[{"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","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","doi":"10.3390/electronics14081517","main_file_link":[{"url":"https://www.mdpi.com/2079-9292/14/8/1517"}],"volume":14,"author":[{"first_name":"Roland","last_name":"Unruh","id":"34289","full_name":"Unruh, 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"}],"date_updated":"2025-05-05T12:34:00Z","intvolume":"        14","citation":{"ama":"Unruh R, Böcker J, Schafmeister F. Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple. <i>Electronics</i>. 2025;14(8). doi:<a href=\"https://doi.org/10.3390/electronics14081517\">10.3390/electronics14081517</a>","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>.","apa":"Unruh, R., Böcker, J., &#38; Schafmeister, F. (2025). Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple. <i>Electronics</i>, <i>14</i>(8), Article 1517. <a href=\"https://doi.org/10.3390/electronics14081517\">https://doi.org/10.3390/electronics14081517</a>","bibtex":"@article{Unruh_Böcker_Schafmeister_2025, title={Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple}, volume={14}, DOI={<a href=\"https://doi.org/10.3390/electronics14081517\">10.3390/electronics14081517</a>}, number={81517}, journal={Electronics}, publisher={MDPI AG}, author={Unruh, Roland and Böcker, Joachim and Schafmeister, Frank}, year={2025} }","mla":"Unruh, Roland, et al. “Adaptive DC-Link Voltage Control for 22 KW, 40 KHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple.” <i>Electronics</i>, vol. 14, no. 8, 1517, MDPI AG, 2025, doi:<a href=\"https://doi.org/10.3390/electronics14081517\">10.3390/electronics14081517</a>.","short":"R. Unruh, J. Böcker, F. Schafmeister, Electronics 14 (2025)."},"publication_identifier":{"issn":["2079-9292"]},"publication_status":"published","article_number":"1517","department":[{"_id":"52"}],"user_id":"34289","_id":"59805","status":"public","type":"journal_article"},{"doi":"10.1109/DMC62632.2024.10812131","title":"Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection","author":[{"full_name":"Förster, Nikolas","last_name":"Förster","first_name":"Nikolas"},{"full_name":"Wallscheid, Oliver","last_name":"Wallscheid","first_name":"Oliver"},{"first_name":"Frank","last_name":"Schafmeister","full_name":"Schafmeister, Frank"}],"date_created":"2026-01-06T08:06:24Z","date_updated":"2026-01-06T08:07:50Z","citation":{"ama":"Förster N, Wallscheid O, Schafmeister F. Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection. In: <i>2024 IEEE Design Methodologies Conference (DMC)</i>. ; 2024:1-8. doi:<a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">10.1109/DMC62632.2024.10812131</a>","ieee":"N. Förster, O. Wallscheid, and F. Schafmeister, “Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection,” in <i>2024 IEEE Design Methodologies Conference (DMC)</i>, 2024, pp. 1–8, doi: <a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">10.1109/DMC62632.2024.10812131</a>.","chicago":"Förster, Nikolas, Oliver Wallscheid, and Frank Schafmeister. “Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection.” In <i>2024 IEEE Design Methodologies Conference (DMC)</i>, 1–8, 2024. <a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">https://doi.org/10.1109/DMC62632.2024.10812131</a>.","short":"N. Förster, O. Wallscheid, F. Schafmeister, in: 2024 IEEE Design Methodologies Conference (DMC), 2024, pp. 1–8.","bibtex":"@inproceedings{Förster_Wallscheid_Schafmeister_2024, title={Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection}, DOI={<a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">10.1109/DMC62632.2024.10812131</a>}, booktitle={2024 IEEE Design Methodologies Conference (DMC)}, author={Förster, Nikolas and Wallscheid, Oliver and Schafmeister, Frank}, year={2024}, pages={1–8} }","mla":"Förster, Nikolas, et al. “Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection.” <i>2024 IEEE Design Methodologies Conference (DMC)</i>, 2024, pp. 1–8, doi:<a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">10.1109/DMC62632.2024.10812131</a>.","apa":"Förster, N., Wallscheid, O., &#38; Schafmeister, F. (2024). Dual-Active Bridge Sequential Pareto Optimization for Fast Pre-Design and Final Component Selection. <i>2024 IEEE Design Methodologies Conference (DMC)</i>, 1–8. <a href=\"https://doi.org/10.1109/DMC62632.2024.10812131\">https://doi.org/10.1109/DMC62632.2024.10812131</a>"},"page":"1-8","year":"2024","language":[{"iso":"eng"}],"keyword":["MOSFET","Thermal resistance","Surface resistance","Bridge circuits","Zero voltage switching","Pareto optimization","Capacitance","Numerical