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Special Issue "Wireless Power Transfer 2018"

A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (15 October 2018)

Special Issue Editors

Guest Editor
Dr. Hongjian Sun

Department of Engineering, Durham University, Stockton Road, Durham DH1 3LE, UK
Website | E-Mail
Interests: smart grids; cognitive radio; wireless power transfer; Internet of things
Guest Editor
Dr. Jing Jiang

Department of Engineering, Durham University, Stockton Road, Durham DH1 3LE, UK
Website | E-Mail
Interests: wireless communication technologies; smart grids; cognitive radio; wireless power transfer; electric vehicle

Special Issue Information

Dear Colleagues,

Wireless Power Transfer 2018 is a continuation of the previous and successful Special Issue, “Wireless Power Transfer 2016”. Wireless power transfer technologies, as an attractive alternative to cabled charging, are attracting widespread interest in the fields of home electronics, medical implants, electric vehicles, and aerospace industries, due to their convenient and safe characteristics. However, we are facing a number of significant challenges, such as the low cost efficiency and power transfer efficiency, and the high sensitivity to misalignment and distance. All of these require collaborative and sustained efforts from the Societies of Electronics, Power and Energy, Communications, and Computing over the years to come. To promote the development and innovations, this Special Issue is dedicated to publishing research results of wireless power transfer technologies spanning across multiple disciplines. Potential research topics include, but are not limited to:

  • Wireless power transfer for mobile devices (e.g., smart phones, tablets), electric vehicles (e.g., PHEVs, buses, trains), home appliances, medical implants, and other industry applications;
  • Design of electronics, components, coils, and magnetics in wireless power transfer;
  • Modeling, simulation, and control of wireless power transfer systems;
  • Analysis of data and environmental impacts in wireless power transfer;
  • Joint power-communication-computing system design (such as wireless information and power transfer);
  • Applications of wireless power transfer in larger environments (such as smart homes, smart cities and Internet of Things).

Dr. Hongjian Sun
Dr. Jing Jiang
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access bimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • wireless power transfer
  • electric vehicle
  • smart phones
  • medical implants
  • wireless information and power transfer
  • electronics design
  • components design
  • coils design
  • magnetics design

Published Papers (16 papers)

