter. The magnetic fields generated by the multiple excitation coils induce a high voltage and current in the transmitter coil. The induced current generates the augmented magnetic field in the transmitter; therefore, a receiver coil that is loosely coupled with the transmitter can collect power from the mains. The input impedance, voltage and current gains, and efficiency of the proposed IPT system are investigated using an equivalent circuit model. The impact of the excitation coil shape on the magnetic couplings is explored using finite element analysis. Based on the investigation, a design for the excitation coil is presented. The feasibility of the proposed system is evaluated using a 4-level experimental test-bed. Measured coil-to-coil and DC-to-load efficiencies of the proposed system are observed to be 88% and 84%, respectively, over a 7 cm air-gap.

Power Handling and Spectral Density Considerations in the Design of Reflectarray Antennas for Wireless High-Power Transfer Applications

Power handling and power spectral density (EIRP-SD) considerations in the design of reflectarray antennas are outlined for wireless high power transfer applications. The impact of fast Fourier Transform (FFT) based pattern analysis methods is considered, including the accuracy of EIRP-SD calculations for regulatory considerations, as well as how to compute those limits. A hybrid pattern analysis appropriate for the practical design of high EIRP-SD reflectarray systems is proposed. To illustrate these concepts, a reflectarray is designed and modeled with this method and the results exhibit agreement with predicted patterns from a full-wave simulation while showing dramatic simulation time improvement. Finally, the power handling, EIRP-SD and gain characteristics are related to each other.

Critical Review of Recent Advancement in Metamaterial Design for Wireless Power Transfer

With increasing penetration of wireless charging technologies comes an ever-rising demand for wireless power transfer (WPT) structures that demonstrate high power transfer and power transfer efficiency (PTE), especially over wide transfer distance. The concern with reliability in adopting wireless charging technologies in consumer and industrial applications (including mobile chargers and dynamic wireless charging of electric vehicles, EVs) stems from fluctuating output power and low power transfer efficiency (PTE). Moreover, the inherently high resonant frequency of existing metamaterial (MM)-based WPT designs imposes a high switching stress on power semiconductors and passive components, resulting in high power dissipation, especially in high power applications. This manuscript presents a critical survey of recent studies and developments in MM-based WPT systems. First, the fundamental concepts and classification of WPT technologies based on magnetic resonant coupling (MRC), inductive coupling etc. are discussed. Going forward, key MM design considerations, including resonance operating frequencies, effective permittivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon _{r}$ </tex-math></inline-formula> ), effective permeability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{r}$ </tex-math></inline-formula> ), numerical modeling, equivalent circuit representations, and 3D fabrication technologies are widely analyzed and critiqued. Additionally, the performance enhancing effect of integrating different MM designs with existing WPT systems are explicitly discussed. Finally, the technical challenges associated with the resonant operating frequencies of MM, miniaturization of MM design footprint, and 3D prototyping are investigated while also presenting potential solutions.

Magnetic Field Leakage Cancellation in Multiple-Input Multiple-Output Wireless Power Transfer Systems

This letter presents a method to cancel magnetic field leakage while maintaining high power transfer efficiency (PTE) in multiple-input multiple-output wireless power transfer systems. To achieve low leakage and high PTE, the problem of PTE maximization under the cancellation condition of the magnetic field leakage is solved, which is a maximization problem of affinely constrained Rayleigh quotients. Subsequently, the optimal amplitudes and phases of the input voltages at the transmitter array and the optimal load impedances at the receivers are shown. This method can further reduce the magnetic field leakage by up to 31 dB compared with the PTE maximization method, while having a PTE drop within 5.5%.

