Resonant Coupling Wireless Power Transfer Research Articles

A MCR‐WPT system based on LCL‐S/P hybrid compensation network with CC/CV and maximum power optimization suiting for battery charging

AbstractA novel magnetic coupling resonance wireless power transfer (MCR‐WPT) system, which has constant‐current (CC) and constant‐voltage (CV) output characteristics suiting for batteries charging, is proposed in this paper. The hybrid compensation topology is adopted; in detail, the LCL‐P circuit topology is used in the CC mode, while the LCL‐S topology is used in the CV mode. Since the switchable components are only located at the receiving side of WPT, the switching can be controlled by the receiving side based on the batteries’ state without data communication between transmitting side and receiving side. Furthermore, an adjustable frequency tuning method which is based on proportion integration (PI) closed‐loop controlled by the transmitting side is applied to maximize the current of the transmitting coil. This method also can solve the frequency splitting problem, improving the stability and power of the system while the distance of the two sides changes. The performance of the proposed WPT system is verified by simulation and experiments. The experiment results show that the load current variation is less than 3% in the CC mode and the load voltage changes less than 5% in the CV mode, as the load resister changes from 5 to 20 Ω.

Multi-objective ant lion optimization for parameter optimization of wireless power transfer systems

The effective transmission distance of a magnetic coupling resonance (MCR) wireless power transfer (WPT) system is an essential index of wireless power transfer. Existing systems often suffer from short transmission distances, low power, and low efficiency. In this paper, a method is proposed for improving the parameters of wireless power transfer systems to enhance the performance of the systems. The main parameters affecting the output power and transmission efficiency are determined by analyzing the MCR WPT system with SS-type topology. In addition, the multi-objective ant lion optimizer is combined with tent chaotic mapping to generate the location information of the initial population by using the distribution and randomness of tent chaotic mapping, which increases the diversity of the people and improves the convergence speed and global search capability of the algorithm to achieve multi-objective parameter optimization, and the optimized model is also analyzed. Experiments show that the optimized MCR WPT system has improved output power and transmission efficiency at a longer distance. The optimal transmission distance of the system is about 0.2 m with a maximum output power of 129.3 W, and the axial offset stability of the system is enhanced. Finally, the effectiveness of the improved model is verified by building a prototype system. It provides a valuable reference for the research of improving wireless power transfer.

A Review of Metamaterials in Wireless Power Transfer.

Wireless power transfer (WPT) is a technology that enables energy transmission without physical contact, utilizing magnetic and electric fields as soft media. While WPT has numerous applications, the increasing power transfer distance often results in a decrease in transmission efficiency, as well as the urgent need for addressing safety concerns. Metamaterials offer a promising way for improving efficiency and reducing the flux density in WPT systems. This paper provides an overview of the current status and technical challenges of metamaterial-based WPT systems. The basic principles of magnetic coupling resonant wireless power transfer (MCR-WPT) are presented, followed by a detailed description of the metamaterial design theory and its application in WPT. The paper then reviews the metamaterial-based wireless energy transmission system from three perspectives: transmission efficiency, misalignment tolerance, and electromagnetic shielding. Finally, the paper summarizes the development trends and technical challenges of metamaterial-based WPT systems.

A Comparative Performance Analysis of Wireless Power Transfer with Parametric Simulation Approach

This paper presents a parametric optimization and normalization approach for coreless Resonant Inductive Coupling Wireless Power Transfer (RIC-WPT) systems. The used system is based on a series–series (SS) compensated circuit via flat spiral coils. Moreover, the recommended approach system finds optimum capacitor values for the best efficiency point where the RIC-WPT system operates. Flat spiral three-dimensional (3D) coils are modelled and parametric analysed with different air gaps in ANSYS-Electronics-Maxwell software which is based on the Finite Element Method (FEM). Then power electronics circuit with a full-bridge inverter is designed in Ansys/Simplorer software. The coils and the power electronics circuit are co-simulated with parametric values. Thus, as a result of parametric simulation studies, the most efficient version of a Wireless Power Transfer (WPT) system structure is proposed with the design and normalized power electronics elements that can be physically applied for the chosen operating frequency value. As a result of the simulation studies, power transmission is realized with an efficiency of approximately 74.31% while the distance between the coils was 200 mm. Furthermore, useful information for WPT designs is been obtained thanks to co-simulation studies by changing power electronics circuit parameters and electromagnetic modelling parameters.

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.

