[{"language":[{"iso":"eng"}],"keyword":["adaptive DC-link voltage","cascaded H-bridge","resonant operation","Full-Bridge Converter","loss minimization","LLC Resonant Converter","peak capacitor voltage reduction"],"abstract":[{"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%).","lang":"eng"}],"publication":"Electronics","title":"Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple","date_created":"2025-05-05T12:27:39Z","publisher":"MDPI AG","year":"2025","issue":"8","article_number":"1517","user_id":"34289","department":[{"_id":"52"}],"_id":"59805","status":"public","type":"journal_article","main_file_link":[{"url":"https://www.mdpi.com/2079-9292/14/8/1517"}],"doi":"10.3390/electronics14081517","author":[{"id":"34289","full_name":"Unruh, Roland","last_name":"Unruh","first_name":"Roland"},{"first_name":"Joachim","orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim"},{"first_name":"Frank","full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister"}],"volume":14,"date_updated":"2025-05-05T12:34:00Z","citation":{"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>","short":"R. Unruh, J. Böcker, F. Schafmeister, Electronics 14 (2025).","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>.","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} }","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>","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>."},"intvolume":"        14","publication_status":"published","publication_identifier":{"issn":["2079-9292"]}},{"year":"2025","citation":{"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} }","short":"R. Unruh, J. Böcker, F. Schafmeister, in: 2025 Energy Conversion Congress &#38;amp;Amp; Expo Europe (ECCE Europe), IEEE, 2025.","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>.","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>","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>","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>.","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>."},"publication_status":"published","title":"Three-Phase Instantaneous Current Controller for Unbalanced Grid Inductors Without DQ Transform for Cascaded H-Bridge Converters","doi":"10.1109/ecce-europe62795.2025.11238538","conference":{"name":"2025 Energy Conversion Congress & Expo Europe (ECCE Europe)","start_date":"2025-09-01","end_date":"2025-09-04","location":"Birmingham, United Kingdom"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/document/11238538"}],"date_updated":"2025-12-16T15:25:38Z","publisher":"IEEE","author":[{"last_name":"Unruh","id":"34289","full_name":"Unruh, Roland","first_name":"Roland"},{"first_name":"Joachim","full_name":"Böcker, Joachim","id":"66","orcid":"0000-0002-8480-7295","last_name":"Böcker"},{"first_name":"Frank","last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank"}],"date_created":"2025-12-16T15:20:55Z","abstract":[{"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.","lang":"eng"}],"status":"public","publication":"2025 Energy Conversion Congress &amp;amp; Expo Europe (ECCE Europe)","type":"conference","keyword":["Cascaded H-Bridge","Current Control","dq Transformation","Linear Regression","Unbalanced Inductors"],"language":[{"iso":"eng"}],"_id":"63157","department":[{"_id":"52"}],"user_id":"34289"},{"publication":"ECCE Europe 2024; IEEE Energy Conversion Congress & Exposition Europe","abstract":[{"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.","lang":"eng"}],"language":[{"iso":"eng"}],"keyword":["Cascaded H-Bridge","Converter Losses","Decentralized Control","Full-Bridge Converter","LLC Resonant Converter"],"year":"2024","date_created":"2024-05-19T14:26:29Z","publisher":"IEEE","title":"Experimentally Verified 22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge Converter","type":"conference","status":"public","user_id":"34289","department":[{"_id":"52"}],"_id":"54356","publication_status":"accepted","publication_identifier":{"isbn":["979-8-3503-6444-6"]},"citation":{"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} }","short":"R. Unruh, J. Böcker, F. Schafmeister, in: ECCE Europe 2024; IEEE Energy Conversion Congress &#38; Exposition Europe, IEEE, Darmstadt, n.d.","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>.","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>","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>.","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>"},"place":"Darmstadt","author":[{"last_name":"Unruh","full_name":"Unruh, Roland","id":"34289","first_name":"Roland"},{"first_name":"Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295","full_name":"Böcker, Joachim","id":"66"},{"first_name":"Frank","last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank"}],"date_updated":"2024-11-28T14:16:05Z","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/10751954"}],"conference":{"end_date":"2024-09-06","location":"Darmstadt, Germany","name":"ECCE Europe 2024","start_date":"2024-09-02"},"doi":"https://doi.org/10.1109/ECCEEurope62508.2024.10751954"},{"file_date_updated":"2025-02-14T15:32:17Z","language":[{"iso":"eng"}],"ddc":["620"],"department":[{"_id":"52"}],"user_id":"71291","_id":"58648","status":"public","file":[{"relation":"main_file","success":1,"content_type":"application/pdf","access_level":"closed","file_name":"EPE_2024_09_02-Experimentally Verified 22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge Converter.pdf","file_id":"58649","file_size":3829411,"creator":"schafmei","date_created":"2025-02-14T15:32:17Z","date_updated":"2025-02-14T15:32:17Z"}],"publication":"Proceedings of the Energy Conversion Congress & Expo (ECCE Europe)","type":"conference","doi":"10.1109/ECCEEurope62508.2024.10751954","conference":{"name":" Energy Conversion Congress & Expo (ECCE Europe)","start_date":"2024-09-02","end_date":"2024-09-06","location":"Darmstadt"},"title":"Experimentally Verified 22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge Converter","author":[{"first_name":"Roland","full_name":"Unruh, Roland","id":"34289","last_name":"Unruh"},{"full_name":"Böcker, Joachim ","last_name":"Böcker","first_name":"Joachim "},{"first_name":"Frank","id":"71291","full_name":"Schafmeister, Frank","last_name":"Schafmeister"}],"date_created":"2025-02-14T15:30:36Z","date_updated":"2025-02-14T15:33:10Z","publisher":"IEEE","citation":{"short":"R. Unruh, J. Böcker, F. Schafmeister, in: Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe), IEEE, 2024.","bibtex":"@inproceedings{Unruh_Böcker_Schafmeister_2024, 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\">10.1109/ECCEEurope62508.2024.10751954</a>}, booktitle={Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe)}, publisher={IEEE}, author={Unruh, Roland and Böcker, Joachim  and Schafmeister, Frank}, year={2024} }","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>Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe)</i>, IEEE, 2024, doi:<a href=\"https://doi.org/10.1109/ECCEEurope62508.2024.10751954\">10.1109/ECCEEurope62508.2024.10751954</a>.","apa":"Unruh, R., Böcker, J., &#38; Schafmeister, F. (2024). Experimentally Verified 22 kW, 40 kHz LLC Resonant Converter Design with new Control for a 1 MW Cascaded H-Bridge Converter. <i>Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe)</i>.  Energy Conversion Congress &#38; Expo (ECCE Europe), Darmstadt. <a href=\"https://doi.org/10.1109/ECCEEurope62508.2024.10751954\">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>","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>Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe)</i>. IEEE; 2024. doi:<a href=\"https://doi.org/10.1109/ECCEEurope62508.2024.10751954\">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  Energy Conversion Congress &#38; Expo (ECCE Europe), Darmstadt, 2024, doi: <a href=\"https://doi.org/10.1109/ECCEEurope62508.2024.10751954\">10.1109/ECCEEurope62508.2024.10751954</a>.","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>Proceedings of the Energy Conversion Congress &#38; Expo (ECCE Europe)</i>. IEEE, 2024. <a href=\"https://doi.org/10.1109/ECCEEurope62508.2024.10751954\">https://doi.org/10.1109/ECCEEurope62508.2024.10751954</a>."},"year":"2024","has_accepted_license":"1","publication_status":"published"},{"date_updated":"2023-10-20T10:01:02Z","publisher":"IEEE","author":[{"first_name":"Roland","last_name":"Unruh","id":"34289","full_name":"Unruh, Roland"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim","first_name":"Joachim"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"}],"date_created":"2023-10-20T07:13:32Z","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"}],"conference":{"name":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","start_date":"2023-09-04","end_date":"2023-09-08","location":"Aalborg, Denmark"},"doi":"10.23919/epe23ecceeurope58414.2023.10264313","publication_status":"published","quality_controlled":"1","publication_identifier":{"isbn":["979-8-3503-1678-0"]},"year":"2023","citation":{"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>.","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} }","short":"R. Unruh, J. Böcker, F. Schafmeister, in: 2023 25th European Conference on Power Electronics and Applications (EPE’23 ECCE Europe), IEEE, 2023.","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>","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>.","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>"},"_id":"48352","user_id":"34289","department":[{"_id":"52"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Third harmonic injection"],"language":[{"iso":"eng"}],"type":"conference","publication":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","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"},{"title":"Zero-Sequence Voltage Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale Electrolyzers by 40%","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"},"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"},{"first_name":"Frank","last_name":"Schafmeister","full_name":"Schafmeister, Frank","id":"71291"},{"first_name":"Joachim","id":"66","full_name":"Böcker, Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295"}],"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.","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.","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.","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} }","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."},"publication_identifier":{"isbn":["978-9-0758-1539-9"]},"publication_status":"published","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","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 %."