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The original system, designed as a combination structure of a linear machine and a wireless power transmission transformer, was designed to overcome the limitations of the wired power supply method used for working robots and transportation equipment in existing smart factories, and improvements in magnetic coupling and power transfer efficiency are needed. In this work, we study the efficiency improvement of a system that can supply wireless power to track-type transportation equipment. For this purpose, electromagnetic properties such as magnetic equivalent resistance, inductance, magnetic coupling rate, and core loss are analyzed using the finite element method. In addition, the results of magnetic field finite element analysis are applied in electrical equivalent circuit modeling to analyze the voltage transfer ratio and input/output characteristics of a CLLC resonant converter designed for wireless power transmission. The efficiency improvements of the proposed model are verified through a comparison of experimental and simulation results after fabricating a prototype. From the results of this study, a more optimized wireless power transmission system design based on the analysis results from an electromagnetic perspective can be realized to improve the efficiency of wireless power transmission. [ABSTRACT FROM AUTHOR]

A novel portable 2.4 GHz antenna beam sensor has been designed and implemented. The functions of the proposed sensor are to observe the spatial radiation distribution by using vision and to measure the spatial radiation power intensity distribution. The antenna beam sensor comprises a 6 * 6 radio frequency (RF) rectenna array. Each RF rectenna is a combination of a patch antenna and a high-efficiency radio frequency-direct current (RF-DC) conversion circuit. The output of each RF rectenna is connected to an LED, and the location of the spatial beam power intensity is determined from the luminous intensity of the LED. Additionally, the spatial beam power intensity distribution is obtained by measuring the output voltage of the RF rectennas. The patch antenna size is 7 x 7 cm2, the measured reflection coefficient of the antenna is greater than 10 dB at 2.4 GHz, and the measured antenna maximum gain is 5.1 dBi. The RF-DC conversion circuit is designed with a 2.4 GHz ten-stage Cockcroft-Walton voltage multiplier rectifier circuit, which can improve the conversion efficiency and beam sensing sensitivity. The RF-DC conversion circuit size is 3.5 x 4.7 cm2. The measured reflection coefficient of the circuit is greater than 10 dB at 2.4 GHz, and the highest measured conversion efficiency is 50.38%. The overall size of the antenna beam sensor is 42 x 42 cm2 and the weight is 1.15 kg. Therefore, the sensor is light and easy to handle, which makes it easy to carry for measurement work. This proposed antenna beam sensor is useful for applications in the research of wireless power transfer, microwave energy harvesting, and antenna radiation beam behavior in air. [ABSTRACT FROM AUTHOR]

The original system, designed as a combination structure of a linear machine and a wireless power transmission transformer, was designed to overcome the limitations of the wired power supply method used for working robots and transportation equipment in existing smart factories, and improvements in magnetic coupling and power transfer efficiency are needed. In this work, we study the efficiency improvement of a system that can supply wireless power to track-type transportation equipment. For this purpose, electromagnetic properties such as magnetic equivalent resistance, inductance, magnetic coupling rate, and core loss are analyzed using the finite element method. In addition, the results of magnetic field finite element analysis are applied in electrical equivalent circuit modeling to analyze the voltage transfer ratio and input/output characteristics of a CLLC resonant converter designed for wireless power transmission. The efficiency improvements of the proposed model are verified through a comparison of experimental and simulation results after fabricating a prototype. From the results of this study, a more optimized wireless power transmission system design based on the analysis results from an electromagnetic perspective can be realized to improve the efficiency of wireless power transmission.

Conventional wireless charging systems cause output power fluctuations during the offset process, and a single topology can cause power reduction or a large impact on the wireless charging network as the coupling mutual inductance changes. For this reason, in this paper, by combining LCC-S and S-S topologies, the high output characteristics of the S-S topology network in the low coupling state and the high output characteristics of the LCC-S topology network in the protection and high coupling in the very low coupling, the power output in the offset state is greatly maintained by combining with the voltage regulation circuit. In this paper, firstly, the theoretical derivation of the working principle of the designed topology is carried out, then the mutual inductance variation range generated by the offset state of the coil is found through finite element simulation, and the accuracy of the theoretical derivation is verified by building a constant power output model of the self-switching system using matlab, and finally, an experimental platform for wireless power transmission is built, and the experimental results confirm that the system power can be maintained within a certain offset range. The output fluctuation is within 5%, which verifies the feasibility and realism of the design.