A secured wireless charging scheme with data transmission

This research task proposes a magnetic resonant coupling wireless power transfer(MRC-WPT) scheme for electric vehicles, which realizes secure data communication between the wireless charging station and the electric vehicle using binary phase shift-keying (BPSK) data transmission, thereby waving any radio frequency(RF) communication links. The secondary side is designed to accept power, while it transmits data back to the primary side simultaneously. The BPSK design ensures data transmission robustness to against disturbance interference. The data are encrypted by the user's biometric features for information security. The magnetic resonance performs better than that of the traditional magnetic induction in the power transmission efficiency against coil misalignments. With the Internet of Thing(IOT) architecture, the encrypted data can be stored and retrieved via the cloud server.

The development of wireless charging technology in the electric vehicle

Greenhouse gas emissions have caused the global climate to deteriorate, and the consumption of oil resources is becoming less cost-effective. Electric vehicles (EVs) are a good way to reduce this negative impact. However, the energy density of batteries is too low compared with oil, so electric cars need to be recharged repeatedly. This paper provides a comprehensive review of all the wireless charging technologies for EVs. The technology principle of Inductively Coupled Power Transfer (ICPT), Magnetically Coupled Resonant Wireless Power Transfer (MCR-WPT) and Microwave Power Transfer (MPT) are discussed by a comparative analysis between the three technologies. The analysis found that MCR-WPT is the best technology because it has high efficiency and very little radiation. After that, wireless charging is expounded from both static and dynamic perspectives. Next, different national requirements and standards for wireless charging are presented. According to the economic and safety analysis, it is found that wireless charging technology can avoid many security risks, reduce the occupied area and has a longer service life than wired charging.

Experimental Results of Ultrahigh-Efficiency Wireless Power Transfer Using Extremely High-Quality Factor Superconducting Coil With Double-Sided Coated Conductor Tape

Extremely high-quality factor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ) superconducting coils comprising two conventional high-temperature superconducting (HTS) coated conductor (CC) tapes, the use of which substantially improves the power transfer efficiency (PTE) of resonant coupling wireless power transfer (WPT), have been developed. In this article, a method for joining two HTS CC tapes by using dielectric film tape was developed. A styrene foam coil-support configuration that has lower effective dielectric loss was also developed. The skin effect of the Ag protection layer was suppressed by making it thinner than the conventional one. A coil using the proposed tape had a measured <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> (resonant frequency: 8.0 MHz) of around 20 000, which is about 20 times that of one using Cu tape. Measurement of the PTE of a WPT system using coils fabricated using the proposed tape for transmitting and receiving demonstrated that the use of coils with an extremely high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> enables a WPT system to achieve a transfer distance much greater than that of a comparable system with Cu coils. Measured PTE of the system using such coils and one using Cu coils were 90% and 28% at a transfer distance of 80 cm. This achievement opens the door to new high-frequency applications of HTS CC tape such as using if for WPT.

Optimization of Magnetically Coupled Resonant Wireless Power Transfer Based on Improved Whale Optimization Algorithm

This study aimed to address the optimization of magnetically coupled resonant wireless power transfer. An equivalent circuit for the wireless power transfer was established and the factors affecting the transmission efficiency were analyzed. To optimize the system, an improved whale optimization algorithm (WOA) was proposed and applied to optimize the optimal matching values of resonant frequency and load resistance. Performance of the improved WOA was tested using different test functions, and the optimized parameters were applied to the transmission efficiency test of the wireless power transfer system. Experiments demonstrated that the improved WOA effectively optimized the transmission efficiency and achieved good application results in the intelligent transfer system.

Gallium Nitride Power Devices in Magnetically Coupled Resonant Wireless Power Transfer Systems

The main function of power devices is to convert electrical energy through high-speed switching, such as AC/DC, high and low voltage conversion, etc. Therefore, the performance of the device directly affects the performance of the power electronic device, thereby further affecting the conversion efficiency of electrical energy. The arrival of the 5G era has greatly increased the demand for gallium nitride (GaN). The development of the wireless communication market has made GaN play a key role in many aspects of human activities. The main aim of this article is to research the application of GaN power devices in magnetically coupled resonant wireless power transfer (WPT) systems. This paper first introduces the related concepts of GaN power devices, magnetic coupling resonance and WPT, and analyzes the construction of magnetic coupling resonance WPT system in detail. Secondly, the energy transmission structure is analyzed, the system is designed and the system loss is calculated and analyzed. The system loss experiment shows that by using the output capacitor of the GaN device, the dead time is optimized, the conduction loss of the switch tube is reduced, the efficiency of the converter device is improved, and the practical application of the GaN device is provided.

