Power Transfer Efficiency Research Articles

IMeP: Impedance Matching Enhanced Power-Delivered-to-Load Optimization for Magnetic MIMO Wireless Power Transfer System

Recently, multiple-input multiple-output (MIMO) technology has been introduced into magnetic resonant coupling (MRC) enabled wireless power transfer (WPT) systems for concurrent charging of multiple devices. However, impedance mismatching phenomena caused by strong TX-RX, TX-TX, or RX-RX coupling greatly affect the power delivered to load (PDL) in practical charging systems. To solve this issue, we propose an effective scheduling algorithm for Impedance Matching–enhanced PDL optimization in MIMO MRC-WPT systems (called IMeP ), which integrates the transmitter scheduling together with the impedance matching techniques, i.e., adjusting TX coils for tuning TX-RX/TX-TX coupling and grouping RXs to separate strongly coupled RX pairs. We formulate this as a joint optimization problem and decouple it into three sub-problems, i.e., current scheduling, coil adjustment, and RX grouping. We then solve them through alternating direction method of multipliers–based, randomized beamforming–based, and graph clique cover–based algorithms, respectively. Extensive experiments are performed on a prototype testbed, and the results demonstrate the effectiveness of our solution. Compared with the state-of-the-art power transfer efficiency maximization solution, the proposed algorithm IMeP achieves a 74.7× performance improvement of PDL on average.

Engineered pseudo and hybrid anapole states in a silicon nanoresonator metasurface

Significant attention has been devoted to realizing non-radiating states (popularly known as anapole states) in several systems due to the strong localization of electromagnetic fields, which can be attained through destructive interference of various dipole moments, yielding fundamental or higher-order anapole states. Recently, it has been shown that the interference of higher-order excitation also permits light manipulation at the nanoscale and provides additional benefits such as efficient power transfer and enhancement in nonlinearities. In this work, we report discrete electric anapole (pseudo and hybrid) by careful design of an all-dielectric metasurface consisting of a silicon nanodisk such that a higher-order toroidal electric dipole (TD) and quadrupole interfere destructively, producing a hybrid anapole at 815 nm, whereas the pseudo anapole is generated when TD and second-order TD minima occur at the same wavelength of 522 nm. The phase plots confirm the findings of these radiationless states. Such dual and distinct non-radiating current configurations may find applications in spectroscopy, sensing, switching, optical nonlinearity, and optomechanics.

The Effect of Boost Coil and Alignment of Transmitting and Receiving Coils on Transmission Efficiency in EV Wireless Power Transfer Systems

As the electric vehicle (EV) market continues to grow, wireless charging technologies are constantly evolving. Considering the limitations of traditional charging methods, the adoption of wireless charging technology is an essential strategy, and the distribution of wireless charging systems is expected to accelerate in the global market with initiatives such as international standards for wireless charging systems. With regard to this technological trend, this study experimentally analyzed the effects of the boost coil and the alignment of the transmitting and receiving coils on the transmission efficiency in wireless power transfer systems. The boost coil amplifies the magnetic field using a high-frequency signal and transfers the field to the receiving coil. Moreover, simulations were conducted based on the theory that using the boost coil could increase the efficiency of wireless power transfer, and the impact of the alignment between the transmitting and receiving coils on the transmission efficiency was also analyzed.

Design and miniaturization of a microsystem to power biomedical implants using grey wolf optimizer-based cuckoo search algorithm

<p>One of the greatest techniques, inductive coupling is frequently utilized in the biomedical sector for wireless energy transfer to implants. The aim of this article is to develop and analyze the effect of inductor geometrical characteristics, distance between transmitter (TX) and receiver (RX) and also the operating frequency on the wireless power transfer system, using grey wolf optimizer-based cuckoo search (GWO-CS) algorithm. Power transfer efficiency (PTE), power provided to load, and other critical components must all be improved or maximized and miniaturaze the microsystem proposed. The invention, design, and optimization of coils square spirals in a wireless energy transfer system using a resonant inductive link are the emphasis of this paper. The GWO-CS approach is evaluated to existing methods, demonstrated by simulations and to demonstrate the effectiveness of the suggested strategy.</p>