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Research

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Open AccessFeature PaperArticle Free Angular-Positioning Wireless Power Transfer Using a Spherical Joint
Energies 2018, 11(12), 3488; https://doi.org/10.3390/en11123488
Received: 14 November 2018 / Revised: 7 December 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
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Abstract
Many studies have investigated resonator structures and winding methods. The aims of this paper are as follows. First, the paper proposes an optimized winding model for a bio-inspired joint for a wireless power transfer (WPT) system. The joint consists of a small spherical
[...] Read more.
Many studies have investigated resonator structures and winding methods. The aims of this paper are as follows. First, the paper proposes an optimized winding model for a bio-inspired joint for a wireless power transfer (WPT) system. The joint consists of a small spherical structure, which rotates inside a hemispherical structure. The transmitter coil (Tx) is wound on the hemisphere structure, and the receiver coil (Rx) is wound on the small sphere. The power is transferred while rotating Rx over a wide range of angular misalignment. In addition, the algorithm design of the proposed winding method is given to get an optimized model. Moreover, the circuit analysis of the WPT system is discussed. Second, the magnetic field density is investigated considering a safety issue, which is linked to human exposure to electromagnetic fields (EMFs). Moreover, EMF mitigation methods are proposed and discussed in detail. Finally, the simulation results are validated by experiments, which have confirmed that the proposed winding method allows the system to rotate up to 85 degrees and achieve an efficiency above 86%. The proposed winding method for the WPT system can be a good technique for some robotic applications or a future replacement of the human joint. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessFeature PaperArticle Characteristic Analysis of Electromagnetic Force in a High-Power Wireless Power Transfer System
Energies 2018, 11(11), 3088; https://doi.org/10.3390/en11113088
Received: 15 October 2018 / Revised: 3 November 2018 / Accepted: 6 November 2018 / Published: 8 November 2018
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Abstract
In order to explore the influence of the electromagnetic force (EMF) on the coupling mechanism in a high-power wireless power transfer (WPT) system, the characteristics of the EMF are investigated by theoretical calculation and simulation. The expressions of the EMF on the WPT
[...] Read more.
In order to explore the influence of the electromagnetic force (EMF) on the coupling mechanism in a high-power wireless power transfer (WPT) system, the characteristics of the EMF are investigated by theoretical calculation and simulation. The expressions of the EMF on the WPT structure with magnetic shielding are derived in time domain and frequency domain, respectively. The EMF is divided into Lorentz force and Kelvin force. The distribution and changing regularity of the EMF on the coil and the magnetic shield under different exciting currents are solved by the finite element model, and the harmonic of the EMF is analyzed in detail. The results show that the coil is subjected to the EMF in both radial and axial directions. The EMF on the magnetic shield is opposite to the EMF on the coil, and the force between the transmitting coil and the receiving coil is repulsive. The frequency of the EMF is twice that of the system resonant frequency. An experimental prototype is built to prove the correctness of the predicted characteristics. It is shown that the EMF should be carefully considered in the application of high-power WPT systems. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Power Stabilization Based on Asymmetric Transceiver in Dynamic Wireless Charging System with Short-Segmented Transmitting Coils for Inspection Robots
Energies 2018, 11(11), 3005; https://doi.org/10.3390/en11113005
Received: 24 September 2018 / Revised: 17 October 2018 / Accepted: 25 October 2018 / Published: 1 November 2018
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Abstract
To solve the issues of frequent and inflexible contact charging system for inspection robots, the dynamic wireless charging system for the moving robot is introduced in this paper. In dynamic wireless charging systems with symmetric transceiver, including a single energized transmitting coil and
[...] Read more.
To solve the issues of frequent and inflexible contact charging system for inspection robots, the dynamic wireless charging system for the moving robot is introduced in this paper. In dynamic wireless charging systems with symmetric transceiver, including a single energized transmitting coil and one receiving coil, the receiving power drops significantly when the receiving coil moves to the boundary position of the energized transmitting coil. An asymmetric transceiver, including the single energized transmitting coil and two identical receiving coils connected in series is proposed for power stabilization during the moving process of the inspection robot. Circuit models of the systems with symmetric and asymmetric transceivers are developed. Expressions for the receiving power and the efficiency in these systems are derived. Then, the characteristics of the receiving power and efficiency varying with the position of receiving devices during one cycle of the switching control of the transmitting coils are investigated comparatively. The receiving power drop issue when the receiving coil is at the switching control position of the transmitting coils in the system with symmetric structure is solved by the proposed asymmetric structure with two receiving coils. Finally, the theoretical analyses are verified by experimental results and conclusions are drawn. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Study of the Circular Flat Spiral Coil Structure Effect on Wireless Power Transfer System Performance
