Design of Asymmetrical Relay Resonators for Maximum Efficiency of Wireless Power Transfer

This paper presents a new design method of asymmetrical relay resonators for maximum wireless power transfer. A new design method for relay resonators is demanded because maximum power transfer efficiency (PTE) is not obtained at the resonant frequency of unit resonator. The maximum PTE for relay resonators is obtained at the different resonances of unit resonator. The optimum design of asymmetrical relay is conducted by both the optimum placement and the optimum capacitance of resonators. The optimum placement is found by scanning the positions of the relays and optimum capacitance can be found by using genetic algorithm (GA). The PTEs are enhanced when capacitance is optimally designed by GA according to the position of relays, respectively, and then maximum efficiency is obtained at the optimum placement of relays. The capacitance of the second resonator tonth resonator and the load resistance should be determined for maximum efficiency while the capacitance of the first resonator and the source resistance are obtained for the impedance matching. The simulated and measured results are in good agreement.

Download Full-text

Maximizing Transfer Efficiency with an Adaptive Wireless Power Transfer System for Variable Load Applications

Energies ◽

10.3390/en14051417 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1417

Author(s):

Jung-Hoon Cho ◽

Byoung-Hee Lee ◽

Young-Joon Kim

Keyword(s):

Loading Condition ◽

Wireless Power Transfer ◽

Input Voltage ◽

Transfer Efficiency ◽

Maximum Efficiency ◽

Variable Load ◽

Power Transfer ◽

Wireless Power ◽

Variable Loading ◽

Power Transfer Efficiency

Electronic devices usually operate in a variable loading condition and the power transfer efficiency of the accompanying wireless power transfer (WPT) method should be optimizable to a variable load. In this paper, a reconfigurable WPT technique is introduced to maximize power transfer efficiency in a weakly coupled, variable load wireless power transfer application. A series-series two-coil wireless power network with resonators at a frequency of 150 kHz is presented and, under a variable loading condition, a shunt capacitor element is added to compensate for a maximum efficiency state. The series capacitance element of the secondary resonator is tuned to form a resonance at 150 kHz for maximum power transfer. All the capacitive elements for the secondary resonators are equipped with reconfigurability. Regardless of the load resistance, this proposed approach is able to achieve maximum efficiency with constant power delivery and the power present at the load is only dependent on the input voltage at a fixed operating frequency. A comprehensive circuit model, calculation and experiment is presented to show that optimized power transfer efficiency can be met. A 50 W WPT demonstration is established to verify the effectiveness of this proposed approach.

Download Full-text

Comparison of the Efficiency and Load Power in Periodic Wireless Power Transfer Systems with Circular and Square Planar Coils

Energies ◽

10.3390/en14164975 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4975

Author(s):

Jacek Maciej Stankiewicz ◽

Agnieszka Choroszucho

Keyword(s):

Power Transmission ◽

Wireless Power Transfer ◽

Load Resistance ◽

Numerical Approach ◽

Maximum Efficiency ◽

Power Transfer ◽

Wireless Power ◽

Load Power ◽

Coil Geometry ◽

Square Planar

In the article, a wireless charging system with the use of periodically arranged planar coils is presented. The efficiency of two wireless power transfer (WPT) systems with different types of inductors, i.e., circular and square planar coils is compared, and two models are proposed: analytical and numerical. With the appropriate selection of a load resistance, it is possible to obtain either the maximum efficiency or the maximum power of a receiver. Therefore, the system is analyzed at two optimum modes of operation: with the maximum possible efficiency and with the highest power transmitted to the load. The analysis of many variants of the proposed wireless power transfer solution was performed. The aim was to check the influence of the geometry of the coils and their type (circular or square) on the efficiency of the system. Changes in the number of turns, the distance between the coils (transmit and receive) as well as frequency are also taken into account. The results obtained from analytical and numerical analysis were consistent; thus, the correctness of the adopted circuit and numerical model (with periodic boundary conditions) was confirmed. The proposed circuit model and the presented numerical approach allow for a quick estimate of the electrical parameters of the wireless power transmission system. The proposed system can be used to charge many receivers, e.g., electrical cars on a parking or several electronic devices. Based on the results, it was found that the square coils provide lower load power and efficiency than compared to circular coils in the entire frequency range and regardless of the analyzed geometry variants. The results and discussion of the multivariate analysis allow for a better understanding of the influence of the coil geometry on the charging effectiveness. They can also be valuable knowledge when designing this type of system.

