Wireless Power Transfer Coils Research Articles

Design and Optimization of Planar Spiral Coils for Powering Implantable Neural Recording Microsystem.

This paper presents a design and optimization method utilizing inductive coupling coils for wireless power transfer in implantable neural recording microsystems, aiming at maximizing power transfer efficiency, which is essential for reducing externally transmitted power and ensuring biological tissue safety. The modeling of inductive coupling is simplified by combining semi-empirical formulations with theoretical models. By introducing the optimal resonant load transformation, the coil optimization is decoupled from an actual load impedance. The complete design optimization process of the coil parameters is given, which takes the maximum theoretical power transfer efficiency as the objective function. When the actual load changes, only the load transformation network needs to be updated instead of rerunning the entire optimization process. Planar spiral coils are designed to power neural recording implants given the challenges of limited implantable space, stringent low-profile restrictions, high-power transmission requirements and biocompatibility. The modeling calculation, electromagnetic simulation and measurement results are compared. The operating frequency of the designed inductive coupling is 13.56 MHz, the outer diameter of the implanted coil is 10 mm and the working distance between the external coil and the implanted coil is 10 mm. The measured power transfer efficiency is 70%, which is close to the maximum theoretical transfer efficiency of 71.9%, confirming the effectiveness of this method.

AC loss mitigation for high temperature superconducting coils in wireless power transfer

AC loss mitigation for high temperature superconducting coils in wireless power transfer

Reducing unwanted emissions of a wireless power transfer coil by using a parasitic loop element

Reducing unwanted emissions of a wireless power transfer coil by using a parasitic loop element

Optimal Design of Transmission Characteristics for Hexagonal Coil Wireless Power Transfer System Based on Genetic Algorithm

Effective optimization methods are used to guide the optimal design of coil parameters, which is significant for improving the transmission performance of the wireless power transfer (WPT) system. Traditional methods mostly rely on the exhaustive attack method and finite element analysis (FEA) to achieve the coil parameter design, which have the disadvantages of complex modeling and time-consumption. To overcome these limitations, this study proposes an optimization strategy based on the genetic algorithm (GA), which considers the actual requirements of the efficiency and power of the WPT system. First, a direct integration method is proposed to simplify the analytical solution process of the mutual inductance between the hexagonal coils. Based on the mutual inductance model, the transmission characteristics of the hexagonal coil WPT system are deeply analyzed by the control variable method. Most importantly, with the proposed optimization objective function and its constraints, the GA is used to automatically achieve multi-parameter optimization of the hexagonal coil. Finally, a 500 W WPT system experimental platform is established, and the experimental results verify the feasibility of the proposed optimization method.

A novel method for calculating the mutual inductance between two perpendicular coils in wireless power transfer

SummaryThe perpendicular coil is increasingly applied in some wireless power transfer (WPT) systems where space position is limited. The existing method of calculating the mutual inductance between perpendicular coils is mainly applied to rectangular and circular coils. However, the practical rectangular coil often has rounded corners, so it unavoidably introduces systematic errors. Concerning this issue, this paper proposed an analytical method to calculate the mutual inductance between mutually perpendicular round‐corner rectangular (RCR) coils. The proposed method is based on a second‐order vector potential (SOVP) model where the mutual inductance between the coils is described as a double integral formula. In this formula, a novel shape and position function is introduced. This shape and position function describes not only RCR coils but also rectangular (including square), circular, and runway ones. A series of experiments were used to validate the proposed method. According to the consistency validation, the proposed method can be more generalized for calculating the mutual inductance of rectangular and circular coils. Through experimental comparison, the proposed method computes the mutual inductance between the perpendicular coil in excellent agreement with the measured ones. Therefore, the proposed method unifies the mutual inductance calculation of mutually perpendicular circular, rectangular (square), runway, and RCR coils and can provide an important basis for designing WPT systems using the above coils.

Solar Wireless Charging For Electric Vehicle While Driving

This paper presents a novel concept of solar wireless charging for electric vehicles (EVs) while driving. The idea is to integrate solar panels into the roads and use wireless charging technology to transfer energy from the solar panels to the EVs. . To overcome these challenges, several approaches have been proposed, including increasing battery capacity, improving charging infrastructure, and using alternative energy sources. One promising approach is to use solar energy to charge EVs while driving. Solar energy is abundant and renewable, and it can be harnessed using solar panels installed on the roads. However, traditional charging methods, such as plug-in charging, have limitations in terms of convenience and efficiency. Wireless charging technology, on the other hand, has the potential to overcome these limitations by enabling charging while driving without the need for physical connections. we propose a novel concept of solar wireless charging for EVs while driving. The proposed system integrates solar panels into the roads and uses wireless charging technology to transfer energy from the solar panels to the Evs. Key words: Electric road system, wireless power transfer, transmitter and receiver coils, power lanes, e-vechile ,charging while driving, no battery drain, easy to use, get charge while running , future oriented.