Energies 2018, 11(11), 2875; https://doi.org/10.3390/en11112875
Received: 19 September 2018 / Revised: 18 October 2018 / Accepted: 18 October 2018 / Published: 23 October 2018
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Abstract
This paper analyses the relationship between the coil design parameters and the system performance, including power transfer efficiency and amount, when circular flat spiral coils are adopted in a wireless power transfer (WPT) system. Coil design variables including outer radius, inner radius, channel
[...] Read more.
This paper analyses the relationship between the coil design parameters and the system performance, including power transfer efficiency and amount, when circular flat spiral coils are adopted in a wireless power transfer (WPT) system. Coil design variables including outer radius, inner radius, channel width and coil turns are thoroughly studied to improve the system performance with a limited maximum outer radius for practical purposes. A two-coil WPT system has been built to verify the analysis, and the experimental results show good consistency with the theoretical calculations and simulation results, which show that the coil design parameters have a significant impact on the system performance, even with the same coil size. In the experiments, the coil-to-coil distance is 150 mm, the maximum coil outer radius is limited in 300 mm, and the DC input voltage and the load resistance are 100 V and 5 Ω, respectively. When the coils are tightly-wound in the most traditional way to maximize the coil size, the coil-system efficiency is 62.6% with only 4.5 W load power. In contrast, the efficiency optimized coil can improve the coil-system efficiency to 91.2% with the outer radius stayed the same. Besides, when the power transfer efficiency and amount are considered simultaneously, the system can achieve 1279 W load power with 85.94% coil-system efficiency. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle An Improved Autonomous Current-Fed Push-Pull Parallel-Resonant Inverter for Inductive Power Transfer System
Energies 2018, 11(10), 2653; https://doi.org/10.3390/en11102653
Received: 8 August 2018 / Revised: 23 September 2018 / Accepted: 1 October 2018 / Published: 4 October 2018
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Abstract
In the inductive power transfer (IPT) system, it is recommended to drive the resonant inverter in zero-voltage switching (ZVS) or zero-current switching (ZCS) operation to reduce switching losses, especially in dynamic applications with variable couplings. This paper proposes an improved autonomous current-fed push-pull
[...] Read more.
In the inductive power transfer (IPT) system, it is recommended to drive the resonant inverter in zero-voltage switching (ZVS) or zero-current switching (ZCS) operation to reduce switching losses, especially in dynamic applications with variable couplings. This paper proposes an improved autonomous current-fed push-pull parallel-resonant inverter, which not only realizes the ZVS operation by tracking the zero phase angle (ZPA) frequency, but also improves the output power and overall efficiency in a wide range by reducing gate losses and switching losses. The ZPA frequencies characteristic of the parallel-parallel resonant circuit in both bifurcation and bifurcation-free regions is derived and verified by theory and experiments, and the comparative experimental results demonstrate that the improved inverter can significantly increase the output power from 7.68 W to 8.74 W and has an overall efficiency ranging from 63.5% to 72.5% compared with the traditional inverter at a 2 cm coil distance. Furthermore, with a 2-fold input voltage (24 V), the improved inverter can achieve an approximate 4-fold output power of 38.9 W and overall efficiency of 83.6% at a 2 cm coil distance. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Analysis and Design of Broadband Simultaneous Wireless Information and Power Transfer (SWIPT) System Considering Rectifier Effect
Energies 2018, 11(9), 2387; https://doi.org/10.3390/en11092387
Received: 10 July 2018 / Revised: 10 August 2018 / Accepted: 14 August 2018 / Published: 11 September 2018
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Abstract
The deployment of internet of things (IOT) devices in several applications is limited by their need of having batteries as a power source. This has led many researchers to make efforts on simultaneous wireless information and power transfer (SWIPT) systems design. Increasing the
[...] Read more.
The deployment of internet of things (IOT) devices in several applications is limited by their need of having batteries as a power source. This has led many researchers to make efforts on simultaneous wireless information and power transfer (SWIPT) systems design. Increasing the bandwidth provides higher capacity; however, due to the narrowband response of conventional power transfer subsystems, power delivery is decreased. In order to design an optimum wideband SWIPT system, first, a realistic model of the system, including antennas and rectifier, should be developed. Then, proper methods to increase the bandwidth of subsystems for optimum power delivery can be proposed. In this paper, a wideband SWIPT system (300 MHz bandwidth at the center frequency of 1.44 GHz) while considering realistic limitations of antennas and rectifiers is designed. To optimize the system performance, a novel power allocation method is proposed. Using this algorithm, Pareto fronts of Shannon channel capacity versus power delivery in three scenarios (broadband antennas without considering rectifier, broadband antennas with narrowband rectifier and broadband antennas with broadband rectifier) are compared. The results show that, without considering the realistic behaviour of the subsystems, the performance is largely overestimated. Furthermore, this model allows for designers to optimize each subsystem directly and assess its effect on the overall SWIPT system performance. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessFeature PaperArticle Wireless Power Charger Based on Class E Amplifier with the Maximum Power Point Load Consideration