Download Full-text

Study on impedance matching and maximum wireless power transfer efficiency of circuits with resonant coupling based on simplified S-matrix

IEICE Electronics Express ◽

10.1587/elex.16.20190156 ◽

2019 ◽

Vol 16 (11) ◽

pp. 20190156-20190156 ◽

Cited By ~ 1

Author(s):

Hiroya Andoh ◽

Keita Tsuzuki ◽

Dai Oikawa ◽

Toko Sugiura ◽

Takehiko Tsukamoto ◽

...

Keyword(s):

Impedance Matching ◽

Wireless Power Transfer ◽

Transfer Efficiency ◽

Power Transfer ◽

Wireless Power ◽

Resonant Coupling ◽

Power Transfer Efficiency

Download Full-text

Coupling Tuning Based Impedance Matching for Maximum Wireless Power Transfer Efficiency

Journal of Computer Science & Computational Mathematics ◽

10.20967/jcscm.2016.04.002 ◽

2016 ◽

pp. 91-96 ◽

Cited By ~ 2

Author(s):

Surajit Das Barman ◽

Ahmed Wasif Reza ◽

Narendra Kumar

Keyword(s):

Impedance Matching ◽

Wireless Power Transfer ◽

Transfer Efficiency ◽

Power Transfer ◽

Wireless Power ◽

Power Transfer Efficiency

Download Full-text

Highly Efficient Target Power Control for Two-Receiver Wireless Power Transfer Systems

Energies ◽

10.3390/en11102726 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2726 ◽

Cited By ~ 6

Author(s):

Weikun Cai ◽

Dianguang Ma ◽

Houjun Tang ◽

Xiaoyang Lai ◽

Xin Liu ◽

...

Keyword(s):

Output Power ◽

High Efficiency ◽

Impedance Matching ◽

Wireless Power Transfer ◽

Mutual Inductance ◽

Maximum Efficiency ◽

Power Transfer ◽

Wireless Power ◽

Target Power ◽

Target Output

Multiple-receiver wireless power transfer (MRWPT) systems have revolutionary potential for use in applications that require transmitting power to multiple devices simultaneously. In most MRWPT systems, impedance matching is adopted to provide maximum efficiency. However, for most MRWPT systems, achieving target power levels and maximal efficiency is difficult because the target output power and maximum efficiency conditions are mostly not satisfied. This study establishes a target power control (TPC) strategy to balance providing target transfer powers and operating under high efficiency. This study is divided into the following points: First, this study derives the optimal mutual inductance to verify that it’s difficult for two-receiver wireless power transfer (WPT) system to achieve both maximum efficiency and power distribution simultaneously; Second, this study illustrates that for impedance matching method the mutual inductances play a more important role than equivalent impedances in increasing the system efficiency, and hence system should give priority in improving the mutual inductance as large as possible; Third, this study proposes a simplified system model which helps to derive the analytic solutions of equivalent impedances; Fourth, this study developed a 100-kHz two-receiver WPT system and establishes a TPC strategy for enabling the system to achieve target output power levels with high efficiency; At last, the proposed system is proved to achieve an efficiency level of more than 90 % and satisfies the target output power levels requirements.

Download Full-text

Application of Shielding Coils in Underwater Wireless Power Transfer Systems

Journal of Marine Science and Engineering ◽

10.3390/jmse7080267 ◽

2019 ◽

Vol 7 (8) ◽

pp. 267

Author(s):

Wang ◽

Song ◽

Mao

Keyword(s):

Autonomous Underwater Vehicles ◽

Wireless Power Transfer ◽

Underwater Vehicles ◽

Transfer Efficiency ◽

Maximum Efficiency ◽

Power Transfer ◽

Wireless Power ◽

Element Analysis ◽

The Finite Element Analysis ◽

Power Transfer Efficiency

Underwater wireless power transfer (WPT) technology can enhance the endurance of the autonomous underwater vehicles (AUV). WPT that based on electromagnetic theory will generate eddy current loss (ECL) in seawater. In this paper, we make use of shielding coils to weaken the electromagnetic field (EMF) in seawater, which can reduce ECL and improve the transfer efficiency. Simplified circuit models were proposed to provide an intuitive and comprehensive analysis of the transfer efficiency and the finite element analysis (FEA) was used to simulate the distribution of EMF. We learn that the system with shielding coils performs better when the operating frequency is relatively high by comparing the power transfer efficiency of the underwater WPT systems with and without the shielding, and its maximum efficiency is higher than the system without shielding. The effect of the shielding coils has the similar influence when compared with the metallic plate. While considering the efficiency and weight of coils, the results show that the shielding coils can be used in the underwater WPT system to improve the power transfer efficiency.

