Optimal Solutions for Underwater Capacitive Power Transfer

Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the available load power and the efficiency of the CPT system as functions of capacitive coupling parameters and derives the required admittance of the load and the source. The experimental results demonstrated that the available power and the efficiency decrease by the increasing of the frequency from 300 kHz to 1 MHz and the separation distance change from 100 to 300 mm. The maximum efficiency solution gives 83% at 300 kHz and a distance of 100 mm, while the maximum power solution gives the maximum normalized power of 0.994 at the same frequency and distance. The CPT system can provide a good solution to charge electric ships and underwater vehicles over a wide separation distance and low-frequency ranges.

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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.

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

Energies ◽

10.3390/en14217253 ◽

2021 ◽

Vol 14 (21) ◽

pp. 7253

Author(s):

Xianyi Duan ◽

Junqing Lan ◽

Yinliang Diao ◽

Jose Gomez-Tames ◽

Hiroshi Hirayama ◽

...

Keyword(s):

Electric Field ◽

Human Body ◽

High Efficiency ◽

Transmission Efficiency ◽

Human Interaction ◽

Whole Body ◽

Maximum Efficiency ◽

Spatial Average ◽

Power Transfer ◽

Resonant Coupling

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

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Gallium Nitride Inverter Design with Compatible Snubber Circuits for Implementing Wireless Charging of Electric Vehicle Batteries

Machines ◽

10.3390/machines8030056 ◽

2020 ◽

Vol 8 (3) ◽

pp. 56 ◽

Cited By ~ 1

Author(s):

Fatemeh Rahmani ◽

Payam Niknejad ◽

Tanushree Agarwal ◽

Mohammadreza Barzegaran

Keyword(s):

Gallium Nitride ◽

Electric Vehicle ◽

Energy Savings ◽

High Efficiency ◽

Harmonic Distortion ◽

Time Frame ◽

Maximum Power ◽

Wireless Charging ◽

Power Transfer ◽

Gate Drivers

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.

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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.

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Capacitive Coupling Wireless Power Transfer with Quasi-LLC Resonant Converter Using Electric Vehicles’ Windows

Electronics ◽

10.3390/electronics9040676 ◽

2020 ◽

Vol 9 (4) ◽

pp. 676 ◽

Cited By ~ 2

Author(s):

KangHyun Yi

Keyword(s):

Electric Vehicles ◽

High Efficiency ◽

High Capacity ◽

Wireless Power Transfer ◽

Capacitive Coupling ◽

Power Transfer ◽

Wireless Power ◽

Very High Frequency ◽

Large Power ◽

Coupling Capacitor

This paper proposes a new capacitive coupling wireless power transfer method for charging electric vehicles. Capacitive coupling wireless power transfer can replace conventional inductive coupling wireless power transfer because it has negligible eddy-current loss, relatively low cost and weight, and good misalignment performance. However, capacitive coupling wireless power transfer has a limitation in charging electric vehicles due to too small coupling capacitance via air with a very high frequency operation. The new capacitive wireless power transfer uses glass as a dielectric layer in a vehicle. The area and dielectric permittivity of a vehicle’s glass is large; hence, a high capacity coupling capacitor can be obtained. In addition, switching losses of a power conversion circuit are reduced by quasi-LLC resonant operation with two transformers. As a result, the proposed system can transfer large power and has high efficiency. A 1.6 kW prototype was designed to verify the operation and features of the proposed system, and it has a high efficiency of 96%.

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