Energies 2018, 11(9), 2378; https://doi.org/10.3390/en11092378
Received: 21 August 2018 / Revised: 31 August 2018 / Accepted: 4 September 2018 / Published: 9 September 2018
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Abstract
The construction of an electromagnetic coupling power transfer system is introduced in this paper. Considering the characteristics of the battery charger, a novel parameter design method based on the load of the maximum power transfer point is proposed. Then, the compensator, resonant circuits,
[...] Read more.
The construction of an electromagnetic coupling power transfer system is introduced in this paper. Considering the characteristics of the battery charger, a novel parameter design method based on the load of the maximum power transfer point is proposed. Then, the compensator, resonant circuits, and some key parameters of the electromagnetic coupler are discussed in detail by constructing a mutual inductance model to carry out impedance calculation and analysis. Coupling coefficient influenced by different magnetic circuits and coil distribution were analyzed by building a finite element model and an equivalent magnetic circuit. Moreover, impedance matching and compensation network parameters were theoretically calculated and simulated. Finally, a wireless power charger based on an open-loop class E amplifier with the maximum power point load consideration was manufactured. Simulation and experiments were done to verify the analyses, and the capability of 4.2 W power delivery at a distance of 10 mm and a peak system efficiency exceeding 72% were demonstrated. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle A Power and Data Decoupled Transmission Method for Wireless Power Transfer Systems via a Shared Inductive Link
Energies 2018, 11(8), 2161; https://doi.org/10.3390/en11082161
Received: 17 July 2018 / Revised: 11 August 2018 / Accepted: 11 August 2018 / Published: 18 August 2018
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Abstract
Wireless Power Transfer (WPT) technology is gaining global popularity. However, in some applications, data transmission is also required to monitor the load states. This paper presents an alternative wireless power and data transmission method via the shared inductive link. With the method, the
[...] Read more.
Wireless Power Transfer (WPT) technology is gaining global popularity. However, in some applications, data transmission is also required to monitor the load states. This paper presents an alternative wireless power and data transmission method via the shared inductive link. With the method, the system presents three characteristics: (1) controllability and stability of the output voltage; (2) miniaturization in volume of the system; (3) decoupled transmission of power and data. The output voltage control is realized by a non-inductive hysteresis control method. In particular, data is transferred when the power transmission is blocked (i.e., the hysteresis switch is off). The interference between power and data transmission is very small. The signal to noise ratio (SNR) performance which is relevant to the interference from power transfer to data transfer and data transfer capacity, is studied and optimized. Both simulation and experimental results have verified the proposed method. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Single-Tube and Multi-Turn Coil Near-Field Wireless Power Transfer for Low-Power Home Appliances
Energies 2018, 11(8), 1969; https://doi.org/10.3390/en11081969
Received: 29 May 2018 / Revised: 20 July 2018 / Accepted: 27 July 2018 / Published: 30 July 2018
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Abstract
Single-tube loop coil (STLC) and multi-turn copper wire coil (MTCWC) wireless power transfer (WPT) methods are proposed in this study to overcome the challenges of battery life during low-power home appliance operations. Transfer power, efficiency, and distance are investigated for charging mobile devices
[...] Read more.
Single-tube loop coil (STLC) and multi-turn copper wire coil (MTCWC) wireless power transfer (WPT) methods are proposed in this study to overcome the challenges of battery life during low-power home appliance operations. Transfer power, efficiency, and distance are investigated for charging mobile devices on the basis of the two proposed systems. The transfer distances of 1–15 cm are considered because the practicality of this range has been proven to be reliable in the current work on mobile device battery charging. For STLC, the Li-ion battery is charged with total system efficiencies of 86.45%, 77.08%, and 52.08%, without a load, at distances of 2, 6, and 15 cm, respectively. When the system is loaded with 100 Ω at the corresponding distances, the transfer efficiencies are reduced to 80.66%, 66.66%, and 47.04%. For MTCWC, the battery is charged with total system efficiencies of 88.54%, 75%, and 52.08%, without a load, at the same distances of 2, 6, and 15 cm. When the system is loaded with 100 Ω at the corresponding distances, the transfer efficiencies are drastically reduced to 39.52%, 33.6%, and 15.13%. The contrasting results, between the STLC and MTCWC methods, are produced because of the misalignment between their transmitters and receiver coils. In addition, the diameter of the MTCWC is smaller than that of the STLC. The output power of the proposed system can charge the latest smartphone in the market, with generated output powers of 5 W (STLC) and 2 W (MTCWC). The above WPT methods are compared with other WPT methods in the literature. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Coupling-Independent Capacitive Wireless Power Transfer Using Frequency Bifurcation