Download Full-text

Maximum efficiency solution for capacitive wireless power transfer with N receivers

Wireless Power Transfer ◽

10.1017/wpt.2020.9 ◽

2020 ◽

Vol 7 (1) ◽

pp. 65-75 ◽

Cited By ~ 1

Author(s):

Ben Minnaert ◽

Mauro Mongiardo ◽

Alessandra Costanzo ◽

Franco Mastri

Keyword(s):

Impedance Matching ◽

Cross Coupling ◽

Wireless Power Transfer ◽

Maximum Efficiency ◽

System Efficiency ◽

Single Variable ◽

Power Transfer ◽

Wireless Power ◽

Multiple Devices ◽

Single Receiver

AbstractTypical wireless power transfer (WPT) systems on the market charge only a single receiver at a time. However, it can be expected that the need will arise to charge multiple devices at once by a single transmitter. Unfortunately, adding extra receivers influences the system efficiency. By impedance matching, the loads of the system can be adjusted to maximize the efficiency, regardless of the number of receivers. In this work, we present the analytical solution for achieving maximum system efficiency with any number of receivers for capacitive WPT. Among others, we determine the optimal loads and the maximum system efficiency. We express the efficiency as a function of a single variable, the system kQ-product and demonstrate that load capacitors can be inserted to compensate for any cross-coupling between the receivers.

Download Full-text

A General Method to Parameter Optimization for Highly Efficient Wireless Power Transfer

International Journal of Electrical and Computer Engineering (IJECE) ◽

10.11591/ijece.v6i6.10508 ◽

2016 ◽

Vol 6 (6) ◽

pp. 3217

Author(s):

Kazuya Yamaguchi ◽

Takuya Hirata ◽

Ichijo Hodaka

Keyword(s):

Impedance Matching ◽

Mathematical Expression ◽

Wireless Power Transfer ◽

Load Resistance ◽

Power Transfer ◽

Wireless Power ◽

Highly Efficient ◽

Working Frequency ◽

Matched Impedance ◽

General Method

<pre>This paper proposes a new and general method to optimize a working frequency and a load resistance in order to realize highly efficient wireless power transfer. It should be noticed that neither resonant frequency nor matched impedance maximizes efficiency of wireless power transfer circuit, in general. This paper establishes a mathematical model of a commonly used wireless power transfer circuit, and derives a mathematical expression of circuit efficiency which involves a working frequency, a load resistance and the other parameters as symbols. This enables us to find the optimal working frequency and load resistance. The result of this paper is compared with results by a method based on resonance and impedance matching, and then clarified by a numerical example.</pre>

Download Full-text

A High-Efficiency Self-Synchronous RF–DC Rectifier Based on Time-Reversal Duality for Wireless Power Transfer Applications

Electronics ◽

10.3390/electronics11010090 ◽

2021 ◽

Vol 11 (1) ◽

pp. 90

Author(s):

Ying Wang ◽

Gao Wei ◽

Shiwei Dong ◽

Yazhou Dong ◽

Xumin Yu ◽

...

Keyword(s):

Time Reversal ◽

High Efficiency ◽

Design Method ◽

Wireless Power Transfer ◽

Operating Mode ◽

Load Resistance ◽

Input Power ◽

Adjustment Process ◽

Power Transfer ◽

Wireless Power

An RF–DC rectifier is an important part in a wireless power transfer system. Diode-based rectifiers are widely used in low-power harvesting scenarios, and for high power, a transistor based on the time-reversal duality was proposed. This paper presents a high-efficiency self-synchronous RF–DC rectifier based on a waveform-guided design method and an improved rectification model of a commercial GaN device. The main contributions of this paper are that (1) an improved transistor model with correct reverse bias is built for accurate rectifier simulation, and (2) a new design method of self-synchronous RF–DC rectifier is proposed: as soon as the operating mode of the rectifier, input power, and DC load are set, matching and coupling network can be calculated directly based on waveform-guided method, thus design and adjustment process of a conventional power amplifier (PA) due to the duality between a PA and a rectifier would no longer be required. A 5.8 GHz self-synchronous RF–DC rectifier is designed for validation, and the optimum RF–DC conversion efficiency is 68% with 12 W input power as well as 19.9 V output DC potential with 50 Ω load resistance. The proposed rectifier is suitable for high input power rectification applications of wireless power transfer.

Download Full-text