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Konferenzveröffentlichung
A GaN-based DC/DC converter for e-vehicles applications
(IEEE, 2020)
This paper presents a 4 kW GaN-based galvanically isolated bidirectional DC/DC converter suitable for on-board auxiliary power supply systems, interconnecting the HV battery with the LV power system. To enable the trend towards higher levels of electrification, a second LV level of 48 V is introduced to supply the high-power consumers, relieving the 12 V grid on the one hand and/or avoiding using additional costly isolated converters connected to the HV batteries on the other. The built converter prototypes aim to ...
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Quality Improvement In Manual Assembly By Software-Based Evaluation Of Human Misconduct
(European Safety and Reliability Association, 2019)
For reaching a level of high quality, production processes must be carried out both, economically and reliably. Despite automation and digitalization, manual assembly operations still constitute a key element for creating efficient production processes. However, in practice, creating robust and efficient manual assembly processes often fails because the occurrence of human errors cannot be quantified prospectively. Therefore, a corresponding procedure has been developed at the institutes of the authors. The module-based ...
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. ...
Konferenzveröffentlichung
The logarithmic finite element method
(International Center for Numerical Methods in Engineering (CIMNE), 2018)
The Logarithmic finite element (LogFE) method extends the Ritz-Galerkin method to approximations on a non-linear finite-dimensional manifold in the infinitedimensional solution space. Formulating the interpolant on the logarithmic space allows for a novel treatment of the rotational component of the deformation, and induces a strong coupling between rotations and translations. The Logarithmic finite element method provides
a transformation of the initial configuration that is not restricted to an isoparametric formulation.
Konferenzveröffentlichung
Controlled magnetic devices in power electronic applications
(IEEE, 2017)
Almost all power electronic converters require magnetic devices and some properties of the converters can be controlled with magnetics. New magnetic materials enable implementation of magnetic control of converters also in high switching frequency applications. The presented paper gives an overview about controllability of magnetic devices in theory and practice, simulation approaches and examples. The focus is on electrically controllable magnetic devices. This means that an additional control winding is wound on ...
Konferenzveröffentlichung
Design of Photovoltaic Microinverter for Off-Grid and Grid-Parallel Applications
(VDE Verlag, 2014)
The design and construction of a 500VA microinverter for photovoltaic applications is presented. The developed microinverter is capable of operating as a standalone AC voltage source for small loads or, alternatively, as a grid-parallel system. Possible applications are therefore small off-grid installations as well as installations where space constraints do not allow enough modules to be combined to use string inverters. The design of the microinverter is based on a two stage concept. Two alternative topologies for ...
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.
Konferenzveröffentlichung
Beyond Ritz-Galerkin: Finite element approximations on a manifold in the configuration space [Abstract]
(Institute of Structural Analysis and Antiseismic Research, School of Civil Engineering, National Technical University of Athens (NTUA), 2016)
An extension of the Ritz-Galerkin method, based on finding approximations on a finite-dimensional manifold of functions (i.e., not a linear subspace) in the infinite-dimensional exact configuration space, will be presented. This new approach is particularly efficient in computing geometrically exact solutions for problems involving large rotations.
Konferenzveröffentlichung
Coupling atomistic models with continuous finite beam elements [Abstract]
(Institute of Structural Analysis and Antiseismic Research, School of Civil Engineering, National Technical University of Athens (NTUA), 2016)
Concurrent simulations of atomistic (discrete) and continuum models are one key to perform static calculations of large atomistic structures. Occurring ghost forces at the interfaces between discrete (atomistic) and continuous regions are a major challenge for the definition of such interfaces. The so called virtual projection method [1] is a class of force-based a/c schemes which reduce (or even avoid) ghost forces. This class of coupling schemes is able to deal with atomistic models consisting of bonded, multi-body ...