@article{63838, abstract = {{Industrial electrification is increasing to reduce fossil fuel dependence, alongside a growing share of volatile renewables. A secure and reliable energy supply is crucial for industry, leading to a shift from centralised to decentralised grid structures. DC microgrids becoming increasingly popular in industry, since they enable energy recuperation from braking, reduce components and cables, and integrate storage and local generation to manage supply interruptions or peak loads. EVs add further synergies by serving as mobile storage units, helping to store and redistribute locally generated renewable energy. This paper analyses how EV integration in droop-controlled DC grids can contribute to a more stable, low-emission and peak-reduced load profile to the supply grid through load shifting and bridge interruptions. A droop-controlled DC grid model has been developed, incorporating an EV charging park based on probability functions. Scalable scenarios allow for diverse condition analysis using an energy management system that utilises fuzzy logic and sequential MILP optimisation. It has been shown that a 7% improvement of coefficient represented grid-serving behaviour is possible by load shifting. It has also been demonstrated that an optimised EMS can reduce the demand-based CO2 emissions by 41kg for a representative day compared to a fuzzy logic EMS. At the same time peak load is decreased yielding a more constant residual load. These results highlight the potential of a controlled bidirectional charging infrastructure in DC grids and underscore the need to explicitly consider charging processes to ensure a residual load as constant as possible.}}, author = {{Rahlf, Henning Christoph and Knorr, Lukas and Althoff, Simon and Meschede, Henning}}, issn = {{2666-9552}}, journal = {{Smart Energy}}, keywords = {{DC-grid, Droop control, Grid-serving behaviour, Grid stability, Bidirectional charging, Sequential decision, MILP optimisation}}, publisher = {{Elsevier BV}}, title = {{{Analysis of bidirectional EV charging infrastructures within industrial DC grids}}}, doi = {{10.1016/j.segy.2026.100227}}, year = {{2026}}, } @article{59805, abstract = {{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%).}}, author = {{Unruh, Roland and Böcker, Joachim and Schafmeister, Frank}}, issn = {{2079-9292}}, journal = {{Electronics}}, keywords = {{adaptive DC-link voltage, cascaded H-bridge, resonant operation, Full-Bridge Converter, loss minimization, LLC Resonant Converter, peak capacitor voltage reduction}}, number = {{8}}, publisher = {{MDPI AG}}, title = {{{Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple}}}, doi = {{10.3390/electronics14081517}}, volume = {{14}}, year = {{2025}}, } @article{50649, abstract = {{The energy turnaround and the shift towards sustainable mobility threaten the stability of European energy distribution grids due to substantially increasing load fluctuations and power demand. These challenges can critically impact assets in the distribution grid—e.g., switchgears—intensifying the need to plan, conduct, and manage the maintenance of such assets. Predictive maintenance strategies that analyze assets' current and historical condition data have been discussed as promising approaches toward that end. However, the extant research focuses on designing and improving analytical algorithms or information technology (IT) artifacts while not considering how a maintenance service is cocreated by companies with IT. This research article posits that IT and service must be aligned closely, presenting an ensemble artifact comprising a digital industrial platform and a smart service system for predictive maintenance on the distribution grid. The artifact is evaluated by conducting a willingness-to-pay analysis with asset operators, documenting their demand for condition monitoring and predictive maintenance as an integrated solution, although they still struggle with even getting the condition data of their assets. Building on these results, we formalize the knowledge in the form of design principles and implications for managing the maintenance of critical assets in the distribution grid.