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.

Development of an Interactive Circuits and Systems Seminar (iCASS) and its effectiveness

Abstract: In this paper, we describe a development of an interactive educational tool in Circuits and Systems (iCASS) and its introductory effect to the College of Technology. The purpose of this tool is to help teacher’s lecture and student’s self-learning. This tool can be used for on-line learning, can be easily integrated into an E-Learning platform for distance learning, and can be used in the classroom with notebook computer and over-head projector, via Internet or CD-ROM. For the purpose of implementation, we produce a set of teaching materials using HTML text and Java Applets for interactive animation. As a result, the proposed tool can be used as a self-learning tool independent of time and working place. Moreover, in this tool, the movement of the engineering model isn’t only seen, but hearing as sound is also very effective in study. Futhermore, this tool might be canceled ”squiffy doo” of the simulation by connecting an actual model and computer. We describe that the proposed tool has an effect for interest attachment to students and allow to speed up the learning process. The E-Leaning tool as presented at the conference can be found at http://www.sia.co.jp/˜icass/index.html.

Alternating average power in a multi-cell power converter

Abstract: A method includes receiving a periodic voltage by a power converter comprising a plurality of converter cells and, in a series of time frames of equal duration, alternating an average power level of power converted by at least one converter cell of the plurality of converter cells. Each of the series of time frames corresponds to a time period between sequential zero crossings of the periodic voltage.

Inductive component and high-frequency filter device

Abstract: The invention relates to an inductive component having a planar conductive track structure. The planar conductive track structure is surrounded along a predetermined section by a ferromagnetic core. For targeted control of the current flow inside the planar conductive track structure and, in particular, of the current density in the cross-section of the planar conductive track structure, gaps are provided in a targeted manner in the ferromagnetic core. The gaps in the ferromagnetic core are arranged in regions above and/or below the planar conductive track structure.

Ac-ac 컨버터 회로

Abstract: 회로 전체의 소형화를 도모할 수 있는 AC-AC 컨버터 회로를 제공한다. AC-AC 컨버터 회로(100)는, 교류 전압(V12)을 다른 교류 전압(V22)으로 변환하는 AC-AC 컨버터 회로이다. 정류 회로(16)는 교류 전압(V12)을 정류한다. 인버터 회로(22)는 다른 교류 전압(V22)을 생성한다. Z 소스 회로(20)는 정류 회로(16)와 인버터 회로(22) 사이에 마련되어 있다.

Duty-Cycle Dependent Phase Shift Modulation of Dual Three-Phase Active Bridge Four-Port AC–DC/DC–AC Converter Eliminating Low Frequency Power Pulsations

Abstract: A recently introduced Dual Three-Phase Active Bridge Converter (D3ABC) provides two three-phase ac ports (ac${}_{1}$ and ac${}_{2}$), two dc ports (dc${}_{1}$ and dc${}_{2}$), and galvanic isolation between the ports ac${}_{1}$, dc${}_{1}$ (primary side) and ac${}_{2}$, dc${}_{2}$ (secondary side). Previously documented studies confirm that the D3ABC is generally capable of transferring power between all four ports. However, it has been found challenging to operate the converter if ac voltages with different line frequencies, $f_{1} e f_{2}$, are present at the ports ac${}_{1}$ and ac${}_{2}$. Such operation causes Low-Frequency (LF) power pulsations in the converter's dc links, leading to fluctuating dc link voltages and distorted phase currents. In this paper, a new duty-cycle dependent phase shift modulation scheme is proposed that eliminates such LF power pulsations and substantially increases the theoretical maximum transmittable power between primary and secondary sides compared to previous work. The new modulation scheme is developed on the basis of analytical considerations, which are supported by the results of numerical calculations, and verified by means of circuit simulations and experimental results. A hardware demonstrator originally designed for a rated power of $\text{8}\,$kW when operated from ac${}_{1}$ to dc${}_{2}$ at the European low-voltage ac mains ($V_{\mathrm{ac,1}} = \text{230}\,{\rm V}$ line-to-neutral rms, $V_{\mathrm{dc,1}} = \text{800}\,{\rm V}$, $V_{\mathrm{dc,2}} = \text{400}\,{\rm V}$) is used for experimental verification. Since the operation with $f_{1} e f_{2}$ leads to an increase of the currents in the converter, the experimental verification is conducted at half voltages and for a reduced power of $\text{2}\,$kW that is transferred from ac${}_{1}$ to ac${}_{2}$ at substantially different primary-side and secondary-side line frequencies of $f_{1} = \text{50}\,$Hz and $f_{2} = \text{77}\,$Hz. The measured results agree well with the simulated results. In particular, the dc link voltages show almost constant waveforms, which confirms the correct operation of the proposed modulation scheme.

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.