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The recent developments in electric vehicle (EV) necessities the requirement of a human intervention free charging system for safe and reliable operation. Wireless power transfer (WPT) technology shows promising options to automate the charging process with user convenience. However, the operation of the WPT system is designed to operate at a high-frequency (HF) range, which requires proper control and modulation technique to improve the performance of power electronic modules. This paper proposes a dead-time (DT) integrated Pulse Density Modulation (PDM) technique to provide better control with minimal voltage and current ripples at the switches. The proposed technique is investigated using a LCC-LCL compensated WPT system, which predominantly affects the high-frequency voltage and current ripples. The performance analysis is studied at different density conditions to explore the impact of the integrated PDM approach. Moreover, the PDM technique gives better control over the power transfer at different levels of load requirement. The simulation and experimental analysis was performed for a 3.7 kW WPT prototype test system under different modes of operation of the high-frequency power converters. Both the simulated and experimental results demonstrate that the proposed PDM technique effectively enhances the efficiency of the HF inverter while significantly reducing output current ripples, power dissipation and improving the overall WPT system efficiency to 92%, and leading to a reduction in the power loss in the range of 10% to 20%. This leads to improved overall system control and performance. [ABSTRACT FROM AUTHOR]

System identification is an effective method to model a wireless power transfer system when it is used for wireless charging of electric vehicles. However, system identification using raw data directly is often unsatisfactory due to the inevitable noise interference from system operation and signal acquisition. This study proposes an improved wavelet threshold denoising (WTD) algorithm with optimized algorithm parameters and design methods. First, the number of decomposition layers is determined based on the signal spectrum diagram. Second, adaptive thresholds are designed for different decomposition layers. Third, the hierarchical threshold is combined with the hardness adjustable threshold function. Last, recursive least squares is employed to obtain a system model with the data denoised by the proposed method. Experiments demonstrate that the improved WTD method increases the accuracy of system identification to 85.42%, which verifies the effectiveness of the proposed method. An internal model controller is also designed based on the obtained model. [ABSTRACT FROM AUTHOR]

Conventional automobiles are not eco-friendly; hence, a larger section of commuters expect battery electric vehicles (BEVs). BEVs are relatively safer and cleaner and invoke more constructive charging techniques for electric vehicles (EVs), including both wired and wireless approaches. Wired charging is common despite several serious problems, such as unkempt wiring and hazardous wet environmental conditions. In contrast, wireless charging is more convenient and adaptable regarding requirement of less conducting cables and facilitation of system mobility while dynamic mode of charging. Additionally, the nonexistence of physical galvanic connections is a noticeable advantage from the perspective of reliability, durability, low maintenance, and safety. Consequential from the above-mentioned unique advantages, primarily in general the inductively coupled wireless power transmission system is often used for the wireless charging of batteries in an EV. While showing this merit, this paper discusses a broad review of the general charging topologies for EV, different power pad structures and their features. Further, the magnetic core's shape and features, various compensation topologies and their feature are discussed. Different optimization techniques are presented and investigated regarding optimization of critical parameters. Majorly transmission power, transmission efficiency, transmission distance, loss of magnetic coupler and the electromagnetic field exposure in the neighboring environment are highlighted to maximize the effectiveness of the magnetic coupler and decrease the effect of WPT on the environment. Moreover, this review suggests different optimization algorithms for designing power pads for the wireless charging of EVs. Finally, the wireless charging issues and remedial measures are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a ferrite-loaded inverted microstrip line (IML)-based artificial magnetic conductor (AMC) with a novel design that can provide complete magnetic shielding at the backside of the transmitting (Tx) coil while slightly improving the power transfer efficiency (PTE) of a wireless power transfer system (WPTS). The target frequency of the WPTS application is approximately 6.78 MHz. In the proposed design, the AMC is placed behind the Tx coil, and its magnetic shielding capability and PTE performance were verified through simulations and measurements. The size of the proposed AMC is 528 × 528 × 6.6 mm3. The measurement results verified that, compared with the Tx coil without an AMC surface, the proposed ferrite-loaded IML-based AMC can provide complete magnetic shielding while improving the PTE of the WPTS by approximately 8.05%. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wireless power transfer (WPT) systems can be utilized to charge batteries of electrically powered vehicles with a power transfer in the order of tens of kilowatts. The low frequency source currents in the WPT system emanate magneto‐quasistatic fields that induce electric fields inside the body tissues of exposed persons. This article compares the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) recommended 99th percentile of the voxel averaged electric field strengths inside the body model determined by commercial simulation tools and the co‐simulation scalar potential finite difference scheme. Furthermore, the body model resolution is enhanced to 1 × 1 × 1 mm3 which results in about eight times larger numbers of degrees of freedom than obtained by using the ICNIRP recommended resolution. The fine resolution body model electric field values (and also the resulting simulation times) are compared against field values of the coarser model recommended by ICNIRP. To cover a broad range of exposure scenarios, the comparisons are presented for different configurations of a WPT system of an electric vehicle and also for varying postures of the human body as passenger and bystanding person. [ABSTRACT FROM AUTHOR]

