[{"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","keyword":["adaptive DC-link voltage","cascaded H-bridge","resonant operation","Full-Bridge Converter","loss minimization","LLC Resonant Converter","peak capacitor voltage reduction"],"language":[{"iso":"eng"}],"year":"2025","issue":"8","title":"Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple","publisher":"MDPI AG","date_created":"2025-05-05T12:27:39Z","status":"public","type":"journal_article","article_number":"1517","_id":"59805","user_id":"34289","department":[{"_id":"52"}],"citation":{"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>.","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>","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>","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).","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} }"},"intvolume":"        14","publication_status":"published","publication_identifier":{"issn":["2079-9292"]},"main_file_link":[{"url":"https://www.mdpi.com/2079-9292/14/8/1517"}],"doi":"10.3390/electronics14081517","date_updated":"2025-05-05T12:34:00Z","author":[{"first_name":"Roland","full_name":"Unruh, Roland","id":"34289","last_name":"Unruh"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","full_name":"Böcker, Joachim","id":"66","first_name":"Joachim"},{"full_name":"Schafmeister, Frank","id":"71291","last_name":"Schafmeister","first_name":"Frank"}],"volume":14},{"language":[{"iso":"eng"}],"keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Third harmonic injection"],"department":[{"_id":"52"}],"user_id":"34289","_id":"48352","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"}],"publication":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","type":"conference","doi":"10.23919/epe23ecceeurope58414.2023.10264313","conference":{"start_date":"2023-09-04","name":"2023 25th European Conference on Power Electronics and Applications (EPE'23 ECCE Europe)","location":"Aalborg, Denmark","end_date":"2023-09-08"},"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","author":[{"first_name":"Roland","last_name":"Unruh","full_name":"Unruh, Roland","id":"34289"},{"orcid":"0000-0002-8480-7295","last_name":"Böcker","full_name":"Böcker, Joachim","id":"66","first_name":"Joachim"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"}],"date_created":"2023-10-20T07:13:32Z","publisher":"IEEE","date_updated":"2023-10-20T10:01:02Z","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","quality_controlled":"1","publication_identifier":{"isbn":["979-8-3503-1678-0"]},"publication_status":"published"},{"type":"preprint","status":"public","abstract":[{"text":"Sodium-ion capacitors (SICs) have great potential in energy storage due to their low cost, the abundance of Na, and the potential to deliver high energy and power simultaneously. This paper demonstrates a template-assisted method to induce graphitic nanodomains and micro-mesopores into nitrogen-doped carbons. This study elucidates that these graphitic nanodomains are beneficial for Na+ storage. The obtained N-doped carbon (As8Mg) electrode achieved a reversible capacity of 254 mA h g−1 at 0.1 A g−1. Moreover, the As8Mg-based SIC device achieves high combinations of power/energy densities (52 W kg−1 at 204 Wh kg−1 and 10,456 W kg−1 at 51 Wh kg−1) with outstanding cycle stability (99.7% retention over 10000 cycles at 0.2 A g−1). Our findings provide insights into optimizing carbon’s microstructure to boost sodium storage in the pseudo-capacitive mode. ","lang":"eng"}],"user_id":"98120","_id":"47447","language":[{"iso":"eng"}],"keyword":["sodium ion capacitor","anode","template","N-doped carbons","graphitic nanodomains"],"citation":{"ieee":"N. Lopez Salas <i>et al.</i>, “Template-induced graphitic nanodomains in nitrogen-doped carbons enable high-performance sodium-ion capacitors - ACCEPTED MANUSCRIPT.” 2023.","chicago":"Lopez Salas, Nieves, Chun  Li, Zihan Song, Minliang Liu, Enrico Lepre, Markus Antonietti, Junwu Zhu, Jian Liu, and Yongsheng Fu. “Template-Induced Graphitic Nanodomains in Nitrogen-Doped Carbons Enable High-Performance Sodium-Ion Capacitors - ACCEPTED MANUSCRIPT,” 2023.","ama":"Lopez Salas N, Li C, Song Z, et al. Template-induced graphitic nanodomains in nitrogen-doped carbons enable high-performance sodium-ion capacitors - ACCEPTED MANUSCRIPT. Published online 2023.","mla":"Lopez Salas, Nieves, et al. <i>Template-Induced Graphitic Nanodomains in Nitrogen-Doped Carbons Enable High-Performance Sodium-Ion Capacitors - ACCEPTED MANUSCRIPT</i>. 