Evaluation of a delta-connection of three single-phase unity power factor rectifier modules (/spl Delta/-rectifier) in comparison to a direct three-phase rectifier realization

In this paper, the voltage and current stress of a delta-connection of three single-phase boost-type unity power factor rectifier modules (Δ-Rectifier) is analyzed in order to perform a design comparable to a direct three-phase three-level six-switch unity power factor (conventional) rectifier system. The conduction losses of the power semiconductors are calculated using analytical approximations of the average and RMS values of the component currents, the switching losses are taken from previous experimental investigations. Based on this data an overview of the estimated power losses is given for the Δ-rectifier as well as for the conventional rectifier for 10 kW output power, 800 VDC output and 320 V/400 V/480 V/530 V (RMS, line-to-line) mains voltage. These investigations finally lead to efficiency and component count figures. Furthermore, special attention is paid to the control of the whole three-phase system, including the DC/DC converter output stages of the line-to-line modules of the Δ-rectifier. Finally, topics of the continuation of the research are identified as, e.g., the realization of a prototype in order to verify the theoretical results experimentally also for unbalanced mains voltage conditions and with nonideal components such as nonlinear input inductors employing iron powder cores and the analysis of a Δ-rectifier being formed by single-stage SEPIC-type line-to-line modules.