---
_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: 2023 25th European Conference on Power Electronics and Applications
(EPE’23 ECCE Europe). IEEE; 2023. doi:10.23919/epe23ecceeurope58414.2023.10264313'
apa: Unruh, R., Böcker, J., & 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. 2023 25th European Conference on Power Electronics
and Applications (EPE’23 ECCE Europe). 2023 25th European Conference on Power
Electronics and Applications (EPE’23 ECCE Europe), Aalborg, Denmark. https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313
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={10.23919/epe23ecceeurope58414.2023.10264313},
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 2023 25th European Conference on Power Electronics
and Applications (EPE’23 ECCE Europe). IEEE, 2023. https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313.
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: 10.23919/epe23ecceeurope58414.2023.10264313.'
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.”
2023 25th European Conference on Power Electronics and Applications (EPE’23
ECCE Europe), IEEE, 2023, doi:10.23919/epe23ecceeurope58414.2023.10264313.
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:
24th European Conference on Power Electronics and Applications (EPE’22 ECCE
Europe). IEEE; 2022.'
apa: Unruh, R., Schafmeister, F., & Böcker, J. (2022). Zero-Sequence Voltage
Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale
Electrolyzers by 40%. 24th European Conference on Power Electronics and Applications
(EPE’22 ECCE Europe). 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 24th European Conference on Power Electronics and
Applications (EPE’22 ECCE Europe). 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%.” 24th
European Conference on Power Electronics and Applications (EPE’22 ECCE Europe),
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'
...
---
_id: '29938'
abstract:
- lang: eng
text: Modular solid-state transformers (SSTs) are a promising technology in converting
power from a 10kV three-phase medium voltage to a lower DC-voltage in the range
of 100…400V to provide pure DC power to applications such as electrolyzers for
hydrogen generation, data centers with a DC power distribution and DC micro grids.
Modular SSTs which can be interpreted as modular multilevel converters with an
isolated DC-DC output stage per module, are designed with redundant modules to
increase reliability. Usually, each of the three arms operates independently,
and therefore, only a fixed number of faulty modules can be compensated in each
arm, even if all modules are operational in the remaining two arms. With the proposed
zero-sequence voltage injection, up to 100% more faulty modules can be compensated
in an arm by employing the same hardware. In addition, module power imbalances
are nearly eliminated by utilizing a fundamental frequency zero-sequence voltage.
A dominant 3rd harmonic zero-sequence voltage injection in combination with the
5th, 7th and several higher order harmonics with adaptive (small) amplitudes minimize
the required arm voltages at steady-state. For nominal operation or symmetrical
faults, the proposed technique is equivalent to the well known Min-Max voltage
injection, which already reduces the peak arm voltage by 13.4% compared to a constant
star point potential. A statistical analysis proves, that the expected number
of tolerable faulty modules of the 1MW SST increases by 12% without the need for
additional hardware.
author:
- first_name: Roland
full_name: Unruh, Roland
id: '34289'
last_name: Unruh
- first_name: Jarren
full_name: Lange, Jarren
id: '78801'
last_name: Lange
- 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, Lange J, Schafmeister F, Böcker J. Adaptive Zero-Sequence Voltage
Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault
Conditions. In: 23rd European Conference on Power Electronics and Applications
(EPE’21 ECCE Europe). IEEE; 2021. doi:https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542'
apa: Unruh, R., Lange, J., Schafmeister, F., & Böcker, J. (2021). Adaptive Zero-Sequence
Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical
Fault Conditions. 23rd European Conference on Power Electronics and Applications
(EPE’21 ECCE Europe). 23rd European Conference on Power Electronics and Applications
(EPE’21 ECCE Europe), Ghent, Belgium. https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542
bibtex: '@inproceedings{Unruh_Lange_Schafmeister_Böcker_2021, title={Adaptive Zero-Sequence
Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical
Fault Conditions}, DOI={https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542},
booktitle={23rd European Conference on Power Electronics and Applications (EPE’21
ECCE Europe)}, publisher={IEEE}, author={Unruh, Roland and Lange, Jarren and Schafmeister,
Frank and Böcker, Joachim}, year={2021} }'
chicago: Unruh, Roland, Jarren Lange, Frank Schafmeister, and Joachim Böcker. “Adaptive
Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate
for Asymmetrical Fault Conditions.” In 23rd European Conference on Power Electronics
and Applications (EPE’21 ECCE Europe). IEEE, 2021. https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542.
ieee: 'R. Unruh, J. Lange, F. Schafmeister, and J. Böcker, “Adaptive Zero-Sequence
Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical
Fault Conditions,” presented at the 23rd European Conference on Power Electronics
and Applications (EPE’21 ECCE Europe), Ghent, Belgium, 2021, doi: https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542.'
mla: Unruh, Roland, et al. “Adaptive Zero-Sequence Voltage Injection for Modular
Solid-State Transformer to Compensate for Asymmetrical Fault Conditions.” 23rd
European Conference on Power Electronics and Applications (EPE’21 ECCE Europe),
IEEE, 2021, doi:https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542.
short: 'R. Unruh, J. Lange, F. Schafmeister, J. Böcker, in: 23rd European Conference
on Power Electronics and Applications (EPE’21 ECCE Europe), IEEE, 2021.'
