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.

Comparison of electrostatic precipitator power supplies with low effects on the mains

Abstract: In this article, the distortions caused by the power supplies employed in Electrostatic Precipitators (ESP) are investigated, and means for improving the line power quality are proposed. Multi-pulse and PWM rectifier topologies and other concepts including hybrid systems and active filters are evaluated in order to identify suitable systems for ESP applications. A comparison of the studied systems rated to 60 kW and fully designed employing commercial components is shown. The ESP systems efficiency, power density, current harmonic THD, among others features are used for the assessment. The loss calculations are extended to a variable chip area to allow a fair comparison between the studied systems. Finally, the VIENNA 6-switches rectifier and active filter concepts are chosen and experimental analyses are carried out, verifying the performance and feasibility of the proposed systems.

The Input Impedance of Common-Mode and Differential-Mode Noise Separators

Abstract: This paper discusses the $\Delta$ -networks and other circuits designed to separate the conducted electromagnetic interference (EMI) into its common mode (CM) and differential mode (DM) components. The input impedances of CM/DM separators must be 50 $\Omega$ resistive in the measurement frequency range, and they must be independent of the values of the noise signals and noise source impedances. The conditions for achieving such input impedances are derived. It is shown that many of the proposed separators, including the $\Delta$ -network suggested in the International Special Committee on Radio Interference (CISPR) 16-1-2 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements and, consequently, to the oversizing of EMI filters and design by trial and error.

Wide bandwidth low complexity isolated current sensor to be employed in a 10 kW/500 kHz three-phase unity power factor PWM rectifier system

Abstract: A current sensor employing a Hall-based field sensing ASIC in combination with a current transformer is proposed. The sensor is characterized by a measuring range of /spl plusmn/50 A, an upper bandwidth limit of 20 MHz and high dV/dt-immunity up to 10 kV//spl mu/s. The sensor functional principle and dimensioning are discussed in detail. Parameters determining the sensor bandwidth are clarified, the theoretical considerations are verified by experiments. Finally, measures for further increasing the sensor bandwidth are proposed.

PEEC modelling of toroidal magnetic inductor in frequency domain

Abstract: In this paper, a detailed 3D Partial Element Equivalent Circuit (PEEC) model of a toroidal coil with a magnetic core is developed. The PEEC problem in the presence of magnetic materials is solved in the frequency domain via a magnetic current/charge approach, i.e. replacing the magnetized objects by a distribution of equivalent fictitious magnetic currents/charges in free space. The simulation parameters are the winding and magnetic core properties. The permeability is either taken from datasheets or determined by measuring the series equivalent impedance. To verify the proposed 3D PEEC model, calculated and measured impedance values are compared for several winding arrangements and core materials. A good agreement between simulation and measurements is presented up to the first resonant frequency. For higher frequencies, a more accurate specification of the permeability is required, as well as the core dielectric property has to be considered.

Three-Phase PWM Power Conversion – The Route to Ultra High Power Density and Efficiency

Abstract: A review of three-phase PWM converter topologies which do show a low complexity / high reliability and high efficiency and power density and are therefore of main interest for a future industrial application is presented. A three-switch/level boost-type PWM rectifier (VIENNA Rectifier), a buck+boost-type PWM rectifier with wide output voltage range and the AC/AC Sparse Matrix Converter concept are discussed in detail and topics to be treated in the course of further research are identified. Finally, it is shown how the aspects being relevant for the realization of highly compact converter systems could be integrated into education in the field.

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.