Local Heat Generation Analysis Method of Ferrite Cores for Wireless Power Transfer Coil Considering Compressive Stress

This paper presents a method for measuring the iron loss of ferrite cores under compressive stress. Moreover, a novel methodology is proposed for analyzing the local heat generation of ferrite cores for wireless power transfer by considering an increase in the iron loss because of compressive stress. The effectiveness of the proposed analysis method is experimentally verified.

Design of anti-misalignment PCB coil for wireless power transfer

This paper focuses on the problem of the non-uniform magnetic field distribution in short-distance magnetic coupled wireless power transfer (MC-WPT) systems, which causes the transfer power and power transfer efficiency to decrease when the transmitter and receiver coils are offset. At first, the distribution law of the magnetic field generated by the printed circuit board (PCB) coil is studied. A new method is proposed to design the transmitter coil, which combines a genetic algorithm (GA) with a partial element equivalent circuit (PEEC). The appropriate turn radii are first obtained by the GA, and the quality factor is further evaluated by the PEEC to select the optimal coil turns. Finally, the PCB coils with uneven pitches are fabricated, and experiments are carried out on an MC-WPT system. The effective power transfer area is expanded noticeably and the high efficiency of the system remains stable, which is very useful to provide a wider working space and steady wireless energy supply for mobile objects.

Receiver-Position-Based Unbalanced-Current Control for a Three- to Single-Phase Wireless Power Transfer System for AGVs

Conventionally, three-phase wireless power transfer systems apply balanced currents with open loop control. The balanced current enables the receiver coil to receive uniform power regardless of its position. The phase-coil away from the receiver coil, however, dissipates the same power as that close to the receiver coil while the far phase-coil contributes to little power transfer. This paper presents a receiver-position-based unbalanced-current control. In the unbalanced-current control, a close phase-coil has higher current amplitude than far phase-coils. Therefore, the proposed control can improve the transfer efficiency in comparison with the system with the balanced-current control. The proposed control can dynamically estimate a moving receiver position with the voltage and current in the three-phase inverter and can generate required currents owing to its feedback control. The experiments using the system with a prototype of three- to single-phase wireless power transfer coil and a fabricated inverter implementing the proposed control prove that the system can dynamically transfer uniform power to a moving automatic guided vehicle (AGV) and can perform with 5% improvement in transfer efficiency in comparison with a system implementing the balanced-current control.

Cage-Embedded Crown-Type Dual Coil Wireless Power Transfer Based Microwave Brain Stimulation System for Untethered and Moving Mice.

This study proposes a novel brain-stimulated mouse experiment system which is insensitive to the variations in the position and orientation of a mouse. This is achieved by the proposed novel crown-type dual coil system for magnetically coupled resonant wireless power transfer (MCR-WPT). In the detailed system architecture, the transmitter coil consists of a crown-type outer coil and a solenoid-type inner coil. The crown-type coil was constructed by repeating the rising and falling at an angle of 15 ° for each side which creates the H-field diverse direction. The solenoid-type inner coil creates a magnetic field distributed uniformly along the location. Therefore, despite using two coils for the Tx system, the system generates the H-field insensitive to the variations in the position and angle of the receiver system. The receiver is comprised of the receiving coil, rectifier, divider, LED indicator, and the MMIC that generates the microwave signal for stimulating the brain of the mouse. The system resonating at 2.84 MHz was simplified to easy fabrication by constructing 2 transmitter coils and 1 receiver coil. A peak PTE of 19.6% and a PDL of 1.93 W were achieved, and the system also achieved an operation time ratio of 89.55% in vivo experiments. As a result, it is confirmed that experiments could proceed for approximately 7 times longer through the proposed system compared to the conventional dual coil system.

Novel coil design and analysis for high-power wireless power transfer with enhanced Q-factor

The power transfer efficiency (PTE) is a crucial aspect for effective wireless power transfer (WPT) applications. The quality factor (Q) of the WPT coil plays a critical role in ensuring higher PTE. In this paper, a novel method of improving the Q of a WPT coil is proposed. Resistance reduction techniques are presented which involves variation of the trace pitch, width, and thickness. This approach targets the high AC losses centered in the inner turns, which subsequently results in an increased Q. Numerical analysis with respect to the inductance and resistance models are presented, analyzed, and compared to that of the EM simulation results. To verify the efficacy of the proposed coil structure, a prototype is fabricated where good agreement is achieved between the measured and simulated results. The proposed coil attained a quality factor increment of about 19.24% at 85 kHz in comparison to the conventional one. The proposed technique can be used to optimize planar spiral coils to attain higher Q.

