Inductive Power Transfer based on Variable Compensation Capacitance to Achieve an EV Charging Profile with Constant Optimum Load

Francesca Grazian, Thiago Batista Soeiro, Pavol Bauer

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)
29 Downloads (Pure)


Wireless charging must be highly efficient throughout the entire battery charging profile to compete in the electric vehicle (EV) industry. Thus, optimum load matching is commonly used: it operates at the equivalent load that maximizes the efficiency, which depends on the coil's alignment. In this article, the optimum load is made independent of the coils' position by changing the system's resonant frequency through switch-controlled capacitors (SCCs). This eliminates the need for load-side voltage control. The output current follows the battery voltage rise during the battery charging cycle to always match the optimum load, which can be achieved by regulating the input voltage via the power factor correction (PFC) converter. This method is called here constant optimum load (COL). Two SCC topologies have been implemented in a 3.7-kW hardware demonstrator. The one implementing the half-wave modulation achieves higher efficiency than the one employing full-wave modulation, with 96.30% at 3.2 kW and aligned coils. When misalignment occurs, the half-wave modulation technique results in higher efficiency than the conventional-fixed compensation, where the efficiency is lower by up to 0.68% at partial load. Based on these results, the proposed COL method is proven suitable for 3.7-kW EV-static wireless charging achieving one of the highest peak efficiencies listed in today's literature for the same power class.

Original languageEnglish
Pages (from-to)1230-1244
Number of pages15
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Issue number1
Publication statusPublished - 2022

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • Batteries
  • Coils
  • Compensation networks
  • control
  • Couplings
  • Inductive charging
  • inductive power transfer
  • Magnetic resonance
  • magnetic resonant coupling
  • optimum load matching
  • Power electronics
  • soft-switching
  • switch-controlled capacitors
  • Voltage control
  • wireless charging
  • zero voltage switching


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