Energies 2018, 11(7), 1912; https://doi.org/10.3390/en11071912
Received: 28 June 2018 / Revised: 17 July 2018 / Accepted: 20 July 2018 / Published: 22 July 2018
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Abstract
Capacitive wireless power transfer can be realized by mutually coupled capacitors operating at a common resonant frequency. An optimal load exists that maximizes either the efficiency or the power transfer to the load. In this work, we utilize the frequency bifurcation effect to
[...] Read more.
Capacitive wireless power transfer can be realized by mutually coupled capacitors operating at a common resonant frequency. An optimal load exists that maximizes either the efficiency or the power transfer to the load. In this work, we utilize the frequency bifurcation effect to propose a frequency agile mode that allows for a nearly coupling-independent regime. We analytically determine the operating conditions of the coupling-independent mode based on the different system gains. In this way, we obtain a solution that achieves nearly constant efficiency and power transfer, even at varying coupling. We compare our results to inductive wireless power transfer where a perfect coupling-independent mode is achievable. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle The Effect of Fractional Orders on the Transmission Power and Efficiency of Fractional-Order Wireless Power Transmission System
Energies 2018, 11(7), 1774; https://doi.org/10.3390/en11071774
Received: 26 May 2018 / Revised: 20 June 2018 / Accepted: 2 July 2018 / Published: 6 July 2018
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Abstract
To avoid the problems of integer-order magnetic resonant wireless power transmission (WPT) systems, such as low output power and transmission efficiency, high resonant frequency, frequency splitting, and parameter coupling, a novel WPT system based on the fractional-order calculus theory is proposed; the resonant
[...] Read more.
To avoid the problems of integer-order magnetic resonant wireless power transmission (WPT) systems, such as low output power and transmission efficiency, high resonant frequency, frequency splitting, and parameter coupling, a novel WPT system based on the fractional-order calculus theory is proposed; the resonant frequency and coupling coefficient can be regulated by the fractional order, so that this system has completely different transmission characteristics from the integer-order WPT system. Therefore, in this paper, the circuit model based on the phasor method of fractional-order WPT system is established, and the output power and transmission efficiency of the system are analyzed. In addition, the comparative analysis of output power and transmission efficiency under different fractional orders are performed to estimate the optimal combination of fractional orders, which is beneficial to produce better characteristics of output power and transmission efficiency and provides a theoretical basis for the design and implementation of an experimental system. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle A Novel Output Power Control of Wireless Powering Kitchen Appliance System with Free-Positioning Feature
Energies 2018, 11(7), 1671; https://doi.org/10.3390/en11071671
Received: 8 June 2018 / Revised: 22 June 2018 / Accepted: 22 June 2018 / Published: 27 June 2018
PDF Full-text (6636 KB) | HTML Full-text | XML Full-text
Abstract
To achieve a free-positioning wireless power transfer (WPT) system, the output power must be regulated throughout the operation. This paper presents a novel output power control of a WPT system, based on the model predictive control (MPC). The output power is predicted by
[...] Read more.
To achieve a free-positioning wireless power transfer (WPT) system, the output power must be regulated throughout the operation. This paper presents a novel output power control of a WPT system, based on the model predictive control (MPC). The output power is predicted by utilizing the system’s mathematical model. The optimal duty cycle for a desired output power is obtained through the minimization of the objective function, which is simple and easy to implement, with no need for gain tuning. The proposed controller is implemented on the primary side, without any measurement or communication devices on the secondary side. This reduces the cost, size, and complexity of the WPT system. The load resistance and mutual inductance identification method is also introduced. It is based on the reflected impedance knowledge, where only the information of primary current is required. Experimental results of the output power step response show better performance compared with conventional Proportional-Integral (PI) control. The proposed controller is experimentally validated on a 200 W kettle. The output power can be kept constant at 200 W while the kettle is laterally moved. With the proposed controller, the kettle can be placed freely up to 7 cm from the align position, which is 63.64% of the primary coil’s outer radius. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Optimal Efficiency Tracking Control Scheme Based on Power Stabilization for a Wireless Power Transfer System with Multiple Receivers
Energies 2018, 11(5), 1232; https://doi.org/10.3390/en11051232
Received: 29 March 2018 / Revised: 3 May 2018 / Accepted: 4 May 2018 / Published: 12 May 2018
PDF Full-text (8416 KB) | HTML Full-text | XML Full-text
Abstract
With the increase of charging requirements in electrical equipment, the wireless power transfer (WPT) system with multiple receivers has gained more attention as the charging power and efficiency of a WPT system depends on the equivalent reflected impedance of the load. Based on
[...] Read more.
