---
_id: '48352'
abstract:
- lang: eng
  text: Star-connected cascaded H-bridge Converters require large DC-link capacitors
    to buffer the second-order harmonic voltage ripple. First, it is analytically
    proven that the DC-link voltage ripple is proportional to the apparent converter
    power and does not depend on the power factor for nominal operation with sinusoidal
    reference arm voltages and currents. A third-harmonic zero-sequence voltage injection
    with an optimal amplitude and phase angle transforms the 2nd harmonic to a 4th
    harmonic DC-link voltage ripple. This reduces the voltage ripple by exactly 50%
    for all power factors at steady-state at balanced conditions. However, this requires
    54% additional modules for unity power factor operation and even 100% for pure
    reactive power operation to account for the increased reference arm voltages due
    to the large amplitude of the optimal third-harmonic injection. If not enough
    modules are available, an adaptive discontinuous PWM is utilized to still minimize
    the voltage ripple for the given number of modules and power factor. With a very
    limited number of modules (modulation index is 1.15), the proposed method still
    reduces the DC-link voltage ripple by 24.4% for unity power factor operation.
    It requires the same number of modules as the commonly utilized 3rd harmonic injection
    with 1/6 of the grid voltage amplitude and achieves superior results. Simulations
    of a 10 kV/1 MVA system confirm the analysis.
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. An Optimized Third-Harmonic Injection Reduces
    DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all Power
    Factors. In: <i>2023 25th European Conference on Power Electronics and Applications
    (EPE’23 ECCE Europe)</i>. IEEE; 2023. doi:<a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">10.23919/epe23ecceeurope58414.2023.10264313</a>'
  apa: Unruh, R., Böcker, J., &#38; Schafmeister, F. (2023). An Optimized Third-Harmonic
    Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to
    50% for all Power Factors. <i>2023 25th European Conference on Power Electronics
    and Applications (EPE’23 ECCE Europe)</i>. 2023 25th European Conference on Power
    Electronics and Applications (EPE’23 ECCE Europe), Aalborg, Denmark. <a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313</a>
  bibtex: '@inproceedings{Unruh_Böcker_Schafmeister_2023, title={An Optimized Third-Harmonic
    Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to
    50% for all Power Factors}, DOI={<a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">10.23919/epe23ecceeurope58414.2023.10264313</a>},
    booktitle={2023 25th European Conference on Power Electronics and Applications
    (EPE’23 ECCE Europe)}, publisher={IEEE}, author={Unruh, Roland and Böcker, Joachim
    and Schafmeister, Frank}, year={2023} }'
  chicago: Unruh, Roland, Joachim Böcker, and Frank Schafmeister. “An Optimized Third-Harmonic
    Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to
    50% for All Power Factors.” In <i>2023 25th European Conference on Power Electronics
    and Applications (EPE’23 ECCE Europe)</i>. IEEE, 2023. <a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313</a>.
  ieee: 'R. Unruh, J. Böcker, and F. Schafmeister, “An Optimized Third-Harmonic Injection
    Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all
    Power Factors,” presented at the 2023 25th European Conference on Power Electronics
    and Applications (EPE’23 ECCE Europe), Aalborg, Denmark, 2023, doi: <a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">10.23919/epe23ecceeurope58414.2023.10264313</a>.'
  mla: Unruh, Roland, et al. “An Optimized Third-Harmonic Injection Reduces DC-Link
    Voltage Ripple in Cascaded H-Bridge Converters up to 50% for All Power Factors.”
    <i>2023 25th European Conference on Power Electronics and Applications (EPE’23
    ECCE Europe)</i>, IEEE, 2023, doi:<a href="https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313">10.23919/epe23ecceeurope58414.2023.10264313</a>.
  short: 'R. Unruh, J. Böcker, F. Schafmeister, in: 2023 25th European Conference
    on Power Electronics and Applications (EPE’23 ECCE Europe), IEEE, 2023.'
conference:
  end_date: 2023-09-08
  location: Aalborg, Denmark
  name: 2023 25th European Conference on Power Electronics and Applications (EPE'23
    ECCE Europe)
  start_date: 2023-09-04
date_created: 2023-10-20T07:13:32Z
date_updated: 2023-10-20T10:01:02Z
department:
- _id: '52'
doi: 10.23919/epe23ecceeurope58414.2023.10264313
keyword:
- Cascaded H-Bridge
- Solid-State Transformer
- Capacitor voltage ripple
- Zero sequence voltage
- Third harmonic injection
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/10264313
publication: 2023 25th European Conference on Power Electronics and Applications (EPE'23
  ECCE Europe)
publication_identifier:
  isbn:
  - 979-8-3503-1678-0
publication_status: published
publisher: IEEE
quality_controlled: '1'
status: public
title: An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded
  H-Bridge Converters up to 50% for all Power Factors
type: conference
user_id: '34289'
year: '2023'
...
