System Identification and Tuning of Wireless Power Transfer Systems with Multiple Magnetically Coupled Resonators

Johan Winges, Thomas Rylander, Carl Petersson, Christian Ekman, Lars-Åke Johansson, Tomas McKelvey


We present a procedure for system identification and tuning of a wireless power transfer (WPT) system with four magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductance and losses of the coils.
This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3~kW power transfer with 91\% system efficiency over an air-gap distance of approximately 20~cm.


Wireless power transfer (WPT); magnetically coupled resonators; system identification; tuning; Bayesian estimation; impedance matching; charging electric vehicles

Full Text:



S. Li and C. C. Mi, “Wireless Power Transfer for Electric Vehicle Applications,” IEEE J. Emerg. Sel. Top. Power Electron., vol. 3, no. 1, pp. 4–17, Mar 2015.

F. Musavi and W. Eberle, “Overview of wireless power transfer technologies for electric vehicle battery charging,” IET Power Electron., vol. 7, no. 1, pp. 60–66, Jan 2014.

B. Esteban, M. Sid-Ahmed, and N. C. Kar, “A Comparative Study of Power Supply Architectures in Wireless EV Charging Systems,” IEEE Trans. Power Electron., vol. 30, no. 11, pp. 6408–6422, Nov 2015.

A. Kurs, A. Karalis, R. Moffatt, J. D. Joannopoulos, P. Fisher, and M. Soljacic, “Wireless Power Transfer via Strongly Coupled Magnetic Resonances,” Science, vol. 317, no. 5834, pp. 83–86, Jul 2007. [Online]. Available:

A. P. Sample, D. a. Meyer, and J. R. Smith, “Analysis, Experimental Results, and Range Adaptation of Magnetically Coupled Resonators for Wireless Power Transfer,” IEEE Trans. Ind. Electron., vol. 58, no. 2, pp. 544–554, Feb 2011.

S. Aldhaher, P. C.-K. Luk, and J. F. Whidborne, “Electronic tuning of misaligned coils in wireless power transfer systems,” IEEE Trans. Power Electron., vol. 29, no. 11, pp. 5975–5982, 2014.

SAE Standard, “J2954, Wireless Power Transfer for Light-Duty Plug-In/Electric Vehicles and Alignment Methodology,” 2016. [Online]. Available: 201605/

T. C. Beh, M. Kato, T. Imura, S. Oh, and Y. Hori, “Automated impedance matching system for robust wireless power transfer via magnetic resonance coupling,” IEEE Trans. Ind. Electron., vol. 60, no. 9, pp. 3689–3698, Sep 2013.

S. Li, W. Li, J. Deng, T. D. Nguyen, and C. C. Mi, “A double-sided LCC compensation network and its tuning method for wireless power transfer,” IEEE Trans. Veh. Technol., vol. 64, no. 6, pp. 2261–2273, Jun 2015.

M. E. Halpern and D. C. Ng, “Optimal tuning of inductive wireless power links: Limits of performance,” IEEE Trans. Circuits Syst. I Regul. Pap., vol. 62, no. 3, pp. 725–732, 2015.

M. Kiani and M. Ghovanloo, “The Circuit Theory Behind Coupled-Mode Magnetic Resonance-Based Wireless Power Transmission,” IEEE Trans. Circuits Syst. I Regul. Pap., vol. 59, no. 9, pp. 2065–2074, Sep 2012. [Online]. Available:

S. Y. R. Hui, W. Zhong, and C. K. Lee, “A Critical Review of Recent Progress in Mid-Range Wireless Power Transfer,” IEEE Trans. Power Electron., vol. 29, no. 9, pp. 4500–4511, Sep 2014. [Online]. Available:

K. Lee and S. H. Chae, “Power Transfer Efficiency Analysis of Intermediate-Resonator for Wireless Power Transfer,” IEEE Trans. Power Electron., vol. 8993, no. c, pp. 1–1, 2017. [Online]. Available:

W. Zhong, C. K. Lee, and S. Y. Ron Hui, “General analysis on the use of Tesla’s resonators in domino forms for wireless power transfer,” IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 261–270, 2013.

X. Liu and G. Wang, “A Novel Wireless Power Transfer System with Double Intermediate Resonant Coils,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 2174–2180, 2016.

D. Lin, J. Yin, and S. Y. R. Hui, “Parameter identification of wireless power transfer systems using input voltage and current,” Energy Convers. Congr. Expo. (ECCE), 2014 IEEE, pp. 832–836, 2014.

“System identification and tuning of wpt systems,” in 2017 IEEE International Conference on Environment and Electrical Engineering and 2017 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I CPS Europe), June 2017, pp. 1–5.

S. M. Kay and M. K. Steven, Fundamentals of Statistical Signal Processing: Estimation Theory. Englewood Cliffs, NJ, USA: Prentice-Hall, Inc., 1993.

COMSOL AB, “COMSOL Multiphysics® v. 5.2,” Stockholm, Sweden, 2016. [Online]. Available:

The MathWorks Inc., “Matlab®,” Natick, Massachusetts, United States, 2017. [Online]. Available:



  • There are currently no refbacks.

Copyright (c) 2018 Johan Winges, Thomas Rylander, Carl Petersson, Christian Ekman, Lars-Åke Johansson and Tomas McKelvey

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.