An efficient design of LC-compensated hybrid wireless power transfer system for electric vehicle charging applications

Wireless power transfer (WPT) is the technology of transferring the electric power through a time-varying electric or magnetic field acting as a transmission medium. A combination between the inductive power transfer (IPT) and the capacitive power transfer (CPT) has been recently developed to benefit from the merits of both systems in order to realize high power transfer with high efficiency through large air gaps and misalignment distances. The output power capability of the existing designs is still limited and needs further enhancement. In this paper, a new hybrid inductive and capacitive wireless power transfer model is proposed, analyzed and simulated. The inductive part composes of a circular spiral coil integrated with a helical coil and supported with cross shape ferrite bars in order to enhance the magnetic coupling ability. The capacitive part consists of four cylindrically evacuated square plates compatible with the inductive part size to facilitate the combination process. Firstly, the system structure is designed using Maxwell-3D simulation tool, then an equivalent circuit model is derived in detail to explicate the working principle. Secondly, a 10.1 kW hybrid system is designed and simulated using MATLAB/Simulink and ANSYS/Simplorer. Excluding the inverter and the rectifier internal losses and considering only the AC losses of the coils represented in their parasitic resistance, a high resultant efficiency equal to 99.37% at a resonant frequency of 1 MHz is achieved. Generally, the results show that the hybrid system could perform better under different air gaps and misalignments than the inductive and the capacitive systems separately.

Optimal Solutions for Underwater Capacitive Power Transfer.

Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the available load power and the efficiency of the CPT system as functions of capacitive coupling parameters and derives the required admittance of the load and the source. The experimental results demonstrated that the available power and the efficiency decrease by the increasing of the frequency from 300 kHz to 1 MHz and the separation distance change from 100 to 300 mm. The maximum efficiency solution gives 83% at 300 kHz and a distance of 100 mm, while the maximum power solution gives the maximum normalized power of 0.994 at the same frequency and distance. The CPT system can provide a good solution to charge electric ships and underwater vehicles over a wide separation distance and low-frequency ranges.

A Wireless Power and Data Transfer IC for Neural Prostheses Using a Single Inductive Link With Frequency-Splitting Characteristic.

This paper presents a frequency-splitting-based wireless power and data transfer IC that simultaneously delivers power and forward data over a single inductive link. For data transmission, frequency-shift keying (FSK) is utilized because the FSK modulation scheme supports continuous wireless power transmission without disruption of the carrier amplitude. Moreover, the link that manifests the frequency-splitting characteristic due to a close distance between coupled coils provides wide bandwidth for data delivery without degrading the quality factors of the coils. It results in large power delivery, high data rate, and high power transfer efficiency. The presented IC fabricated in a 180-nm BCD process simultaneously achieves up-to-115-mW wireless power delivery to the load and 2.5-Mb/s downlink data rate over the single inductive link. The measured overall power efficiency from the DC power supply at the transmitter module to the load at the receiver module reaches 56.7 % at its maximum, and the bit error rate is lower than 10 -6 at 2.5 Mb/s. As a result, the figure of merit (FoM) for data transmission is enhanced by 2 times, and the FoM for power delivery is improved by 38.7 times compared to prior state-of-the-arts using a single inductive link.

Metal Object Detection in a Wireless High-Power Transfer System Using Phase–Magnitude Variation

Recently, wireless charging technologies for large moving objects, such as electric vehicles and robots, have been actively researched. The power transmitting and receiving coils in most large moving objects are structurally separated by a given distance, which exposes a high output power to the outside world. If a foreign metal object enters the area between these two coils during wireless power transfer, fire hazards or equipment damage may occur. Therefore, we propose a method for detecting foreign metal objects in the gap between the transmitting and receiving coils in a wireless high-power transfer system. A resonant detection coil set is used to exploit the change induced in electrical characteristics when a foreign metal object is inserted. The mutual inductance of the foreign metal object changes the impedance of the detection coil set. We developed a simple circuit to detect both the magnitude and phase change of the voltage signal according to the altered impedance. Additionally, we implemented a prototype of a wireless power transfer system with a detection system to verify that even small foreign metal objects can be detected effectively.

