Implementing an Impedance Compression Network to Compensate for Misalignments in a Wireless Power Transfer System

Jungwon Choi, Jiale Xu, Rawad Makhoul, Juan M.Rivas Davila

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


This paper presents an impedance compression network (ICN) design in a wireless power transfer (WPT) system to compensate for distance or alignment variations between coils. In midrange WPT applications, magnetic resonant coupling coils are mainly implemented to achieve high efficiency for charging batteries. However, a distance or horizontal alignment variation between coils changes their coupling coefficient, and it decreases the overall performance of WPT systems because the zero voltage switching in a resonant inverter is lost. In order to reduce coil impedance variation, we propose an ICN that compresses variations in coil impedance. The ICN consists of a resistance compression network and a phase compression network to suppress magnitude and phase variations, respectively, in the coil impedance. Only passive components, such as inductors and capacitors, are used to implement an ICN.

Original languageEnglish (US)
Article number8424425
Pages (from-to)4173-4184
Number of pages12
JournalIEEE Transactions on Power Electronics
Issue number5
StatePublished - May 2019

Bibliographical note

Funding Information:
Manuscript received October 6, 2017; revised February 7, 2018 and May 8, 2018; accepted July 24, 2018. Date of publication August 1, 2018; date of current version March 29, 2019. This work was supported by Daihen Corporation through the Stanford SystemX Alliance FMA (Faculty, Mentor, Advisor) Research Program. Recommended for publication by Associate Editor O. C. Onar. (Corresponding author: Jungwon Choi.) J. Choi, J. Xu, and J. M. Rivas are with Stanford University, Stanford, CA 94305 USA (e-mail:,;; jmrivas@

Publisher Copyright:
© 1986-2012 IEEE.


  • Impedance compression network
  • magnetic resonant coupling
  • resonant inverter
  • wireless power transfer


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