Magnetically Coupled Resonant Wireless Power Transfer Research Articles

A novel LCC‐C(CL)2 compensation network for efficient magnetically coupled resonant wireless power transfer for EV charging

AbstractDue to the intrinsic limitations, for example, limited adjustment freedom, the traditional wireless power transfer (WPT) systems cannot maintain high efficiency under variable loading conditions. To well solve this problem, a family of general magnetically coupled resonant WPT (MCR‐WPT) compensation topologies composed of LCC‐C with an ‐stage LC structure, or LCC‐C(CL) , is proposed in this paper. Under the guideline of the generalized structure, some existing topologies are derived for verification, with new topologies established with unique advantages. From the LCC‐C(CL) structures, a suitable topology can be selected to achieve a desired design purpose, such as constant voltage transmission, constant current transmission, or high‐efficiency transmission. Prototype experiments and comparisons are conducted in this work, which demonstrate the effectiveness and applicability of the proposed LCC‐C(CL) MCR‐WPT converter family and the parameter design method. Experimental results also show that the new topology can maintain high‐efficiency power transfer for a wide range of loads. Even under light loading conditions, the power transfer efficiency is 30% higher than the traditional benchmark topology. The proposed WPT approach will have wide applications for on‐road wireless electric vehicle charging.

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.

Reconfigurable PCB Coil Array Loaded With PIN Diodes for Improving Transmission Efficiency in MCR-WPT Systems

In this letter, we propose a reconfigurable coil array by loading PIN diodes to solve the problem of transmission efficiency degradation due to lateral misalignment in magnetically coupled resonant wireless power transfer (MCR-WPT) systems. The reconfiguration of the coil array is achieved by changing the capacitance of the coil array through the ON/OFF of the PIN diodes, thus adjusting the magnitude of the induced current and achieving higher transmission efficiency. By specifying one of the four loaded PIN diodes in the transmitting (Tx) coil array as ON state by the relative position of the receiving (Rx) coil to the Tx coil array, a significant improvement in transmission efficiency with a wider area of strong coupling can be obtained compared to a conventional Tx coil array without loading PIN diodes. This can be used in high efficient multi-coil versus single-coil WPT systems to provide more positioning freedom for Rx coil.

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.

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.

An Adaptive Control Strategy for Underwater Wireless Charging System Output Power with an Arc-Shaped Magnetic Core Structure

Aiming at the problem of unstable output power of wireless charging systems for autonomous underwater vehicles (AUVs), a magnetic coupler (MC) with an arc-shaped core structure is introduced and an output power stabilization control strategy based on mutual inductance identification algorithm is proposed. Firstly, an arc-shaped MC with high tolerances, excellent magnetic coupling and weak electromagnetic interference (EMI) is designed for the cylinder-shaped AUV. Based on ANSYS Maxwell simulation, an analysis of the magnetic field and comparative misalignment tests are carried out for the arc-shaped and the double dipole core structures. Secondly, a mathematical model of the LCC-S type magnetically coupled resonant wireless power transfer (MCR-WPT) system is developed, and a particle swarm parameter identification algorithm with adaptive inertia weights is proposed. Finally, the output power is steadily controlled by real-time adaptation of the duty cycle for the Buck-Boost circuit. The results show there is a maximum error within 2.5% in mutual inductance identification when the load is changed from 0 Ω to 12 Ω and the mutual inductance is changed from 25 μH to 50 μH. The system output power is steady at around 680 W with a maximum fluctuation rate of 4.90%, which verifies the efficiency of the power stabilization control strategy.

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.

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.

Analysis and Design of Wireless Power Transfer System for Rotational Inertial Navigation Application

Cables or slip-rings are often used to power loads on a rotating unit in the rotation modulated inertial navigation system (RMINS). However, these power supply methods have the disadvantages of cable winding and slip ring friction and wear, which reduces the reliability and life of the RMINS. Therefore, this paper applies magnetic coupling resonant wireless power transfer (MCRWPT) technology to the RMINS to avoid the shortcomings of the above power supply methods. Furthermore, according to the structure and working characteristics of the RMINS, a simple design method of the MCRWPT system without any feedback control is proposed. Based on the ANSYS simulation, the magnetic shielding structure is designed to reduce magnetic leakage, and the efficiency of the MCRWPT system is optimized by designing the excitation frequency. Experiments verify the effectiveness of the proposed method. The experimental results show that the designed MCRWPT system can achieve an efficiency of 74.6% with an output power of 10 W and has been successfully applied to the uniaxial rotation module inertial navigation system. Finally, the design method of the MCRWPT system is simple, and it has guiding significance for the design of the wireless power transfer system in the RMINS.