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. In an inductive wireless power transfer (WPT) system, the transferred power depends on the coupling between the transmitter coil and the receiver coil and, consequently, on their spatial positioning with respect to each other. Since this positioning needs to be as flexible as possible, one can design various construction shapes for the coils, in terms of both winding geometry and core geometry. The system efficiency for different positionings and configurations can be assessed if the structure and distribution of the electromagnetic field (EMF) in the space close to the system are determined. In this context, this paper proposes an investigation method based on measuring the intensity of the electromagnetic field generated by the emitting coil in the WPT space in terms of both modulus and direction. The measurements needed to be performed at a sufficient number of points, so that the entire field was determined. The EMF value was estimated by linear spatial interpolation between the measured points. Moreover, this paper presents the method and the results of investigations carried out only in the presence of the emitting coil. Calibration or correction solutions were also proposed to obtain sufficient accuracy, and the viability of the method was therefore demonstrated. [ABSTRACT FROM AUTHOR]

This paper proposes a three‐phase wireless power transfer (WPT) system with a three‐phase‐to‐three‐phase matrix converter. The proposed system directly converts power from an AC grid to high‐frequency AC for WPT. The three‐phase WPT system with the matrix converter is effectively expands the lifetime of the WPT system. A novel hybrid commutation method, which is suitable for the WPT system with a resonant characteristic, is proposed to avoid the commutation failure of the matrix converter. The strategy of the proposed hybrid commutation is based on an estimation of the current direction considering the resonant characteristics and elimination of commutation in the critical area. The proposed commutation method achieves an AC input‐current total harmonic distortion (THD) of 4.7% with the resonant three‐phase load without a current sensor on the high‐frequency side. Furthermore, the proposed WPT system achieves a system efficiency of 88.2% at a load of 4 kW. [ABSTRACT FROM AUTHOR]

In recent times, wireless power transfer systems have been identified as a reliable option to supply power to medical implants. Up to now, Wireless Power Transfer Systems (WPTS) have only been used to charge batteries of low-power medical implants. However, for medical implants requiring a relatively higher power, such as a ventricular assist device, which is an implanted blood pump in the patient's abdominal cavity, an external power supply has been used. When WPTS is used for medical implants, it increases the number of required power converter stages and hardware complexity along with the volume, which tends to reduce the overall efficiency. In addition, the existence of uncertainties in WPTS-based medical implants, such as load and mutual inductance variations, can lead to system instability or poor performance. The focus of this paper is to design a WPTS to supply power to the pump motor directly through its inverter based on the requirements of the motor drive system (MDS) without resorting to an additional DC-to-DC converter stage. To this end, the constraints that the drive system imposes upon WPTS have been identified. In addition, to make a reliable closed-loop operation, a µ-synthesis robust controller is designed to make sure the system maintains its stability and performance with respect to the system's existing uncertainties. A number of experimental results are provided to verify the effectiveness of the adopted WPTS design approach and the corresponding closed-loop controller for WPTS. Furthermore, the experimental findings for the maximum efficiency tracking (MET) approach (to minimize WPTS coil losses) and constant DC link voltage control approach are shown and compared. According to experimental results and system efficiency analysis, the former appears to perform better. The system dynamic performance analysis, on the other hand, demonstrates the latter's advantage. [ABSTRACT FROM AUTHOR]

Abstract Dual windings parallel (DWP) coils are often used in high‐power wireless charging applications to reduce current stress and internal resistance. Due to the inconsistent self‐inductance and strong coupling of the two windings, the advantages of the DWP coils cannot be fully utilized. In particular, the current stresses of the two windings are different, which will cause one of the stress to exceed the limit, and the temperature rise is too high. The reason for the current imbalance in the two windings is analysed in this work, and a distributed capacitor compensation method is proposed to balance the current stress in the two windings. Finally, a WPT system with the DWP transmitting coil was built as an example to demonstrate the effectiveness of the proposed method. The experimental results show that the current ratio in two windings decreased from 1.70 to 1.05 after using the proposed compensation method.