With the increase of charging requirements in electrical equipment, the wireless power transfer (WPT) system with multiple receivers has gained more attention as the charging power and efficiency of a WPT system depends on the equivalent reflected impedance of the load. Based on the circuit model analysis of a single receiver WPT system, this paper investigated the multiple-receiver WPT system. The relationship between the mutual inductance, load, and system efficiency was discussed and the optimal load, the equivalent reflected impedance, and power division method were analyzed to design the proposed system control scheme. With the use of the perturbation and observation (P&O) algorithm control method, the current of transfer and receivers were regulated to achieve stable constant power charging. Furthermore, when searching the minimum input power of the system, the optimal efficiency under a fixed power division ratio was also received. The validity of the proposed system control method was confirmed by simulation and experimental results. Under the proposed control method, an efficiency above 80% can be achieved for a multiple-receiver WPT system with a fixed power division ratio working at 6.78 MHz. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle A Three-Coil Inductively Power Transfer System with Constant Voltage Output
Energies 2018, 11(3), 673; https://doi.org/10.3390/en11030673
Received: 23 January 2018 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 16 March 2018
Cited by 1 | PDF Full-text (4658 KB) | HTML Full-text | XML Full-text
Abstract
For a traditional 2-coil system outputting constant voltage (CV), the transfer efficiency decreases drastically as transfer distance increases. To solve this problem, this essay proposes a 3-coil system which could achieve CV output and Zero Phase Angle (ZPA) conditions with specific parameter values.
[...] Read more.
For a traditional 2-coil system outputting constant voltage (CV), the transfer efficiency decreases drastically as transfer distance increases. To solve this problem, this essay proposes a 3-coil system which could achieve CV output and Zero Phase Angle (ZPA) conditions with specific parameter values. This 3-coil system could partly relief transfer efficiency fall at a long transfer distance, without any complicated controls. In order to achieve CV and ZPA condition, this essay devises the parameter values based on the decoupling 3-coil model, and a prototype is designed accordingly to verify these characteristics. With 10 cm transfer distance, output voltage deviation is 5.5% as the load varies from 12 Ω to 200 Ω, proving that the output voltage almost keeps constant with load change. Furthermore, with software simulation, a comparison experiment between the proposed 3-coil system and a Series-Inductor-Capacitor-Inductor (S-LCL) compensated 2-coil system is built to verify the efficiency improvement. The transfer distance change leads to the differentiation of voltage gain for both 2-coil and 3-coil systems. So, the input voltage for both systems and the compensated capacitor in receiver loop of the 3-coil system are manipulated for keeping 60 V output voltage on the 12 Ω load. With distance increasing from 10 cm to 20 cm, transfer efficiency varies from 92.61 to 48.9% for the 2-coil system, and from 92.89 to 84.26% for the 3-coil system, effectively proving the efficiency improvement. The experiment and simulation results prove the effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Open AccessArticle Mitigation Conducted Emission Strategy Based on Transfer Function from a DC-Fed Wireless Charging System for Electric Vehicles
Energies 2018, 11(3), 477; https://doi.org/10.3390/en11030477
Received: 5 February 2018 / Revised: 18 February 2018 / Accepted: 20 February 2018 / Published: 25 February 2018
Cited by 2 | PDF Full-text (10024 KB) | HTML Full-text | XML Full-text
Abstract
The large dv/dt and di/dt outputs of power devices in wireless charging system (WCS) in electric vehicles (EVs) always introduce conducted electromagnetic interference (EMI) emissions. This paper proposes a mitigation conducted emission strategy based on transfer function from a direct current fed (DC-fed)
[...] Read more.
The large dv/dt and di/dt outputs of power devices in wireless charging system (WCS) in electric vehicles (EVs) always introduce conducted electromagnetic interference (EMI) emissions. This paper proposes a mitigation conducted emission strategy based on transfer function from a direct current fed (DC-fed) WCS for EVs. A complete test for the DC-fed WCS is set up to measure the conducted emission of DC power cables in a frequency range of 150 kHz–108 MHz. An equivalent circuit with high-frequency parasitic parameters for WCS for EV is built based on measurement results to obtain the characteristics of conducted emission from WCS. The transfer functions of differential mode (DM) interference and common mode (CM) interference were established. A judgment method of using transfer functions to determine the dominated interference mode responsible for EMI is proposed. From the comparison of simulation results between CM or DM and CM+DM interference, it can be seen that the CM interference is the dominated interference mode which causes the conducted EMI in WCS in EVs. A strategy of giving priority to the dominated interference mode is proposed for designing the CM interference filter. Finally, the conducted voltage experiment is performed to verify the mitigation conducted emission strategy. The conducted voltage of simulation and experiment is decreased respectively by 21.17 and 21.4 dBμV at resonance frequency 30 MHz. The conduced voltage at frequency range of 150 kHz–108 MHz can be mitigated to below the limit level-3 of CISPR25 standard (GB/T 18655-2010) by adding the CM interference filters. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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Review

