[{"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Third harmonic injection"],"language":[{"iso":"eng"}],"_id":"48352","user_id":"34289","department":[{"_id":"52"}],"abstract":[{"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.","lang":"eng"}],"status":"public","type":"conference","publication":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","title":"An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all Power Factors","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/10264313"}],"doi":"10.23919/epe23ecceeurope58414.2023.10264313","conference":{"location":"Aalborg, Denmark","end_date":"2023-09-08","start_date":"2023-09-04","name":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)"},"publisher":"IEEE","date_updated":"2023-10-20T10:01:02Z","date_created":"2023-10-20T07:13:32Z","author":[{"last_name":"Unruh","id":"34289","full_name":"Unruh, Roland","first_name":"Roland"},{"full_name":"Böcker, Joachim","id":"66","orcid":"0000-0002-8480-7295","last_name":"Böcker","first_name":"Joachim"},{"first_name":"Frank","full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister"}],"year":"2023","citation":{"short":"R. Unruh, J. Böcker, F. Schafmeister, in: 2023 25th European Conference on Power Electronics and Applications (EPE’23 ECCE Europe), IEEE, 2023.","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} }","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>.","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>","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>","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>.","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>."},"publication_status":"published","quality_controlled":"1","publication_identifier":{"isbn":["979-8-3503-1678-0"]}},{"year":"2022","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.","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.","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.","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.","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} }","short":"R. Unruh, F. Schafmeister, J. Böcker, in: 24th European Conference on Power Electronics and Applications (EPE’22 ECCE Europe), IEEE, 2022."},"publication_identifier":{"isbn":["978-9-0758-1539-9"]},"publication_status":"published","title":"Zero-Sequence Voltage Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale Electrolyzers by 40%","conference":{"name":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)","start_date":"2022-09-05","end_date":"2022-09-09","location":"Hanover, Germany"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9907278"}],"publisher":"IEEE","date_updated":"2023-10-23T09:04:23Z","date_created":"2022-12-02T12:47:38Z","author":[{"first_name":"Roland","last_name":"Unruh","id":"34289","full_name":"Unruh, Roland"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"},{"first_name":"Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295","full_name":"Böcker, Joachim","id":"66"}],"abstract":[{"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 %.","lang":"eng"}],"status":"public","publication":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)","type":"conference","keyword":["Cascaded H-Bridge","Solid-State Transformer","Zero sequence voltage","Third harmonic injection","Capacitor voltage ripple"],"language":[{"iso":"eng"}],"_id":"34176","department":[{"_id":"52"}],"user_id":"34289"},{"_id":"29938","user_id":"34289","department":[{"_id":"52"}],"keyword":["Solid-State Transformer","Zero sequence voltage","Fault handling strategy","Power balance control technique","Three-phase system"],"language":[{"iso":"eng"}],"type":"conference","publication":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","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."}],"status":"public","publisher":"IEEE","date_updated":"2022-09-09T12:01:42Z","author":[{"last_name":"Unruh","id":"34289","full_name":"Unruh, Roland","first_name":"Roland"},{"first_name":"Jarren","last_name":"Lange","id":"78801","full_name":"Lange, Jarren"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"},{"id":"66","full_name":"Böcker, Joachim","orcid":"0000-0002-8480-7295","last_name":"Böcker","first_name":"Joachim"}],"date_created":"2022-02-21T16:31:34Z","title":"Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault Conditions","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9570542"}],"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"},"doi":"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542","publication_status":"published","publication_identifier":{"isbn":["978-9-0758-1537-5"]},"year":"2021","citation":{"apa":"Unruh, R., Lange, J., Schafmeister, F., &#38; Böcker, J. (2021). Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault Conditions. <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>. 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), Ghent, Belgium. <a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>","short":"R. Unruh, J. Lange, F. Schafmeister, J. Böcker, in: 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), IEEE, 2021.","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={<a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>}, 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} }","mla":"Unruh, Roland, et al. “Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault Conditions.” <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>, IEEE, 2021, doi:<a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>.","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: <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>. IEEE; 2021. doi:<a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>","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 <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>. IEEE, 2021. <a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>.","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: <a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542</a>."}},{"status":"public","abstract":[{"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.","lang":"eng"}],"type":"conference","publication":"PCIM Europe digital days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management","language":[{"iso":"eng"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Full-Bridge"],"user_id":"34289","department":[{"_id":"52"}],"_id":"29940","citation":{"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.","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 <i>PCIM Europe Digital Days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. VDE, 2020.","ama":"Unruh R, Schafmeister F, Fröhleke N, Böcker J. 1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications. In: <i>PCIM Europe Digital Days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. 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.","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} }","mla":"Unruh, Roland, et al. “1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications.” <i>PCIM Europe Digital Days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>, VDE, 2020.","apa":"Unruh, R., Schafmeister, F., Fröhleke, N., &#38; Böcker, J. (2020). 1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications. <i>PCIM Europe Digital Days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. PCIM Europe digital days 2020, Germany."},"year":"2020","publication_status":"published","publication_identifier":{"isbn":["978-3-8007-5245-4"]},"main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9178138"}],"conference":{"location":"Germany","end_date":"2020-07-08","start_date":"2020-07-07","name":"PCIM Europe digital days 2020"},"title":"1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications","date_created":"2022-02-21T16:42:30Z","author":[{"first_name":"Roland","full_name":"Unruh, Roland","id":"34289","last_name":"Unruh"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"},{"first_name":"Norbert","last_name":"Fröhleke","full_name":"Fröhleke, Norbert"},{"first_name":"Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295","id":"66","full_name":"Böcker, Joachim"}],"publisher":"VDE","date_updated":"2023-10-20T11:52:39Z"}]