This paper presents an active rectifier design with a gate charge recycling technique. Gate switching increases the switching losses of the active rectifier, therefore, as a way to reduce switching losses, the gate charge recycling technique is proposed. The output power of 15 W is achieved to enable rapid charging using the three standards for wireless charging mode, magnetic induction (WPC and PMA), and magnetic resonance (A4WP). Power-sharing is used to lower the amount of power consumed by each standard mode core. In WPC, and PMA mode zero current sensing (ZCS) technique has been used while in the A4WP mode, the digitally controlled delay adjustment (DCDA) technique has been employed. By using a gate charge recycling block, the efficiency has been considerably improved due to the lower power consumption. It aims to increase the overall efficiency by reusing switching loss using the gate charge recycling block, and it has effectiveness by allowing three standard modes to operate with one single chip. The proposed design combines charge-recycling with zero current sensing techniques to improve power efficiency. The layout size is $4.75~\mu \text{m}^{2}$ . The achieved efficiency is 98.6 % in the magnetic induction method (WPC/PMA) at 15 W, and 94.86 % in the magnetic resonance method (A4WP) with an output power level of 15 W. The chip is fabricated in the BCD $0.18~\mu \text{m}$ CMOS process.

Missiles mounted on maritime vessels have two types of loads. One is the operating load consumed just before launch, and the other is the safety sensors load that must always be activated for safety. Because the operating load consumes a large power capacity, the power generated by the vessel’s own power generators must be supplied. Meanwhile, the loads for safety sensors are supplied through an energy storage system (ESS) because the safety sensors must be supplied with power even when the generators stop. However, the voltage difference between the generated power and the ESS power reaches ten times or more. Therefore, there is a problem in that the input of the two power sources with a large input difference must be transferred to two loads through only a pair of coils. To solve this problem, a WPT system is proposed to overcome the voltage difference between the generated power and the ESS power. The design method of the proposed system is analyzed mathematically, and it is verified through simulations and experiments. The proposed system has a maximum dc to dc power transfer efficiency of 76.8% with a capacity of 550 W and has the advantage that power is continuously supplied to the sensor loads even if the input voltage source is changed. In addition, by operating the proposed WPT system under a wide load range of 200 W to 1000 W, the effectiveness of the proposed WPT system is proved.

This paper presents a four-plate undersea capacitive wireless power transfer (CPT) system for underwater applications such as autonomous underwater vehicles (AUVs). Generally, a CPT system transfers the power based on electric fields. The complex resonant compensation networks are used to make the CPT system work in the resonant condition. The resonant voltage is always very high. It will be a big challenge to the human safety. In this paper, a virtual electrons periodic reciprocating flow theory is proposed for the CPT system. In one switching cycle, the electrons firstly flow in the forward direction through the forward path and then flow in the inverse direction through the inverse path. The CPT system has been deeply studied with the vacuum dielectric or the air dielectric. However, for the CPT system, there are few papers to show the underwater application. In this paper, an undersea four-plate CPT system is designed and studied in the underwater condition. The two coupling capacitors and other elements of the CPT system could build a closed-loop path. A small value inductor is adapted as a resonant compensation network for the four-plate CPT system. The DC voltage is inverted to the AC voltage in the primary side with the single-phase full-bridge inverter. The resonant voltage is rectified to the DC voltage in the secondary side with the single-phase full-bridge diode rectifier. A 100 W power level CPT system is constructed to verify the theory analysis and the calculation. The theory analysis is verified by the simulated and experimental results. The stable output voltage and load power are achieved in this paper.

In an inductive wireless power transfer (WPT) system, the transferred power depends on the coupling between the transmitter coil and the receiver coil and, consequently, on their spatial positioning with respect to each other. Since this positioning needs to be as flexible as possible, one can design various construction shapes for the coils, in terms of both winding geometry and core geometry. The system efficiency for different positionings and configurations can be assessed if the structure and distribution of the electromagnetic field (EMF) in the space close to the system are determined. In this context, this paper proposes an investigation method based on measuring the intensity of the electromagnetic field generated by the emitting coil in the WPT space in terms of both modulus and direction. The measurements needed to be performed at a sufficient number of points, so that the entire field was determined. The EMF value was estimated by linear spatial interpolation between the measured points. Moreover, this paper presents the method and the results of investigations carried out only in the presence of the emitting coil. Calibration or correction solutions were also proposed to obtain sufficient accuracy, and the viability of the method was therefore demonstrated.

