---
_id: '63157'
abstract:
- lang: eng
  text: Three-phase cascaded H-bridge converters (CHBs) in star configuration require
    reliable current controllers to evenly charge the module DC-link capacitors. Conventionally,
    a current control in dq-coordinates is utilized. At steady state, the resulting
    calculated reference arm voltages are sinusoidal, have identical amplitudes and
    show a phase shift of 120 degree to each other. For balanced grid inductors, the
    resulting grid currents also have the same amplitude. However, own simulations
    show that unbalanced grid inductors always lead to different grid current amplitudes
    (4% difference in this case). As a result, the averaged charging module powers
    differ and the peak DC-link capacitor voltage rises as well. In the first step,
    an adaptation of an existing zero-sequence voltage injection is proposed. For
    balanced grid inductors, it converges to the 3rd harmonic voltage injection which
    can reduce the peak-to-peak DC-link voltage ripple up by to 50% and balances the
    power between the phases. However, unbalanced grid inductors still lead to the
    same unbalanced grid currents of 4%. Therefore, a new method with 4 integrators
    based on linear regression is proposed to achieve sinusoidal grid currents for
    unbalanced inductors. The proposed method has a similar transient dynamic as the
    conventional dq control, but balances the grid currents nearly ideally. Simulation
    results of a 1MW cascaded H bridge and a scaled-down prototype verify the proposed
    method.
author:
- first_name: Roland
  full_name: Unruh, Roland
  id: '34289'
  last_name: Unruh
- first_name: Joachim
  full_name: Böcker, Joachim
  id: '66'
  last_name: Böcker
  orcid: 0000-0002-8480-7295
- first_name: Frank
  full_name: Schafmeister, Frank
  id: '71291'
  last_name: Schafmeister
citation:
  ama: 'Unruh R, Böcker J, Schafmeister F. Three-Phase Instantaneous Current Controller
    for Unbalanced Grid Inductors Without DQ Transform for Cascaded H-Bridge Converters.
    In: <i>2025 Energy Conversion Congress &#38;amp;Amp; Expo Europe (ECCE Europe)</i>.
    IEEE; 2025. doi:<a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">10.1109/ecce-europe62795.2025.11238538</a>'
  apa: Unruh, R., Böcker, J., &#38; Schafmeister, F. (2025). Three-Phase Instantaneous
    Current Controller for Unbalanced Grid Inductors Without DQ Transform for Cascaded
    H-Bridge Converters. <i>2025 Energy Conversion Congress &#38;amp;Amp; Expo Europe
    (ECCE Europe)</i>. 2025 Energy Conversion Congress &#38; Expo Europe (ECCE Europe),
    Birmingham, United Kingdom. <a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">https://doi.org/10.1109/ecce-europe62795.2025.11238538</a>
  bibtex: '@inproceedings{Unruh_Böcker_Schafmeister_2025, title={Three-Phase Instantaneous
    Current Controller for Unbalanced Grid Inductors Without DQ Transform for Cascaded
    H-Bridge Converters}, DOI={<a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">10.1109/ecce-europe62795.2025.11238538</a>},
    booktitle={2025 Energy Conversion Congress &#38;amp;amp; Expo Europe (ECCE Europe)},
    publisher={IEEE}, author={Unruh, Roland and Böcker, Joachim and Schafmeister,
    Frank}, year={2025} }'
  chicago: Unruh, Roland, Joachim Böcker, and Frank Schafmeister. “Three-Phase Instantaneous
    Current Controller for Unbalanced Grid Inductors Without DQ Transform for Cascaded
    H-Bridge Converters.” In <i>2025 Energy Conversion Congress &#38;amp;Amp; Expo
    Europe (ECCE Europe)</i>. IEEE, 2025. <a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">https://doi.org/10.1109/ecce-europe62795.2025.11238538</a>.
  ieee: 'R. Unruh, J. Böcker, and F. Schafmeister, “Three-Phase Instantaneous Current
    Controller for Unbalanced Grid Inductors Without DQ Transform for Cascaded H-Bridge
    Converters,” presented at the 2025 Energy Conversion Congress &#38; Expo Europe
    (ECCE Europe), Birmingham, United Kingdom, 2025, doi: <a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">10.1109/ecce-europe62795.2025.11238538</a>.'
  mla: Unruh, Roland, et al. “Three-Phase Instantaneous Current Controller for Unbalanced
    Grid Inductors Without DQ Transform for Cascaded H-Bridge Converters.” <i>2025
    Energy Conversion Congress &#38;amp;Amp; Expo Europe (ECCE Europe)</i>, IEEE,
    2025, doi:<a href="https://doi.org/10.1109/ecce-europe62795.2025.11238538">10.1109/ecce-europe62795.2025.11238538</a>.
  short: 'R. Unruh, J. Böcker, F. Schafmeister, in: 2025 Energy Conversion Congress
    &#38;amp;Amp; Expo Europe (ECCE Europe), IEEE, 2025.'
conference:
  end_date: 2025-09-04
  location: Birmingham, United Kingdom
  name: 2025 Energy Conversion Congress & Expo Europe (ECCE Europe)
  start_date: 2025-09-01
date_created: 2025-12-16T15:20:55Z
date_updated: 2025-12-16T15:25:38Z
department:
- _id: '52'
doi: 10.1109/ecce-europe62795.2025.11238538
keyword:
- Cascaded H-Bridge
- Current Control
- dq Transformation
- Linear Regression
- Unbalanced Inductors
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/document/11238538
publication: 2025 Energy Conversion Congress &amp;amp; Expo Europe (ECCE Europe)
publication_status: published
publisher: IEEE
status: public
title: Three-Phase Instantaneous Current Controller for Unbalanced Grid Inductors
  Without DQ Transform for Cascaded H-Bridge Converters
type: conference
user_id: '34289'
year: '2025'
...