simulation","Optimization","Resistance heating","Pareto Optimization","Dual-Active Bridge","ZVS","Inductor Optimization","Transformer Optimization","Heat Sink Optimization"],"user_id":"83383","department":[{"_id":"52"}],"_id":"63497","status":"public","type":"conference","publication":"2024 IEEE Design Methodologies Conference (DMC)"},{"publication":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","type":"conference","status":"public","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"}],"department":[{"_id":"52"}],"user_id":"34289","_id":"48352","language":[{"iso":"eng"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Third harmonic injection"],"publication_identifier":{"isbn":["979-8-3503-1678-0"]},"quality_controlled":"1","publication_status":"published","citation":{"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>.","ama":"Unruh R, Böcker J, Schafmeister F. An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all Power Factors. In: <i>2023 25th European Conference on Power Electronics and Applications (EPE’23 ECCE Europe)</i>. IEEE; 2023. doi:<a href=\"https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313\">10.23919/epe23ecceeurope58414.2023.10264313</a>","apa":"Unruh, R., Böcker, J., &#38; Schafmeister, F. (2023). An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all Power Factors. <i>2023 25th European Conference on Power Electronics and Applications (EPE’23 ECCE Europe)</i>. 2023 25th European Conference on Power Electronics and Applications (EPE’23 ECCE Europe), Aalborg, Denmark. <a href=\"https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313\">https://doi.org/10.23919/epe23ecceeurope58414.2023.10264313</a>","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."},"year":"2023","author":[{"last_name":"Unruh","full_name":"Unruh, Roland","id":"34289","first_name":"Roland"},{"first_name":"Joachim","full_name":"Böcker, Joachim","id":"66","orcid":"0000-0002-8480-7295","last_name":"Böcker"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"}],"date_created":"2023-10-20T07:13:32Z","date_updated":"2023-10-20T10:01:02Z","publisher":"IEEE","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","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/10264313"}],"title":"An Optimized Third-Harmonic Injection Reduces DC-Link Voltage Ripple in Cascaded H-Bridge Converters up to 50% for all Power Factors"},{"_id":"34176","department":[{"_id":"52"}],"user_id":"34289","keyword":["Cascaded H-Bridge","Solid-State Transformer","Zero sequence voltage","Third harmonic injection","Capacitor voltage ripple"],"language":[{"iso":"eng"}],"publication":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)","type":"conference","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","date_updated":"2023-10-23T09:04:23Z","publisher":"IEEE","date_created":"2022-12-02T12:47:38Z","author":[{"full_name":"Unruh, Roland","id":"34289","last_name":"Unruh","first_name":"Roland"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"},{"first_name":"Joachim","full_name":"Böcker, Joachim","id":"66","last_name":"Böcker","orcid":"0000-0002-8480-7295"}],"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"}],"publication_identifier":{"isbn":["978-9-0758-1539-9"]},"publication_status":"published","year":"2022","citation":{"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.","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.","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.","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} }","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."}},{"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","type":"conference","publication":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","keyword":["Solid-State Transformer","Zero sequence voltage","Fault handling strategy","Power balance control technique","Three-phase system"],"language":[{"iso":"eng"}],"_id":"29938","user_id":"34289","department":[{"_id":"52"}],"year":"2021","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>.","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} }","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>"},"publication_status":"published","publication_identifier":{"isbn":["978-9-0758-1537-5"]},"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"}],"doi":"https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542","conference":{"name":"23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)","start_date":"2021-09-06","end_date":"2021-09-10","location":"Ghent, Belgium"},"date_updated":"2022-09-09T12:01:42Z","publisher":"IEEE","author":[{"full_name":"Unruh, Roland","id":"34289","last_name":"Unruh","first_name":"Roland"},{"last_name":"Lange","id":"78801","full_name":"Lange, Jarren","first_name":"Jarren"},{"last_name":"Schafmeister","full_name":"Schafmeister, Frank","id":"71291","first_name":"Frank"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","id":"66","full_name":"Böcker, Joachim","first_name":"Joachim"}],"date_created":"2022-02-21T16:31:34Z"},{"year":"2020","citation":{"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>.","short":"R. Unruh, F. Schafmeister, J. Böcker, in: 