Powering implanted sensors that monitor human activity using spider‐web coil wireless power transfer

AbstractImplantable biomedical devices (IBMD) and biomedical sensors (BMS) enhance patients’ quality of life by monitoring vital signs, detecting diseases, and replacing malfunctioning organs. However, IBMDs and BMSs require battery power to operate, and they have limited battery life. Wireless power transfer (WPT) is one practical way to address this limitation. In this paper, the authors designed and implemented WPT‐based magnetic resonant coupling (MRC) using a spider‐web coil (SWC) (WPT–MRC–SWC) that supplies the proposed IBMD, including accelerometer sensors, the single‐chip microcontroller ATmega 328, and the nRF24L01 wireless protocol, with power. The WPT–MRC–SWC examines acceleration measurements on three knee‐joint axes (X, Y, and Z) in five different positions: sitting, standing, walking, lying down, and jogging. The SWC of transmitters and receivers (implanted) exhibits an operating frequency of 1.78 MHz with a series/parallel (S/P) configuration. The implanted system's data, transmitted outside the human body using nRF24L01, operates at 2.4 GHz. The results reveal that WPT provides 5 V at an air gap of 60 mm between the receiver and transmitter coils, indicating that it can run or charge IBMD batteries without failure. This study validates the effectiveness of the WPT–MRC–SWC by applying it to an actual application.

Analysis of Losses in Two Different Control Approaches for S-S Wireless Power Transfer Systems for Electric Vehicle

This paper presents the study and detailed analysis of converter losses at different stages together with the series-series (S-S) compensating coils in wireless power transfer (WPT) systems, via two distinct approaches to control the power converters. The two approaches towards wireless DC–DC power flow control are termed as the Single Active High-Frequency Wireless Power Transfer (SAHFWPT) system and the Dual Active High-Frequency Wireless Power Transfer (DAHFWPT) system. The operation of converters in SAHFWPT and DAHFWPT are controlled by the extended phase shift (EPS) and dual phase shift method respectively. The general schematic of the SAHFWPT system consists of an active bridge and a passive bridge, while the schematic of the DAHFWPT system consists of both active bridges. The efficiency evolutions of ideal SAHFWPT and DAHFWPT are far away from the real ones. Moreover, this article analyzes the operation and losses of the uni-directional power flow of the WPT system, i.e., from the DC bus in the primary side to the battery load in the secondary side. The loss estimation includes high-frequency switching losses, conduction losses, hard turn on and turn off coil losses, etc. Moreover, the efficiency of the WPT system depends on operation of the converter. A 50 W–3600 W Power range system at a resonant frequency of 85 kHz is implemented in MATLAB/SIMULATION to demonstrate the validity of the proposed method.

PT Symmetry-Based AUV Dual Transmission Coil Wireless Power Transfer System Design

Autonomous underwater vehicles (AUVs) are widely used for ocean exploration; however, the way they are replenished becomes the biggest issue limiting their range and efficiency. A dual transmission coil wireless power transfer (DTCWPT) system based on parity–time (PT) symmetry is proposed in this paper to realize an autoadaptive constant power transmission. A shielded housing structure for coils is equipped to realize WPT in the ocean. In the offset experiments, the proposed dual transmitting coil structure was able to achieve a stable power transmission of 39 W within an offset range of 8.1 cm. It is obvious that the DTCWPT system based on PT symmetry could charge an AUV in the ocean with high robustness. This paper provides a novel solution based on DTCWPT for AUV energy supply. The proposed DTCWPT system could offer remarkable improvements in the navigation performance of AUVs.

Theorizing a Simple Ferrite Cored Coil Using Image Coils in Wireless Power Transfer

The technology of wireless power transfer, which wirelessly transmits power to any device, has been widely studied. Wireless power transfer using magnetic field resonance involves the use of coils and a material called ferrite, which improves the transmission characteristics. Until now, electromagnetic field analysis has been used to design ferrite cored coils, but electromagnetic field analysis requires a long analysis time and a computer with a large amount of memory. In this study, the ferrite shield and coil are represented as a image coil under the condition that the positional relationship between the ferrite shield and the coil does not change. This enabled the derivation of mutual inductance only by numerical analysis, which had been difficult up to now. In addition, experiments have shown that when the coil size does not change, mutual inductance can be derived only by numerical analysis using arbitrary coil parameters, regardless of the number of turns and pitch. The average error in deriving the design value was 5.2%. This facilitated the design of ferrite cored coils at 85 kHz and contributed greatly to the design of the system.

Field Cancellation for Circuits Encircled by VHF Wireless Power Transfer Coils

Components and circuits encircled by wireless power transfer coils allow miniaturization but require field cancellation for components and circuits that are sensitive to the magnetic field. Very high frequency operation reduces the volume and number of components, which makes encirclement within WPT coils easier. A field cancellation method is investigated to minimize the magnetic field for the encircled circuits in WPT coils using a two-coil structure toward the best cancellation performance, practical construction, and minimum cost. The WPT and canceling coils are driven together by a single current-mode class D power converter with opposite-phase currents to optimize the field cancellation within the coils. Using this cancellation method, the magnetic field for the encircled circuits was reduced by 99% in hardware compared to that without cancellation.