Robust Class E2 Wireless Power Transfer System Based on Parity–Time Symmetry

Thanks to the superiority of zero-voltage switching (ZVS), the Class E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> topology has become a promising candidate in wireless power transfer (WPT) at medium and small power levels. However, in practical applications, it is a challenging and significant issue to maintain robust WPT under varying transfer distances, especially for the highly sensitive Class E power amplifier (PA). To solve this issue, the parity–time (PT) theory is initially developed into the Class E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> WPT system. A general design procedure for the PT-symmetry-based Class E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> WPT system is proposed, including the parameters of the Class E PA, resonant tank, and Class E rectifier. The power losses and efficiencies of the above-mentioned components are analytically derived as well. The ZVS operation is quantitatively described for the PT-symmetry-based Class E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> WPT system, demonstrating that the maximum phase variation with coupling coefficient is rather small and independent of the natural resonant frequency, thereby achieving robust and highly efficient power transfer. Finally, the prototype with current feedback control to guarantee the PT mechanism and ZVS is built. The experimental results illustrate that under various coupling coefficients, robust and efficient power transfer is realized by a 165-W prototype with about 92.6% efficiency.

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

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

Experimental review of an improving system on wireless power transfer via auto tuning of frequency

&lt;span lang="EN-US"&gt;Wireless power transfer for electric vehicles is focused because these vehicles cannot run long distance without frequently charging. If these vehicles are charged from outside wirelessly, for example an alternating current (AC) power supply is embed under road, the problem is going to be solved. However, efficiency of wireless power transfer depends on various factors, therefore many contrivances should be considered to realize optimal transfer. In this paper, we focused on frequency of inverter, and created auto tuning system of it in response to the distance of inductors. On this system, frequency was modified automatically by a microcontroller and sensor at the same time position of a load changed. Finally, we confirmed that voltage of light emitting diode (LED) was improved by utilizing our system compared with non-tuning frequency.&lt;/span&gt;

Design of anti-misalignment PCB coil for wireless power transfer

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

Design of a wireless charging system in DC microgrids with accurate output regulation and optimal efficiency

This paper presents a general circuit and control design method for wireless power transfer (WPT) systems in DC microgrids to achieve optimal power transfer efficiency, while maintain accurate output voltage regulation. An auxiliary inductor is added at the transmitter resonator to form a current sink to ensure zero voltage switching (ZVS) of the primary-side full-bridge inverter with even extreme-light load conditions. Besides, an adaptive proportional-integral (PI) controller is adopted to track the output voltage references by regulating the phase shift angle of the phase shift control for the full-bridge inverter. The coefficients of the adaptive proportional-integral controller are determined by the inductor of the auxiliary inductor. Both simulation and experimental results have validated the effectiveness of the proposed circuit and control design in achieving optimal efficiency and output voltage regulation for wireless power transfer systems in DC microgrids with source and load variations.

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

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

Enhancing Power Transmission Stability of AUV’s Wireless Power Transfer System with Compact Planar Magnetic Coupler

In this paper, a wireless power transfer (WPT) system with a compact planar magnetic coupler for an autonomous underwater vehicle (AUV) is proposed. A passive induction (PI) coil is integrated into the circular transmitter (Tx) coil to build a uniform magnetic field (UMF), which can guarantee the stable output of the WPT system under uncertain radial and axial misalignments for AUV. Based on normalized magnetic induction intensity distribution analysis, a UMF constructing method with a PI coil is given, aiming to eliminate the fluctuation of magnetic field intensity, and the PI coil design principles and flow chart are obtained. The theoretical analysis shows the proposed integrated coil can effectively enhance the radial misalignment tolerance compared with a conventional circular spiral coil. The zero-phase angle (ZPA) input condition can be achieved by adjusting the series capacitor connected with the Tx coil in S-S compensation topology. Experimental results show that the proposed magnetic coupler containing an integrated coil significantly improves the stability of output power and power transfer efficiency within the possible radial and axial misalignments compared with a conventional coupler. It was demonstrated that the output power changes less than 5.5% and the power transfer efficiency maintains at approximately 84.5% in arbitrary radial positions within the possible working region with an axial transfer distance of 50 mm in saltwater.

