Wireless Power Transfer by Using Magnetically Coupled Resonators

Abstract

In this chapter, a wireless power transmission system based on magnetic resonance coupling circuit was carried out. Mathematical expressions of optimal coupling coefficients were examined with the coupling model. Equivalent circuit parameters were calculated with Maxwell D software, and then, the equivalent circuit was solved using MATLAB technical computing software. The transfer efficiency of the system was derived using the electrical parameters of the equivalent circuit. System efficiency was analyzed depending on the different air gap values for various characteristic impedances using PSIM circuit simulation software. Since magnetic resonance coupling involves creating a resonance and transferring the power without the radiation of electromagnetic waves, resonance frequency is a key parameter in system design. The aim of this research was to define the efficiency according to variations of coefficients in wireless power transfer WPT system. In order to do that, the calculation procedure of mutual inductance between two self-resonators is performed by Maxwell software. Equivalent circuit is solved in circuit simulator PSIM platform. The calculations show that using the parameters that are obtained by magnetic analysis can be used for the equivalent circuit which has the capability to provide the efficiency using electrical quantities. The chapter discusses the application of this approach to a coil excited by a sinusoidal voltage source and a receiver coil, which receives energy voltage and current. Both could be obtained to calculate the instantaneous power and efficiency. To do so, the waveforms for voltage and current were obtained and computed with the PSIM circuit simulator. As the air gap between the coils increased, the coupling between the coils was weakened. The impedance of the circuit varied as the air gap changed, affecting the power transfer efficiency. In order to determine the differences between the software programs, efficiency values were calculated using three kinds of software. And it is concluded that equivalent circuit analysis by means of numerical computing is proper to obtain the voltage and current waveforms. Correspondingly, transmission efficiency can be calculated using the electrical relations.

Near-Field Communications (NFC) for Wireless Power Transfer (WPT): An Overview

“…The transferred power is maximum at resonance frequency when load current in the circuit becomes maximum, at a given resonance frequency, Eq. (15) describes the condition for maximum power transfer efficiency [29]:…”

“…Twoloop and four-loop coil systems were studied for magnetic resonance coupling based WPT system [30]. In order to achieve maximum power transfer efficiency, several studies have been done such as loop to coil coupling manipulation [29], automated impedance matching [31], adaptive frequency tuning [32], circuit structure manipulation [33], improving WPT for future portable consumer electronics using large transmitter coil system [34] and improving efficiency by four-coil system for deep brain simulation [35]. There are studies, which focused on misalignment between receiver and transmitter coil for applications such as wireless EV charging system [36] and wireless mobile phone charging system [37,38].…”

Optimization of Wireless Power Transfer Configuration for High Efficiency Achievement

“…The resonance considered is focused towards the resonator system which must have a high quality factor for efficient energy transfer. High quality factor of electromagnetic resonators normally made from the conductive components which have relatively narrow resonant frequency widths [8]. On top of that, resonator system enable energy exchange between the resonators when are placed close to one another.…”

Comparison and selection strategy of compensating topologies in two coil resonant wireless power transfer system

“…This technology is used for applications such as electrical vehicles, consumer electronics, and biomedical applications where the conventional wired system is undesirable (Hasanzadeh and Vaez-Zadeh, 2015;Tang and Cheng, 2020;Keerthi et al, 2018). The basic principle of the electromagnetically coupled resonance based WPT system is that two coils with the same resonant frequency can efficiently transfer energy (Agcal et al, 2016). Since the efficiency of inductive power transfer based on magnetic induction becomes lower as the air gap distance increases, their popularity has decreased in recent years and has been replaced by electromagnetic resonance coupling (Nataraj et al, 2018;Zeng et al, 2021;Aydin et al, 2021;Bekiroglu et al, 2018;Heidarian and Burgess, 2020).…”

“…As a result, the power factor gets very small and starts to approach zero as the frequency increases leading to higher VA rating with reduced efficiency. In WPT applications, four types of compensation circuit topologies are used (Agcal et al, 2016;Ravikiran and Keshri, 2017;Zavrel and Kindl, 2018). In this study comparisons of different compensation topologies have been investigated for WPT systems.…”