Because a transmitter-side controller of an inductive power transfer (IPT) system cannot directly measure its load conditions, i.e., receiver-side output voltages and currents, wireless communications are commonly used in many IPT systems. However, the wireless communication can cause a devastating failure of the IPT system because of its tens of milliseconds delays and frequent data losses. The mismatch between the transmitted and the received power can destroy the receiver-side power converters. In this article, receiver-side load voltage and current observers for a series–series tuned IPT system are proposed using the well-known disturbance observer theories. A load current observer that has a 10 kHz estimation bandwidth and a load voltage observer that has a 200 Hz bandwidth are proposed. The estimated load voltage and current have much faster dynamics than the wireless feedback signals without any data loss. Therefore, the proposed observers can bring significant advances in reliability and performance of the IPT system. Design guidelines for the observers that have low steady-state errors and fast dynamics are suggested. The theoretical performances of the proposed observers are evaluated by simulations and experiments. The simulated frequency- and time-domain responses of the proposed observers are consistent with the theoretical results. An experimental testbed was built to evaluate the proposed observers. The estimated current follows its actual value in 0.1 ms and the estimated voltage follows its measured value in 4 ms as expected from the simulations. [ABSTRACT FROM AUTHOR]

Dual windings parallel (DWP) coils are often used in high‐power wireless charging applications to reduce current stress and internal resistance. Due to the inconsistent self‐inductance and strong coupling of the two windings, the advantages of the DWP coils cannot be fully utilized. In particular, the current stresses of the two windings are different, which will cause one of the stress to exceed the limit, and the temperature rise is too high. The reason for the current imbalance in the two windings is analysed in this work, and a distributed capacitor compensation method is proposed to balance the current stress in the two windings. Finally, a WPT system with the DWP transmitting coil was built as an example to demonstrate the effectiveness of the proposed method. The experimental results show that the current ratio in two windings decreased from 1.70 to 1.05 after using the proposed compensation method. [ABSTRACT FROM AUTHOR]

This paper describes a wireless power transfer (WPT) system operating at 2.4 GHz, which is based on waveform optimization technique and a wide input power range rectifier. This latter consists of an RF‐to‐dc power conversion circuit based on circulators. The waveform optimization is then applied in order to enhance the power conversion efficiency at very low input power levels. The proposed WPT system was prototyped and tested in open and closed loop configurations with different types of obstacles placed between the transmitter and the receiver. The generation of power‐optimized waveforms and the control process in the closed loop configuration were carried out using software‐defined radio. The obtained experimental results validate the wide input power behavior of the two proposed WPT systems especially when dealing with very low input power levels and relatively dynamic environments. In fact, for the two WPT systems featured a distance of 1 m and a transmitted power of 50mw, dc power levels of about 38 and 11 μW are harvested in the cases of no obstacle and low attenuation obstacle respectively. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent times, wireless power transfer systems have been identified as a reliable option to supply power to medical implants. Up to now, Wireless Power Transfer Systems (WPTS) have only been used to charge batteries of low-power medical implants. However, for medical implants requiring a relatively higher power, such as a ventricular assist device, which is an implanted blood pump in the patient’s abdominal cavity, an external power supply has been used. When WPTS is used for medical implants, it increases the number of required power converter stages and hardware complexity along with the volume, which tends to reduce the overall efficiency. In addition, the existence of uncertainties in WPTS-based medical implants, such as load and mutual inductance variations, can lead to system instability or poor performance. The focus of this paper is to design a WPTS to supply power to the pump motor directly through its inverter based on the requirements of the motor drive system (MDS) without resorting to an additional DC-to-DC converter stage. To this end, the constraints that the drive system imposes upon WPTS have been identified. In addition, to make a reliable closed-loop operation, a µ-synthesis robust controller is designed to make sure the system maintains its stability and performance with respect to the system’s existing uncertainties. A number of experimental results are provided to verify the effectiveness of the adopted WPTS design approach and the corresponding closed-loop controller for WPTS. Furthermore, the experimental findings for the maximum efficiency tracking (MET) approach (to minimize WPTS coil losses) and constant DC link voltage control approach are shown and compared. According to experimental results and system efficiency analysis, the former appears to perform better. The system dynamic performance analysis, on the other hand, demonstrates the latter’s advantage.

This paper proposes a bidirectional undersea capacitive wireless power transfer system (BD-UCWPT) for the autonomous underwater vehicles (AUVs). The two H-Bridge circuits are adapted in the proposed BD-UCWPT system to achieve the bidirectional power flow. The H-Bridge circuit is built based on the GaN devices. As a result, the high switching frequency, and low power loss could be reached. The two LCLC compensation networks are respectively used in the transmitter side and receiver side. The simulation work is conducted with the Ansys Maxwell, PSIM and MATLAB. In the experiments, two seawater bags are added in the middle of two metal plates of CS1 and CS2 to model the seawater condition, respectively. In order to verify the theory analysis, a 100W experimental BD-UCWPT system is constructed. The experiments have been conducted in air and in seawater, respectively. The simulated and experimental results are compared with each other. It shows that, with this BD-UCWPT system, the power of AUVs could flow bidirectionally. The stable operation and high efficiency of BD-UCWPT system is verified. The research work in this paper could facilitate the application of wireless power transfer (WPT) system for AUVs and other undersea devices.