Comparison of One-Way and Two-Way Coupled Simulation for Thermal Investigation of Vehicular Wireless Power Transfer Modules

The thermal management of the vehicular module is key to the design of efficient wireless power transfer systems. In order to predict the thermal behavior by simulation, the mutual interaction of the electromagnetic and thermal fields must be taken into account. This multiphysical coupling leads to extensive computational effort. One approach to reduce the complexity by limiting the interdependencies between the domains is one-way coupling. This paper examined the applicability of one-way and two-way coupling for the prediction of the thermal management of an exemplary vehicular wireless power transfer module. The electromagnetic–thermal behavior of the proposed module was systematically studied by experiments and simulations on the component and module level. The performed studies showed that both simulation approaches accurately capture the transient thermal behavior of the coil and ferrites on the component level, whereas the one-way coupled simulation underpredicts the power losses caused by shielding by more than 20%, leading to a steady-state temperature difference of 15 K. As a result, on the module level, the two-way coupled simulation model provides a more accurate representation of the electromagnetic–thermal behavior of the proposed car pad module. Therefore, the authors recommend using a two-way coupling approach for the thermal dimensioning of wireless power transfer modules for electric vehicles.

Efficient Distributed Wireless Power Transfer System for Multiple Wearable Sensors through Textile Coil Array

When it is necessary to detect various physiological signals of the human body, clothing embroidered with near-field effect patterns can be used as a long-term power supply medium to supply power to long-distance transmitters and receivers to form a wireless power supply system. The proposed system uses an optimized parallel circuit to achieve a power transfer efficiency of more than five times higher than that of the existing series circuit. The power transfer efficiency of simultaneously supplying energy to multiple sensors is increased higher than five times and even more when only one sensor is coupled. When powering eight sensors at the same time, the power transmission efficiency can reach 25.1%. Even when eight sensors powered by the coupled textile coils are reduced to one, the power transfer efficiency of the whole system can reach 13.21%. Additionally, the proposed system is also applicable when the number of sensors ranges from 2 to 12.

An Enhancement of Power Quality With Efficient Active Power Transfer Capability in a PV–BSS-Fed UAPF for Microgrid Realization

This article investigates the enhancement of power quality with an efficient active power transfer capability in a universal active power filter (UAPF) integrated with a photovoltaic (PV) and battery storage system (BSS). The UAPF operates as a bidirectional interface between the PV–BSS and point of interconnection for microgrid realization. A new control strategy is proposed to extract fast and accurate voltage and current reference signals to operate the system in a desired manner. Here, the extraction of load voltages and calculation of load and reference powers are used to generate the reference signals, thereby comparing with actual signals with hysteresis controller to produce switching pulses of converters. As a result, the shunt and series converters form a robust system by acting as a current-controlled voltage source and voltage-controlled current source, respectively. It eliminates the need for adaptive filters and low-pass filters to extract the fundamental component of the load current. Furthermore, it increases the conversion efficiency of converters and improves the static and dynamic performance of the system. The proposed system is developed with a 1-kVA prototype laboratory setup using a field-programmable gate array controller and extensively tested with various test conditions such as grid voltage fluctuations, nonlinear and imbalanced load, and change in irradiance.

Transmitter Coils Selection Method for Wireless Power Transfer System With Multiple Transmitter Coils and Single Receiver Coil

This article proposes transmitter coils selection method for maximum power transfer efficiency in the wireless power transfer (WPT) system with multiple transmitter coils and a single receiver coil (MTSR). The proposed method is divided into two main steps. First, transmitter coil selection criteria that can achieve maximum efficiency are derived by analyzing the relative magnitude of the coupling coefficient between each coil. Next, a method for calculating the relative coupling coefficients used for the criteria only with the input current value is presented. This method differs from previous studies in that it can be applied when some transmission coils are deactivated. Therefore, it is possible to select the optimal transmitter coil combination in consideration of the characteristics of the receiver coil using the proposed method without information on the receiver coil. By the proposed transmitter coils selection criteria, the power transfer efficiency has an average of 96.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.5% when the output power is 300 W, even with the position change of the receiver coil. In addition, it is confirmed that the proposed coupling coefficient extraction method has a slight error of 2.5% compared to the measured value by a vector network analyzer.

Wirelessly Powered 3-D Printed Headstage Based Neural Stimulation System for Optogenetic Neuromodulation Application

