@inproceedings{29895, author = {{Korthauer, Bastian and Rehlaender, Philipp and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{2021 IEEE Applied Power Electronics Conference and Exposition (APEC)}}, publisher = {{IEEE}}, title = {{{Design and Analysis of a Regenerative Snubber for a 2.2 kW Active-Clamp Forward Converter with Low-Voltage Output}}}, doi = {{10.1109/apec42165.2021.9487130}}, year = {{2021}}, } @inproceedings{29850, abstract = {{In electric vehicles (EV) the large common-mode (CM) capacitance comprising capacitive parasitics of the traction battery as well as explicit Y-capacitors connecting within specific loads the high-voltage DC-system (HV-system) to ground, can cause issues when using non-isolated EV Chargers. One solution for a power factor correction (PFC) rectifier that is capable to operate with a non-isolated DC-DC converter, is the three-phase four-wire full-bridge PFC, with split DC-link, whose midpoint is connected to the mains neutral. Therefore, it provides very stable potentials at the DC-link rails and accordingly can be classified as Zero-CM topology, which facilitates a common-mode-free operation. When to be operated at a single-phase supply, which is a common requirement for On-board chargers (OBCs) this topology results in the voltage-doubler PFC (V2-PFC) being characterised by a comparably large DC-link voltage ripple at mains frequency. If the DC-link capacitance shall be minimized, for instance to avoid lifetime-limited electrolytic capacitors, two more circuits in addition to the original V2-PFC are proposed for keeping the common-mode-free operation: A balancing circuit (BC), that balances the voltages over the split capacitors and a ripple port (RP), that buffers the 100 Hz power pulsation of the mains. For both circuits the available two bridge legs of the three-phase topology in single-phase operation may be utilized. A 3.7 kW laboratory sample verifies the functionality of the additional circuits in conjunction with the V2-PFC and achieves an efficiency of 95 %.}}, author = {{Strothmann, Benjamin and Book, Gerrit and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{PCIM Europe digital days 2021; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management}}, pages = {{1--8}}, title = {{{Single-Phase Operation of Common-Mode-Free Bidirectional Three-Phase PFC-Rectifier for Non-Isolated EV Charger with Minimized DC-Link}}}, year = {{2021}}, } @inproceedings{29871, abstract = {{LLC resonant converters typically employ power MOSFETs in their inverter stage. The generally weak reverse recovery behaviour of the intrinsic body diodes of those MOSFETs causes significant turn-on losses when being forced to hard commutations. Continuous operation in this way will lead to self-destruction of the transistors. Consequently, zero-voltage switching (ZVS) is essential in a MOSFET-based inverter stage. To ensure ZVS, the LLC converter is operated in the inductive region. On the contrary, IGBTs show dominant turn-off losses and are therefore conventionally not applied in LLC converters typically requiring high switching frequencies to achieve low output voltages. However, if the LLC converter is intentionally designed for capacitive operation, zero-current switching (ZCS) is enabled and thus robust and cost-efficient IGBTs can be applied in the inverter stage. The aim of this work is to investigate the use IGBTs in the inverter of an LLC converter. The theory behind the capacitive operated LLC is derived using a switched simulation model and compared with the fundamental harmonic approximation (FHA). The results prove FHA to be useless for practical converter design. Instead, a stress value analysis based on switched model simulations is proposed to the design a capacitive operated LLC utilizing ZCS. A 2 kW prototype for on-board EV applications was built to verify the theory and design approach. The prototype confirms the derived theory and thus the deployment of IGBTs in the inverter stage of LLC resonant converters. Synchronous rectification turns out to require a specific control solution, but if given the resulting efficiency in the most critical operation point exceeds the value of a MOSFET-based (inductive operated) LLC-design of an identical application. Therefore, this concept should be further developed.