}],"status":"public","publication":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)","type":"conference"},{"language":[{"iso":"eng"}],"keyword":["Solid-State Transformer","Zero sequence voltage","Fault handling strategy","Power balance control technique","Three-phase system"],"department":[{"_id":"52"}],"user_id":"34289","_id":"29938","status":"public","abstract":[{"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.","lang":"eng"}],"publication":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","type":"conference","conference":{"start_date":"2021-09-06","name":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","location":"Ghent, Belgium","end_date":"2021-09-10"},"doi":"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9570542"}],"title":"Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault Conditions","date_created":"2022-02-21T16:31:34Z","author":[{"first_name":"Roland","id":"34289","full_name":"Unruh, Roland","last_name":"Unruh"},{"first_name":"Jarren","last_name":"Lange","id":"78801","full_name":"Lange, Jarren"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"},{"first_name":"Joachim","full_name":"Böcker, Joachim","id":"66","orcid":"0000-0002-8480-7295","last_name":"Böcker"}],"date_updated":"2022-09-09T12:01:42Z","publisher":"IEEE","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: <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>.","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>","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>.","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} }"},"year":"2021","publication_identifier":{"isbn":["978-9-0758-1537-5"]},"publication_status":"published"},{"_id":"29893","user_id":"34289","department":[{"_id":"34"},{"_id":"52"}],"keyword":["Phase-Shifted Full Bridge","Full-Bridge Converter","Phase-Shift Control","Phase-Shift Modulation","LLC Converter","Thermal Balancing"],"language":[{"iso":"eng"}],"type":"conference","publication":"2021 IEEE Applied Power Electronics Conference and Exposition (APEC)","abstract":[{"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.","lang":"eng"}],"status":"public","publisher":"IEEE","date_updated":"2023-10-20T11:50:25Z","date_created":"2022-02-20T21:19:46Z","author":[{"first_name":"Philipp","last_name":"Rehlaender","full_name":"Rehlaender, Philipp","id":"69469"},{"last_name":"Unruh","id":"34289","full_name":"Unruh, Roland","first_name":"Roland"},{"first_name":"Frank","last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank"},{"full_name":"Böcker, Joachim","id":"66","last_name":"Böcker","orcid":"0000-0002-8480-7295","first_name":"Joachim"}],"title":"Alternating Asymmetrical Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching Losses to Reduce Thermal Imbalances","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9487104"}],"conference":{"name":"2021 IEEE Applied Power Electronics Conference and Exposition (APEC)","start_date":"2021-06-14","end_date":"2021-06-17","location":"Phoenix, AZ, USA"},"doi":"10.1109/apec42165.2021.9487104","publication_status":"published","publication_identifier":{"isbn":["978-1-7281-8950-5"]},"year":"2021","citation":{"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>","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.","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} }","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>","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>."}},{"publication_identifier":{"isbn":["978-9-0758-1537-5"]},"publication_status":"published","citation":{"apa":"Rehlaender, P., Unruh, R., Hankeln, L., Schafmeister, F., &#38; Böcker, J. (2021). Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration. <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/EPE21ECCEEurope50061.2021.9570674\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570674</a>","mla":"Rehlaender, Philipp, et al. “Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration.” <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>, IEEE, 2021, doi:<a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570674\">10.23919/EPE21ECCEEurope50061.2021.9570674</a>.","short":"P. Rehlaender, R. Unruh, L. Hankeln, F. Schafmeister, J. Böcker, in: 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), IEEE, 2021.","bibtex":"@inproceedings{Rehlaender_Unruh_Hankeln_Schafmeister_Böcker_2021, title={Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration}, DOI={<a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570674\">10.23919/EPE21ECCEEurope50061.2021.9570674</a>}, booktitle={23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)}, publisher={IEEE}, author={Rehlaender, Philipp and Unruh, Roland and Hankeln, Lars and Schafmeister, Frank and Böcker, Joachim}, year={2021} }","ama":"Rehlaender P, Unruh R, Hankeln L, Schafmeister F, Böcker J. Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration. 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/EPE21ECCEEurope50061.2021.9570674\">10.23919/EPE21ECCEEurope50061.2021.9570674</a>","chicago":"Rehlaender, Philipp, Roland Unruh, Lars Hankeln, Frank Schafmeister, and Joachim Böcker. “Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration.” In <i>23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe)</i>. IEEE, 2021. <a href=\"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570674\">https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570674</a>.","ieee":"P. Rehlaender, R. Unruh, L. Hankeln, F. Schafmeister, and J. Böcker, “Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration,” 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/EPE21ECCEEurope50061.2021.9570674\">10.23919/EPE21ECCEEurope50061.2021.9570674</a>."