---
_id: '59805'
abstract:
- lang: eng
  text: The LLC converter achieves the highest efficiency in resonant operation. Conventionally,
    the input DC-link voltage is controlled to operate the LLC converter at resonance
    for the given operating point. However, the DC-link capacitor voltage shows a
    low-frequency voltage ripple (typically the second harmonic of grid frequency)
    in cascaded converters so that the LLC has to adapt its switching frequency within
    the grid period. Conventionally, the LLC converter operates 50% of the time above
    the resonant frequency of 40 kHz and 50% below resonance. Both operating conditions
    cause additional losses. However, experimental measurements indicate that the
    below-resonance operation causes significantly higher losses than above-resonance
    operation due to much higher primary and secondary transformer currents. It is
    better to increase the DC-link voltage by 30% of the peak-to-peak low-frequency
    voltage ripple to mostly avoid below-resonance operation (i.e., from 650 V to
    680 V in this case). With the proposed control, the LLC converter operates about
    75% of time over resonance and only 25% of time below resonance. The overall efficiency
    increases from 97.66% to 97.7% for the average operating point with an 80% load
    current. This corresponds to a 2% total loss reduction. Finally, the peak resonance
    capacitor voltage decreases from 910 V to 790 V (−13%).
article_number: '1517'
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. Adaptive DC-Link Voltage Control for 22
    kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple. <i>Electronics</i>.
    2025;14(8). doi:<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>
  apa: Unruh, R., Böcker, J., &#38; Schafmeister, F. (2025). Adaptive DC-Link Voltage
    Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage
    Ripple. <i>Electronics</i>, <i>14</i>(8), Article 1517. <a href="https://doi.org/10.3390/electronics14081517">https://doi.org/10.3390/electronics14081517</a>
  bibtex: '@article{Unruh_Böcker_Schafmeister_2025, title={Adaptive DC-Link Voltage
    Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage
    Ripple}, volume={14}, DOI={<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>},
    number={81517}, journal={Electronics}, publisher={MDPI AG}, author={Unruh, Roland
    and Böcker, Joachim and Schafmeister, Frank}, year={2025} }'
  chicago: Unruh, Roland, Joachim Böcker, and Frank Schafmeister. “Adaptive DC-Link
    Voltage Control for 22 KW, 40 KHz LLC Resonant Converter Considering Low-Frequency
    Voltage Ripple.” <i>Electronics</i> 14, no. 8 (2025). <a href="https://doi.org/10.3390/electronics14081517">https://doi.org/10.3390/electronics14081517</a>.
  ieee: 'R. Unruh, J. Böcker, and F. Schafmeister, “Adaptive DC-Link Voltage Control
    for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple,”
    <i>Electronics</i>, vol. 14, no. 8, Art. no. 1517, 2025, doi: <a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>.'
  mla: Unruh, Roland, et al. “Adaptive DC-Link Voltage Control for 22 KW, 40 KHz LLC
    Resonant Converter Considering Low-Frequency Voltage Ripple.” <i>Electronics</i>,
    vol. 14, no. 8, 1517, MDPI AG, 2025, doi:<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>.
  short: R. Unruh, J. Böcker, F. Schafmeister, Electronics 14 (2025).
date_created: 2025-05-05T12:27:39Z
date_updated: 2025-05-05T12:34:00Z
department:
- _id: '52'
doi: 10.3390/electronics14081517
intvolume: '        14'
issue: '8'
keyword:
- adaptive DC-link voltage
- cascaded H-bridge
- resonant operation
- Full-Bridge Converter
- loss minimization
- LLC Resonant Converter
- peak capacitor voltage reduction
language:
- iso: eng
main_file_link:
- url: https://www.mdpi.com/2079-9292/14/8/1517
publication: Electronics
publication_identifier:
  issn:
  - 2079-9292
publication_status: published
publisher: MDPI AG
status: public
title: Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering
  Low-Frequency Voltage Ripple
type: journal_article
user_id: '34289'
volume: 14
year: '2025'
...
---
_id: '54356'
abstract:
- lang: eng
  text: "Although there are numerous design and control methodologies for the LLC
    resonant converter,\r\nthey often do not consider decentralized control strategies
    to operate them as isolated DC-DC converters within a\r\ncascaded H-bridge. The
    total output power of all LLC converters must be constant to supply a load such
    as a wa-\r\nter electrolyzer. However, each individual LLC converter can vary
    its output power as long as the total output\r\npower remains constant. This opens
    new possibilities in increasing the system efficiency and robustness. Usually,\r\nthe
    DC-link voltage of each module capacitor shows a 2nd harmonic voltage ripple.