2020 22nd European Conference on Power Electronics and Applications (EPE’20 ECCE Europe), IEEE, 2020.","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>","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>.","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>.","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>"},"publication_status":"published","title":"Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design","doi":"10.23919/epe20ecceeurope43536.2020.9215687","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)"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9215687"}],"publisher":"IEEE","date_updated":"2022-02-21T17:00:16Z","author":[{"last_name":"Unruh","full_name":"Unruh, Roland","id":"34289","first_name":"Roland"},{"last_name":"Schafmeister","full_name":"Schafmeister, Frank","id":"71291","first_name":"Frank"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","full_name":"Böcker, Joachim","id":"66","first_name":"Joachim"}],"date_created":"2022-02-21T16:33:14Z","abstract":[{"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.","lang":"eng"}],"status":"public","publication":"2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)","type":"conference","keyword":["Multilevel converters","Resonant converter","High voltage power converters","ZVS Converters","Combination MMC LLC"],"language":[{"iso":"eng"}],"_id":"29939","department":[{"_id":"52"}],"user_id":"34289"},{"_id":"29940","user_id":"34289","department":[{"_id":"52"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Full-Bridge"],"language":[{"iso":"eng"}],"type":"conference","publication":"PCIM Europe digital days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management","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."}],"status":"public","publisher":"VDE","date_updated":"2023-10-20T11:52:39Z","author":[{"first_name":"Roland","last_name":"Unruh","full_name":"Unruh, Roland","id":"34289"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"},{"first_name":"Norbert","last_name":"Fröhleke","full_name":"Fröhleke, Norbert"},{"first_name":"Joachim","full_name":"Böcker, Joachim","id":"66","last_name":"Böcker","orcid":"0000-0002-8480-7295"}],"date_created":"2022-02-21T16:42:30Z","title":"1-MW Full-Bridge MMC for High-Current Low-Voltage (100V-400V) DC-Applications","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9178138"}],"conference":{"end_date":"2020-07-08","location":"Germany","name":"PCIM Europe digital days 2020","start_date":"2020-07-07"},"publication_status":"published","publication_identifier":{"isbn":["978-3-8007-5245-4"]},"year":"2020","citation":{"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.","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} }","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.","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.","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.","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.","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."}},{"language":[{"iso":"eng"}],"keyword":["Full-bridge","High voltage power converters","LLC resonant converter","Multilevel converters","ZVS Converters"],"user_id":"34289","department":[{"_id":"52"}],"_id":"29880","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"}],"type":"conference","publication":"2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL)","main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9265771"}],"doi":"10.1109/compel49091.2020.9265771","conference":{"start_date":"2020-11-09","end_date":"2020-11-12"},"title":"11kW, 70kHz LLC Converter Design with Adaptive Input Voltage for 98% Efficiency in an MMC","author":[{"last_name":"Unruh","id":"34289","full_name":"Unruh, Roland","first_name":"Roland"},{"first_name":"Frank","last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank"},{"first_name":"Joachim","id":"66","full_name":"Böcker, Joachim","last_name":"Böcker","orcid":"0000-0002-8480-7295"}],"date_created":"2022-02-18T16:29:08Z","date_updated":"2024-11-28T14:19:07Z","publisher":"IEEE","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>","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>.","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>.","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>","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.","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>."