A negative impedance converter (NIC) has been combined with a wireless power transfer (WPT) system to maximize the system efficiency based on non-foster theory. The NIC is composed of transistor, voltage divider, capacitor, and inductor for impedance matching, and resonant circuit operating at 6.78 MHz. The desired negative impedance can be controlled by tunable impedance in the NIC. In this paper, the loss of the transmitting coil is reduced to 0.1 Ω, yielding a quality factor of 7,050, which is 19.1 times higher than that of the conventional coil. The WPT system with the NIC provides high power transfer efficiency (PTE) at various transmission distances. The experimental results are improved from 64% to 96% and from 5% to 55% at the transmission distances of 50 and 200 mm, respectively. Furthermore, the PTE is enhanced from 38% to 87% and from 2% to 38% at the diagonal misalignment distance of 0 and 150 mm, respectively, at a transmission distance of 100 mm. The proposed technology for increasing the receiving power in the receiving coil with a higher PTE can be utilized for numerous applications in the industrial, scientific, and medical band, with a restricted radio frequency power on the transmitter side.

We analyze the electromagnetic field of a wireless power transfer system using the 3-D parallel finite element method on K computer, which is a super computer in Japan. It is clarified that the electromagnetic field of the wireless power transfer system can be analyzed in a practical time using the parallel computation on K computer, moreover, the accuracy of the loss calculation becomes better as the mesh division of the shield becomes fine.

Aiming at the constant current charging and the constant voltage charging mode of the power battery pack in an electric vehicle, this paper proposes a double‐sided LCL variable compensation topology in a magnetically coupled resonance wireless power transfer system. With the proposed topology, the complexity of the circuit design and control will be simplified. The mathematical model for the double‐sided LCL topology is established using a two‐port network, and the output characteristics of constant current mode and constant voltage mode are studied on. By compensation analysis, the double‐sided LCL topology is improved and designed. The specific parameter configuration method and compensation conversion circuit are developed. Load characteristics analysis of variable compensation topology is given. A MATLAB Simulink simulation model and a prototype were built. Both the simulation results and the experiment results show the validity of the proposed variable compensation topology and parameter configuration method. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The mutual inductance between the primary and secondary coils is an important parameter in the wireless power transfer system, and the mutual inductance calculation of coils in many complicated circumstances has been studied. However, the mutual inductance calculation of two circular coils in arbitrary relative position with magnetic tiles have not been solved. In this study, an analytical formula of the mutual inductance with respect to the parameters of the system such as arbitrary relative position, geometry, and the properties of the magnetic tiles is proposed. The proposed formula is derived from the proposed parameter vector method, and the proposed parameter vector method can not only be used to explore the tendencies of the mutual inductance in arbitrary relative position, but also provide a fairly concise and general method for mutual inductance calculation. The finite‐element analysis and experimental results validated the reliability and accuracy of the proposed formula, and an accuracy of a few parts in a thousand can be readily attainable. [ABSTRACT FROM AUTHOR]

Metal object detection (MOD) and detection of position (DoP) of pick‐up coils are increasingly critical to the commercialisation of the wireless power transfer system. In this study, a detection scheme based on phase‐detection, which can both realise the function of MOD and DoP, is newly introduced. The method is based on the principle that the presence of metal objects and pick‐up coils both affect the impedance phase of the detection coil loop. Comparing with the traditional detection methods, which is based on measuring the absolutely value of impedance in detection loop, the malfunction is avoided by adopting phase difference as the criterion of the existence of metal objects and pick‐up coils. An inexpensive and high‐precision sensing circuit is newly designed to acquire the phase difference accurately. Simulation models and experiments are conducted to verify the feasibility of the proposed detection scheme. The Δδ of the detection coil circuit with a coin placed reaches −5.17, while the Δδ of other detection coils without metal objects keeps zero. In the meantime, the position of the pick‐up coil is identified because the Δδ of these detection coils closer to the centre of the pick‐up coil varies more significantly while other coils vary slightly. [ABSTRACT FROM AUTHOR]

The application of the metamaterial (MM) in wireless power transfer (WPT) system has received a great deal of attention in improving the transfer efficiency and reducing the leakage of electromagnetic field (EMF) in recent years. However, most of the analytical methods for MM‐inspired WPT system are based on microwave technologies, such as negative refraction effect, magnetic dipole coupling model and magneto‐inductive wave theory. In this study, the equivalent circuit model of the MM in the WPT system is analysed in detail. Two different types of MMs, Mu‐Negative‐Magnetic (MNM) and Mu‐Near‐Zero (MNZ), are constructed to verify this method. In particular, a tuning strategy by changing the distances between the drive (load) loop and internal coils is established to improve the power transfer efficiency for the WPT system with the MNM‐MM. In addition, the MNZ‐MM is described to cancel EMF leakage in the WPT systems by this method. Moreover, a series of practical experiments are carried out to prove the numerical analysis, which are well consistent with the theoretical solution employed by the Advanced Design System software. Finally, the combination of two types of MMs applied in the WPT system is also discussed. [ABSTRACT FROM AUTHOR]