The application of wireless power transmission technology is becoming more and more extensive. However, in practical applications, the problem of reducing the energy transmission efficiency caused by the offset of the coupling coil needs to be solved urgently. Changing the coil structure is a widely adopted method to deal with this problem. Based on the characteristics of the existing magnetic coupling resonant wireless power transmission system and the principle of the anti-offset coil, this paper innovatively designs a new type of quadrilateral overlapping wireless power transfer coupling coil, which has a strong anti-offset capability. The new type of coil model was built in the simulation and experiment, and the relevant parameters were measured. Experimental results verify that the proposed coil structure has an excellent anti-offset capability. [ABSTRACT FROM AUTHOR]

With the application of electrical equipment, magnetically coupled resonant (MCR) wireless power transfer (WPT) technology has become an effective means to improve equipment intelligence. The MCR‐WPT system is a loosely coupled system, and the resonant frequency may be split or detuned due to the changes of load or transferring distance, resulting in the system transfer efficiency (TE) greatly reduced. To solve the problems of limited speed and accuracy in the existing frequency tracking methods, this paper analyzes the relation between the detuning rate and the system TE, proposing an adaptive frequency tracking control method based on fuzzy radial basis function neural network control. The neural network outputs proportion–integration–differentiation parameters to adjust the inverter drive circuit, and the frequency of inverter drive circuit is adjusted nonlinearly in real time to ensure the accurate frequency tracking of the MCR‐WPT system. The simulation and experimental results show that the proposed method can enhance the tracking ability of the resonant frequency, and effectively improve the system TE. [ABSTRACT FROM AUTHOR]

The article discusses issues, problems and methods for solving them related to the transfer of energy to transplanted assisted circulation devices, which allow for efficient, safe and stable energy transfer. One of the promising methods of energy transfer is wireless energy transfer, which allows patients with implantable devices to lead a more active life, avoiding infection and rejection of the devices.

Wireless laser power transmission is a promising technique in the far-field wireless power supply with the advantages of high-power density, and small transmitter and receiver sizes. This article proposes a high-efficiency pulse width modulation-based wireless laser power transmission step-down system based on an 808 nm laser diode and gallium arsenide photovoltaic cells. The output voltage of the proposed system is controlled with the use of pulse width modulation of the laser diode in the transmitter without switch tubes and rectifier diodes in the receiver. The model of the proposed system is built, and characteristics of the system is analyzed based on the state-space averaging method. Additionally, the steady and dynamic operations, as well as the efficiency analyses, are investigated and evaluated experimentally. With the use of the propounded system, when the load is 3 ohms and the output voltage is 1.5 V, a converter efficiency of 96.6% is obtained that is ~10% and ~5% higher than those of continuous wireless power transmission constant voltage systems with asynchronous and synchronous buck converters, respectively.

We introduce a novel RF to DC wireless power transmission implantable rectenna system at Industrial, Scientific and Medical bands (ISM 902.8-928 MHz). An embedded circular antenna receives the externally emitted energy from a patch antenna and converts it to DC power by a rectifying circuit. The system is associated with a metallic reflector which is placed behind the human body enhancing the reception. The rectifying circuit efficiency and the total system's efficiency are determined for different external antenna to human body distances and various embedded depths with or without the reflector. Experimental results, obtained in a realistic environment, validate the predicted performance and provide an initial evaluation of the transmission link. Porcine tissue and bovine tissue are both used during the measurements and results are compared against simulations.