},"year":"2020","publication_status":"published","quality_controlled":"1","publication_identifier":{"unknown":["978-1-7281-7160-9"]}},{"status":"public","abstract":[{"text":"In this work we study the resonant and coherent properties of single InP-based InAs quantum dots, which show an optical emission in the telecom C-band and L-band. High-resolution resonant photocurrent spectroscopy on p–i–n devices reveals narrow linewidths and fully resolved fine structure splittings. We observe Lorentzian line shapes, which allow for the extraction of dephasing times as a function of the applied bias voltage. Coherent ps laser excitation results in pronounced Rabi rotations with increasing pulse area. For π-pulse excitation, we obtain more than 93 % of the theoretically expected photocurrent amplitude. Our results also demonstrate that such state-of-the-art InP-based quantum dots for the telecom band exhibit promising key parameters comparable to well-established InAs/GaAs counterparts.","lang":"eng"}],"publication":"Applied Physics B","type":"journal_article","language":[{"iso":"eng"}],"keyword":["Bias Voltage","Optical Parametric Oscillator","Molecular Beam Epitaxy Growth","Internal Electric Field","Dephasing Time"],"article_type":"original","department":[{"_id":"15"},{"_id":"230"},{"_id":"35"}],"user_id":"49428","_id":"4244","intvolume":"       122","citation":{"apa":"Gordon, S., Yacob, M., Reithmaier, J. P., Benyoucef, M., &#38; Zrenner, A. (2016). Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm. <i>Applied Physics B</i>, <i>122</i>(2). <a href=\"https://doi.org/10.1007/s00340-015-6279-6\">https://doi.org/10.1007/s00340-015-6279-6</a>","bibtex":"@article{Gordon_Yacob_Reithmaier_Benyoucef_Zrenner_2016, title={Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm}, volume={122}, DOI={<a href=\"https://doi.org/10.1007/s00340-015-6279-6\">10.1007/s00340-015-6279-6</a>}, number={2}, journal={Applied Physics B}, publisher={Springer Nature}, author={Gordon, S. and Yacob, M. and Reithmaier, J. P. and Benyoucef, M. and Zrenner, Artur}, year={2016} }","short":"S. Gordon, M. Yacob, J.P. Reithmaier, M. Benyoucef, A. Zrenner, Applied Physics B 122 (2016).","mla":"Gordon, S., et al. “Coherent Photocurrent Spectroscopy of Single InP-Based Quantum Dots in the Telecom Band at 1.5 Μm.” <i>Applied Physics B</i>, vol. 122, no. 2, Springer Nature, 2016, doi:<a href=\"https://doi.org/10.1007/s00340-015-6279-6\">10.1007/s00340-015-6279-6</a>.","chicago":"Gordon, S., M. Yacob, J. P. Reithmaier, M. Benyoucef, and Artur Zrenner. “Coherent Photocurrent Spectroscopy of Single InP-Based Quantum Dots in the Telecom Band at 1.5 Μm.” <i>Applied Physics B</i> 122, no. 2 (2016). <a href=\"https://doi.org/10.1007/s00340-015-6279-6\">https://doi.org/10.1007/s00340-015-6279-6</a>.","ieee":"S. Gordon, M. Yacob, J. P. Reithmaier, M. Benyoucef, and A. Zrenner, “Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm,” <i>Applied Physics B</i>, vol. 122, no. 2, 2016.","ama":"Gordon S, Yacob M, Reithmaier JP, Benyoucef M, Zrenner A. Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm. <i>Applied Physics B</i>. 2016;122(2). doi:<a href=\"https://doi.org/10.1007/s00340-015-6279-6\">10.1007/s00340-015-6279-6</a>"},"year":"2016","issue":"2","publication_identifier":{"issn":["0946-2171","1432-0649"]},"publication_status":"published","doi":"10.1007/s00340-015-6279-6","title":"Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm","volume":122,"date_created":"2018-08-29T08:30:59Z","author":[{"first_name":"S.","last_name":"Gordon","full_name":"Gordon, S."},{"first_name":"M.","last_name":"Yacob","full_name":"Yacob, M."},{"first_name":"J. P.","last_name":"Reithmaier","full_name":"Reithmaier, J. P."},{"first_name":"M.","last_name":"Benyoucef","full_name":"Benyoucef, M."