    However, the total stored energy\r\nin all DC-link capacitors is constant within
    a grid period for a balanced three-phase system. By controlling each\r\nLLC converter’s
    output power locally to be proportional to the energy stored in its DC-link capacitor,
    modules with\r\na lower instantaneous DC-link voltage transfer less power to the
    load than modules with a higher DC-link voltage.\r\nAs a result, a higher efficiency,
    voltage gain and lower peak resonant capacitor voltage can be achieved with the\r\nsame
    components. The 22.2kW experimental prototype of the LLC converter reaches an
    efficiency of over 97% at\r\nresonance which is similar to the precalculated value."
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. Experimentally Verified 22 kW, 40 kHz LLC
    Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge Converter.
    In: <i>ECCE Europe 2024; IEEE Energy Conversion Congress &#38; Exposition Europe</i>.
    IEEE. doi:<a href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>'
  apa: Unruh, R., Böcker, J., &#38; Schafmeister, F. (n.d.). Experimentally Verified
    22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded
    H-Bridge Converter. <i>ECCE Europe 2024; IEEE Energy Conversion Congress &#38;
    Exposition Europe</i>. ECCE Europe 2024, Darmstadt, Germany. <a href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>
  bibtex: '@inproceedings{Unruh_Böcker_Schafmeister, place={Darmstadt}, title={Experimentally
    Verified 22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1
    MW Cascaded H-Bridge Converter}, DOI={<a href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>},
    booktitle={ECCE Europe 2024; IEEE Energy Conversion Congress &#38; Exposition
    Europe}, publisher={IEEE}, author={Unruh, Roland and Böcker, Joachim and Schafmeister,
    Frank} }'
  chicago: 'Unruh, Roland, Joachim Böcker, and Frank Schafmeister. “Experimentally
    Verified 22 KW, 40 KHz LLC Resonant Converter Design with New Control for a 1
    MW Cascaded H-Bridge Converter.” In <i>ECCE Europe 2024; IEEE Energy Conversion
    Congress &#38; Exposition Europe</i>. Darmstadt: IEEE, n.d. <a href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>.'
  ieee: 'R. Unruh, J. Böcker, and F. Schafmeister, “Experimentally Verified 22 kW,
    40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge
    Converter,” presented at the ECCE Europe 2024, Darmstadt, Germany, doi: <a href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>.'
  mla: Unruh, Roland, et al. “Experimentally Verified 22 KW, 40 KHz LLC Resonant Converter
    Design with New Control for a 1 MW Cascaded H-Bridge Converter.” <i>ECCE Europe
    2024; IEEE Energy Conversion Congress &#38; Exposition Europe</i>, IEEE, doi:<a
    href="https://doi.org/10.1109/ECCEEurope62508.2024.10751954">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>.
  short: 'R. Unruh, J. Böcker, F. Schafmeister, in: ECCE Europe 2024; IEEE Energy
    Conversion Congress &#38; Exposition Europe, IEEE, Darmstadt, n.d.'
conference:
  end_date: 2024-09-06
  location: Darmstadt, Germany
  name: ECCE Europe 2024
  start_date: 2024-09-02
date_created: 2024-05-19T14:26:29Z
date_updated: 2024-11-28T14:16:05Z
department:
- _id: '52'
doi: https://doi.org/10.1109/ECCEEurope62508.2024.10751954
keyword:
- Cascaded H-Bridge
- Converter Losses
- Decentralized Control
- Full-Bridge Converter
- LLC Resonant Converter
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/10751954
place: Darmstadt
publication: ECCE Europe 2024; IEEE Energy Conversion Congress & Exposition Europe
publication_identifier:
  isbn:
  - 979-8-3503-6444-6
publication_status: accepted
publisher: IEEE
status: public
title: Experimentally Verified 22 kW, 40 kHz LLC Resonant Converter Design with new
  Control for a 1 MW Cascaded H-Bridge Converter
type: conference
user_id: '34289'
year: '2024'
...
---
_id: '29893'
abstract:
- lang: eng
  text: Phase-shift modulated full bridge converters suffer from thermal imbalances
    of the inverter switches. The lagging leg switches are subject to larger commutation
    currents compared to those of the leading leg as the transformer current reduces
    in the freewheeling interval. Furthermore, after this interval, the energy in
    the series inductance may not be large enough to achieve zero-voltage switching
    (ZVS) for the leading leg. Both effects result in thermal imbalances. This paper
    analyzes the alternating-asymmetrical phase-shift modulation to achieve balanced
    conduction and switching losses for all four switches while showing that this
    modulation is easily implemented on standard DSPs. The modulation has been implemented
    to LLC converters where experimental measurement results proved its effectiveness
    for LLC converters by reducing the temperature deviation from 6.3 K to only 0.2
    K such that the peak temperature is reduced from 95 °C to 92 °C. The paper also
    proves that the modulation can be utilized to improve the efficiency of LLC converters
    operated at very low gains while simultaneously reducing the junction temperature
    of all four switches compared to the conventional complementary modulation. Finally,
    EMI implications are analyzed, which show that the modulation may be beneficial
    for reducing the common-mode emissions around the operating frequency.
