Johann W. Kolar

Bio: Johann W. Kolar is an academic researcher from ETH Zurich. The author has contributed to research in topics: Rectifier & Three-phase. The author has an hindex of 97, co-authored 965 publications receiving 36902 citations. Previous affiliations of Johann W. Kolar include Alstom & Infineon Technologies.

Vorrichtung zum elektromagnetischen Schweben und Antreiben.

Abstract: Die Erfindung betrifft eine Vorrichtung zum elektromagnetischen Schweben und Antreiben und/oder zur beruhrungslosen Energiegewinnung aus der Umgebung und/oder zur beruhrungslosen Geschwindigkeitserfassung, umfassend mindestens ein erstes Rotorelement (1), wobei das erste Rotorelement (1) eine zylindrische Anordnung von Permanentmagneten ist, wobei die Permanentmagnete angeordnet sind, um ein helikales Magnetfeld zu bilden, wobei das erste Rotorelement (1) angeordnet ist, um um eine erste Achse zu rotieren, ein Statorelement (2), das angeordnet ist, um magnetisch mit dem Magnetfeld des ersten Rotorelements in Wechselwirkung zu treten, und dadurch eine relative Kraft zwischen dem ersten Rotorelement (1) und dem Statorelement (2) zu erzeugen.

A New Ground Power Unit (GPU) Supply for Aircraft Applications

Abstract: Nowadays, electrical energy is the alternative to supply aircraft systems. In this paper a new converter for ground power units supply in aircraft applications is proposed. The topology consists of a rectifier with an active current injection circuit linked to a three level neutral point clamped converter. The design procedure is detailed in this paper showing the principal requirements for the safe operation of the converter. Simulation results validate the satisfying performance of the proposed system.

Advanced Synergetic Charge Control of Three-Phase PFC Buck-Boost Current DC-Link EV Chargers

Abstract: An advanced synergetic charge-based mains cur-rent control (ASC) for three-phase power factor correction (PFC) buck-boost current DC-link AC/DC converters, which integrate a front-end buck-type current DC-link PFC rectifier and a DC/DC boost converter output stage, is proposed. The charge control is embedded in the synergetic (coordinated) control of the two converter stages, retaining all advantageous features such as only a minimum number of switches operating at any given time and a seamless transition between buck-and boost-mode. Compared to conventional synergetic current control (CSC) with synchronous sampling or oversampling, the ASC achieves an reduction of the AC-side current harmonics (simulated total harmonic distortion lower by up to 30 %) for operation over a wide output voltage range from 200 to 1000 V without increased implementation complexity or hardware cost. Furthermore, the ASC improves the light-load efficiency by inherently enabling a smooth transition into discontinuous conduction mode (DCM) without additional modifications of the control structure. Finally, the proposed ASC can control a system featuring significantly higher DC-link current ripples without a degradation of the grid current quality, which facilitates more compact DC-link inductor and hence converter realizations.

High-Bandwidth Isolated Voltage Measurements With Very High Common Mode Rejection Ratio for WBG Power Converters

Abstract: Galvanically isolated voltage measurements are becoming increasingly important for the characterization of converter systems with fast switching Wide-Bandgap (WBG) semiconductors. A very high Common Mode Rejection Ratio (CMRR) $> 80$dB for frequencies up to several tens of MHz is required to accurately measure, e.g., the high-side gate-source or drain-source voltage in a half-bridge, or voltages on floating potentials as, e.g., found in multi-level converters. Common to all listed measurement scenarios is the fast changing reference potential, which acts as Common Mode (CM) disturbance. This article derives the minimum necessary CMRR at different frequencies to constrain the time-domain measurement error below a certain limit. Thereby, only the switched voltage and the voltage transition rate ($ {\text{d}{v}/\text{d}{t}}$) of the CM disturbance have to be considered and not the actual converter switching frequency $ {{f}_\text{sw}}$. Afterwards, a galvanically isolated measurement system with a CMRR $ {>\,100}\,$dB up to $ {100}\,$MHz and an analog measurement bandwidth of $ {130\,}$MHz is presented. Critical design aspects to achieve this performance are investigated. Compared to commercially available isolated voltage probes, the presented measurement system does not require any additional equipment like an oscilloscope to perform and visualize measurements, since the data is already digitized/sampled and thus can be transmitted directly to a host device (e.g., computer or monitoring system) with corresponding Graphical User Interface (GUI) software. Experimental verification in frequency- and time-domain confirms that the performance is on par with the best commercially available isolated voltage probes.

Automated Insertion of Objects Into an Acoustic Robotic Gripper

Abstract: Acoustic levitation forces can be used to manipulate small objects and liquid without mechanical contact or contamination To use acoustic levitation for contactless robotic grippers, automated insertion of objects into the acoustic pressure field is necessary This work presents analytical models based on which concepts for the controlled insertion of objects are developed Two prototypes of acoustic grippers are implemented and used to experimentally verify the lifting of objects into the acoustic field Using standing acoustic waves and by dynamically adjusting the acoustic power, the lifting of high-density objects (>7 g/cm3) from acoustically transparent surfaces is demonstrated Moreover, a combination of different acoustic traps is used to lift lower-density objects from acoustically reflective surfaces The provided results open up new possibilities for the implementation of acoustic levitation in robotic grippers, which have the potential to be used in a variety of industrial applications

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Multilevel inverters: a survey of topologies, controls, and applications

Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.