},{"first_name":"Artur","full_name":"Zrenner, Artur","id":"606","orcid":"0000-0002-5190-0944","last_name":"Zrenner"}],"publisher":"Springer Nature","date_updated":"2022-01-06T07:00:41Z"},{"title":"Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems","date_created":"2019-05-13T13:53:25Z","author":[{"first_name":"Waleed","last_name":"Al-Ashtari","full_name":"Al-Ashtari, Waleed"},{"last_name":"Hunstig","full_name":"Hunstig, Matthias","first_name":"Matthias"},{"first_name":"Tobias","full_name":"Hemsel, Tobias","id":"210","last_name":"Hemsel"},{"first_name":"Walter","last_name":"Sextro","full_name":"Sextro, Walter","id":"21220"}],"date_updated":"2022-01-06T07:04:20Z","citation":{"chicago":"Al-Ashtari, Waleed, Matthias Hunstig, Tobias Hemsel, and Walter Sextro. “Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems.” In <i>Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013</i>, 159–61. Berichte Aus Dem IDS. Hannover, Germany, 2013.","ieee":"W. Al-Ashtari, M. Hunstig, T. Hemsel, and W. Sextro, “Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems,” in <i>Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013</i>, 2013, no. 05/2013, pp. 159–161.","ama":"Al-Ashtari W, Hunstig M, Hemsel T, Sextro W. Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems. In: <i>Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013</i>. Berichte aus dem IDS. Hannover, Germany; 2013:159-161.","short":"W. Al-Ashtari, M. Hunstig, T. Hemsel, W. Sextro, in: Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013, Hannover, Germany, 2013, pp. 159–161.","bibtex":"@inproceedings{Al-Ashtari_Hunstig_Hemsel_Sextro_2013, place={Hannover, Germany}, series={Berichte aus dem IDS}, title={Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems}, number={05/2013}, booktitle={Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013}, author={Al-Ashtari, Waleed and Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}, year={2013}, pages={159–161}, collection={Berichte aus dem IDS} }","mla":"Al-Ashtari, Waleed, et al. “Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems.” <i>Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013</i>, no. 05/2013, 2013, pp. 159–61.","apa":"Al-Ashtari, W., Hunstig, M., Hemsel, T., &#38; Sextro, W. (2013). Characteristics of Piezoelectric Energy Harvesters in Autonomous Systems. In <i>Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013</i> (pp. 159–161). Hannover, Germany."},"page":"159-161","place":"Hannover, Germany","year":"2013","issue":"05/2013","quality_controlled":"1","language":[{"iso":"eng"}],"keyword":["Energy harvesting","harvester modeling","load dependence","generated voltage"],"series_title":"Berichte aus dem IDS","user_id":"55222","department":[{"_id":"151"}],"_id":"9796","status":"public","abstract":[{"text":"A basic autonomous system powered by a piezoelectric harvester contains three components apart from the harvester: a fullwave rectifier, a reservoir capacitor and an electronic device performing the primary task of the system. In this contribution, a model describing the operation of such a system is derived. It is found that in steady-state operation, the piezoelectric harvester experiences two alternating load conditions due to the rectification process. These alternating load conditions can have a significant effect on the operation of the harvester and must be considered in the design of autonomous systems. The results also show that such an autonomous system works efficiently if it is connected to a high impedance load and excited by a frequency matching the anti-resonance frequency of the piezoelectric harvester.","lang":"eng"}],"type":"conference","publication":"Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop, Hannover, Germany, 14.-17.7.2013"},{"keyword":["Dynamic Power Management","Dynamic Voltage and Frequency Scaling","Hard Real-Time","Multi-core Processor"],"language":[{"iso":"eng"}],"_id":"36920","user_id":"5786","department":[{"_id":"672"}],"editor":[{"last_name":"Weghorn","full_name":"Weghorn, Hans","first_name":"Hans"}],"abstract":[{"text":"In the electronic system development, energy consumption is clearly becoming one of the most important design concerns. From the system level point of view, Dynamic Power Management (DPM) and Dynamic Voltage and Frequency Scaling (DVFS) are two mostly applied techniques to adjust the tradeoff between the performance and power dissipation at runtime. In this paper, we study the problem of combined application of both techniques with regard to hard real-time systems running on cluster-based multi-core processors. To optimize the processor energy consumption, a heuristic based on simulated annealing with efficient termination criterion is proposed. The experiment results show that the proposed algorithm outperforms the existing approaches in terms of the energy reduction. ","lang":"eng"}],"status":"public","type":"conference","publication":"Proceedings of the International Conference on Applied Computing (AC)","title":"An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors","date_updated":"2023-01-16T12:15:44Z","date_created":"2023-01-16T12:12:58Z","author":[{"first_name":"Da","last_name":"He","full_name":"He, Da"},{"id":"16243","full_name":"Müller, Wolfgang","last_name":"Müller","first_name":"Wolfgang"}],"place":"Fort