2023.","bibtex":"@article{Lopez Salas_Li_Song_Liu_Lepre_Antonietti_Zhu_Liu_Fu_2023, title={Template-induced graphitic nanodomains in nitrogen-doped carbons enable high-performance sodium-ion capacitors - ACCEPTED MANUSCRIPT}, author={Lopez Salas, Nieves and Li, Chun  and Song, Zihan and Liu, Minliang and Lepre, Enrico and Antonietti, Markus and Zhu, Junwu and Liu, Jian and Fu, Yongsheng}, year={2023} }","short":"N. Lopez Salas, C. Li, Z. Song, M. Liu, E. Lepre, M. Antonietti, J. Zhu, J. Liu, Y. Fu, (2023).","apa":"Lopez Salas, N., Li, C., Song, Z., Liu, M., Lepre, E., Antonietti, M., Zhu, J., Liu, J., &#38; Fu, Y. (2023). <i>Template-induced graphitic nanodomains in nitrogen-doped carbons enable high-performance sodium-ion capacitors - ACCEPTED MANUSCRIPT</i>."},"year":"2023","author":[{"first_name":"Nieves","orcid":"https://orcid.org/0000-0002-8438-9548","last_name":"Lopez Salas","full_name":"Lopez Salas, Nieves","id":"98120"},{"first_name":"Chun ","full_name":"Li, Chun ","last_name":"Li"},{"last_name":"Song","full_name":"Song, Zihan","first_name":"Zihan"},{"first_name":"Minliang","full_name":"Liu, Minliang","last_name":"Liu"},{"last_name":"Lepre","full_name":"Lepre, Enrico","first_name":"Enrico"},{"last_name":"Antonietti","full_name":"Antonietti, Markus","first_name":"Markus"},{"last_name":"Zhu","full_name":"Zhu, Junwu","first_name":"Junwu"},{"first_name":"Jian","full_name":"Liu, Jian","last_name":"Liu"},{"full_name":"Fu, Yongsheng","last_name":"Fu","first_name":"Yongsheng"}],"date_created":"2023-09-26T10:11:50Z","date_updated":"2026-01-08T13:16:49Z","title":"Template-induced graphitic nanodomains in nitrogen-doped carbons enable high-performance sodium-ion capacitors - ACCEPTED MANUSCRIPT"},{"title":"Zero-Sequence Voltage Reduces DC-Link Capacitor Demand in Cascaded H-Bridge Converters for Large-Scale Electrolyzers by 40%","conference":{"location":"Hanover, Germany","end_date":"2022-09-09","start_date":"2022-09-05","name":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)"},"main_file_link":[{"url":"https://ieeexplore.ieee.org/abstract/document/9907278"}],"date_updated":"2023-10-23T09:04:23Z","publisher":"IEEE","date_created":"2022-12-02T12:47:38Z","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"},{"first_name":"Joachim","id":"66","full_name":"Böcker, Joachim","orcid":"0000-0002-8480-7295","last_name":"Böcker"}],"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.","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.","short":"R. Unruh, F. Schafmeister, J. Böcker, in: 24th European Conference on Power Electronics and Applications (EPE’22 ECCE Europe), 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.","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} }"},"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":[{"text":"Cascaded H-bridge Converters (CHBs) are a promising solution in converting power from a three-phase medium voltage of 6.6 kV...30 kV to a lower DC-voltage in the range of 100 V...1 kV to provide pure DC power to applications such as electrolyzers for hydrogen generation, data centers with a DC power distribution and DC microgrids. CHBs can be interpreted as modular multilevel converters with an isolated DC-DC output stage per module, require a large DC-link capacitor for each module to handle the second harmonic voltage ripple caused by the fluctuating input power within a fundamental grid period. Without a zero-sequence voltage injection, star-connected CHBs are operated with approximately sinusoidal arm voltages and currents. The floating star point potential enables to utilize different zero-sequence voltage injection techniques such as a third-harmonic injection with 1/6 of the grid voltage amplitude or a Min-Max voltage injection. Both well-known methods have the advantage to reduce the peak arm voltage and thereby the number of required modules by 13.4 % (to √ 3 2). This paper proves analytically that the third-harmonic