Optimizing the Power Output for a Capacitive Wireless Power Transfer System with NNN receivers (original) (raw)

Capacitive Wireless Power Transfer with Multiple Transmitters: Efficiency Optimization

Energies

Wireless power transfer with multiple transmitters can have several advantages, including more robustness against misalignment and extending the mobility and range of the receiver(s). In this work, the efficiency maximization problem is analytically solved for a capacitive wireless power transfer system with multiple coupled transmitters and a single receiver. It is found that the system efficiency can be increased by adding more transmitters. Moreover, it is proven that the cross-coupling between the transmitters can be eliminated by adding shunt susceptances at the input ports. Optimal values for the input currents and receiver load are determined to achieve maximum efficiency. As well the optimal load, the optimal input currents and the maximum efficiency are independent on the cross-coupling. By impedance-matching the internal conductances of the generators, the maximum-efficiency solution also becomes the one that provides the maximum output power. Finally, by expressing each t...

Optimal Coupling for Capacitive Wireless Power Transfer with One Repeater

2022 52nd European Microwave Conference (EuMC)

In order to extend the range of capacitive wireless power transfer, an electric field repeater between transmitter and receiver can be applied. In this work, a network formalism is adopted to analytically describe and maximize the system efficiency of a repeater setup. The resonator components, resistive losses, load and supply impedances are considered fixed and given. The efficiency is varied by acting on the coupling between transmitter, repeater and receiver only. It is found that it is only possible to optimize the system by varying the coupling between repeater and receiver while keeping the coupling between transmitter and repeater fixed. A condition, dependent on the value of the load, is determined for which the maximization solution exists. The analytical solution is verified through circuital simulations.

Gain Expressions for Capacitive Wireless Power Transfer with One Electric Field Repeater

Electronics

In this paper, the use of a repeater element between the transmitter and the receiver of a capacitive wireless power transfer system for achieving larger transfer distances is analyzed. A network formalism is adopted and the performance described by using the three power gains usually adopted in the context of two-port active networks. The analytical expressions of the gains as function of the network elements are derived. Assuming that the parameters of the link are given and fixed, including the coupling factors between transmitter, repeater and receiver, the conditions for maximizing the different gains by acting on the network terminating impedances (i.e., load and internal source conductance) are determined. The analytical formulas are verified through circuital simulations.

Wireless power transfer between one transmitter and two receivers: optimal analytical solution

Wireless power transfer, 2016

This paper focuses on non-radiative wireless power transfer implemented by means of a resonant magnetic coupling. The case of one transmitter and two receivers is considered and a rigorous analytical procedure is developed demonstrating that maximum power transfer or maximum efficiency can be achieved by appropriately selecting the load values. Both cases of coupled and uncoupled receivers are solved; closed formulas are derived for the optimal loads, which maximize either power or efficiency. It is shown that the resistances that realize maximum power transfer are always greater than the resistances that realize maximum efficiency. According to this observation, an optimal range of operation for the load resistances is also determined. Furthermore, it is demonstrated that in the case where the receivers are coupled the introduction of appropriate compensating reactances allows retrieving the same results corresponding to the uncoupled case both for powers and efficiency. Theoretical data are validated by comparisons with numerical results.

Maximizing the Power Transfer for a Mixed Inductive and Capacitive Wireless Power Transfer System

2018 IEEE Wireless Power Transfer Conference (WPTC), 2018

Nowadays, near-field wireless power transfer is realized by inductive or capacitive coupling. Power transmission is accomplished by a time-varying magnetic or electric field as medium, respectively. Recently, mixed or hybrid wireless power transfer is being developed as a possible mean to increase the power density of the system by utilizing both the magnetic and the electric near-field. The fundamental basics of mixed coupling are well understood. However, the implications of the mixed coupling theory on wireless power transfer applications is not rigorously described. Moreover, no general description is available that allows for a detailed comparison between current hybrid systems, especially for a series topology of inductive and capacitive coupling. In this work, we analytically solve a general mixed wireless power transfer configuration with series topology. We determine the optimal load to maximize the amount of power transfer and calculate the maximum achievable output power. The analytical derivation is validated by numerical simulation in SPICE. Our solution allows for a better fundamental understanding of the mixed wireless link and can serve as a reference point to evaluate the performance of mixed systems with regard to power transfer. Index Terms-capacitive power transmission, electromagnetic coupling, hybrid coupling, inductive power transmission, mixed coupling, mutual coupling, wireless power transmission.