Fully Implantable Neural Stimulator with Variable Parameters

Neural implantable systems have promoted the development of neurosurgery research and clinical practice. However, traditional tethered neural implants use physical wires for power supply and signal transmission, which have many restrictions on implant targets. Therefore, untethered, wireless, and controllable neural stimulation has always been widely recognized as the engineering goal of neural implants. In this paper, magnetically coupled resonant wireless power transfer (MCR-WPT) technology is adopted to design and manufacture a wireless stimulator for the electrical stimulation experiment of nerve repair. In the process of device development, SCM technology, signal modulation, demodulation, wireless power supply, and integration/packaging are used. Through experimental tests, the stimulator can output single-phase pulse signals with a variable frequency of (1–20 Hz), a duty cycle of (1–50%), and voltage. The average power is approximately 25 mW. The minimum pulse width of the signal is 200 μs and the effective distance of transmission is 1–4 cm. The stimulator can perform low-frequency, safe and controllable wireless stimulation.

Research on Dual-LCC MCRWPT system based on controlled rectifier

Among many types of Wireless Power Transfer (WPT) technology, Magnetically Coupled Resonance Wireless Power Transfer (MCRWPT) technology has been studied more and more due to its stable transmission Power and strong anti-interference ability. In this paper, the operating characteristics of the Dual-LCC MCRWPT system based on the secondary side controlled rectifier are analyzed, and the variation of the system current with D, the phase relationship between the input voltage and current of the resonant network, the phase relationship between the output voltage and current of the resonant network, and the variation of the input and output load of the system are studied in depth. Through the simulation analysis of inverter MOSFET switching state, verify the effectiveness of the controlled rectifier control mode and the rationality of theoretical analysis, provide a solid theoretical basis for the optimization of the controlled rectifier control mode.

Genetic-Algorithm-Based Optimization of a 3D Transmitting Coil Design with a Homogeneous Magnetic Field Distribution in a WPT System

In magnetically coupled resonant wireless power transfer (MCR-WPT) systems, the nonhomogeneous magnetic field of the transmitting coil can lead to frequency splitting phenomena and lower efficiency. In this paper, a 3D transmitting coil (TX) with a homogeneous magnetic field distribution is proposed. The proposed coil structure consists of two layers with different numbers of turns per layer, i.e., with different current distributions. To achieve a homogeneous magnetic field distribution with a high magnetic field value and a low profile of the 3D coil structure, the optimal layer placement and current distribution were optimized using a genetic algorithm (GA). The prototype of the optimized coil was fabricated, and its magnetic field distribution was measured. The measurement results agreed more than 95% with the simulation results. The measured homogeneous area was at least 12.5% larger than reported in the literature. By using a different current distribution, the profile of the 3D coil structure was successfully reduced by 29% and the average magnetic field value was increased by 25% compared to our previous work.

Wireless power transfer system with enhanced efficiency by using frequency reconfigurable metamaterial

The wireless power transfer (WPT) system has been widely used in various fields such as household appliances, electric vehicle charging and sensor applications. A frequency reconfigurable magnetic resonant coupling wireless power transfer (MRCWPT) system with dynamically enhanced efficiency by using the frequency reconfigurable metamaterial is proposed in this paper. The reconfigurability is achieved by adjusting the capacitance value of the adjustable capacitor connected in the coil of the system. Finite element simulation results have shown that the frequency reconfigurable electromagnetic metamaterial can manipulate the direction of the electromagnetic field of the system due to its abnormal effective permeability. The ultra-thin frequency reconfigurable metamaterial is designed at different working frequencies of 14.1 MHz, 15 MHz, 16.2 MHz, 17.5 MHz, 19.3 MHz, 21.7 MHz and 25 MHz to enhance the magnetic field and power transfer efficiency (PTE) of the system. Frequency reconfigurable mechanism of the system with the frequency reconfigurable metamaterial is derived by the equivalent circuit theory. Finally, further measurement which verifies the simulation by reasonable agreement is carried out. PTE of the system by adding the metamaterial are 59%, 73%, 67%, 66%, 65%, 60% and 58% at different working frequencies. PTE of the system with and without the metamaterial is 72% and 49% at the distance of 120 mm and the frequency of 15 MHz, respectively.

Reduction in Human Interaction with Magnetic Resonant Coupling WPT Systems with Grounded Loop

Wireless power transfer (WPT) systems have attracted considerable attention in relation to providing a reliable and convenient power supply. Among the challenges in this area are maintaining the performance of the WPT system with the presence of a human body and minimizing the induced physical quantities in the human body. This study proposes a magnetic resonant coupling WPT (MRC-WPT) system that utilizes a resonator with a grounded loop to mitigate its interaction with a human body and achieve a high-efficiency power transfer at a short range. Our proposed system is based on a grounded loop to reduce the leakage of the electric field, resulting in less interaction with the human body. As a result, a transmission efficiency higher than 70% is achieved at a transmission distance of approximately 25 cm. Under the maximum-efficiency conditions of the WPT system, the use of a resonator with a grounded loop reduces the induced electric field, the peak spatial-average specific absorption rate (psSAR), and the whole-body averaged SAR by 43.6%, 69.7%, and 65.6%, respectively. The maximum permissible input power values for the proposed WPT systems are 40 and 33.5 kW, as prescribed in the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines to comply with the limits for local and whole-body average SAR.

