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.

Design and Analysis of a New Drive-Integrated Auxiliary Dc-Dc Converter for Hybrid Vehicles

Abstract: Cost, volume and weight are three major driving forces in the automotive area. This is also true for hybrid electric vehicles, which attract more and more attention due to increasing fuel costs and pollution. Since the energy distribution system causes a significant share of the volume/costs, a new concept for integrating dc-dc converters, which transfer the power between the low- and high-voltage buses, in the inverter/drive system is presented in this paper. There, the basic operation principle, analytical design equations and control strategies for improving the efficiency are explained. These considerations are validated by simulations and measurements.

Speed detecting device and method

Abstract: The invention relates to a speed detecting device and a speed detecting method which detect the speed in a non-contact manner, and which can detect the moving speed of a relative moving body with highprecision even if a gap between an excitation coil or a detection coil and the relative moving body changes. The device includes more than one excitation coil for generating a magnetic flux corresponding to an alternating current; a plurality of detection coils each generating an induced voltage corresponding to a magnetic flux produced by an eddy current generated on a conductive relative movingbody, the eddy current being generated so as to correspond to a moving speed of the relative moving body; a current and voltage measuring portion for measuring current flowing through the excitationcoil and the voltage at two ends of the excitation coil; a gap estimation portion for estimating, based on a current flowing through the excitation coil and a voltage across the excitation coil, a gapbetween the relative moving body and the excitation coil; and a speed estimation portion for estimating, based on the gap estimated by the gap estimation portion and the induced voltage generated ineach of the plurality of detection coils, the moving speed of the relative moving body.

Power converter with a snubber circuit

Abstract: A power converter circuit includes a switching circuit with at least one electronic switch, a capacitor configured to provide or receive a voltage with a predefined voltage level, at least one first inductor, and a snubber circuit. The snubber circuit includes at least one second inductor inductively coupled to the at least one first inductor and electrically coupled to the capacitor.

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.