Johann W. Kolar

Last Name

Kolar

First Name

Johann W.

ORCID

0000-0002-6000-7402

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Publications 1 - 10 of 1118

Load-Independent Voltage Balancing of Multi-Level Flying Capacitor Converters in Quasi-2-Level Operation
Czyz, Piotr; Papamanolis, Panteleimon; Bruguera, Francesc T.; et al. (2021)
Electronics
Quasi-2-level (Q2L) operation of multi-level bridge-legs, especially of flying-capacitor converters (FCC), is an interesting option for realizing single-cell power conversion in applications whose system voltages exceed the ratings of available power semiconductors. To ensure equal voltage sharing among a Q2L-FCC’s switches, the voltages of a Q2L-FCC’s minimized flying capacitors (FCs) must always be balanced. Thus, we propose a concept for load-independent FC voltage balancing: For non-zero load current, we use a model predictive control (MPC) approach to identify the commutation sequence of the individual switches within a Q2L transition that minimizes the FC or cell voltage errors. In case of zero load current, we employ a novel MPC-based approach using cell multiple switching (CMS), i.e., the insertion of additional zero-current commutations within a Q2L transition, to exchange charge between the FCs via the charging currents of the switches’ parasitic capacitances. Experiments with a 5-level FCC half-bridge demonstrator confirm the validity of the derived models and verify the performance of the proposed load-independent balancing concept.
Conceptualization and Multiobjective Optimization of the Electric System of an Airborne Wind Turbine
Kolar, Johann W.; Friedli, Thomas; Krismer, Florian; et al. (2013)
IEEE Journal of Emerging and Selected Topics in Power Electronics
Experimental Verification of Sinusoidal Approximation in the Analysis of Three-Phase Twelve-Pulse Output Voltage Type Rectifiers
Pejović, Predrag; Kolar, Johann W.; Šviković, Vladimir (2009)
15th International Symposium on Power Electronics, Ee 2009
Control System Design and Experimental Verification of a Self-Bearing Double-Stator Linear-Rotary Actuator
Giuffrida, Rosario V.; Miric, Spasoje; Horat, Andreas; et al. (2021)
2021 13th International Symposium on Linear Drives for Industry Applications (LDIA)
Integrated Linear Rotary Actuators (LiRAs) offer a compact solution which can achieve high dynamics when coupled linear and rotary motions are required. As a further step in integration, the LiRA can be equipped with Active Magnetic Bearings, which however requires a special winding configuration and feedback control of the magnetically levitated mover's position to operate. In this paper a control-oriented analysis of a Self-Bearing (SB) Double-Stator (DS) LiRA is conducted, providing an insight on simultaneous bearing force and torque generation and deriving an electromechanical dynamic model which is linearized and used to design a 6-DoF cascaded position control system. This is then implemented in hardware and verified, bringing a prototype of the SB DS LiRA into full operation, tracking a linear-rotary mission profile with radial deviations of the levitated mover's position below 75 μm.
Optimizing repulsive lorentz forces for a levitating induction cooker
Zingerli, Claudius M.; Nussbaumer, Thomas; Kolar, Johann W. (2014)
2014 International Power Electronics Conference (IPEC-Hiroshima 2014 - ECCE ASIA)
In this paper we study a novel way of induction cooking. Traditionally, an alternating magnetic field is used to induce currents in a ferromagnetic pan to heat foods. We use non-ferromagnetic materials and optimize the design for high repulsive forces in order to levitate the pan while simultaneously heating it and its contents. Our approach is simulation-based to study the influence of different parameters and to perform multidimensional analyses for high force versus power or loss goals. Finally, an experimental prototype has been realized and successfully operated.
The Essence of Three-Phase PFC Rectifier Systems
Kolar, Johann W. (2012)
Tutorial at IECON 2012
iGSE-C$_{\mathrm{x}}$ – a New Normalized Steinmetz Model for Class II Multilayer Ceramic Capacitors
Menzi, David; Heller, Morris; Kolar, Johann W. (2021)
IEEE Open Journal of Power Electronics
Ferroelectric Class II ceramic capacitors allow for highly compact converter realizations, but are showing relatively high losses for large-signal excitations which must be taken into account in the system dimensioning. Recent literature introduced the iGSE-C Q , a Steinmetz model based on the macroscopic capacitor Q-U hysteresis, allowing to accurately predict the losses of X7R capacitors. However, the model is specific for each single device, i.e., is insufficient to characterize losses in devices of the same series and manufacturer, which are employing the same dielectric material but with different voltage rating or nominal capacitance value. In this publication, based on basic physical properties we propose a new Steinmetz model, the iGSE-C X based on the relative dielectric material D-E hysteresis, which is applicable to all devices of a capacitor series. The iGSE-C X loss modeling technique is demonstrated for the TDK X7R, the TDK X7T, as well as the Knowles Syfer X7R series. Finally, the iGSE-C X is employed to estimate the large-signal losses of the capacitors of a three-phase inverter and shown to offer sufficient accuracy for a first power circuit design.
Multifunctional Self-Bearing Linear-Rotary Actuators
Miric, Spasoje; Giuffrida, Rosario V.; Bortis, Dominik; et al. (2022)
Common Mode Modelling and Filter Design for a Three-Phase Buck-Type Pulse Width Modulated Rectifier System
Heldwein, Marcelo L.; Nussbaumer, Thomas; Kolar, Johann W. (2010)
IET Power Electronics
SiC power semiconductors in HEVs
Wrzecionko, Benjamin; Biela, Jürgen; Kolar, Johann W. (2009)
2009 35th Annual Conference of IEEE Industrial Electronics

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Johann W. Kolar

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