The application of wireless power transmission technology is becoming more and more extensive. However, in practical applications, the problem of reducing the energy transmission efficiency caused by the offset of the coupling coil needs to be solved urgently. Changing the coil structure is a widely adopted method to deal with this problem. Based on the characteristics of the existing magnetic coupling resonant wireless power transmission system and the principle of the anti-offset coil, this paper innovatively designs a new type of quadrilateral overlapping wireless power transfer coupling coil, which has a strong anti-offset capability. The new type of coil model was built in the simulation and experiment, and the relevant parameters were measured. Experimental results verify that the proposed coil structure has an excellent anti-offset capability.

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]

Wireless laser power transmission is a promising technique in the far-field wireless power supply with the advantages of high-power density, and small transmitter and receiver sizes. This article proposes a high-efficiency pulse width modulation-based wireless laser power transmission step-down system based on an 808 nm laser diode and gallium arsenide photovoltaic cells. The output voltage of the proposed system is controlled with the use of pulse width modulation of the laser diode in the transmitter without switch tubes and rectifier diodes in the receiver. The model of the proposed system is built, and characteristics of the system is analyzed based on the state-space averaging method. Additionally, the steady and dynamic operations, as well as the efficiency analyses, are investigated and evaluated experimentally. With the use of the propounded system, when the load is 3 ohms and the output voltage is 1.5 V, a converter efficiency of 96.6% is obtained that is ∼10% and ∼5% higher than those of continuous wireless power transmission constant voltage systems with asynchronous and synchronous buck converters, respectively. [ABSTRACT FROM AUTHOR]

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.

A new method of power control for wireless power transmission (WPT) system has been proposed and analysed. The circuit and method suggested in this study holds good promise of reducing switching loss in the high‐frequency converter of WPT. The effect of misalignment between transmitter and receiver coils has been analysed and a simple remedial method has been proposed. The desirability of frequency tuning of converter's output voltage under varying degrees of misalignment has been highlighted. The conventional perturb and observe method for maximum power point tracking has been gainfully employed here to achieve the required frequency tuning of the proposed converter. The proposed methods are implemented and tested on laboratory scale. Some suggestions have been given for augmenting driver assistance system aimed at limiting lateral misalignment in dynamic WPT system. The suggested algorithm is tested in a laboratory environment using a simple communication system. [ABSTRACT FROM AUTHOR]

Principle of magnetic resonance coupling wireless power transmission system was analyzed by use of mutual inductance theory. Impedance matching theory and corresponding parameter calculation methods were introduced. A model of magnetic resonance coupling wireless power transmission system containing an impedance matcher was built by equaling variation of mutual inductance between sending coil and receiving coil to variation of the system impedance parameters. The simulation result proves that magnetic resonance coupling wireless power transmission system containing an impedance matcher can improve load power effectively under the same condition.

This article addresses the problem of hard switching caused by the change of equivalent load in a wireless power transfer (WPT) system based on a class E inverter. Based on the load-sensitive characteristics of the class E inverter, the coil structure is improved, and the self/mutual inductance compensation method of the transmitting coil is proposed to realize a wide range of soft switching. On the basis of fully considering the coupling relationship between the source and load coils, a coil structure with multiple coils in series on the primary side is proposed, and the cross-coupling relationship between the coils is analyzed in detail and simplified. The inverter parameters and coupling mechanism were adjusted by means of coil series reverse connection. Combined with the parameter influence law and the load equivalent principle of the class E inverter, the margin of soft switching at the inverter side was increased and the load offset correction was carried out. The soft-switching effect of the equivalent load from 0 to 3.3 times of ideal load was obtained, and the purpose of improving system reliability and efficiency was achieved. Finally, the feasibility and effectiveness of the proposed method were verified by simulation and experiment.

If the magnetic resonance coupling-based wireless power transmission system has multiple receivers, cross-coupling will occur between the transmitter and the receiver, resulting in the variation of transmission characteristics when compared with the case of a single receiver. To solve this problem, a mutual inductance coupling circuit model for double-relay and multi-load transmission system and a calculation model for mutual inductance between solenoid coils in the same plane have been built to study the transmission characteristics of the system through simulation and testing. The study results show that: the cross-coupling effect between the transmitter and the receiver will cause resonance frequency shift, or even lead to the variation of resonance frequency splitting characteristic; when compared with a single-load system, the multi-load system may increase in total transmission power and efficiency; generally, with the introduction of additional receivers, the receiving power and efficiency of the original loads will decrease; along with the increase in circuit spacing and the decrease in cross-coupling, the transmission characteristics will gradually regress to the state of a single-load system. In this article, the calculation model for mutual inductance is correct and the maximum relative error in these calculating examples is 5.28%.