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Open AccessReview An Overview of Regulation Topologies in Resonant Wireless Power Transfer Systems for Consumer Electronics or Bio-Implants
Energies 2018, 11(7), 1737; https://doi.org/10.3390/en11071737
Received: 31 May 2018 / Revised: 18 June 2018 / Accepted: 25 June 2018 / Published: 3 July 2018
Cited by 1 | PDF Full-text (7148 KB) | HTML Full-text | XML Full-text
Abstract
Owing to its relatively high efficiency, extended transmission range, and less exposure to radio frequency radiation, near-field resonant wireless power transfer (R-WPT) has been widely used in consumer electronics and bio-implants. For most applications, a well-regulated output voltage is required against the coupling
[...] Read more.
Owing to its relatively high efficiency, extended transmission range, and less exposure to radio frequency radiation, near-field resonant wireless power transfer (R-WPT) has been widely used in consumer electronics and bio-implants. For most applications, a well-regulated output voltage is required against the coupling and loading variations, and thus a regulation scheme should be employed in an R-WPT system. To achieve an optimal receiver (RX) or overall efficiency, together with a reduced cost overhead, several regulation schemes have been proposed in recent years, where the regulation can be implemented at either the RX or transmitter (TX) side, or both. These regulation schemes have been reviewed and comprehensively discussed in this paper. Hence, the main contribution of this paper is to provide a guideline for designing the regulation scheme in R-WPT systems. Moreover, potential new topologies of regulation are investigated here. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2018)
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