Capacitive Wireless Power Transfer Research Articles

Rotating wireless power transfer: A new concept for wireless charging systems

Fast and safe charging are current concerns in relation to wireless charging of autonomous guided vehicles (AGVs). Wireless Power Transfer (WPT) is a capable solution and a replacement for conventional contact-based methods. However, resonant inductive and capacitive WPT topologies demand more power as the gap between transmitter and receiver pads increases. These structures, initially developed for electric vehicle applications, do not adequately optimize power transfer and power quality for the smaller surface areas of AGVs. In this paper, a novel topology for wireless charging concept is described and validated. This methodology has been named rotating WPT, with a primary side spinning neodymium magnet disc. The receiver pad is composed of a circular coil with ferrite U-cores. Calculations of the induced voltage over the rotating magnetic field resulted in 1.95 V at an operating frequency of 2.7 kHz. FEM simulation results show approximately 3 V, while laboratory experiments outputted 33 mV at 3.8 kHz. A sinusoidal waveform was observed from prototype, and power was successfully transferred to the receiver end, validating this proposed topology. This novel WPT system has no inverter, rectifier, nor compensation, decreasing reactive power, assembly costs and complexity while transferring power and enhancing power quality.© 2017 Elsevier Inc. All rights reserved.

Capacitive Wireless Power Transfer System with a 3D-Functional Coupler for Maintenance-Free Industrial Robots

Capacitive Wireless Power Transfer System with a 3D-Functional Coupler for Maintenance-Free Industrial Robots

Capacitive Wireless Power Transfer System with Misalignment Tolerance in Flowing Freshwater Environments

Capacitive Wireless Power Transfer System with Misalignment Tolerance in Flowing Freshwater Environments

Modeling, simulation and experimental validation of solid media in capacitive wireless power transfer

Capacitive wireless power transfer (CPT) employs an electric field to transmit energy through a medium. Air is the most often used and a well-understood medium. However, CPT can also bridge other solid media and even benefit from them as the dielectric properties of the medium govern the strength of the capacitive coupling. The parasitic elements of the coupling are influenced by the medium, in particular the leakage resistance. In this work, an analytical model is proposed that quantifies the leakage resistance losses in CPT systems for media. The model is validated by both finite element simulations and experiments on three different media: air, plexiglass and polytetrafluorideethylene (PTFE). As a result, at 1 MHz, the leakage resistance of plexiglass is 6 times higher than that of air while that of PTFE is 1.7 times smaller. This proves that a material with a large dipole moment generates larger losses in the medium which negatively affect system efficiency.

Coupling-Independent Capacitive Wireless Power Transfer With One Transmitter and Multiple Receivers Using Frequency Bifurcation

Coupling-Independent Capacitive Wireless Power Transfer With One Transmitter and Multiple Receivers Using Frequency Bifurcation

Double-sided LC-compensated capacitive wireless power transfer system with admittance-based matching networks

Double-sided LC-compensated capacitive wireless power transfer system with admittance-based matching networks

Wireless power transfer technologies for electric vehicles: Principles, challenges and opportunities

Wireless power transfer (WPT) technology is a promising solution for charging electric vehicles, which have many advantages such as zero emissions, low noise, and convenience. This paper reviews the current state-of-the-art of WPT technology for electric vehicles, focusing on the classification, principle, advantages, and disadvantages of different WPT methods, such as capacitive WPT, inductive WPT, microwave WPT, and laser WPT. The paper also discusses the future trends and challenges of WPT technology, such as coil design, international standards, safety issues, multiple charging modes, and compensation networks. The paper aims to provide a comprehensive overview of WPT technology for electric vehicles and to inspire further research and development in this field.

Design of a Capacitive Wireless Power Transfer System With a Vertical Four-Plate Coupler for Minimum Stray Electric Field

Design of a Capacitive Wireless Power Transfer System With a Vertical Four-Plate Coupler for Minimum Stray Electric Field

Erratum to "Single Wire Capacitive Wireless Power Transfer System for Wearable Biomedical Sensors based on Flexible Graphene Film Material".

In [1], this paper was submitted for the Special Issue on Flexible Biomedical Sensors for Healthcare Applications. The paper was instead published in Volume 16, Issue 6, 2022.

A Review of Power Transfer Systems for Light Rail Vehicles: The Case for Capacitive Wireless Power Transfer

Light rail vehicles (LRVs) are increasingly in demand to sustainably meet the transport needs of growing populations in urban centres. LRVs have commonly been powered from the grid by direct-contact overhead catenary systems (OCS); however, catenary-free direct-contact systems, such as via a “hidden rail”, are popular for new installations. Wireless power transfer (WPT) is an emerging power transfer (PT) technology for e-transport with several advantages over direct contact systems, including improved aesthetics and reduced maintenance requirements; however, they are yet to be utilised in LRV systems. This paper provides a review of existing direct-contact and wireless PT technologies for LRVs, followed by an in-depth critical assessment of inductive power transfer (IPT) and capacitive power transfer (CPT) technologies for LRVs. In particular, the feasibility and advantages of CPT for powering LRVs are presented, highlighting the efficacy of CPT with respect to power transfer capability, safety, and other factors. Finally, limitations and recommendations for future works are identified.