author:
- first_name: Philipp
  full_name: Rehlaender, Philipp
  id: '69469'
  last_name: Rehlaender
- first_name: Roland
  full_name: Unruh, Roland
  id: '34289'
  last_name: Unruh
- first_name: Frank
  full_name: Schafmeister, Frank
  id: '71291'
  last_name: Schafmeister
- first_name: Joachim
  full_name: Böcker, Joachim
  id: '66'
  last_name: Böcker
  orcid: 0000-0002-8480-7295
citation:
  ama: 'Rehlaender P, Unruh R, Schafmeister F, Böcker J. Alternating Asymmetrical
    Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching Losses
    to Reduce Thermal Imbalances. In: <i>2021 IEEE Applied Power Electronics Conference
    and Exposition (APEC)</i>. IEEE; 2021. doi:<a href="https://doi.org/10.1109/apec42165.2021.9487104">10.1109/apec42165.2021.9487104</a>'
  apa: Rehlaender, P., Unruh, R., Schafmeister, F., &#38; Böcker, J. (2021). Alternating
    Asymmetrical Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching
    Losses to Reduce Thermal Imbalances. <i>2021 IEEE Applied Power Electronics Conference
    and Exposition (APEC)</i>. 2021 IEEE Applied Power Electronics Conference and
    Exposition (APEC), Phoenix, AZ, USA. <a href="https://doi.org/10.1109/apec42165.2021.9487104">https://doi.org/10.1109/apec42165.2021.9487104</a>
  bibtex: '@inproceedings{Rehlaender_Unruh_Schafmeister_Böcker_2021, title={Alternating
    Asymmetrical Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching
    Losses to Reduce Thermal Imbalances}, DOI={<a href="https://doi.org/10.1109/apec42165.2021.9487104">10.1109/apec42165.2021.9487104</a>},
    booktitle={2021 IEEE Applied Power Electronics Conference and Exposition (APEC)},
    publisher={IEEE}, author={Rehlaender, Philipp and Unruh, Roland and Schafmeister,
    Frank and Böcker, Joachim}, year={2021} }'
  chicago: Rehlaender, Philipp, Roland Unruh, Frank Schafmeister, and Joachim Böcker.
    “Alternating Asymmetrical Phase-Shift Modulation for Full-Bridge Converters with
    Balanced Switching Losses to Reduce Thermal Imbalances.” In <i>2021 IEEE Applied
    Power Electronics Conference and Exposition (APEC)</i>. IEEE, 2021. <a href="https://doi.org/10.1109/apec42165.2021.9487104">https://doi.org/10.1109/apec42165.2021.9487104</a>.
  ieee: 'P. Rehlaender, R. Unruh, F. Schafmeister, and J. Böcker, “Alternating Asymmetrical
    Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching Losses
    to Reduce Thermal Imbalances,” presented at the 2021 IEEE Applied Power Electronics
    Conference and Exposition (APEC), Phoenix, AZ, USA, 2021, doi: <a href="https://doi.org/10.1109/apec42165.2021.9487104">10.1109/apec42165.2021.9487104</a>.'
  mla: Rehlaender, Philipp, et al. “Alternating Asymmetrical Phase-Shift Modulation
    for Full-Bridge Converters with Balanced Switching Losses to Reduce Thermal Imbalances.”
    <i>2021 IEEE Applied Power Electronics Conference and Exposition (APEC)</i>, IEEE,
    2021, doi:<a href="https://doi.org/10.1109/apec42165.2021.9487104">10.1109/apec42165.2021.9487104</a>.
  short: 'P. Rehlaender, R. Unruh, F. Schafmeister, J. Böcker, in: 2021 IEEE Applied
    Power Electronics Conference and Exposition (APEC), IEEE, 2021.'
conference:
  end_date: 2021-06-17
  location: Phoenix, AZ, USA
  name: 2021 IEEE Applied Power Electronics Conference and Exposition (APEC)
  start_date: 2021-06-14
date_created: 2022-02-20T21:19:46Z
date_updated: 2023-10-20T11:50:25Z
department:
- _id: '34'
- _id: '52'
doi: 10.1109/apec42165.2021.9487104
keyword:
- Phase-Shifted Full Bridge
- Full-Bridge Converter
- Phase-Shift Control
- Phase-Shift Modulation
- LLC Converter
- Thermal Balancing
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/9487104
publication: 2021 IEEE Applied Power Electronics Conference and Exposition (APEC)
publication_identifier:
  isbn:
  - 978-1-7281-8950-5
publication_status: published
publisher: IEEE
status: public
title: Alternating Asymmetrical Phase-Shift Modulation for Full-Bridge Converters
  with Balanced Switching Losses to Reduce Thermal Imbalances
type: conference
user_id: '34289'
year: '2021'
...