This study reports, for the first time, the use of coupled‐line‐based impedance matching in wireless power transfer (WPT) system. The transmitter and receiver of the WPT system are realised by microstrip feed line and symmetric coupled line at the top plane. The ground plane is realised with triangular‐shaped defect along with the excitation slot mounted by an external capacitor. The defect in the ground plane and the external capacitor regulate the resonant frequency and also enable miniaturisation of the WPT system. The design is augmented with a systematic analytical approach for impedance matching and a simplified design procedure for the WPT system. A novel equivalent circuit model consisting of parallel LC network and coupled lines is also developed for the evaluation of the proposed WPT system design technique. A prototype of the system operating at 300 MHz developed on Rogers RO4350B substrate achieves a peak efficiency of 80% at a transmission distance of 17 mm. An excellent agreement between the measured and the electromagnetic simulated results is a testament of the robustness of the proposed design technique. Furthermore, evaluation of the commonly used WPT‐related figure of merit shows significant enhancement when compared to the existing state of the art. [ABSTRACT FROM AUTHOR]

The wireless power transfer (WPT) system has been widely researched due to its inherent advantages compared with the traditional plug‐in charging system over security, flexibility, convenience and so on. Compared with the two‐coil WPT system, the three‐coil WPT system has been proven to have higher efficiency over a relatively long transmission distance. In many applications, WPT systems are required to have the load‐independent constant current output (CCO) characteristic and zero phase angle (ZPA) operation. This study proposes a three‐coil WPT system that can achieve the CCO and ZPA operation through flexible parameter design. First, the detailed mathematical deduction for the CCO and ZPA operation is given. Then, a comprehensive analysis of the three‐coil WPT system is conducted in term of parameter design, the sensitivity of the CCO to changes in compensation parameters, implementation of zero voltage switching operation and efficiency analysis. Furthermore, a detailed efficiency comparison with the SS WPT system is performed to reflect the high efficiency of the proposed three‐coil system, and the additional performance of the proposed three‐coil system is compared with previous related works to verify its advantages further. Finally, the correctness of the theoretical analysis is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

Misalignments between the transmitter and receiver coils would in some cases lead to a significant decline in transmission power and efficiency in the wireless power transfer system. This study presents an integrated two‐layer receiver to improve the tolerance of horizontal misalignment. On the lower layer of the integrated receiver, two coplanar spiral coils, which are decoupled and work as the auxiliary repeater, are designed to help keep a stable power transmission between transmitter coils on the track and the main receiver coil on the upper layer. Then, the optimisation model based on the Bayesian algorithm is established for the proposed receiver structure and some key parameters are optimised. A sensor‐coil‐based positioning approach is also proposed to achieve on–off control of the transmitter coils. The simulation results show that the system based on the optimised integrated receiver has a stable output power with a variation lower than 13.17%. Two 300 W dynamic charging prototypes based on the integrated receiver and conventional spiral receiver, respectively, have been developed to verify the effectiveness of the proposed design and the optimisation method. The experimental results match well with the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a new urethral valve to deal with severe urinary incontinence (UI) caused by sphincter injury or dysneuria. This valve consists of a wireless power transfer system and a valve body structure driven by SMA (shape memory alloy) spring. The mechanical model of SMA spring and coupling model of wireless energy transfer are derived. Special attention is also given to the biological effects of electromagnetic filed as the proposed device is powered by wireless power transfer system. This valve is validated by simulation experiment and the models are used to investigate the influence of SMA spring parameters, control parameters and coil parameters on the driving characteristics of the proposed urethral valve. [ABSTRACT FROM AUTHOR]

This paper proposes a 3D scanning magnetic resonance wireless power transfer system to eliminate dead-zones and improve transmission efficiency. This system consists of an oscillator, power amplifier, microcontroller unit, personal computer, pan-tilt motor, transceiver coil, rectifier, and wireless communication units. This system provides the maximum voltage to the receiver within a short timeframe using the zone-based maximal transmission efficiency searching process algorithm. From the measurement results, it can be observed that the time to find the maximum transmission efficiency with this algorithm is 11 times faster than that of the full scan by 5° and that the position error of maximum transmission efficiency is less significant. [ABSTRACT FROM AUTHOR]

The power saving issue and clean energy harvesting for wireless and cost-affordable electronics (e.g., IoT applications, sensor nodes or medical implants), have recently become attractive research topics. With this in mind, the paper addresses one of the most important parts of the energy conversion system chain – the power management unit. The core of such a unit will be formed by an inductorless, low-voltage DC-DC converter based on the cross-coupled dynamic-threshold charge pump topology. The charge pump utilizes a power-efficient ON/OFF regulation feedback loop, specially designed for strict low-voltage start-up conditions by a driver booster. Taken together, they serve as the masters to control the charge pump output (up to 600 mV), depending on the voltage value produced by a renewable energy source available in the environment. The low-power feature is also ensured by a careful design of the hysteresis-based bulk-driven comparator and fully integrated switched-capacitor voltage divider, omitting the static power consumption. The presented converter can also employ the on-chip RF-based energy harvester for use in a wireless power transfer system.

