Time-Domain Analysis of Wireless Power Transfer System Behavior Based on Coupled-Mode Theory

Shim, Hyunjin; Nam, Sangwook; Lee, Bomson

doi:2016.16.4.219

J. Electromagn. Eng. Sci > Volume 16(4); 2016 > Article

Journal of Electromagnetic Engineering and Science 2016;16(4):219-224.
DOI: https://doi.org/10.5515/JKIEES.2016.16.4.219

Time-Domain Analysis of Wireless Power Transfer System Behavior Based on Coupled-Mode Theory

Hyunjin Shim¹, Sangwook Nam¹, Bomson Lee²

¹School of Electrical Engineering and Computer Science, Institute of New Media and Communications, Seoul National University
²Department of Electronics and Radio Engineering, School of Electronics and Information, Kyung Hee University

Correspondence: Hyunjin Shim,Email: californiashim89@gmail.com

Abstract

In this paper, coupled-mode theory (CMT) is used to obtain a transient solution analytically for a wireless power transfer system (WPTS) when unit energy is applied to one of two resonators. The solutions are compared with those obtained using equivalent circuit-based analysis. The time-domain CMT is accurate only when resonant coils are weakly coupled and have large quality factors, and the reason for this inaccuracy is outlined. Even though the time-domain CMT solution does not describe the WPTS behavior precisely, it is accurate enough to allow for an understanding of the mechanism of energy exchange between two resonators qualitatively. Based on the time-domain CMT solution, the critical coupling coefficient is derived and a criterion is suggested for distinguishing inductive coupling and magnetic resonance coupling of the WPTS.

Key words: Coupling Coefficient, Coupled-Mode Theory (CMT), Power Transfer Efficiency (PTE), Quality Factor (Q), Transient Circuit Theory, Wireless Power Transmission (WPT)