injection with 1/6 of the grid voltage amplitude reduces the second harmonic voltage ripple by only 15.1 % compared to no-voltage injection for unity power factor operation and balanced grid voltages. Then it is shown, that the Min-Max injection has the often overlooked advantage of reducing the second harmonic voltage ripple by even 18.8 %. By applying the here proposed zero-sequence voltage injection in saturation modulation, the second harmonic voltage ripple of the DC-link capacitors is reduced by even 24.3 %, while still requiring the same number of modules as the Min-Max injection. For a realistic number of reserve modules, the overall energy ripple in the DC-link capacitors is reduced by 40 %.","lang":"eng"}],"status":"public","publication":"24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe)","type":"conference"},{"_id":"29940","department":[{"_id":"52"}],"user_id":"34289","keyword":["Cascaded H-Bridge","Solid-State Transformer","Capacitor voltage ripple","Zero sequence voltage","Full-Bridge"],"language":[{"iso":"eng"}],"publication":"PCIM Europe digital days 2020; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management","type":"conference","abstract":[{"text":"A full-bridge modular multilevel converter (MMC) is compared to a half-bridge-based MMC for high-current low-voltage DC-applications such as electrolysis, arc welding or datacenters with DC-power distribution. Usually, modular multilevel converters are used in high-voltage DC-applications (HVDC) in the multiple kV-range, but to meet the needs of a high-current demand at low output voltage levels, the modular converter concept requires adaptations. In the proposed concept, the MMC is used to step-down the three-phase medium-voltage of 10 kV. Therefore, each module is extended by an LLC resonant converter to adapt to the specific electrolyzers DC-voltage range of 142-220V and to provide galvanic isolation. The proposed MMC converter with full-bridge modules uses half the number of modules compared to a half-bridge-based MMC while reducing the voltage ripple by 78% and capacitor losses by 64% by rearranging the same components to ensure identical costs and volume. For additional reliability, a new robust algorithm for balancing conduction losses during the bypass phase is presented.","lang":"eng"}],"status":"public","date_updated":"2023-10-20T11:52:39Z","publisher":"VDE","author":[{"first_name":"Roland","last_name":"Unruh","full_name":"Unruh, Roland","id":"34289"},{"last_name":"Schafmeister","id":"71291","full_name":"Schafmeister, Frank","first_name":"Frank"},{"first_name":"Norbert","last_name":"Fröhleke","full_name":"Fröhleke, Norbert"},{"first_name":"Joachim","id":"66","full_name":"Böcker, Joachim","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","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"}],"publication_identifier":{"isbn":["978-3-8007-5245-4"]},"publication_status":"published","year":"2020","citation":{"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.","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.","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.","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.","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."}},{"publication":"Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on","type":"conference","status":"public","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."}],"department":[{"_id":"151"}],"user_id":"55222","_id":"9568","language":[{"iso":"eng"}],"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"],"page":"324-327","citation":{"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>.","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.","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>.","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>"},"year":"2008","date_created":"2019-04-29T11:16:13Z","author":[{"first_name":"Fu","last_name":"Bo","full_name":"Bo, Fu"},{"full_name":"Ting, Li","last_name":"Ting","first_name":"Li"},{"id":"210","full_name":"Hemsel, Tobias","last_name":"Hemsel","first_name":"Tobias"}],"date_updated":"2022-01-06T07:04:16Z","doi":"10.1109/SPAWDA.2008.4775801","title":"A simple pre-stress estimating method of langevin transducers"}]