}}, author = {{Urbaneck, Daniel and Rehlaender, Philipp and Böcker, Joachim and Schafmeister, Frank}}, booktitle = {{2021 IEEE Applied Power Electronics Conference and Exposition (APEC)}}, location = {{Arizona}}, title = {{{LLC Converter in Capacitive Operation Utilizing ZCS for IGBTs – Theory, Concept and Verification of a 2 kW DC-DC Converter for EVs}}}, year = {{2021}}, } @article{30030, author = {{Stender, Marius and Wallscheid, Oliver and Böcker, Joachim}}, issn = {{0885-8993}}, journal = {{IEEE Transactions on Power Electronics}}, keywords = {{Electrical and Electronic Engineering}}, number = {{11}}, pages = {{13261--13274}}, publisher = {{Institute of Electrical and Electronics Engineers (IEEE)}}, title = {{{Accurate Torque Control for Induction Motors by Utilizing a Globally Optimized Flux Observer}}}, doi = {{10.1109/tpel.2021.3080129}}, volume = {{36}}, year = {{2021}}, } @inproceedings{30031, author = {{Stender, Marius and Wallscheid, Oliver and Böcker, Joachim}}, booktitle = {{2021 IEEE 19th International Power Electronics and Motion Control Conference (PEMC)}}, publisher = {{IEEE}}, title = {{{Accurate Torque Estimation for Induction Motors by Utilizing a Hybrid Machine Learning Approach}}}, doi = {{10.1109/pemc48073.2021.9432615}}, year = {{2021}}, } @inproceedings{30029, author = {{Stender, Marius and Wallscheid, Oliver and Böcker, Joachim}}, booktitle = {{IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society}}, publisher = {{IEEE}}, title = {{{Combined Electrical-Thermal Gray-Box Model and Parameter Identification of an Induction Motor}}}, doi = {{10.1109/iecon48115.2021.9589225}}, year = {{2021}}, } @inproceedings{30032, author = {{Stender, Marius and Wallscheid, Oliver and Böcker, Joachim}}, booktitle = {{2021 IEEE 19th International Power Electronics and Motion Control Conference (PEMC)}}, publisher = {{IEEE}}, title = {{{Gray-Box Loss Model for Induction Motor Drives}}}, doi = {{10.1109/pemc48073.2021.9432491}}, year = {{2021}}, } @inproceedings{29665, author = {{Hanke, Sören and Wallscheid, Oliver and Böcker, Joachim}}, publisher = {{IET Digital Library}}, title = {{{Comparison of Artificial Neural Network and Least Squares Prediction Models for Finite-Control-Set Model Predictive Control of a Permanent Magnet Synchronous Motor}}}, doi = {{10.1049%2Ficp.2021.1122}}, year = {{2021}}, } @article{21251, author = {{Kirchgässner, Wilhelm and Wallscheid, Oliver and Böcker, Joachim}}, issn = {{0885-8969}}, journal = {{IEEE Transactions on Energy Conversion}}, number = {{3}}, pages = {{2059 -- 2067}}, title = {{{Data-Driven Permanent Magnet Temperature Estimation in Synchronous Motors with Supervised Machine Learning: A Benchmark}}}, doi = {{10.1109/tec.2021.3052546}}, volume = {{36}}, year = {{2021}}, } @article{21557, author = {{Brosch, Anian and Wallscheid, Oliver and Böcker, Joachim}}, issn = {{1551-3203}}, journal = {{IEEE Transactions on Industrial Informatics}}, title = {{{Torque and Inductances Estimation for Finite Model Predictive Control of Highly Utilized Permanent Magnet Synchronous Motors}}}, doi = {{10.1109/tii.2021.3060469}}, year = {{2021}}, } @inproceedings{30340, author = {{Hagemeyer, Marc and Wallmeier, Peter and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{Proc. 36th IEEE Applied Power Electronics Conference (APEC)}}, location = {{Phoenix, AZ, USA}}, pages = {{569 -- 576}}, publisher = {{IEEE}}, title = {{{Comparison of unidirectional Three- and Four-Wire based Boost PFC-Rectifier Topologies for Non-Isolated Three-Phase EV On-Board Chargers under Common-Mode Aspects}}}, year = {{2021}}, } @inproceedings{29938, abstract = {{Modular solid-state transformers (SSTs) are a promising technology in converting power from a 10kV three-phase medium voltage to a lower DC-voltage in the range of 100…400V to provide pure DC power to applications such as electrolyzers for hydrogen generation, data centers with a DC power distribution and DC micro grids. Modular SSTs which can be interpreted as modular multilevel converters with an isolated DC-DC output stage