}}, author = {{zur Heiden, Philipp and Priefer, Jennifer and Beverungen, Daniel}}, issn = {{0018-9391}}, journal = {{IEEE Transactions on Engineering Management}}, keywords = {{Design science research, digital platform, distribution grid, IS design, predictive maintenance, smart services}}, pages = {{3641--3655}}, publisher = {{Institute of Electrical and Electronics Engineers (IEEE)}}, title = {{{Predictive Maintenance on the Energy Distribution Grid—Design and Evaluation of a Digital Industrial Platform in the Context of a Smart Service System}}}, doi = {{10.1109/tem.2024.3352819}}, volume = {{71}}, year = {{2024}}, } @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{19393, abstract = {{To provide a simple instrument to operate residential Load-Shifting or Demand-Side-Management systems, the measurement of the actual grid frequency seems to be an appropriate method. Due to the present inflexibility and the lack of sufficient throttling capabilities of lignite and nuclear power plants, a surplus of electricity generation occurs during periods of high wind and solar power generation. While the specific CO2- emission is decreasing then ‒ due to the increased share of Renewables, the grid frequency is increasing (to a certain limit). Using the grid frequency as an indicator to switch-on and off certain loads (loads that do not require power permanently (e.g. dishwashers, washing machines, dryers, fridges and freezers, heaters) could provide a simple, inexpensive demand-side management indicator to lower specific CO2‒emssions and costs (if a dynamic consumption tariff is available). To check the truthfulness of that hypothesis, the grid and frequency data of the German grid of the year 2018 have been collected and a the correlation between grid frequency, power surplus, share of renewables vs. CO2-contents and price at the European energy exchange (EEX) have been calculated. The results show: Correlation between frequency and share of renewables is quite low (r = 0.155) due to the fact that primary grid control quickly compensates deviations from the 50 Hz nominal frequency. There is a good anti-correlation (r = - 0.687) between the EEX‒prices and the share of renewables in the grid. Over the years, correlation between electricity trading prices (EEX) and CO2 emissions is quite good (r =0.665), within the one year (2018) that correlation almost doesn’t exist, possibly due to the inflexibility of the bulky lignite power plants that even operate at negative prices. }}, author = {{Krauter, Stefan and Zhang, L.}}, booktitle = {{Proceedings of the 37th European Photovoltaic Solar Energy Conference, 07 - 11 September 2020.}}, issn = {{ 3-936338-73-6}}, keywords = {{Keywords: Load-Shifting, Demand-Side-Management, DSM, grid frequency, EEX, electricity trading prices, renewable share, flexibility, emissions, CO2}}, location = {{online}}, pages = {{1815 -- 1817}}, title = {{{Triggering Demand‒Side‒Management: Correlation of electricity prices, share of renewables, CO2‒contents, and grid‒frequency in the German electricity grid.}}}, doi = {{10.4229/EUPVSEC20202020-6BV.5.9}}, year = {{2020}}, } @inproceedings{19390, abstract = {{Due to the strong reduction of PV prices, storage plays a dominating role in overall system costs. A steeper elevation angle would result in a more balanced seasonal PV yield, at the cost of PV yield reductions during summer, but allowing reduced storage capacities. Additionally, the effect of a single-axis tracking system has been investigated, generating more electricity during the morning and evening hours, thus reducing daily storage requirements. The necessary PV size and storage capacities required for the German energy supply (1,500 TWh after electrification of all sectors) via 100% renewable energies and a 50% solar share have been calculated via the HOMER Pro software, considering the bridging of periods of "dark lulls“ in winter, using costs of 2030 (Table 1). Results: The increase of module elevation angles above the typical 30° leads to a reduction of investment and supply costs. The optimum is reached at a cost reduction of -1.5% for an elevation angle at the latitude of the installation site. An explanation is that high elevation angles are favorable for clear winter days, but not at all for the critical days with diffuse irradiance only, so the battery capacity must be increased. For the same reason, tracking systems do not offer any cost advantage (at least for the ones without an option for horizontal positioning during diffuse days).