---
_id: '34176'
abstract:
- lang: eng
  text: Cascaded H-bridge Converters (CHBs) are a promising solution in converting
    power from a three-phase medium voltage of 6.6 kV...30 kV to a lower DC-voltage
    in the range of 100 V...1 kV to provide pure DC power to applications such as
    electrolyzers for hydrogen generation, data centers with a DC power distribution
    and DC microgrids. CHBs can be interpreted as modular multilevel converters with
    an isolated DC-DC output stage per module, require a large DC-link capacitor for
    each module to handle the second harmonic voltage ripple caused by the fluctuating
    input power within a fundamental grid period. Without a zero-sequence voltage
    injection, star-connected CHBs are operated with approximately sinusoidal arm
    voltages and currents. The floating star point potential enables to utilize different
    zero-sequence voltage injection techniques such as a third-harmonic injection
    with 1/6 of the grid voltage amplitude or a Min-Max voltage injection. Both well-known
    methods have the advantage to reduce the peak arm voltage and thereby the number
    of required modules by 13.4 % (to √ 3 2). This paper proves analytically that
    the third-harmonic injection with 1/6 of the grid voltage amplitude reduces the
    second harmonic voltage ripple by only 15.1 % compared to no-voltage injection
    for unity power factor operation and balanced grid voltages. Then it is shown,
    that the Min-Max injection has the often overlooked advantage of reducing the
    second harmonic voltage ripple by even 18.8 %. By applying the here proposed zero-sequence
    voltage injection in saturation modulation, the second harmonic voltage ripple
    of the DC-link capacitors is reduced by even 24.3 %, while still requiring the
    same number of modules as the Min-Max injection. For a realistic number of reserve
    modules, the overall energy ripple in the DC-link capacitors is reduced by 40
    %.
author:
- 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: 'Unruh R, Schafmeister F, Böcker J. Zero-Sequence Voltage Reduces DC-Link Capacitor
    Demand in Cascaded H-Bridge Converters for Large-Scale Electrolyzers by 40%. In:
    <i>24th European Conference on Power Electronics and Applications (EPE’22 ECCE
    Europe)</i>. IEEE; 2022.'
  apa: Unruh, R., Schafmeister, F., &#38; Böcker, J. (2022). Zero-Sequence Voltage
    Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale
    Electrolyzers by 40%. <i>24th European Conference on Power Electronics and Applications
    (EPE’22 ECCE Europe)</i>. 24th European Conference on Power Electronics and Applications
    (EPE’22 ECCE Europe), Hanover, Germany.
  bibtex: '@inproceedings{Unruh_Schafmeister_Böcker_2022, title={Zero-Sequence Voltage
    Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale
    Electrolyzers by 40%}, booktitle={24th European Conference on Power Electronics
    and Applications (EPE’22 ECCE Europe)}, publisher={IEEE}, author={Unruh, Roland
    and Schafmeister, Frank and Böcker, Joachim}, year={2022} }'
  chicago: Unruh, Roland, Frank Schafmeister, and Joachim Böcker. “Zero-Sequence Voltage
    Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale
    Electrolyzers by 40%.” In <i>24th European Conference on Power Electronics and
    Applications (EPE’22 ECCE Europe)</i>. IEEE, 2022.
  ieee: R. Unruh, F. Schafmeister, and J. Böcker, “Zero-Sequence Voltage Reduces DC-Link
    Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale Electrolyzers
    by 40%,” presented at the 24th European Conference on Power Electronics and Applications
    (EPE’22 ECCE Europe), Hanover, Germany, 2022.
  mla: Unruh, Roland, et al. “Zero-Sequence Voltage Reduces DC-Link Capacitor Demand
    in Cascaded H-Bridge Converters for Large-Scale Electrolyzers by 40%.” <i>24th
    European Conference on Power Electronics and Applications (EPE’22 ECCE Europe)</i>,
    IEEE, 2022.
  short: 'R. Unruh, F. Schafmeister, J. Böcker, in: 24th European Conference on Power
    Electronics and Applications (EPE’22 ECCE Europe), IEEE, 2022.'
conference:
  end_date: 2022-09-09
  location: Hanover, Germany
  name: 24th European Conference on Power Electronics and Applications (EPE'22 ECCE
    Europe)
  start_date: 2022-09-05
date_created: 2022-12-02T12:47:38Z
date_updated: 2023-10-23T09:04:23Z
department:
- _id: '52'
keyword:
- Cascaded H-Bridge
- Solid-State Transformer
- Zero sequence voltage
- Third harmonic injection
- Capacitor voltage ripple
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/9907278
publication: 24th European Conference on Power Electronics and Applications (EPE'22
  ECCE Europe)
publication_identifier:
  isbn:
  - 978-9-0758-1539-9
publication_status: published
publisher: IEEE
status: public
title: Zero-Sequence Voltage Reduces DC-Link Capacitor Demand in Cascaded H-Bridge
  Converters for Large-Scale Electrolyzers by 40%
type: conference
user_id: '34289'
year: '2022'
...