5G Magnetic Resonance Coupling Planar Spiral Coil Wireless Power Transfer

Wireless Power Transfer in the 5G frequency band is the most promising technology to power up ubiquitous small electronic devices as well as IoT devices. A strongly coupled magnetic resonance WPT technique that focuses on near-field electromagnetic energy has been proposed in this paper. However, most Magnetic Resonance Coupling Wireless Power Transfer (MRC WPT) applications have been designed in kHz and MHz frequency spectrum. This paper demonstrates Planar Spiral Coil Magnetic Resonance Coupling (PSC MRC) WPT designs at 5G (GHz) frequencies. Also, the transformation technique of the low frequency (kHz and MHz) magnetic resonance circuit model equations to high frequency (GHz) circuit model equations to achieve a high-efficiency power transfer. PSC MRC WPT designs structure antennas are designed at 3.4 - 3.5 GHz in the form of circular and square shapes with 1 turn coil. The proposed antenna structures are firstly being optimized in a full-wave electromagnetic simulator, CST Microwave Studio to resonate at the 3.4 - 3.5 GHz band. Then, the close-loop equations to determine the efficiency of 5G Magnetic Resonance Coupling Planar Spiral Coil Wireless Power Transfer is designed. Lastly, the results are compared with the simulation and calculated parts. The highest efficiency of the PSC MRC circular antenna is 31.58 % when the distance is at 2 mm, and 31.26 and 31.02 % when the distance is at 3 and 4 mm, respectively. The efficiency of circular PSC MRC is found to be 25 % better than the efficiency of square shape design. HIGHLIGHTS IoT devices need to be charged and maintained as the network system has massive numbers of sensors. Wireless power transfer is a promising technology to power up IoT devices This paper proposed, a WPT technique based on strongly coupled magnetic resonance which focuses on the near-field electromagnetic energy. This technique can extend the distance of the power transfer between the transmitter and the receiver The transformation technique of the low frequency (kHz and MHz) magnetic resonance circuit model equations to high frequency (GHz) circuit model equations to achieve a high-efficiency PSC MRC WPT design structure is introduced in this paper This novel technique can be applied to effectively design PSC MRC Antenna WPT for 5G applications. Most reported Magnetic Resonance Coupling Wireless Power Transfer (MRC WPT) applications have been designed in kHz and MHz frequency spectrum GRAPHICAL ABSTRACT

Position Estimation of Multiple Receiving Coils and Power Transmission Control for WPT without Feedback

It is important to determine the position of the receiver (Rx) coils in wireless power transfer (WPT) system, and to control the power transmitted to the Rx coil based on this result. In particular, in a situation where there is no feedback between the primary side and the secondary side, it is difficult to control the received power because the information is limited. In this paper, a method for determining the position of the Rx coils and controlling the received power using limited parameters in a feedback-free WPT system is proposed. The proposed method is verified by constructing a 4×2 WPT system, and it is validated that the simulation result and the experimental result are consistent well. Furthermore, arbitrary power can be transmitted to the Rx coil based on the result of the position of the Rx coil. The experiment is conducted by transmitting about 1W to Rx 1 and Rx 2, and the efficiency for Rx 1 is about 32.93%, Rx 2 is 25.03%, and the overall efficiency is confirmed to be 57.96%.

Analysis of Repetitive Bending on Flexible Wireless Power Transfer (WPT) PCB Coils for Flexible Wearable Devices

In this article, we first designed, measured, and analyzed flexible wireless power transfer (WPT) coils with repetitive bending cycles. To analyze any changes in electrical characteristics through repetitive bending cycles, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times3$ </tex-math></inline-formula> cm flexible printed circuit board (PCB) coils were fabricated using polyimide substrates. Different coil configurations are designed to find a mechanically robust, flexible PCB coil design. First, we analyzed single-layer and double-layer coils. Generally, via is the mechanically weakest part of the PCB, hence the diameter of the via varies to observe the effect of repetitive bending cycle. Ten thousand bending cycles with a bending radius of 3 mm and a bending cycle frequency of 1 Hz were used to analyze the electrical changes. Moreover, the bending position of the coil is varied to observe the bending effect. The flexible coil’s direct current (dc) resistance is measured during the bending cycle. After the repetitive bending test is completed, the coil impedance is analyzed in a frequency domain. As a result, we conclude that the flexible WPT coil is robust from mechanical stress when the layer of the coil is single a layer, the bending line is applied vertically, and the diameter of the via is small.

Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer

Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This article proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured dc-to-dc efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78-MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.