}}, author = {{Krauter, Stefan and Rustemovic, D. and Khatibi, Arash}}, booktitle = {{Proceedings of the 37th European Photovoltaic Solar Energy Conference, 07 - 11 September 2020}}, isbn = {{3-936338-73-6}}, keywords = {{Energy Storage, PV system integration, Large Grid-connected PV systems, Simulation, Energy Supply Options}}, location = {{online}}, pages = {{1818 -- 1819}}, title = {{{Reduction of required storage capacities for a 100% renewable energy supply in Germany, if new PV systems are installed with east-west tracking systems at increased elevation angles}}}, doi = {{10.4229/EUPVSEC20202020-6BV.5.10}}, year = {{2020}}, } @inproceedings{19383, abstract = {{Due to the present inflexibility and the lack of sufficient throttling capabilities of lignite and nuclear power plants, a surplus of electricity generation occurs during periods of high wind and solar power generation in the German electricity grid. While the specific CO2-emission is decreasing then - due to the increased share of Renewables, the grid frequency should be increasing (to a certain limit). Using the grid frequency as an indicator to switch-on and -off certain loads (loads that do not require power permanently (e.g. dishwashers, washing machines, dryers, fridges and freezers, heaters) could provide a simple, inexpensive demand-side-management indicator to lower specific CO2-emissions and costs (if a dynamic consumption tariff is applied). To check the truthfulness of that hypothesis, the grid and frequency data of the German grid of the year 2018 have been collected and the correlations between grid frequency, share of renewables, CO2-contents, and actual price at the European energy exchange (EEX) have been calculated. The results show: Correlation between grid frequency and the share of renewables is quite low (r=0.155) due to the fact that primary grid control quickly compensates deviations from the 50 Hz nominal frequency. As expected, there is a good anti-correlation (r=-0.687) between the EEX-prices and the share of renewables in the grid. Over the years, correlation between electricity trading prices (EEX) and CO2 emissions is quite good (r=0.665), within the one year (2018) that correlation almost doesn't exist, possibly due to the inflexibility of the bulky lignite baseload power plants that even operate at negative prices.}}, author = {{Krauter, Stefan and Zhang, L.}}, booktitle = {{Proceedings of the 47th IEEE Photovoltaic Specialists Conference (PVSC 47) 2020}}, keywords = {{CO2, EEX, Grid frequency, DSM, electricity price, Renewable share}}, location = {{online}}, pages = {{1672--1674}}, title = {{{Correlation of grid-frequency, electricity prices, share of Renewables and CO2-contents of German electricity grid to enable inexpensive triggering of Demand-Side-Management}}}, doi = {{10.1109/PVSC45281.2020.9300487}}, year = {{2020}}, } @inproceedings{12952, author = {{Dreiling, Dmitrij and Feldmann, Nadine and Henning, Bernd}}, keywords = {{piezoelectric materials, piezoelectric properties, DC bias field, non-linear material parameters}}, location = {{Nürnberg}}, publisher = {{AMA Service GmbH}}, title = {{{A DC bias approach to the characterisation of non-linear material parameters of piezoelectric ceramics}}}, doi = {{10.5162/sensoren2019/5.1.2}}, year = {{2019}}, } @inproceedings{1998, abstract = {{Nearly all existing HPC systems are operated by resource management systems based on the queuing approach. With the increasing acceptance of grid middleware like Globus, new requirements for the underlying local resource management systems arise. Features like advanced reservation or quality of service are needed to implement high level functions like co-allocation. However it is difficult to realize these features with a resource management system based on the queuing concept since it considers only the present resource usage. In this paper we present an approach which closes this gap. By assigning start times to each resource request, a complete schedule is planned. Advanced reservations are now easily possible. Based on this planning approach functions like diffuse requests, automatic duration extension, or service level agreements are described. We think they are useful to increase the usability, acceptance and performance of HPC machines. In the second part of this paper we present a planning based resource management system which already covers some of the mentioned features.}}, author = {{Hovestadt, Matthias and Kao, Odej and Keller, Axel and Streit, Achim}}, booktitle = {{Proc. Workshop on Job Scheduling Strategies for Parallel Processing (JSSPP)}}, keywords = {{High Performance Computing, Service Level Agreement, Grid Resource, Resource Management System, Advance Reservation}}, pages = {{1--20}}, title = {{{Scheduling in HPC Resource Management Systems: Queuing vs. Planning}}}, doi = {{10.1007/10968987_1}}, volume = {{2862}}, year = {{2003}}, }