Coupler Loss Analysis of Magnetically Coupled Resonant Wireless Power Transfer System

The demand for electric vehicles has increased over the past few years. Wireless power transfer for electric vehicles provides more flexibility than traditional plug-in charging technology. Charging couplers are critical components in wireless power transfer systems. The thermal effect produced by the magnetic coupler in work will cause the temperature of the device to rise rapidly, affecting the work efficiency, transfer power, operation reliability, and service life. This paper modeled and analyzed each component's temperature distribution characteristics and thermal behavior. Firstly, the magnetic coupler's mutual inductance and magnetic circuit model are established, and the thermal model of the magnetic coupler analyzes the heat generation process. The thermal models of the coupler under three different magnetic core distributions are established, and the temperature rise of each component is obtained. The temperature rise of different parts of the coupler is verified by the temperature rise test structure of the experiment.

Autonomous Resonant Frequency Tuner for a 6.78MHz Inductive Coupling Wireless Power Transfer System to Stably Maximize Repeater Current

Recently, the resonant inductive coupling wireless power transfer (RIC-WPT) technique is being widely used to charge small IoT devices dispersed in a wide area, e. g., an office desk and warehouse rack. In this application, the repeater is utilized to expand the chargeable area without an additional AC power source. The repeater comprises a LC resonator commonly with a high-quality factor to induce large current in the repeater coil. However, this causes the problem that the repeater performance is highly susceptible to the variation in its resonant frequency due to the manufacturing tolerance of coil inductance and resonant capacitance as well as the variation of the magnetic coupling between the transmitter and repeater coils. To solve this problem, a previous study has proposed a concept of the autonomous resonant frequency tuning circuit to stably maximize repeater coil current, although this study implemented a part of this control system as a practical circuit. This paper aims to develop a complete autonomous resonant frequency tuning circuit that implements the aforementioned concept. The proposed circuit adjusts the resonant frequencies of the transmitter and repeater by utilizing the Automatic Tuning Assist Circuits. These frequencies are optimized using the infrared wireless signal communication from the transmitter to the repeater. Along with the operating principle of the proposed circuit, this study presents detailed circuit design as well as the experimental results, which verified the stable autonomous maximization of the repeater coil current against the variation in the resonant frequency of the repeater resonator.

Analysis of four-coil magnetic resonance coupling wireless power transfer system based on LCC-SSS compensation network

The classical four-coil magnetic resonance coupling wireless power transfer (MRC-WPT) system usually uses a Series-Series-Series-Series (SSSS) compensation network, while its input series resistance and load resistance are designed approximately. I It is a remarkable fact that the power loss of the input series resistance adversely affects the overall efficiency of the WPT system, but the absence of the resistance will lead to the input current surge when the four-coil system is detuned, which is not conducive to the stability of the security of the circuit system. With this aim in mind, an Inductance-Capacitance-Capacitance-Series-Series-Series (LCC-SSS) compensation network is proposed in this paper, which removes the input series resistance to improve the total efficiency on the premise of ensuring the reliability of the system. Relation between transmission efficiency, transmission power and parameters of LCC-SSS compensation network, the parametric calculation method of LCC compensation network is presented. Finally, the experimental results compare the transmission power and efficiency of the two compensation networks and verify the correctness of the LCC-SSS compensation network.

Communication-Less Receiver-Side Resonant Frequency Tuning for Magnetically Coupled Wireless Power Transfer Systems

Compensating for deviations in the resonant frequency is crucial in magnetic resonance coupling wireless power transfer (WPT) systems. Thus, this study proposes a communication-less receiver-side resonant frequency-tuning scheme that compensates for the reactance in the receiver without communicating with the transmitter. The proposed scheme comprises an inductor-capacitor-capacitor compensation topology at the transmitter and a half-bridge circuit at the receiver, whose operating phase is set to be orthogonal to the receiver current. Resonant frequency tuning can be achieved by adjusting the DC voltage applied to the half-bridge circuit to maximize the power received at the load. The reactance compensation ability of the proposed scheme is analyzed through experiments on a 200 kHz WPT system. When the secondary capacitance deviated from –20% to +20%, the efficiency degradation was maintained within 6.7% with the proposed scheme, whereas the efficiency degraded by up to 33.3% without compensation.

Cylindrical Magnetically Coupled Resonant Wireless Power Transfer System Based on Flexible PCB Coils

In this letter, we design a magnetically coupled resonant wireless power transfer (MCR-WPT) system on the conformal cylindrical surface based on the flexible printed circuit (FPC) coils. The coil has the advantages of small size, lightweight, and high bendability. We combine mathematics and simulations to explore the relationship between the self-inductance/mutual inductance of the flexible coil and the bending radius of the conformal cylindrical surface. Both theoretical and simulation results show that as the bending radius decreases linearly, the self-inductance and mutual inductance of the coil also decrease nonlinearly. In addition, as the bending radius decreases, the transmission efficiency (TE) decreases, and the resonant frequency shifts to a higher range. Finally, measured and simulated results agree well, which further validates the conclusions.