Frequency tracking and tuning control of wireless power transfer system

A tuning control method with frequency tracking function is proposed to improve the degradation of efficiency caused by coil detuning in magnetically-coupled resonant wireless power transfer. Firstly, the detuning mechanism is studied by combining the AC impedance characteristics of the series resonant circuit, and the feedback control circuit is constructed by using a modified phase-locked loop, which outputs a variable frequency PWM wave to regulate the operating frequency of the high frequency inverter and maintains the phase difference between the inverter output voltage and the original side current within the error range. The Matlab/Simulink simulation results show that the design can successfully transfer the system to a new resonant state with short regulation period and high control accuracy, which can effectively improve the transmission efficiency and load power of the system.

Multifrequency and Multiload MCR-WPT System Using Hybrid Modulation Waves SPWM Control Method

To satisfy independent and controllable power supply requirements for loads with different frequencies and power levels, a multifrequency and multiload (MFML) magnetic coupling resonant wireless power transfer (MCR-WPT) system using hybrid modulation waves sinusoidal pulsewidth modulation (HMW-SPWM) control method is proposed in this article. Based on SPWM, loading a hybrid modulation wave formed by superimposing multifrequency modulation waves to drive the inverter, so the multifrequency hybrid current on the primary side can be obtained. According to the principle of mutual inductance coupling, inductive power with different frequencies is obtained and then separated by multiresonant networks on the secondary side for loads with different frequencies. First, the structure and working principle of a MFML MCR-WPT system controlled by HMW-SPWM are introduced. Then, taking a dual-frequency and dual-load MCR-WPT system as an example, the system is mathematically modeled. Besides, parameters design criteria for reducing interfrequency interference is studied. After that, load characteristics and power factor are analyzed to select appropriate parameters. Furthermore, dynamic characteristics are analyzed. Finally, theoretical results are validated by experiments. The experimental results show that the MFML MCR-WPT system controlled by HMW-SPWM realizes independent and controllable wireless power supply for loads with different frequencies and power levels.

Parameter Optimization of Double LCC MCRWPT System Based on ZVS

At present, magnetically coupled resonance wireless power transfer (MCRWPT) is the main technology used in electric vehicle wireless power transfer (WPT) due to its advantages of high transmission power and high efficiency. The resonant compensation circuit of the system generally adopts the double LCC (DLCC) structure, which has many capacitor and inductor components. Therefore, it is necessary to optimize the circuit parameters to improve the transmission performance of the system. In this study, the DLCC compensation circuit was modeled and analyzed to lay the foundation for parameter optimization. Secondly, the size parameters of the energy transmitting and receiving coil were determined, and the influence of the change of the primary and secondary compensation inductance on the circuit element stress and output performance was analyzed to determine the optimal compensation inductance value. Thirdly, the realization condition of zero voltage switching (ZVS) was analyzed, the relationship between the input impedance angle of the compensation circuit and the component parameter value was obtained, and a parameter optimization control strategy for realizing ZVS was proposed. Finally, through simulation and experiment, it was concluded that under different power levels, the efficiency of the parameter optimization strategy proposed in this study is as high as 91.86%, increasing by about 1%. Therefore, the research undertaken in this study can promote the development of WPT technology and has certain practical significance.

A Comprehensive Review of Midrange Wireless Power Transfer Using Dielectric Resonators

Magnetic resonant coupling (MRC) is one of the techniques that are widely used in wireless power transfer (WPT) systems. The technique is commonly used for enhancing distance while maintaining power transfer efficiency (PTE). Many studies have investigated new technologies to extend the distance of MRC while maintaining high PTE values. The most promising technique to date in MRC is the addition of a resonator between the transmitter and the receiver coil. The implementation of the resonator varies based on different designs, sizes, and material types, although the outcomes remain unsatisfactory. By introducing dielectric material resonators, PTE can be improved by lowering the ohmic loss which becomes a problem on conventional resonators. This study presents a general overview on the use of dielectric material as a resonator in MRC WPT technology and its technological development. The basic operation of MRC WPT is summarized with up-to-date technical improvements related to dielectric material as a resonator in the field of WPT. An overview of the current limitations and challenges of this technique is also highlighted in this study.