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 Experimental Analysis of a Selfbearing Double-Stator Linear-Rotary Actuator

Abstract: Linear-rotary actuators (LiRAs) are today used in industry applications where a controlled linear and rotary motion is necessary such as pick-and-place robots, servo actuation of gearboxes or tooling machines. However, in special industry applications that require high purity and/or high precision positioning, the usage of conventional LiRAs with mechanical bearings is limited. Therefore, in this paper a LiRA with integrated magnetic bearings, i.e. a selfbearing/bearingless LiRA, is analyzed. The actuator employs concentrically arranged linear and rotary stators placed inside and outside a cylindrically shaped mover, which results in a so-called selfbearing double-stator (SBDS) LiRA. A FEM geometry optimization of the SBDS LiRA is performed and Pareto performance plots concerning linear force and torque generation are obtained. A SBDS LiRA hardware demonstrator and an 18-phase inverter power supply hardware prototype are built and their operation is experimentally verified by rotary and linear position step response measurements.

Method for switching loss minimum controlling of buck-boost converter, utilized in hybrid vehicle, involves implementing complete discharge of capacitance of transistors such that diodes begin to conduct before course of locking times

Abstract: The method involves shaping current in an inductor by a control so that switching of transistors takes place by power supply of anti-parallel free wheeling diodes. Parasitic output capacitance of the transistors that are switched off, is charged on a value of voltages (U9, U10) lying between a positive terminal of a bridge section of the switched-on transistor and switched off transistor and reference potential. Complete discharge of the capacitance of the switched on transistors is implemented such that the diodes begin to conduct before the course of locking times (36, 40, 44).

High-Dynamics Low-Cost Flow Control With Solenoid Actuator for Ultrahigh Purity Applications

Abstract: This paper presents a noninvasive closed-loop flow control system in a compact design for high-purity or aggressive chemical applications. The novel topology with a solenoid activated valve and an ultrasonic-based flow measurement permits precise flow control with rapid response time at a very low price. In this paper, the mechanical setup, power electronics, implemented closed-loop control, and the measurement of flow and valve stroke are discussed. Finally, the performance of the system is verified by a laboratory prototype.

Future Challenges for Research and Teaching in Power Electronics

Abstract: Power electronics is a key technology for modern societies and has reached a high level of development over the last decades. Accordingly, the question about future perspectives and challenges in research and teaching arises. Starting from a brief discussion of past performance improvements in main application areas, the potentials and limits of future advancements of power semiconductor technology and passive components, i.e. capacitors, magnetics, cooling systems, interconnections and packages / integration techniques are discussed. Subsequently, power converter topologies and control and modulation concepts are reviewed and main research targets are highlighted for each area. The second part of the presentation focuses on a paradigm shift from considering single converters to converter systems, i.e. cascaded converters or converter clusters, which is a typical situation found today in datacenters or More Electric Aircraft and will become widespread with the realization of the Smart Grid. Furthermore, the required extension of the analysis of power converters from switching frequency cycles to the whole life cycle is highlighted. Finally, resulting challenges for academic research and teaching which must be tackled in order to continue the highly dynamic development of the area of Power Electronics are identified.

Three-Phase AC-DC Converters with Passive, Active and Hybrid Current Injection Circuits - Part II

Abstract: AC-DC Three-phase converters are highly well known for having enhanced power quality with unity displacement power factor, low total harmonic pollution on the AC side, and controllable DC output with unidirectional or bidirectional power flow. The second part of this paper presents a review of several three-phase AC-DC converters with active current injection circuits, including some hybrid configurations, detailing their respective topologies and characteristics.

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.