Power factor correction topologies and small-signal modeling. I: Single-phase and three-phase power factor correction. II: Small-signal analysis of converters in discontinuous conduction mode

Part I: This thesis is motivated by the increasing demand for power quality improvement. Power factor correction topologies for both single- and the three-phase utility lines are investigated and new modes of operation are introduced. The discussed topologies are so-called automatic power factor correctors. The current shaping function is a natural property of these circuits, and no extra current control loop is necessary. In both the single- and three-phase cases, a control method is introduced which provides full output regulation and simultaneously reduces the distortion of the input current at no extra cost. Whereas in the single-phase topology, galvanic isolation is easily obtained, in the three-phase topology, some obstacles have to be overcome. The isolated three-phase converter has an inherent output voltage ripple. This problem is analyzed and a solution is presented. Results obtained on experimental circuits agree well with the prediction and therefore confirm the validity of the analysis. Part II: The small-signal behavior of converters in discontinuous conduction mode (DCM) is investigated using an alternative approach. Transfer functions obtained by state-space averaging in DCM do not provide accurate results at higher frequencies. A correction term is introduced that can be added to the transfer function. This greatly enhances the accuracy. For converters operating in DCM, the state-space averaging method as originally introduced is relatively complicated if more than one element operates in discontinuous conduction mode. In this thesis, a standardized procedure is introduced to perform state-space averaging. Also, the complexity of this procedure does not increase as the number of discontinuous states increases.