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. [ABSTRACT FROM AUTHOR]

This paper presents a compact model of mutual inductance between two planar inductors, which is essential to design and optimize a wireless power transmission system. The tracks of the planar inductors are modeled as constant current carrying filaments, and the mutual inductance between individual filaments is determined by Neumann's integral. The proposed model is derived by solving Neumann's integral using a series expansion technique. This model can predict the mutual inductance at various axial and lateral displacements. Mutual coupling between planar inductors is computed by a 3-D electromagnetic (EM) solver, and the proposed model shows good agreement with these numerical results. Different types of planar inductors were fabricated on a printed circuit board (PCB) or silicon wafer. Using these inductors, wireless power links were constructed for applications like implantable biomedical devices and contactless battery charging systems. Mutual inductance was measured for each of the cases, and the comparison shows that the proposed model can predict mutual coupling suitably. [ABSTRACT FROM AUTHOR]

Aiming at the problem that how to locate the induction devices' position automatically in the wireless power transmission system, the influence of the transverse displacement of the induction devices on the coupling coefficient between the induction devices is analyzed, and the whole core coil simulation analysis is been done by the large-scale finite element software COMSOL, which have also been verified through experiments. The results show that the coupling coefficient between the induction devices decreases first, then increases, finally decreases with the increase of induction devices' transverse displacement. The theoretical result has positive effect on the efficiency measuring of the whole system, and which is helpful to the research on the automatic location of induction devices. [ABSTRACT FROM AUTHOR]

This article addresses the problem of hard switching caused by the change of equivalent load in a wireless power transfer (WPT) system based on a class E inverter. Based on the load-sensitive characteristics of the class E inverter, the coil structure is improved, and the self/mutual inductance compensation method of the transmitting coil is proposed to realize a wide range of soft switching. On the basis of fully considering the coupling relationship between the source and load coils, a coil structure with multiple coils in series on the primary side is proposed, and the cross-coupling relationship between the coils is analyzed in detail and simplified. The inverter parameters and coupling mechanism were adjusted by means of coil series reverse connection. Combined with the parameter influence law and the load equivalent principle of the class E inverter, the margin of soft switching at the inverter side was increased and the load offset correction was carried out. The soft-switching effect of the equivalent load from 0 to 3.3 times of ideal load was obtained, and the purpose of improving system reliability and efficiency was achieved. Finally, the feasibility and effectiveness of the proposed method were verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

The use of a wireless power transmission system (WPTS) in modern applications, such as consumer electronics, renewable energy sources (RESs) and electric vehicles (EVs), can significantly increase the safety and convenience of the power supply. However, low efficiency is a major hurdle to the use of a WPTS in these applications. In this article, an adaptive virtual impedance controller (AVIC) is presented to enhance the wireless power transfer (WPT) efficiency of a photovoltaic generator (PVG) to the load. In the proposed controller, a unique method is employed to adaptively estimate the coefficient of coupling and resonant frequency of the WPTS coils as a function of the distance between the coils. Moreover, a modified incremental conductance (IC) based maximum power tracking (MIC-MPPT) technique is presented to operate the PVG at MPPT mode. The proposed MIC-MPPT is tested via a hardware prototype and the controller validation is carried out in the MATLAB/SIMULINK environment under various uncertainties, such as intermittent irradiance, variable load, and the distance between transmitter (Tx) and receiver (Rx) coils. Finally, a comparative analysis between the proposed controller and the conventional non-adaptive and adaptive resonant frequency controller is presented which confirms the superiority of the proposed controller. [ABSTRACT FROM AUTHOR]