A Constant Output Capacitive Wireless Power Transfer System Based on Parity-Time Symmetric

In existing capacitive wireless power transfer (CPT) systems, the coupling capacitance of the traditional couplers is usually small, which will lead to a significant decrease in the power transfer capability when the transfer distance increases. Thus, it is a big challenge to achieve stable output power and constant transfer efficiency under different coupling capacitance. In this work, the circuit model of the CPT system with double-side LC compensation network is established firstly. Then, based on the parity-time (PT) symmetric theory, a primary-side control strategy is presented to achieve stable output power and constant high transfer efficiency when the coupling capacitance changes. Finally, the experimental results show that when the insertion depth of the stack array coupler changes from 60 to 180 mm, the output power of the proposed CPT prototype is almost stable at 25W, and the transfer efficiency is kept at around 88%, which verifies the feasibility and effectiveness of the proposed design.

A Novel Anti-Offset Interdigital Electrode Capacitive Coupler for Mobile Desktop Charging

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.

Optimization of a capacitive wireless power transfer system with two electric field repeaters

SummaryIn this paper, a capacitive wireless power transfer link with two repeaters between the transmitter and receiver is analyzed. The performance of the system is optimized by maximizing the different gains. Two approaches of practical interest are analytically studied and solved. First, the couplings between different resonators is considered fixed and the optimal load and source of the system are determined as function of the network characteristics. Second, the performance is optimized by varying the couplings between resonators for a configuration with a given (nonideal) source and load. The analytical results are verified through circuital simulations. It is demonstrated that, under certain conditions, both approaches allow for the maximization of the different gains, resulting in more optimization options than a single repeater configuration.

Frequency splitting characteristics analysis of capacitive wireless power transfer

Frequency splitting characteristics analysis of capacitive wireless power transfer

Single Wire Capacitive Wireless Power Transfer System for Wearable Biomedical Sensors Based on Flexible Graphene Film Material.

This paper provides a special flexible graphene film based capacitive wireless power transfer (FGCPT) system for powering biomedical sensors of smart wearable devices. The graphene conductive material is flexible, transparent, highly conductive, and impermeable to most gases and liquids. Generally, the coupling structure of capacitive wireless power transfer (CPT) system is consisted of metal plates. However, it is hard to use for the biomedical sensors as the low power density and big volume. The shape of graphene conductive material could be easily built and changed according to the application requirements. In this paper, the power supply of biomedical sensing system could be accomplished by a single graphene film which is acted as the receiver of FGCPT system. The 200 mW power level is achieved with the maximum 9 V output voltage. The theory and calculation are verified by the simulated and experimental results.

Machine Learning Approach of Optimal Frequency Tuning for Capacitive Wireless Power Transfer System

Wireless power transmission has become a remarkable research topic due to its enormous application potential. Recent advances in machine learning have been shown to be the most promising approach that offers significant capabilities in the wireless power transfer system (WPTS) for selecting the optimal frequency tuning to achieve high efficiency performance. However, developing an automated frequency-tuned system remains a challenge. In this study, a novel frequency-tuned method is presented that utilises machine learning-based models such as neural networks (NN), support vector regression (SVR), and linear regression (LR) to estimate the best efficiency provided by the frequency level at the most optimal frequency tuning level from the experimental dataset, which is capable of aiding in the selection of the most efficient WPTS design. The results show that the SVR has the highest degree of accuracy, making it a promising option for optimising the tuning of power transfer systems while enhancing their performance efficiency. Keywords—Efficiency, frequency tuning, machine learning, neural network, power transfer

Efficient Method for Computing Capacitance Changes between Electrodes due to Foreign Objects in Capacitive WPT Systems

In this paper, a foreign object detection method based on an integral formula is derived for capacitive wireless power transfer systems. The formula expresses the capacitance changes of the system and can predict even very small changes with high accuracy and computational efficiency, as the change is directly evaluated from the electric field in the volume of the foreign object. First, the derivation of the integral formula is presented, then a simple configuration is investigated using the finite element method.

Feasibility Analysis of a Reduced Capacitive Wireless Power Transfer System Model for Transportation Electrification Applications

A practical approach in modeling a capacitive wireless power transfer (CPT) system that utilizes an electrostatic field for the power transfer is presented in this article. The reduced capacitance model (RCM) is derived from the conventional six capacitance model (SCM) for the CPT system in view of the large charging area applications, such as electric vehicle charging. The effect of the same side and cross-coupling capacitances diminishes when the separation distance between the same side plate pair is large enough, and the reduced capacitance model (RCM) is obtained. A bipolar capacitive-link dispersion distance proposed in this article acts as an indicator to decide the use of RCM or SCM depending on the application. Furthermore, RCM attains unity voltage gain and load-independent operation at the designed single resonant frequency, unlike the SCM, where the influence of multiple resonant frequencies is predominant. An experimental validation is performed to determine the effectiveness of the RCM.

Parity-Time Symmetric Capacitive Wireless Power Transfer with Extended Transfer Distance

Parity-Time Symmetric Capacitive Wireless Power Transfer with Extended Transfer Distance

Capacitive Coupler for Wireless Power Transfer to Intravascular Implant Devices

In this letter, we analyze a capacitive coupler for wireless power transfer (WPT) to intravascular implant devices using a stent that contacts the vessel wall for vasodilation as a power receiver. We focus on the effect of conductivity on the transfer efficiency of capacitive WPT and verify the relationship between the maximum transfer efficiency and conductivity based on an equivalent circuit, including arteries and body tissues. We also measure the permittivity and conductivity of biological tissues and explain the appropriate measurement method for each biological tissue. Then, we design the electrode size of the capacitive coupler, and the experimental results of CWPT are presented. We can transfer power into blood vessels through a subcutaneous fatty skin with an efficiency of 35% at 434 MHz, which is the ISM band.