Worth, Texas, USA","year":"2013","citation":{"ieee":"D. He and W. Müller, “An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors,” in <i>Proceedings of the International Conference on Applied Computing (AC)</i>, 2013.","chicago":"He, Da, and Wolfgang Müller. “An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors.” In <i>Proceedings of the International Conference on Applied Computing (AC)</i>, edited by Hans Weghorn. Fort Worth, Texas, USA, 2013.","bibtex":"@inproceedings{He_Müller_2013, place={Fort Worth, Texas, USA}, title={An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors}, booktitle={Proceedings of the International Conference on Applied Computing (AC)}, author={He, Da and Müller, Wolfgang}, editor={Weghorn, Hans}, year={2013} }","mla":"He, Da, and Wolfgang Müller. “An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors.” <i>Proceedings of the International Conference on Applied Computing (AC)</i>, edited by Hans Weghorn, 2013.","short":"D. He, W. Müller, in: H. Weghorn (Ed.), Proceedings of the International Conference on Applied Computing (AC), Fort Worth, Texas, USA, 2013.","ama":"He D, Müller W. An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors. In: Weghorn H, ed. <i>Proceedings of the International Conference on Applied Computing (AC)</i>. ; 2013.","apa":"He, D., &#38; Müller, W. (2013). An Energy-Efficient Heuristic for Hard Real-Time System on Multi-Core Processors. In H. Weghorn (Ed.), <i>Proceedings of the International Conference on Applied Computing (AC)</i>."},"publication_identifier":{"isbn":["978-989-8533-20-3 "]}},{"year":"2008","page":"324-327","citation":{"ama":"Bo F, Ting L, Hemsel T. A simple pre-stress estimating method of langevin transducers. In: <i>Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium On</i>. ; 2008:324-327. doi:<a href=\"https://doi.org/10.1109/SPAWDA.2008.4775801\">10.1109/SPAWDA.2008.4775801</a>","chicago":"Bo, Fu, Li Ting, and Tobias Hemsel. “A Simple Pre-Stress Estimating Method of Langevin Transducers.” In <i>Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium On</i>, 324–27, 2008. <a href=\"https://doi.org/10.1109/SPAWDA.2008.4775801\">https://doi.org/10.1109/SPAWDA.2008.4775801</a>.","ieee":"F. Bo, L. Ting, and T. Hemsel, “A simple pre-stress estimating method of langevin transducers,” in <i>Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on</i>, 2008, pp. 324–327.","apa":"Bo, F., Ting, L., &#38; Hemsel, T. (2008). A simple pre-stress estimating method of langevin transducers. In <i>Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on</i> (pp. 324–327). <a href=\"https://doi.org/10.1109/SPAWDA.2008.4775801\">https://doi.org/10.1109/SPAWDA.2008.4775801</a>","short":"F. Bo, L. Ting, T. Hemsel, in: Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium On, 2008, pp. 324–327.","bibtex":"@inproceedings{Bo_Ting_Hemsel_2008, title={A simple pre-stress estimating method of langevin transducers}, DOI={<a href=\"https://doi.org/10.1109/SPAWDA.2008.4775801\">10.1109/SPAWDA.2008.4775801</a>}, booktitle={Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on}, author={Bo, Fu and Ting, Li and Hemsel, Tobias}, year={2008}, pages={324–327} }","mla":"Bo, Fu, et al. “A Simple Pre-Stress Estimating Method of Langevin Transducers.” <i>Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium On</i>, 2008, pp. 324–27, doi:<a href=\"https://doi.org/10.1109/SPAWDA.2008.4775801\">10.1109/SPAWDA.2008.4775801</a>."},"title":"A simple pre-stress estimating method of langevin transducers","doi":"10.1109/SPAWDA.2008.4775801","date_updated":"2022-01-06T07:04:16Z","date_created":"2019-04-29T11:16:13Z","author":[{"full_name":"Bo, Fu","last_name":"Bo","first_name":"Fu"},{"last_name":"Ting","full_name":"Ting, Li","first_name":"Li"},{"first_name":"Tobias","last_name":"Hemsel","id":"210","full_name":"Hemsel, Tobias"}],"abstract":[{"lang":"eng","text":"A simple pre-stress estimate method of Langevin transducers is studied. The measurement setup consists of a capacitor, an impedance converter and a voltmeter. Based on the piezoelectric equation and the basic circuit theory, the mathematical expression between the pre-stress and the voltage across the capacitor is derived. The pre-stress level can then be calculated out of the measurement of the capacitor voltage. In order to evaluate the precision of this method, a force washer is used to measure the pre-stress of the Langevin transducer. The result shows the pre-stress level obtained from this method is 30-40\\% higher than the pre-stress level measured by the force washer. This method is simple and can be used to estimate the pre-stress of various Langevin transducers. The precision of this method can be raised if d33 is identified under different pre-stress levels."