Showing papers by "Johann W. Kolar published in 1998"

VIENNA rectifier II-a novel single-stage high-frequency isolated three-phase PWM rectifier system

Abstract: Based on an analysis of basic realization possibilities, the structure of the power circuit of a new single-stage three-phase boost-type PWM rectifier system (VIENNA Rectifier II) is developed. This system has continuous sinusoidal time behavior of the input currents and high-frequency isolation of the output voltage which is controlled in a highly dynamic manner. As compared to a conventional two-stage realization, this system has substantially lower complexity and allows to realize several isolated output circuits with minimum effort. The basic function of the new PWM rectifier system is described based on the conducting states occurring within a pulse period. Furthermore, a straightforward space vector oriented method for the system control is proposed which guarantees a symmetric magnetization of the transformer. Also, it makes possible a sinusoidal control of the mains phase currents in phase with the associated phase voltages. By digital simulation the theoretical considerations, the stresses on the power semiconductors of the new converter system are determined. Finally, problems of a practical realization of the system are discussed, as well as the direct start-up and the short circuit protection of the converter. Also, the advantages and disadvantages of the new converter system are compiled in the form of an overview.

How to include the dependency of the R/sub DS(on/) of power MOSFETs on the instantaneous value of the drain current into the calculation of the conduction losses of high-frequency three-phase PWM inverters

Abstract: In this paper, the conduction losses of power MOSFETs are calculated analytically for application in three-phase voltage DC-link pulsewidth modulation (PWM) power converter systems. Contrary to a conventional calculation, the dependency of the turn-on behavior on the drain current is considered in terms of a quadratic approximation. The derived relationships are represented graphically; they can be included directly into the dimensioning of the power transistors.

Direct three-phase single-stage flyback-type power factor corrector

Abstract: Based on the work of Hui and Chung (see ibid., vol. 33, no. 15, p.1274-76, 1997) a three-phase converter system consisting of three single-phase flyback-type AC/DC converter modules in star-connection is proposed and investigated.

Power MOSFET's on the Instantaneous Value of the Drain Current into the Calculation of the Conduction Losses of High-Frequency Three-Phase PWM Inverters

Abstract: In this paper, the conduction losses of power MOS- FET's are calculated analytically for application in three-phase voltage dc-link pulsewidth modulation (PWM) converter systems. Contrary to a conventional calculation, the dependency of the turn-on behavior on the drain current is considered in terms of a quadratic approximation. The derived relationships are represented graphically; they can be included directly into the dimensioning of the power transistors.

Design and experimental evaluation of the loss-free braking resistor concept for applications in integrated converter machine systems

Abstract: If the braking resistor of a conventional dissipative braking system (braking chopper) of a three-phase AC motor drive is replaced by a thyristor bridge (loss-free braking resistor) controlled in the full inverter operation, the braking energy of the drive can be fed back into the mains. This means that the current flowing into the mains via always two phases from the DC link is controlled by the power transistor of the braking chopper. In this paper, this regenerative braking system is discussed based on a 10 kW laboratory model.