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The conjugate image theory provides a methodology to determine the optimal circuit for a given wireless link. In this work, we compare the application of this theory between inductive and capacitive wireless power transfer, extended to non-symmetric configurations. We apply the conjugate image theory for mixed coupling and demonstrate that the results for inductive and capacitive coupling can be deduced...
Wireless charging to mobile devices with metal cases has been plagued with poor efficiency (∼ 40%) and low power capability with traditional magnetic resonance (MR) technology. This paper will present a controlled resonance technology to use the metal case to enhance the coupling between the RX and TX windings, and to count for the inductance and coupling changes by modulating the resonance in RX...
This paper presents the design of a nonlinear wireless power transfer receiver. In the proposed receiver, a switch is introduced to control the quality factor of the impedance at the power receiving interface. The effective impedance can then be adjusted by jointly varying the switching timing and DC loading to deliver the required power while improving the conversion efficiency at the same time....
In this paper, we presented a novel pixelated structure for electrode plates and initiate an innovative design of capacitive couplers for wireless charging. This research aims to improve the poor performance of traditional electrode plates in the literature when the plates are rotated 90 degrees. This research utilized optimization technique to design the distribution of the positive (and negative)...
Wireless charging is a key technology for electric vehicles. Owing to strict area limits within a vehicle, low heat generation is important for realizing a thermally plausible coil. We therefore propose a parallel-connected bilayer coil to reduce heat generation. The effectiveness of the proposed coil was demonstrated by experimental continuous operation for more than 8 hours.
Wireless power transfer technology is widely used in implantable medical devices, electric vehicles and other field, but the problem of magnetic coupling resonance technology is that transmission efficiency is limited by transmission distance, which restricts the popularization and application of this technology. Aiming at the problem existing in the magnetic coupling resonance wireless energy transfer...
Wireless power transfer (WPT) systems are suitable for applications such as integration of Electric Vehicles (EV) with the utility grids. However, physical misalignments between the magnetic couplers are unavoidable and can introduce variations in self-, leakage- and mutual-inductances, which invariably detune the compensation networks employed by the transmitter and receiver of a wireless power transfer...
This paper focuses on the design of the magnetic coupler in the wireless charging system for electric vehicles. A solenoid type magnetic coupler is used for the better ability of magnetic coupling than the plate type magnetic coupler under the condition of mid-range wireless power transfer. The factors of coupling coefficient are analyzed in two kinds of ways, magnetic circuit theory and mutual inductance...
In previous work, we have proposed a cone-shaped shifting medium shell that can shift the enclosed region forward to a given position. The shifting shell is a metamaterial device proposed according to transformation optics. It can be applied in a wireless power transfer system by covering the coils to move them closer in magnetic field and enhance the mutual inductance between the coils. However,...
Wireless power transfer (WPT) technology has been considered as a promising power supply method for modern trams with electric double layer capacitors (EDLC). However, in real case, factors such as parking misalignments, load variations and coils inclination would result in a deviation of coils mutual inductance, which may adversely impact on system transmitting efficiency. Therefore, an approximately...
While many companies have provided wireless charging technologies to users recently, a charging distance is very short due to a drastic drop of magnetic fields. A lot of researches have been carried out steadily to increase the wireless charging distance. Magnetic beamforming is one of promising technologies to achieve this vision. However, conventional magnetic beamforming schemes require complex...
This paper presents the study and analysis of the LCC-C Wireless Power Transfer (WPT). The study aims to understand the characteristic and behavior of the proposed resonant compensation under various variables such as the load, frequency, and coupling coefficient. This study can be used as a consideration for the selection of the compensation network for a specific purpose of WPT. To verify the theoretical...
This paper presents a novel power flow controller for wireless power transfer systems. The proposed method regulates the output voltage to a constant level by discharging the output filter capacitor when the voltage across the load is higher than a desired level. Unlike the traditional DC/DC topologies, the proposed controller doesn't require a bulky DC inductor which results in a compact system....
This paper starts with the basics of contactless energy transfer systems for charging of electric vehicles and discusses reactive power compensation networks for single-phase and three-phase systems. After presenting a small scale model of a three-phase prototype with distributed windings, results from measurements and simulations will be described for further investigations.
Misalignment between the transmitter coil and the receiver coil would in some cases lead to significant power and efficiency decline in a wireless power transfer system. This paper implements the LCC compensation topology to improve the horizontal misalignment tolerance under a certain load condition. The reason for the efficiency decline under misalignment is firstly analyzed based on the equivalent...
Metal obstacles will be heated due to the eddying effect, if its location is between two coils belonging with the wireless power transfer system applying in the electric vehicle, and safety problems may occur easily. If metal obstacles is large, there will be efficiency decline, frequency detuning and other issues. So it is very important to detect the metal obstacles. In this paper, the theory about...
This paper introduces a new Wireless Power Transfer (WPT) system based on single pair of electric field coupling without a current return path. Such a single-contact Capacitive Power Transfer (CPT) system helps to enhance the coupling tolerance between the coupled plates. A class E converter is designed to drive an LCLC resonant circuit to boost the voltage at the primary side of the coupling plate,...
The wireless power transfer efficiency of tunable load impedance is addressed in this paper. The load impedance is a key factor to dominant the whole system efficiency. This paper addresses individual efficiency of the transmitter, receiver, resonant coils by the variation of load impedance. Afterward, the integration of transmitter, receiver, resonant coils to achieve a power trasfer system. Measurement...
Proper selection of magnetic material is very important to maximize the power transfer efficiency (PTE) in case of the conductor in the receiving coil. The effects of the relative permeability and loss tangent of the magnetic material are investigated. A relatively low complex permeability ensures a high efficiency in wireless power transfer system (WPT) at 6.78 MHz. To maximize the PTE, the properties...
For Wireless power transfer with multi-pickup, cross coupling among multi receivers is an inevitable problem which will greatly influence the system performance. Due to its complexity, there is not one identification method yet. This paper proposes a cross coupling-coefficient estimation method, only the primary current is need to be detected. By decoupled one secondary pickup circuit, the mutual...
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