}],"status":"public","publication":"Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on","type":"conference","keyword":["capacitors","impedance convertors","piezoelectric transducers","stress analysis","Langevin transducers","basic circuit theory","capacitor","impedance converter","piezoelectric equation","pre-stress estimating method","voltmeter","Capacitors","Educational institutions","Equations","Force measurement","Impedance measurement","Manufacturing","Mechatronics","Piezoelectric transducers","Voltage","Voltmeters","Langevin transducer","capacitor","piezoelectric element","pre-stress"],"language":[{"iso":"eng"}],"_id":"9568","department":[{"_id":"151"}],"user_id":"55222"},{"publication_identifier":{"issn":["1075-6787"]},"quality_controlled":"1","year":"2008","citation":{"bibtex":"@inproceedings{Uribe_Stroop_Hemsel_Wallaschek_2008, title={Development of a biomedical tissue differentiation system using piezoelectric actuators}, DOI={<a href=\"https://doi.org/10.1109/FREQ.2008.4622963\">10.1109/FREQ.2008.4622963</a>}, booktitle={Frequency Control Symposium, 2008 IEEE International}, author={Uribe, David Oliva and Stroop, Ralf and Hemsel, Tobias and Wallaschek, Jörg}, year={2008}, pages={91–94} }","mla":"Uribe, David Oliva, et al. “Development of a Biomedical Tissue Differentiation System Using Piezoelectric Actuators.” <i>Frequency Control Symposium, 2008 IEEE International</i>, 2008, pp. 91–94, doi:<a href=\"https://doi.org/10.1109/FREQ.2008.4622963\">10.1109/FREQ.2008.4622963</a>.","short":"D.O. Uribe, R. Stroop, T. Hemsel, J. Wallaschek, in: Frequency Control Symposium, 2008 IEEE International, 2008, pp. 91–94.","apa":"Uribe, D. O., Stroop, R., Hemsel, T., &#38; Wallaschek, J. (2008). Development of a biomedical tissue differentiation system using piezoelectric actuators. In <i>Frequency Control Symposium, 2008 IEEE International</i> (pp. 91–94). <a href=\"https://doi.org/10.1109/FREQ.2008.4622963\">https://doi.org/10.1109/FREQ.2008.4622963</a>","ieee":"D. O. Uribe, R. Stroop, T. Hemsel, and J. Wallaschek, “Development of a biomedical tissue differentiation system using piezoelectric actuators,” in <i>Frequency Control Symposium, 2008 IEEE International</i>, 2008, pp. 91–94.","chicago":"Uribe, David Oliva, Ralf Stroop, Tobias Hemsel, and Jörg Wallaschek. “Development of a Biomedical Tissue Differentiation System Using Piezoelectric Actuators.” In <i>Frequency Control Symposium, 2008 IEEE International</i>, 91–94, 2008. <a href=\"https://doi.org/10.1109/FREQ.2008.4622963\">https://doi.org/10.1109/FREQ.2008.4622963</a>.","ama":"Uribe DO, Stroop R, Hemsel T, Wallaschek J. Development of a biomedical tissue differentiation system using piezoelectric actuators. In: <i>Frequency Control Symposium, 2008 IEEE International</i>. ; 2008:91-94. doi:<a href=\"https://doi.org/10.1109/FREQ.2008.4622963\">10.1109/FREQ.2008.4622963</a>"},"page":"91-94","date_updated":"2022-01-06T07:04:16Z","date_created":"2019-04-29T13:07:39Z","author":[{"full_name":"Uribe, David Oliva","last_name":"Uribe","first_name":"David Oliva"},{"first_name":"Ralf","last_name":"Stroop","full_name":"Stroop, Ralf"},{"first_name":"Tobias","last_name":"Hemsel","full_name":"Hemsel, Tobias","id":"210"},{"full_name":"Wallaschek, Jörg","last_name":"Wallaschek","first_name":"Jörg"}],"title":"Development of a biomedical tissue differentiation system using piezoelectric actuators","doi":"10.1109/FREQ.2008.4622963","type":"conference","publication":"Frequency Control Symposium, 2008 IEEE International","abstract":[{"text":"In neurosurgery, delineation of tumor boundaries during resection of brain tumors is of substantial relevance. During operation distinction between tumor and healthy tissue rely on the abilities of the surgeon based on visual and tactile differentiation. In this paper a high sensitivity actuator-sensor system using a piezoelectric bimorph is presented. Frequency shift and transfer function of the bimorphpsilas voltages are detected and evaluated. Sensorpsilas sensitivity is evaluated using two frequency controls strategies: A phase-locked loop (PLL) and a self-oscillating circuit. Results of measurements conducted on gel-phantoms are presented and discussed.","lang":"eng"}],"status":"public","_id":"9576","user_id":"55222","department":[{"_id":"151"}],"keyword":["biomedical