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Konferenzveröffentlichung
Impact of implementation of auxiliary bias-windings on controllable inductors for power electronic converters
(IEEE, 2020)
Magnetic devices are an important part of electronic converters. They can be used to control some properties of the converters. There are three different control methods using an auxiliary bias-winding. In the presented paper, the impact of the implementation of the auxiliary bias-winding was studied for mixed biasing. Seven different designs were investigated in small signal measurements and 3D-FEM-simulations. The results were proven by calculated results of equivalent diagram circuits, which have been developed. ...
Dissertation
Long-term voltage stability of electric power systems hosting inverter-interfaced energy sources
(2021)
The study of power system dynamics refers to the motion of electro-mechanical and electro-magnetic quantities such as voltages, currents, rotational speeds, angles and powers under the action of forces caused by system disturbances. For decades, such dynamics have been extensively dominated by large Synchronous Generators (SGs). Not a surprising statement, considering that the power systems that we know today were built based on the SG concept since the closing decades of the 19th century. It all began in 1891, when ...
Konferenzveröffentlichung
Weight reduction of DC/DC converters using controllable inductors
(VDE Verlag, 2019-07)
Controllable inductors can be realized by introducing auxiliary windings into the device that partially saturate the core and allow variation of the inductance value. This can be used to achieve zero-voltage switching in a DC/DC converter over a wide load range while at the same time the weight of the inductor is reduced. In this paper the possible size and weight reduction and the influence on the efficiency is calculated and compared to other solutions. The results are verified in a prototype.
Working paper
Verbundvorhaben "HELENE" - Hocheffiziente, langlebige und kompakte Leistungselektronik auf GaN-Basis für die Elektromobilität der Zukunft
(2020)
Die vom Fachgebiet Elektrische Energieversorgungssysteme (EVS) am Kompetenzzentrum für Dezentrale Elektrische Energieversorgungstechnik (KDEE) der Universität Kassel durchgeführten und in diesem Bericht vorgestellten Arbeiten haben einen Beitrag zum Verbundvorhaben „Hocheffiziente, langlebige und kompakte Leistungselektronik auf GaN-Basis für die Elektromobilität der Zukunft“ (HELENE) geleistet. Ziel des Gesamtvorhabens war die Untersuchung der Einsatzfähigkeit und die Bewertung und Demonstration von Gewichts- und ...
Dissertation
Gast-Partikel in mikroskaligen, dreidimensionalen Wirts-Partikeln: Herstellung durch Nanoimprintlithographie und ihre Charakterisierung
(2020)
Die Verwendung von Partikeln spielt in vielen alltäglichen Bereichen eine essenzielle Rolle und ist daher im Laufe dieses Jahrhunderts immer mehr in den Fokus der Forschung gerückt. Aktuelle Forschungsarbeiten belegen, dass die Größe und Form der Partikel Einfluss auf verschiedene Anwendungen haben. Ein Beispiel ist die Verwendung als Medikamententräger. Forschungen zeigen, dass ellipsoide Partikel langsamer als sphärische Partikel von Makrophagen internalisiert werden und den Transport von Medikamenten innerhalb des ...
Dissertation
Multilayer Thin-film Structures with Distributed Cavity for Optical Filter and Laser Applications
(2018-12)
This work is aimed at the development of a fabrication process for realization of a chirped filter based laser device (called as coreSEL). Conventional vertical cavity surface emitting lasers (VCSELs) are based on Fabry-Pérot arrangement where the electric field of the resonant mode is mainly located in the cavity region (center) and often causes undesired effects such as mode-jumps. However, coreSEL is based on chirped optical filter which offers a resonant mode with wider spatial distribution of the electric field ...
Dissertation
Entwicklung eines Nanoimprint-Prozesses zur Herstellung von dreidimensional strukturierten Nanopartikeln mit erhöhter mechanischer Stabilität
(2019)
The nanoimprint technology realizes already the production of two-dimensional (2D) shaped nanoparticles of different shapes and materials. These nanoparticles can be applied in advanced applications in material engineering, as well as in biology and particularly in drug-delivery systems. This work presents three-dimensional (3D) shaped nanoparticles with T-, L- and step-like cross-sections, implemented by substrate conformal imprint lithography (SCIL) and a manual soft-imprint technique. Further, 2D shaped nanoparticles ...
Konferenzveröffentlichung
Asymmetric Contributions to Instantaneous Reserve by Generation, Loads, and Storage
(2022)
In the course of decarbonization, interconnected systems will have to be prepared for recurring situations during which they are fed by mostly inverter-based generation. Today, the stabilizing influence of the rotating masses directly coupled to the grid via synchronous generators on every frequency change is essential. The inherent immediate reaction of synchronous generators on voltage-angle changes and frequency variations is called instantaneous reserve. During dynamic situations such as load or generation changes ...
Aufsatz
Effect of Auger recombination and leakage on the droop in InGaN/GaN quantum well LEDs
(Optical Society of America, 2014)
We investigate the effect of the epitaxial structure and the acceptor doping profile on the efficiency droop in InGaN/GaN LEDs by the physics based simulation of experimental internal quantum efficiency (IQE) characteristics. The device geometry is an integral part of our simulation approach. We demonstrate that even for single quantum well LEDs the droop depends critically on the acceptor doping profile. The Auger recombination was found to increase stronger than with the third power of the carrier density and has ...
Dissertation
Development, Verification and Analysis of a Fault Injection Tool for Improving Dependability of FPGA Systems
(2019-11)
Field Programmable Gate Array (FPGA) has been involved in various applications in the last couple of decades, such as aerospace, biomedical instrumentation, safety-critical systems, and spacecraft, due to their remarkable features. These features include parallelism, reconfiguration, self-healing capabilities, availability, low cost and low design turn-around time. FPGA devices are sensitive to Single Event Effects (SEE), which can be caused by various sources, such as α-particles, cosmic rays, atmospheric neutrons, ...