conference:
end_date: 2021-09-10
location: Ghent, Belgium
name: 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE
Europe)
start_date: 2021-09-06
date_created: 2022-02-21T16:31:34Z
date_updated: 2022-09-09T12:01:42Z
department:
- _id: '52'
doi: https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542
keyword:
- Solid-State Transformer
- Zero sequence voltage
- Fault handling strategy
- Power balance control technique
- Three-phase system
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/9570542
publication: 23rd European Conference on Power Electronics and Applications (EPE'21
ECCE Europe)
publication_identifier:
isbn:
- 978-9-0758-1537-5
publication_status: published
publisher: IEEE
status: public
title: Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer
to Compensate for Asymmetrical Fault Conditions
type: conference
user_id: '34289'
year: '2021'
...
---
_id: '29940'
abstract:
- lang: eng
text: A full-bridge modular multilevel converter (MMC) is compared to a half-bridge-based
MMC for high-current low-voltage DC-applications such as electrolysis, arc welding
or datacenters with DC-power distribution. Usually, modular multilevel converters
are used in high-voltage DC-applications (HVDC) in the multiple kV-range, but
to meet the needs of a high-current demand at low output voltage levels, the modular
converter concept requires adaptations. In the proposed concept, the MMC is used
to step-down the three-phase medium-voltage of 10 kV. Therefore, each module is
extended by an LLC resonant converter to adapt to the specific electrolyzers DC-voltage
range of 142-220V and to provide galvanic isolation. The proposed MMC converter
with full-bridge modules uses half the number of modules compared to a half-bridge-based
MMC while reducing the voltage ripple by 78% and capacitor losses by 64% by rearranging
the same components to ensure identical costs and volume. For additional reliability,
a new robust algorithm for balancing conduction losses during the bypass phase
is presented.
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: Norbert
full_name: Fröhleke, Norbert
last_name: Fröhleke
- first_name: Joachim
full_name: Böcker, Joachim
id: '66'
last_name: Böcker
orcid: 0000-0002-8480-7295
citation:
ama: 'Unruh R, Schafmeister F, Fröhleke N, Böcker J. 1-MW Full-Bridge MMC for High-Current
Low-Voltage (100V-400V) DC-Applications. In: PCIM Europe Digital Days 2020;
International Exhibition and Conference for Power Electronics, Intelligent Motion,
Renewable Energy and Energy Management. VDE; 2020.'
apa: Unruh, R., Schafmeister, F., Fröhleke, N., & Böcker, J. (2020). 1-MW Full-Bridge
MMC for High-Current Low-Voltage (100V-400V) DC-Applications. PCIM Europe Digital
Days 2020; International Exhibition and Conference for Power Electronics, Intelligent
Motion, Renewable Energy and Energy Management. PCIM Europe digital days 2020,
Germany.
bibtex: '@inproceedings{Unruh_Schafmeister_Fröhleke_Böcker_2020, title={1-MW Full-Bridge
MMC for High-Current Low-Voltage (100V-400V) DC-Applications}, booktitle={PCIM
Europe digital days 2020; International Exhibition and Conference for Power Electronics,
Intelligent Motion, Renewable Energy and Energy Management}, publisher={VDE},
author={Unruh, Roland and Schafmeister, Frank and Fröhleke, Norbert and Böcker,
Joachim}, year={2020} }'
chicago: Unruh, Roland, Frank Schafmeister, Norbert Fröhleke, and Joachim Böcker.
“1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications.”
In PCIM Europe Digital Days 2020; International Exhibition and Conference for
Power Electronics, Intelligent Motion, Renewable Energy and Energy Management.
VDE, 2020.
ieee: R. Unruh, F. Schafmeister, N. Fröhleke, and J. Böcker, “1-MW Full-Bridge MMC
for High-Current Low-Voltage (100V-400V) DC-Applications,” presented at the PCIM
Europe digital days 2020, Germany, 2020.
mla: Unruh, Roland, et al. “1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V)
DC-Applications.” PCIM Europe Digital Days 2020; International Exhibition and
Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy
Management, VDE, 2020.
short: 'R. Unruh, F. Schafmeister, N. Fröhleke, J. Böcker, in: PCIM Europe Digital
Days 2020; International Exhibition and Conference for Power Electronics, Intelligent
Motion, Renewable Energy and Energy Management, VDE, 2020.'
conference:
end_date: 2020-07-08
location: Germany
name: PCIM Europe digital days 2020
start_date: 2020-07-07
date_created: 2022-02-21T16:42:30Z
date_updated: 2023-10-20T11:52:39Z
department:
- _id: '52'
keyword:
- Cascaded H-Bridge
- Solid-State Transformer
- Capacitor voltage ripple
- Zero sequence voltage
- Full-Bridge
language:
- iso: eng
main_file_link:
- url: https://ieeexplore.ieee.org/abstract/document/9178138
publication: PCIM Europe digital days 2020; International Exhibition and Conference
for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management
publication_identifier:
isbn:
- 978-3-8007-5245-4
publication_status: published
publisher: VDE
status: public
title: 1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications
type: conference
user_id: '34289'
year: '2020'
...