measurement","brain","cancer","neurophysiology","phantoms","phase locked loops","piezoelectric actuators","surgery","tactile sensors","transfer functions","tumours","PLL","biomedical tissue differentiation system","brain tumor resection","frequency control","frequency shift","gel-phantom","high sensitivity actuator-sensor system","neurosurgery","phase-locked loop","piezoelectric actuators","piezoelectric bimorph","self-oscillating circuit","sensor sensitivity","tactile differentiation","tactile sensor system","transfer function","tumor boundary","visual differentiation","Biomedical measurements","Circuits","Frequency control","Neoplasms","Neurosurgery","Phase locked loops","Piezoelectric actuators","Surges","Transfer functions","Voltage"],"language":[{"iso":"eng"}]},{"publication":"Ultrasonics Symposium, 2004 IEEE","type":"conference","abstract":[{"lang":"eng","text":"Several positioning tasks demand translatory drive instead of rotary motion. To achieve drives that are capable e.g. to drive the sunroof of a car or to lift a car's window, multiple miniaturized motors can be combined. But in this case many other questions arise: the electromechanical behavior of the individual motors differs slightly, the motor characteristics are strongly dependent on the driving parameters and the driven load, many applications need some extra power for special cases like overcoming higher forces periodically. Thus, the bundle of motors has to act well organized and controlled to get an optimized drive that is not oversized and costly."}],"status":"public","_id":"9519","department":[{"_id":"151"}],"user_id":"55222","keyword":["drives","electromechanical effects","linear motors","ultrasonic motors","car sunroof","car window","electromechanical behavior","high power ultrasonic linear motors","multiple miniaturized motors","positioning tasks","translatory drive","Costs","Electromagnetic forces","Frequency","Laboratories","Manufacturing","Mechatronics","Micromotors","Ultrasonic imaging","Vibrations","Voltage"],"language":[{"iso":"eng"}],"publication_identifier":{"issn":["1051-0117"]},"quality_controlled":"1","issue":"Vol.2","year":"2004","page":"1161-1164","intvolume":"         2","citation":{"bibtex":"@inproceedings{Hemsel_Mracek_Wallaschek_Vasiljev_2004, title={A novel approach for high power ultrasonic linear motors}, volume={2}, DOI={<a href=\"https://doi.org/10.1109/ULTSYM.2004.1417988\">10.1109/ULTSYM.2004.1417988</a>}, number={Vol.2}, booktitle={Ultrasonics Symposium, 2004 IEEE}, author={Hemsel, Tobias and Mracek, Maik and Wallaschek, Jörg and Vasiljev, Piotr}, year={2004}, pages={1161–1164} }","short":"T. Hemsel, M. Mracek, J. Wallaschek, P. Vasiljev, in: Ultrasonics Symposium, 2004 IEEE, 2004, pp. 1161–1164.","mla":"Hemsel, Tobias, et al. “A Novel Approach for High Power Ultrasonic Linear Motors.” <i>Ultrasonics Symposium, 2004 IEEE</i>, vol. 2, no. Vol.2, 2004, pp. 1161–64, doi:<a href=\"https://doi.org/10.1109/ULTSYM.2004.1417988\">10.1109/ULTSYM.2004.1417988</a>.","apa":"Hemsel, T., Mracek, M., Wallaschek, J., &#38; Vasiljev, P. (2004). A novel approach for high power ultrasonic linear motors. In <i>Ultrasonics Symposium, 2004 IEEE</i> (Vol. 2, pp. 1161–1164). <a href=\"https://doi.org/10.1109/ULTSYM.2004.1417988\">https://doi.org/10.1109/ULTSYM.2004.1417988</a>","ama":"Hemsel T, Mracek M, Wallaschek J, Vasiljev P. A novel approach for high power ultrasonic linear motors. In: <i>Ultrasonics Symposium, 2004 IEEE</i>. Vol 2. ; 2004:1161-1164. doi:<a href=\"https://doi.org/10.1109/ULTSYM.2004.1417988\">10.1109/ULTSYM.2004.1417988</a>","ieee":"T. Hemsel, M. Mracek, J. Wallaschek, and P. Vasiljev, “A novel approach for high power ultrasonic linear motors,” in <i>Ultrasonics Symposium, 2004 IEEE</i>, 2004, vol. 2, no. Vol.2, pp. 1161–1164.","chicago":"Hemsel, Tobias, Maik Mracek, Jörg Wallaschek, and Piotr Vasiljev. “A Novel Approach for High Power Ultrasonic Linear Motors.” In <i>Ultrasonics Symposium, 2004 IEEE</i>, 2:1161–64, 2004. <a href=\"https://doi.org/10.1109/ULTSYM.2004.1417988\">https://doi.org/10.1109/ULTSYM.2004.1417988</a>."},"date_updated":"2022-01-06T07:04:16Z","volume":2,"author":[{"first_name":"Tobias","last_name":"Hemsel","id":"210","full_name":"Hemsel, Tobias"},{"last_name":"Mracek","full_name":"Mracek, Maik","first_name":"Maik"},{"full_name":"Wallaschek, Jörg","last_name":"Wallaschek","first_name":"Jörg"},{"first_name":"Piotr","full_name":"Vasiljev, Piotr","last_name":"Vasiljev"}],"date_created":"2019-04-29T08:12:06Z","title":"A novel approach for high power ultrasonic linear motors","doi":"10.1109/ULTSYM.2004.1417988"}]