},"year":"2021","date_created":"2022-02-20T21:29:48Z","author":[{"first_name":"Philipp","id":"69469","full_name":"Rehlaender, Philipp","last_name":"Rehlaender"},{"first_name":"Roland","full_name":"Unruh, Roland","id":"34289","last_name":"Unruh"},{"first_name":"Lars","last_name":"Hankeln","full_name":"Hankeln, Lars"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"},{"last_name":"Böcker","orcid":"0000-0002-8480-7295","id":"66","full_name":"Böcker, Joachim","first_name":"Joachim"}],"date_updated":"2023-02-09T11:01:11Z","publisher":"IEEE","conference":{"start_date":"2021-09-06","name":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","location":"Ghent, Belgium","end_date":"2021-09-10"},"doi":"10.23919/EPE21ECCEEurope50061.2021.9570674","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9570674"}],"title":"Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration","publication":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","type":"conference","status":"public","abstract":[{"lang":"eng","text":"LLC resonant converters are typically unsuitable to be applied for wide voltage-transfer ratio applications. With a full-bridge inverter, however, they can be operated in a variety of different modulations. Most notably, by permanently turning on one MOSFET and turning off the other MOSFET of the same bridge leg, the LLC can be operated in half-bridge configuration reducing the gain by a factor of two. The resonant capacitor is hereby charged to an average voltage of half the input voltage. In this modulation, however, the switch that is permanently turned on is stressed by the complete resonant current while exhibiting no switching losses. This paper proves that the frequency-doubler modulation can better balance the losses among all MOSFETs and should be the preferred mode of operation favored over the conventional half-bridge modulation. This paper analyzes the beneficial loss distribution, proposes an on-the-fly morphing modulation and discusses potential operating strategies to further reduce the junction temperature. Furthermore, it is shown that this modulation can also be altered to achieve the asymmetrical LLC operation. Experimental measurement results show that the modulation results in a substantial decrease of the maximum MOSFET temperature and shows that the converter can be smoothly transitioned during operation from full-bridge modulation to the frequency-doubler half-bridge operation and back."}],"department":[{"_id":"34"},{"_id":"52"}],"user_id":"34289","_id":"29899","language":[{"iso":"eng"}],"keyword":["Resonant converter","High frequency power converter","Switched-mode power supply","Converter control","Control methods for electrical systems"]},{"publication_status":"published","citation":{"ieee":"R. Unruh, F. Schafmeister, and J. Böcker, “Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design,” presented at the 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe), Lyon, France, 2020, doi: <a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">10.23919/epe20ecceeurope43536.2020.9215687</a>.","chicago":"Unruh, Roland, Frank Schafmeister, and Joachim Böcker. “Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design.” In <i>2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe)</i>. IEEE, 2020. <a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687</a>.","ama":"Unruh R, Schafmeister F, Böcker J. Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design. In: <i>2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe)</i>. IEEE; 2020. doi:<a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">10.23919/epe20ecceeurope43536.2020.9215687</a>","short":"R. Unruh, F. Schafmeister, J. Böcker, in: 2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe), IEEE, 2020.","bibtex":"@inproceedings{Unruh_Schafmeister_Böcker_2020, title={Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design}, DOI={<a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">10.23919/epe20ecceeurope43536.2020.9215687</a>}, booktitle={2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe)}, publisher={IEEE}, author={Unruh, Roland and Schafmeister, Frank and Böcker, Joachim}, year={2020} }","mla":"Unruh, Roland, et al. “Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design.” <i>2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe)</i>, IEEE, 2020, doi:<a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">10.23919/epe20ecceeurope43536.2020.9215687</a>.","apa":"Unruh, R., Schafmeister, F., &#38; Böcker, J. (2020). Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design. <i>2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe)</i>. 