This work presents a miniaturized wireless power transfer (WPT) system integrated with a neuromodulation headstage for duty-cycled optical stimulation of freely moving rodents. The proposed WPT system is built using the commercially available off-the-shelf components (COTS) for the optogenetic neuromodulation system consisting of a bridge rectifier, a DC-DC converter, an oscillator circuit, an LED driver, and a μLED. The total power consumption of the stimulation system is 14 mW which is provided using the WPT method. The WPT system includes a novel transmitter (TX) coil implemented on a printed circuit board (PCB), and a solenoid receiver (RX) coil wrapped around a customized 3-D printed headstage. The proposed TX coil is designed in such a way that the magnetic field all across the TX coil is sufficient to provide the required power to the optical stimulation system that is worn as a headstage by the freely moving rat. The headstage device's dimension is 18.75 mm × 21.95 mm, weighing 4.75 g. The ratio of the weight of the headstage and rat is 4.75:300. The proposed system is able to achieve a maximum overall efficiency of ∼63% at 5 cm separation between the TX and RX coils, where the maximum power transfer efficiency (PTE) of the WPT system is ∼88% and the power conversion efficiency (PCE) of the rectifier is 71.6%. The proposed system with reconfigurable stimulation frequency is suitable for exciting different brain areas for long-term health monitoring.

Wireless Information and Power Transfer: A Bottom-Up Multi-Layer Design Framework

The efficiency of wireless information and power transfer (WIPT) systems requires an essential reevaluation and rethinking of the entire transceiver chain, which is characterized by a bottom-up multi-layer design approach. In this article, we introduce and describe the key design layers: “Mathematical modeling,” associated with the investigation of mathematical models for the wireless power transfer process, “Information-theoretic limits,” which refers to the fundamental limits of the WIPT channel, “Link design,” corresponding to signal processing techniques that make WIPT feasible, “System-level perspective,” which studies the developed WIPT techniques from a macroscopic system-level point-of-view, and “Experimental studies,” that refers to real-world implementation of WIPT systems. These layers are well-connected and their interplay is imperative for the effective design of WIPT systems. Specific case studies are discussed, which demonstrates the interdisciplinary nature of the aforementioned multi-layer design framework.

A Compact 3-D Multisector Orientation Insensitive Wireless Power Transfer System

The power conversion efficiency (PCE) in wireless power transfer (WPT) degrades due to angular misalignment between the transmitter (Tx) and the rectenna (Rx) along the azimuth plane. Therefore, a compact 3-D multisector orientation insensitive WPT system is proposed to address this problem. The optimal number of sectors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> ) is determined analytically using patch antenna design equations to mitigate the effects of angular misalignment. In addition, conditions on the receiver antenna radiation pattern are investigated to enhance the performance of the WPT system. Furthermore, the observed conditions are utilized for designing a high gain WPT system at 5.8 GHz with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> sectors. The proposed WPT system provides uniform power harvesting capability in the azimuth plane and 51.2% higher power harvesting capacity than the patch antenna WPT system.

Constant Current Output Control Based on Cross-Coupling Compensation in Multireceiver WPT System Using Active Rectifier

Multireceiver wireless power transfer (multi-Rx WPT) technology is a promising method for charging multiple electronic devices simultaneously. However, the cross-coupling effect between Rxs not only leads to the correlation of output characteristics of each load, but also reduces the power transfer capability and efficiency of WPT systems. This article proposes a method to achieve constant current (CC) output with cross-coupling compensation in multi-Rx WPT systems, thus avoiding tedious parameter measurement and communication between Rxs. The cross-coupling can be compensated adaptively, and the output can be controlled independently and not affected by the fluctuation of system parameters. A closed-loop control strategy based on the phase shift control method of an active rectifier is carried out, which can continuously regulate the load current while maintaining cross-coupling compensation. An optimized phase synchronization auxiliary circuit for multi-Rx WPT systems is presented, which shares the power transfer coils and is not affected by the cross-coupling effect. A 70-W two-load experimental prototype is built to verify the theoretical analysis, and the maximum efficiency reaches 88.1%.

A Simultaneous Power and Data Transmission Technology Based on Coil Multiplexing in Domino-Resonator WPT Systems

To achieve parallel power and data transmission in domino-resonator wireless power transfer (WPT) systems, a novel simultaneous power, and data transfer (SPDT) technology based on coil multiplexing is proposed in this letter. Benefiting from the magnetic field characteristics of the bipolar coil structure, the power and data can be injected into multiplexed coils with different flow directions, leading to opposite induced voltage polarities in each coupling coil. Subsequently, a corresponding resonator circuit is developed to form independent power and data resonance loops. In addition, an injected data transmission scheme is developed for domino-resonator WPT systems. Compared with traditional SPDT methods, additional wave trappers and coupling structures are avoided by this proposed technology, and the interference between power and data transfer is significantly eliminated. A 23.6 W laboratory prototype with five domino resonators is built to validate the feasibility of this proposed technology. The experimental results show that the power transfer efficiency reaches 70% at 50 kb/s data transfer rate.