A Gradient-Descent Optimization Assisted Gray-Box Impedance Modeling of EV chargers

Lu Wang, Zian Qin*, Pavol Bauer

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Extracting an electric vehicle (EV) charger's input impedance with the analytical model (white-box approach) or the frequency sweep (black-box approach) is limited by the parameter confidentiality or the measurement noise, respectively. To overcome these challenges, a gradient-descent (GD) optimization-based gray-box modeling approach is proposed. To start with, a sensitivity study on the analytical impedance model of an EV charger with a typical controller is carried out to identify the influential frequency range per controller and circuit parameter. On top of that, given an EV charger with unknown control and circuit information, a GD optimization-based algorithm for multiple parameter estimation is designed to identify the unknown controller and circuit parameters based on the measured impedance, by assuming the EV charger is using the typical controller. Then, an analytical input impedance of the black-box EV charger can be obtained. Moreover, the low-accuracy issue commonly encountered when estimating multiple parameters with GD optimization is mitigated with the proposed algorithm. Compared to pure frequency sweep, the proposed approach achieves a higher accuracy for the coupling impedance and a comparable accuracy for the diagonal impedance. The effectiveness of the proposed approach is validated by experimental results.

Original languageEnglish
Pages (from-to)8866-8879
Number of pages14
JournalIEEE Transactions on Power Electronics
Issue number7
Publication statusPublished - 2023

Bibliographical note

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care
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.


This project has received funding from the Electronic Components and Systems for European Leadership Joint Undertaking under grant agreement No 876868. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme and Germany, Slovakia, Netherlands, Spain, Italy.


  • EV Charging
  • Power Quality
  • impedance modeling
  • Parameter Estimation
  • Gray Box Model
  • gradient-based optimization
  • Voltage Source Converter (VSC)


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