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe), Lyon, France. <a href=\"https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687\">https://doi.org/10.23919/epe20ecceeurope43536.2020.9215687</a>"},"year":"2020","date_created":"2022-02-21T16:33:14Z","author":[{"last_name":"Unruh","full_name":"Unruh, Roland","id":"34289","first_name":"Roland"},{"first_name":"Frank","id":"71291","full_name":"Schafmeister, Frank","last_name":"Schafmeister"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim","first_name":"Joachim"}],"date_updated":"2022-02-21T17:00:16Z","publisher":"IEEE","conference":{"location":"Lyon, France","end_date":"2020-09-11","start_date":"2020-09-07","name":"22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)"},"doi":"10.23919/epe20ecceeurope43536.2020.9215687","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9215687"}],"title":"Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design","publication":"2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)","type":"conference","status":"public","abstract":[{"lang":"eng","text":"In this paper, a full-bridge modular multilevel converter (MMC) and two half-bridge-based MMCs are evaluated for high-current low-voltage e.g. 100 - 400V 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 10kV, and provide up to 1 MW to the load. 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 six-arm MMC converter with half-bridge modules can be simplified and optimized by removing three arms, and thus halving the number of modules. In addition, the module voltage ripple and capacitor losses are decreased by 22% and 30% respectively. By rearranging the components of the half-bridge MMC to build a MMC consisting of grid-side full-bridge modules, the voltage ripple is further reduced by 78% and capacitor losses by 64%, while ensuring identical costs and volume for all MMCs. Finally, the LLC resonant converter is designed for the most efficient full-bridge MMC. The LLC can not operate at resonance with a fixed nominal module voltage of 770V because the output voltage is varying between 142 - 220V. By decreasing the module voltage down to 600V, additional points of operation can be operated in resonance, and the remaining are closer to resonance. The option to decrease the module voltage down to 600V, increases the number of required modules per arm from 12 to 15, which requires to balance the losses of the LLCs and the grid-side stages."}],"department":[{"_id":"52"}],"user_id":"34289","_id":"29939","language":[{"iso":"eng"}],"keyword":["Multilevel converters","Resonant converter","High voltage power converters","ZVS Converters","Combination MMC LLC"]},{"date_created":"2022-02-21T16:42:30Z","author":[{"first_name":"Roland","id":"34289","full_name":"Unruh, Roland","last_name":"Unruh"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"},{"first_name":"Norbert","full_name":"Fröhleke, Norbert","last_name":"Fröhleke"},{"first_name":"Joachim","orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim"}],"date_updated":"2023-10-20T11:52:39Z","publisher":"VDE","conference":{"end_date":"2020-07-08","location":"Germany","name":"PCIM Europe digital days 2020","start_date":"2020-07-07"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9178138"}],"title":"1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications","publication_identifier":{"isbn":["978-3-8007-5245-4"]},"publication_status":"published","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.","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.","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."},"year":"2020","department":[{"_id":"52"}],"user_id":"34289","_id":"29940","language":[{"iso":"eng"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Full-Bridge"],"publication":"PCIM Europe digital days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management","type":"conference","status":"public","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."}]},{"quality_controlled":"1","publication_identifier":{"unknown":["978-1-7281-7160-9"]},"publication_status":"published","citation":{"ama":"Unruh R, Schafmeister F, Böcker J. 11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC. In: <i>2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)</i>. IEEE; 2020. doi:<a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">10.1109/compel49091.2020.9265771</a>","chicago":"Unruh, Roland, Frank Schafmeister, and Joachim Böcker. “11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC.” In <i>2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)</i>. IEEE, 2020. <a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">https://doi.org/10.1109/compel49091.2020.9265771</a>.","ieee":"R. Unruh, F. Schafmeister, and J. Böcker, “11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC,” 2020, doi: <a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">10.1109/compel49091.2020.9265771</a>.","mla":"Unruh, Roland, et al. “11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC.” <i>2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)</i>, IEEE, 2020, doi:<a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">10.1109/compel49091.2020.9265771</a>.","bibtex":"@inproceedings{Unruh_Schafmeister_Böcker_2020, title={11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC}, DOI={<a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">10.1109/compel49091.2020.9265771</a>}, booktitle={2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)}, publisher={IEEE}, author={Unruh, Roland and Schafmeister, Frank and Böcker, Joachim}, year={2020} }","short":"R. Unruh, F. Schafmeister, J. Böcker, in: 2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL), IEEE, 2020.","apa":"Unruh, R., Schafmeister, F., &#38; Böcker, J. (2020). 