In this work, a resonance frequency tracking system is proposed for general use in RF applications. The proposed system is based on the fact that the minimum input reflection coefficient occurs at the resonance frequencies, and the system consists of a bidirectional coupler, a rectifier and a control unit. The sampled signals from the forward and reflect ports of the bidirectional coupler are taken as an input for the controller unit and the reflection coefficient is calculated by dividing the reflected one to forward one. The control unit systematically changes the source frequency until a minimum reflection coefficient is reached. The frequency that corresponds that minimum reflection coefficient is the instant resonance frequency for the system. After discussing the details of proposed frequency tracking system, the system is applied to a wireless power transfer system based on resonance magnetic coupling. Measurement results of the fabricated circuits and the test results for the control unit are presented.

The metamaterial (MA) has been proved to enhance the efficiency of the wireless power transfer (WPT) system considerably in many studies. This study presents an equivalent circuit model using a qualitative and even quantitative simple explanation for the behaviour of MA in WPT. For this purpose, the electromagnetic field simulation of WPT system with MA is carried out by the high-frequency structure simulation three-dimensional electromagnetic simulator. Also, the authors propose the circuit structure of the WPT system based on MA and explore its characteristics by numerical calculation and advanced design system simulation. The transmission efficiency of the simulator is characterised by reflection coefficient here. Although some methods, such as interference theory, transmission line circuit model, and effective medium theory, have been put forward to explain the physics mechanism of WPT system with MA, some of reactive parameters and the basic physical interpretation have not been expounded clearly so far. Differ from the existing theoretical model, the proposed approach focuses on the effect of the system parameters of MA and transfer coils on the transfer characteristics and is beneficial to the analysis of the complicated system.

In the wireless power transfer system, the front stage power supply is used to efficiently transfer power to the post-stage circuit. As a bridge connecting the front stage power supply and the rear stage circuit of the wireless power transmission system, power converter network is generally placed behind the inverter so as to achieve output filtering of inverter and stability of output voltage and current. This paper analyses the LCC (inductance-capacitance-capacitance) and LCL (inductance-capacitance-inductance) transform network circuit model, and transmission characteristics of LCC and LCL conversion networks are analysed and compared based on two different circuit topologies. By means of parameter calculation, simulation analysis, and parameter optimisation design, it is concluded that both LCC and LCL networks have different characteristics. The results show that for both LCC and LCL network topologies, when the parameters of network components satisfy certain conditions, they can relatively achieve stable voltage or current output within a certain load range to meet the specific power transmission requirements.

The wireless power transfer (WPT) has attracted considerable attention due to its convenience and reliability. However, the electromagnetic leakage of WPT can be harmful to humans and environment. In order to meet safety requirements, electromagnetic leakage to the nearby transmission channel should be controlled below a certain level. Beyond ferrite and metallic shields, several researchers have proposed mu-near-zero metamaterial (MNZ MM). However, little work researches the application of MNZ MM in four-coil WPT systems. Here, the authors propose an optimised MNZ MM for shielding leaked electromagnetic field. Next, the authors setup a miniaturised WPT system loaded with MNZ slab at 13.56 MHz. It can serve as a frequency selector that reflected a specified frequency of 13.56 MHz, while allowing all other frequencies to pass undisturbed. As a result, the transmission efficiency is dramatically reduced at a 30 cm distance. The magnetic field magnitude of the receiver has been decreased. Obviously, the proposed MNZ MM has good performance in magnetic field shielding for WPT systems. [ABSTRACT FROM AUTHOR]

The metamaterial (MA) has been proved to enhance the efficiency of the wireless power transfer (WPT) system considerably in many studies. This study presents an equivalent circuit model using a qualitative and even quantitative simple explanation for the behaviour of MA in WPT. For this purpose, the electromagnetic field simulation of WPT system with MA is carried out by the high-frequency structure simulation three-dimensional electromagnetic simulator. Also, the authors propose the circuit structure of the WPT system based on MA and explore its characteristics by numerical calculation and advanced design system simulation. The transmission efficiency of the simulator is characterised by reflection coefficient here. Although some methods, such as interference theory, transmission line circuit model, and effective medium theory, have been put forward to explain the physics mechanism of WPT system with MA, some of reactive parameters and the basic physical interpretation have not been expounded clearly so far. Differ from the existing theoretical model, the proposed approach focuses on the effect of the system parameters of MA and transfer coils on the transfer characteristics and is beneficial to the analysis of the complicated system. [ABSTRACT FROM AUTHOR]