per module, are designed with redundant modules to increase reliability. Usually, each of the three arms operates independently, and therefore, only a fixed number of faulty modules can be compensated in each arm, even if all modules are operational in the remaining two arms. With the proposed zero-sequence voltage injection, up to 100% more faulty modules can be compensated in an arm by employing the same hardware. In addition, module power imbalances are nearly eliminated by utilizing a fundamental frequency zero-sequence voltage. A dominant 3rd harmonic zero-sequence voltage injection in combination with the 5th, 7th and several higher order harmonics with adaptive (small) amplitudes minimize the required arm voltages at steady-state. For nominal operation or symmetrical faults, the proposed technique is equivalent to the well known Min-Max voltage injection, which already reduces the peak arm voltage by 13.4% compared to a constant star point potential. A statistical analysis proves, that the expected number of tolerable faulty modules of the 1MW SST increases by 12% without the need for additional hardware.}}, author = {{Unruh, Roland and Lange, Jarren and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)}}, isbn = {{978-9-0758-1537-5}}, keywords = {{Solid-State Transformer, Zero sequence voltage, Fault handling strategy, Power balance control technique, Three-phase system}}, location = {{Ghent, Belgium}}, publisher = {{IEEE}}, title = {{{Adaptive Zero-Sequence Voltage Injection for Modular Solid-State Transformer to Compensate for Asymmetrical Fault Conditions}}}, doi = {{https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570542}}, year = {{2021}}, } @inproceedings{29893, abstract = {{Phase-shift modulated full bridge converters suffer from thermal imbalances of the inverter switches. The lagging leg switches are subject to larger commutation currents compared to those of the leading leg as the transformer current reduces in the freewheeling interval. Furthermore, after this interval, the energy in the series inductance may not be large enough to achieve zero-voltage switching (ZVS) for the leading leg. Both effects result in thermal imbalances. This paper analyzes the alternating-asymmetrical phase-shift modulation to achieve balanced conduction and switching losses for all four switches while showing that this modulation is easily implemented on standard DSPs. The modulation has been implemented to LLC converters where experimental measurement results proved its effectiveness for LLC converters by reducing the temperature deviation from 6.3 K to only 0.2 K such that the peak temperature is reduced from 95 °C to 92 °C. The paper also proves that the modulation can be utilized to improve the efficiency of LLC converters operated at very low gains while simultaneously reducing the junction temperature of all four switches compared to the conventional complementary modulation. Finally, EMI implications are analyzed, which show that the modulation may be beneficial for reducing the common-mode emissions around the operating frequency.}}, author = {{Rehlaender, Philipp and Unruh, Roland and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{2021 IEEE Applied Power Electronics Conference and Exposition (APEC)}}, isbn = {{978-1-7281-8950-5}}, keywords = {{Phase-Shifted Full Bridge, Full-Bridge Converter, Phase-Shift Control, Phase-Shift Modulation, LLC Converter, Thermal Balancing}}, location = {{Phoenix, AZ, USA}}, publisher = {{IEEE}}, title = {{{Alternating Asymmetrical Phase-Shift Modulation for Full-Bridge Converters with Balanced Switching Losses to Reduce Thermal Imbalances}}}, doi = {{10.1109/apec42165.2021.9487104}}, year = {{2021}}, } @inproceedings{22218, author = {{Krauter, Stefan and Böcker, Joachim and Freitag, Christine and Hehenkamp, Burkhard and Hilleringmann, Ulrich and Temmen, Katrin and Klaus, Tobias and Rohrer, Nicolaus and Lehmann, Sven}}, booktitle = {{Tagungsband des 36. PV-Symposiums, 18.