Design of high efficiency low frequency wireless power transfer system for electric vehicle charging

Design of high efficiency low frequency wireless power transfer system for electric vehicle charging

Simulating Ultrasound Piezoelectric Power Transfer in the Near Field and Experimental Validations

Background: Acoustic power transfer is a method for wireless energy transfer to implanted medical devices that permits a greater range of separation between transmitter and receiver than is possible with inductive power transfer. In some cases, short-distance ultrasonic power transfer may be employed; consequently, their operation may be complicated by the near-field aspects of piezoelectric acoustic energy transfer. Methods: A piezoelectric energy transfer system consisting of two lead zirconate titanate (PZT) transducers was analyzed in this work using a combination of experimental measurements and computer simulations. Results: Simulations using the COMSOL Software package showed good agreement with measured output voltage as a function of the distance between and alignment of the transmitter and receiver with water as a medium. We also simulated how operating frequency affects power transfer efficiency at various distances between the transmitter and receiver and found reasonable agreement with experiments. We report model predictions for power transfer efficiency as a function of the thickness and diameter of the transmitter and receiver. Conclusion: The results show that with proper choice of parameters, piezoelectric systems can provide high power transfer efficiency in the near-field region.

‘Power-as-a-Service’ – A Hierarchical On-Demand Charging Model for Recharging the Mobile Nodes of MANETs

Battery energy is a crucial issue that limits battery-powered mobile devices’ operational efficiency in Mobile Ad hoc Networks (MANETs). Failure of a node affects both the lifetime and connectivity of a MANET, which has to initiate finding a new route from source to destination. This initiation causes more energy consumption in nodes. Failure of a node also causes network partitions, thereby resulting in sparse networks being formed. Existing energy-efficient strategies only defer the end of a node’s battery lifetime; they could not guarantee the MANET’s nonstop functioning. To address the issues caused by battery depletion, this paper proposes a “Cloud” oriented approach called Power-as-a-Service (PaaS), a hierarchical on-demand charging model for recharging the mobile nodes of the MANET. In PaaS, the MANET is alienated into non-overlapping disjoint zones, and for each zone, one Zone Charging Cloud Node (ZccN) is deployed to recharge the mobile nodes of that particular zone wirelessly. A High-power Charging Cloud Node (HccN) is deployed to wirelessly recharge the ZccNs in the MANET for the entire network. In PaaS, the ZccN recharges both the selected node for recharge and other nodes around the selected node that requested recharge and has higher power transfer efficiency. This strategy of PaaS improves the charging efficiency of cloud chargers by minimizing the urgent charging requests in the future, and thus the operational efficiency of the MANET improves. Extensive simulations indicate that the proposed PaaS model with a hierarchy of cloud chargers improves the operational efficiency of MANETs in terms of reducing the death rate of mobile nodes, thereby improving the lifetime and connectivity probability of MANETs.

Feasibility assessment of next-generation drones powering by laser-based wireless power transfer

Utilizing drones in many applications such as video and photography, farms, search and rescue operations, construction industry for mapping and site monitoring has increased. However, their operating time is limited according to the capacity of their batteries. Therefore, many researchers attempt to enhance the operating time of drones. In this study, to the best of the authors' knowledge for the first time, the feasibility assessment of a laser-based wireless power transfer (WPT) mechanism is theoretically investigated on drone applications to increase their operating time. In this method, drones can be charged during operation wirelessly at a considerable distance with acceptable efficiency. The Analytical code is developed in Engineering Equation Solver (EES) software. The acquired results for the main components of the system have a good agreement with published papers of other researchers. In this study, three commercial photovoltaic (PV) materials were evaluated. The results show that an equipped drone with laser-based WPT system is able to approximately receive net power of 73.5, 62.6, and 33.2 W at a 500 m distance by GaAs, CdTe, and c-Si PV materials, respectively, while the laser module consumes around 600 W electrical power. Moreover, since the optical power of the laser is concentrated on PV panel, a two-phase cooling system is suggested for PV panel to reduce the temperature of the under radiate area. Results demonstrate that the temperature of GaAs PV material without a two-phase cooling system is approximately three times more than the temperature of PV panels with a two-phase cooling system at high power transfer rates.