11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC. <i>2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)</i>. <a href=\"https://doi.org/10.1109/compel49091.2020.9265771\">https://doi.org/10.1109/compel49091.2020.9265771</a>"},"year":"2020","author":[{"first_name":"Roland","id":"34289","full_name":"Unruh, Roland","last_name":"Unruh"},{"first_name":"Frank","full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister"},{"first_name":"Joachim","orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim"}],"date_created":"2022-02-18T16:29:08Z","publisher":"IEEE","date_updated":"2024-11-28T14:19:07Z","conference":{"start_date":"2020-11-09","end_date":"2020-11-12"},"doi":"10.1109/compel49091.2020.9265771","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9265771"}],"title":"11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC","publication":"2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)","type":"conference","status":"public","abstract":[{"text":"Although there are numerous design methodologies for the LLC resonant converter, they often do not consider the possibility of input voltage adjustment. In the proposed concept, a modular multi-level converter (MMC) is used to step-down the three-phase medium voltage of 10 kV, and provide up to 1 MW of pure DC power to the load consisting of electrolyzers for hydrogen generation. Therefore, each module is extended by an LLC resonant converter to adapt to the specific electrolyzers DC voltage range of 142...220 V and to provide galvanic isolation. In order to achieve a high efficiency for a wide range of load conditions, the input voltage of the LLC converter is adjusted between 600 V and 770 V while operating at resonance or close to resonance. The parameters of the 11kW LLC resonant converter with an integrated leakage inductance are systematically optimized to maximize the efficiency for all loads while achieving zero-voltage switching. For a fast estimation of eddy current losses, a new method is proposed, which uses a single FEM simulation to fit newly developed loss equations. The calculated average efficiency is 97.8%. The prototype of the LLC converter reaches a peak efficiency of over 98% at resonance at half load which is similar to the precalculated value.","lang":"eng"}],"department":[{"_id":"52"}],"user_id":"34289","_id":"29880","language":[{"iso":"eng"}],"keyword":["Full-bridge","High voltage power converters","LLC resonant converter","Multilevel converters","ZVS Converters"]},{"language":[{"iso":"eng"}],"department":[{"_id":"52"}],"user_id":"66","_id":"29942","status":"public","abstract":[{"text":"Due to recent developments in MMCs, they are used in many medium-voltage and high-power applications today, but efficient and modular solutions for high-power at low-voltage such as for electrolysis are still required. The proposed Y-MMC converts the grid AC-voltage into a DC-voltages, and an LLC converter is connected to each submodule capacitor to provide the required current to the DC-load. This paper proposes a topology that uses only half the number of submodules and moreover to reduce the effective switching frequency by a third, while preserving the same THD und output power of an YY-MMC.","lang":"eng"}],"publication":"PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management","type":"conference","conference":{"name":"PCIM Europe 2019","start_date":"2019-05-07","end_date":"2019-05-09","location":"Nuremberg, Germany"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/document/8767739"}],"title":"MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses","date_created":"2022-02-21T16:57:29Z","author":[{"first_name":"Roland","id":"34289","full_name":"Unruh, Roland","last_name":"Unruh"},{"first_name":"Frank","last_name":"Schafmeister","full_name":"Schafmeister, Frank","id":"71291"},{"last_name":"Fröhleke","full_name":"Fröhleke, Norbert","first_name":"Norbert"},{"first_name":"Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295","id":"66","full_name":"Böcker, Joachim"}],"publisher":"VDE","date_updated":"2022-02-23T15:49:43Z","citation":{"ama":"Unruh R, Schafmeister F, Fröhleke N, Böcker J. MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses. In: <i>PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. VDE; 2019.","ieee":"R. Unruh, F. Schafmeister, N. Fröhleke, and J. Böcker, “MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses,” presented at the PCIM Europe 2019, Nuremberg, Germany, 2019.","chicago":"Unruh, Roland, Frank Schafmeister, Norbert Fröhleke, and Joachim Böcker. “MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses.” In <i>PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. VDE, 2019.","short":"R. Unruh, F. Schafmeister, N. Fröhleke, J. Böcker, in: PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, VDE, 2019.","mla":"Unruh, Roland, et al. “MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses.” <i>PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>, VDE, 2019.","bibtex":"@inproceedings{Unruh_Schafmeister_Fröhleke_Böcker_2019, title={MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses}, booktitle={PCIM Europe 2019; 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={2019} }","apa":"Unruh, R., Schafmeister, F., Fröhleke, N., &#38; Böcker, J. (2019). MMC-Topology for High-Current and Low-Voltage Applications with Minimal Number of Submodules, Reduced Switching and Capacitor Losses. <i>PCIM Europe 2019; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management</i>. PCIM Europe 2019, Nuremberg, Germany."},"year":"2019","publication_identifier":{"isbn":["978-3-8007-4938-6"]},"publication_status":"published"}]