-26 Mai 2021}}, isbn = {{978-3-948176-14-3}}, keywords = {{Art-D, Afrika, Resilienz, Resilience, Grid stability, robustness, microgrids}}, location = {{Staffelstein / online}}, pages = {{305--309}}, publisher = {{Conexio}}, title = {{{Projekt Art-D Grids: Nachhaltige und stabile Microgrids in Afrika - eine Plattform für Forschung und Lehre für die Entwicklung}}}, year = {{2021}}, } @inproceedings{29899, abstract = {{LLC resonant converters are typically unsuitable to be applied for wide voltage-transfer ratio applications. With a full-bridge inverter, however, they can be operated in a variety of different modulations. Most notably, by permanently turning on one MOSFET and turning off the other MOSFET of the same bridge leg, the LLC can be operated in half-bridge configuration reducing the gain by a factor of two. The resonant capacitor is hereby charged to an average voltage of half the input voltage. In this modulation, however, the switch that is permanently turned on is stressed by the complete resonant current while exhibiting no switching losses. This paper proves that the frequency-doubler modulation can better balance the losses among all MOSFETs and should be the preferred mode of operation favored over the conventional half-bridge modulation. This paper analyzes the beneficial loss distribution, proposes an on-the-fly morphing modulation and discusses potential operating strategies to further reduce the junction temperature. Furthermore, it is shown that this modulation can also be altered to achieve the asymmetrical LLC operation. Experimental measurement results show that the modulation results in a substantial decrease of the maximum MOSFET temperature and shows that the converter can be smoothly transitioned during operation from full-bridge modulation to the frequency-doubler half-bridge operation and back.}}, author = {{Rehlaender, Philipp and Unruh, Roland and Hankeln, Lars and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe)}}, isbn = {{978-9-0758-1537-5}}, keywords = {{Resonant converter, High frequency power converter, Switched-mode power supply, Converter control, Control methods for electrical systems}}, location = {{Ghent, Belgium}}, publisher = {{IEEE}}, title = {{{Frequency-Doubler Modulation for Reduced Junction Temperatures for LLC Resonant Converters Operated in Half-Bridge Configuration}}}, doi = {{10.23919/EPE21ECCEEurope50061.2021.9570674}}, year = {{2021}}, } @unpublished{29655, author = {{Kirchgässner, Wilhelm and Wallscheid, Oliver and Böcker, Joachim}}, booktitle = {{arXiv preprint arXiv:2103.16323}}, title = {{{Thermal Neural Networks: Lumped-Parameter Thermal Modeling With State-Space Machine Learning}}}, year = {{2021}}, } @inproceedings{29884, author = {{Böcker, Joachim}}, booktitle = {{2020 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)}}, publisher = {{IEEE}}, title = {{{Analysis of the Magnetic Skin Effekt in Motors and Inductors}}}, doi = {{10.1109/speedam48782.2020.9161895}}, year = {{2020}}, } @article{21250, author = {{Kirchgässner, Wilhelm and Wallscheid, Oliver and Böcker, Joachim}}, issn = {{0885-8993}}, journal = {{IEEE Transactions on Power Electronics}}, number = {{7}}, pages = {{7480--7488}}, title = {{{Estimating Electric Motor Temperatures with Deep Residual Machine Learning}}}, doi = {{10.1109/tpel.2020.3045596}}, volume = {{36}}, year = {{2020}}, } @inproceedings{29939, abstract = {{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.}}, author = {{Unruh, Roland and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)}}, keywords = {{Multilevel converters, Resonant converter, High voltage power converters, ZVS Converters, Combination MMC LLC}}, location = {{Lyon, France}}, publisher = {{IEEE}}, title = {{{Evaluation of MMCs for High-Power Low-Voltage DC-Applications in Combination with the Module LLC-Design}}}, doi = {{10.23919/epe20ecceeurope43536.2020.9215687}}, year = {{2020}}, } @inproceedings{29894, author = {{Rehlaender, Philipp and Tikhonov, Sergey and Schafmeister, Frank and Böcker, Joachim}}, booktitle = {{2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe)}}, publisher = {{IEEE}}, title = {{{Dual Interleaved 3.6 kW LLC Converter Operating in Half-Bridge, Full-Bridge and Phase-Shift Mode as a Single-Stage Architecture of an Automotive On-Board DC-DC Converter}}}, doi = {{10.23919/epe20ecceeurope43536.2020.9215736}}, year = {{2020}}, }