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

A Linear-Power-Regulated Wireless Power Transfer Method for Decreasing the Heat Dissipation of Fully Implantable Microsystems.

Magnetic coupling resonance wireless power transfer can efficiently provide energy to intracranial implants under safety constraints, and is the main way to power fully implantable brain-computer interface systems. However, the existing maximum efficiency tracking wireless power transfer system is aimed at optimizing the overall system efficiency, but the efficiency of the secondary side is not optimized. Moreover, the parameters of the transmitter and the receiver change nonlinearly in the power control process, and the efficiency tracking mainly depends on wireless communication. The heat dissipation caused by the unoptimized receiver efficiency and the wireless communication delay in power control will inevitably affect neural activity and even cause damage, thus affecting the results of neuroscience research. Here, a linear-power-regulated wireless power transfer method is proposed to realize the linear change of the received power regulation and optimize the receiver efficiency, and a miniaturized linear-power-regulated wireless power transfer system is developed. With the received power control, the efficiency of the receiver is increased to more than 80%, which can significantly reduce the heating of fully implantable microsystems. The linear change of the received power regulation makes the reflected impedance in the transmitter change linearly, which will help to reduce the dependence on wireless communication and improve biological safety in received power control applications.

Extensible Low-Profile Coplanar Wireless Power Transfer System for Multiload Applications With Load-Independence Constant Current Output

This article proposes a low-profile coplanar magnetic coupling resonance wireless power transfer system, which can be expanded segment by segment to power more receivers over a long distance with load-independent constant current output. Due to the low structural profile, it can easily conform to the environment such as desktops, floors, and walls, occupying a small space. By placing low-profile ferrite plates on or under the junctions of adjacent coplanar coils, the main coupling coefficients of the adjacent coils are significantly enhanced, and therefore, the power transmission efficiency (PTE) of the system is greatly improved. With the fixed operating frequency, load-independent current characteristics, simple structure, coplanarity with the environment, good scalability, and high PTE, the system can be easily utilized in various medium and long-range multiload WPT applications. The article describes its principle in detail and clarifies the influence of losses on system performance such as output current characteristics, PTE, and the maximum number of the charging segments. The experimental platform with two and three receivers was established to verify the theory, and the measurement results are in good agreement with the theoretical analysis. The maximum measured PTE reached 93.8% and 93.6% for two and three receivers, respectively.

Modern Advances in Magnetic Materials of Wireless Power Transfer Systems: A Review and New Perspectives.

The magnetic coupling resonant wireless power transfer (MCR-WPT) system is considered to be the most promising wireless power transfer (WPT) method because of its considerable transmission power, high transmission efficiency, and acceptable transmission distance. For achieving magnetic concentration, magnetic cores made of magnetic materials are usually added to MCR-WPT systems to enhance the coupling performance. However, with the rapid progress of WPT technology, the traditional magnetic materials gradually become the bottleneck that restricts the system power density enhancement. In order to meet the electromagnetic characteristics requirements of WPT systems, high-performance Mn-Zn and Ni-Zn ferrites, amorphous, nanocrystalline, and metamaterials have been developed rapidly in recent years. This paper introduces an extensive review of the magnetic materials of WPT systems, concluding with the state-of-the-art WPT technology and the development and application of high-performance magnetic materials. In addition, this study offers an exclusive reference to researchers and engineers who are interested in learning about the technology and highlights critical issues to be addressed. Finally, the potential challenges and opportunities of WPT magnetic materials are presented, and the future development directions of the technology are foreseen and discussed.

Enhancement of robustness to frequency detuning with wireless power transfer based on Van der Pol resonance

AbstractIn near‐field energy transmission, wireless power transfer based on magnetic coupling resonance is preferred. For efficient power transfer, the quality factor of magnetic coupling resonance wireless power transfer (MCR‐WPT) system should be kept at a high value, which makes the system sensitive to frequency detuning. Different from conventional approaches dealing with the problem in linear MCR‐WPT system, this paper proposes a novel MCR‐WPT system, which is based on Van der Pol nonlinear resonant circuit to address the problem of frequency detuning. A nonlinear resistor is introduced, and the nonlinear Van der Pol MCR‐WPT system is established. Based on the mathematical model and the theoretical analysis, it is found that the frequency band is broadened. To validate the performance of the proposed system, extensive simulation and experimental work are conducted. Unlike the traditional linear system, which only peaks at the resonant frequency, the results show that the output of the proposed system is still high within a certain frequency band when the operating frequency deviates from the original resonant frequency. The impact of frequency detuning caused by variation of capacitance is also studied. It can be concluded that the proposed MCR‐WPT system is effective in coping with the frequency detuning.