Efficient and reliable power supply has been considered as the fundamentality of applying monitoring equipment overhead high‐voltage power line (HVPL). Several kinds of energy harvesting devices are investigated and compared. A new power supply scheme, which integrates the online energy harvesting device and the wireless power transfer (WPT) system, is presented. Optimisation design of online energy harvesting device is analysed emphatically by taking both HVPL insulation distance and wireless power supply efficiency into account. For further increasing the harvested energy from power lines, this study discusses the design of specific device structure and the accurate calculation of maximum output power. It is found that essential parameters and exciting current angle contribute to more extracting energy. Meanwhile, in order to expand the transmitting distance with high efficiency, the WPT system with double relay coils is selected. The charging threshold voltage of the load can be further optimised under different transmitting distances by adopting an AC–DC voltage‐doubling rectifier circuit. Simulation and experimental studies show that when the transmitting distance is >1 m, the monitoring equipment can also be charged in a reliable way, which also verifies the correctness and feasibility of the system. [ABSTRACT FROM AUTHOR]

High-frequency wireless power transfer (WPT) technology provides superior compatibility in the alignment with various WPT standards. However, high-efficiency and compact single-phase power switching systems with ideal snubber circuits are required for maximum power transfer capability. This research aims to develop an inverter using Gallium Nitride (GaN) power transistors, optimized RCD (resistor/capacitor/diode) snubber circuits, and gate drivers, each benefitting WPT technology by reducing the switching and conduction loss in charging electric vehicle batteries. A full-bridge GaN inverter was simulated and instituted as part of the wireless charging circuit design. The RCD circuits were adjusted by transferring maximum power from the power supply to the transmitter inductor. For verification of the simulated output, lab-scale experiments were implemented for two half-bridges controlled by gate drivers with corresponding snubber circuits. After authenticating the output results, the GaN inverter was tested with an input range of 30 V to deduce the success of charging electric vehicle batteries within an efficient time frame. The developed inverter, at 80 kHz frequency, was applied in place of a ready-to-use evaluation board, fully reducing less harmonic distortion and greatly increasing WPT system efficiency (~93%). In turn, the designed GaN inverter boasts considerable energy savings, resulting in a more cost-effective solution for manufacturers.

This paper presents a highly efficient three-port converter to integrate energy storage (ES) and wireless power transfer (WPT) systems. The proposed converter consists of a bidirectional DC-DC converter and an AC-DC converter with a resonant capacitor. By sharing an inductor and four switches in the bidirectional DC-DC converter, the bidirectional DC-DC converter operates as a DC-DC converter for ES systems and simultaneously as a DC-AC converter for WPT systems. Here, four switches are turned on under the zero voltage switching conditions. The AC-DC converter for WPT system achieves high voltage gain by using a resonance between the resonant capacitor and the leakage inductance of a receiving coil. A 100-W prototype was built and tested to verify the effectiveness of the converter; it had a maximum power-conversion efficiency of 95.9% for the battery load and of 93.8% for the wireless charging load.

The wireless power transfer (WPT) has attracted considerable attention due to its convenience and reliability. However, the electromagnetic leakage of WPT can be harmful to humans and environment. In order to meet safety requirements, electromagnetic leakage to the nearby transmission channel should be controlled below a certain level. Beyond ferrite and metallic shields, several researchers have proposed mu-near-zero metamaterial (MNZ MM). However, little work researches the application of MNZ MM in four-coil WPT systems. Here, the authors propose an optimised MNZ MM for shielding leaked electromagnetic field. Next, the authors setup a miniaturised WPT system loaded with MNZ slab at 13.56 MHz. It can serve as a frequency selector that reflected a specified frequency of 13.56 MHz, while allowing all other frequencies to pass undisturbed. As a result, the transmission efficiency is dramatically reduced at a 30 cm distance. The magnetic field magnitude of the receiver has been decreased. Obviously, the proposed MNZ MM has good performance in magnetic field shielding for WPT systems.

In this work, inductive power transfer systems with five different compensation topologies are considered: series-series, parallel-series, series-parallel, parallel-parallel and double-sided LCC. State-space models are deduced in order to help engineers perform suitable dynamic analysis in the design process. Linearization procedures such as small signal assumptions are not employed. Finally, an example illustrates how the proposed equations can be used for analysis purposes. [ABSTRACT FROM AUTHOR]