Maximum Power Transfer versus Efficiency in Mid-Range Wireless Power Transfer Systems

Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2015

The condition for maximum power transfer of 2-coils wireless power transfer (WPT) system is derived from circuit analysis and discussed together with the respective WPT system efficiency (η). In the sequence, it is shown that a 4-coils WPT system (which can be divided in source, two communication and load circuits) without power losses at the two communication circuits (ideal 4-coils WPT system) presents, from maximum power transfer and efficiency point of view, a performance similar to those of a 2-coils WPT system. The exception is the influence of coupling coefficient (k): in 2-coils system η increases as k approaches one, while in ideal 4-coils WPT system η increases as k between the two communication coils approaches zero. In addition, realistic 4-coils WPT systems (with power losses at the two communication circuits) are also analyzed showing, for instance, that η presents a maximum as a function of k of the communication coils. In order to validate the presented theory, 4 coils were built, and a setup to perform 2coils and 4-coils WPT systems has been carried out. Practical results show good agreement with the developed theory. Index Terms-Maximum power transfer, power transfer efficiency, relative power transfer, wireless power transfer. I. INTRODUCTION Wireless power transfer (WPT) technology has been widely discussed in the last years [1-6]. For instance, in a recent article the progress in mid-range WPT systems has been critically reviewed discussing, among other topics, the importance of maximum power transfer (MPT) condition and power transfer efficiency (η) in the design of these circuits [1]. However, a specific derivation of MPT condition of WPT systems, from which their η could be properly addressed, was not presented. The aim of this paper is to present the derivation of MPT conditions for 2-coils and 4-coils WPT. Based on the derived MPT conditions, the systems efficiencies are discussed. The strategy adopted in this work to show that the method used to derive the mentioned conditions is correct was to compare its results, whenever possible, with classical MPT theorem conclusions. In this way, it is demonstrated that the theoretical and practical results correspondent to 2-coils and theoretical result related to ideal 4-coils WPT (without power losses at the two communication circuits) systems are coherent with classical MPT theorem conclusions. Of course, the real systems (with losses at communication coils) differ from the ideal circuits, showing a maximum in the efficiency curve. Practical experimentations

A Review of the Current State of Technology of Capacitive Wireless Power Transfer

Energies, 2021

Wireless power transfer allows the transfer of energy from a transmitter to a receiver without electrical connections. Compared to galvanic charging, it displays several advantages, including improved user experience, higher durability and better mobility. As a result, both consumer and industrial markets for wireless charging are growing rapidly. The main market share of wireless power is based on the principle of inductive power transfer, a technology based on coupled coils that transfer energy via varying magnetic fields. However, inductive charging has some disadvantages, such as high cost, heat dissipation, and bulky inductors. A promising alternative is capacitive wireless power transfer that utilizes a varying electric field as medium to transfer energy. Its wireless link consists of conductive plates. The purpose of this paper is to review the state of the art, link the theoretical concepts to practical cases and to indicate where further research is required to take next st...

Efficiency comparison of capacitive wireless power transfer for different materials

International Journal of Power Electronics and Drive System (IJPEDS), 2020

This paper describes the application of several types of materials to act as capacitive plates in a Capacitive Power Transfer (CPT) system. In general, the efficiency of CPT system is greatly influenced by the coupling capacitance which is varied by distances and permittivity values. Thus, this paper intended to compare the performance of CPT system in terms of the output efficiency for several types of capacitive plates. To be specific, copper plate, zinc, and aluminium are used in this work to act as coupling plates to the CPT system. The CPT system in this work applied class E inverter as it has lowest switching losses among its competitors, i.e. class D and class F. The work is validated through experimental setup of CPT system in which copper material provides the best efficiency of the system.

Compensation of Cross Coupling in Multiple-Receiver Wireless Power Transfer Systems

Simultaneous wireless charging of multiple devices is a unique advantage of wireless power transfer (WPT). Meanwhile, the multiple-receiver configuration makes it more challenging to analyze and optimize the operation of the system. This paper aims at providing a general analysis on the multiple-receiver WPT systems and compensation for the influence of the cross coupling. A two-receiver WPT system is first investigated as an example. It shows that theoretically by having derived optimal load reactances the important system characteristics can be preserved such as the original system efficiency, input impedance, and power distribution when there is no cross coupling between receivers. The discussion is then extended to general multiple-receiver WPT systems with more than two receivers. Similar results are obtained that show the possibility of compensating the cross coupling by having the derived optimal load reactances. Finally, the theoretical analysis is validated by model-based calculation and final experiments using real two- and three-receiver systems.