Abstract
Over the past two decades, various power factor correction (PFC) circuits have been proposed and studied to reduce the harmonic and reactive power. However, for a single phase case, there exists inherently double line frequency harmonic. Although an LC series resonant filter can be designed to filter the low frequency harmonic, however, the filter is bulky and heavy. Alternatively, one can use a very large capacitor as a first order passive low pass filter. Again, the volume and reliability become less attractive. Therefore, the major objective of this thesis is focused on proposing an active solution to solve the fundamental problem. Basically, the major contributions of this thesis can be summarized as follows. First, a newly developed single-stage PFC circuit based on the Generalized Zero Vector (GZV) is adopted for reducing the double line frequency harmonic. The well known state-space averaging technique is then used to derive the corresponding mathematical model. Second, for simplifying the analytic solution, an approximate but more practical double line frequency model is also derived. The corresponding analytic relations reveal clearly the double line frequency harmonic generation mechanism. Third, based on this understanding, a feedback control strategy is proposed for reducing the double line frequency harmonic greatly. Fourth, some design criteria are provided for easy parameter decision of the passive components. Finally a 100W prototype with 110Vrms AC input and 48V DC output is constructed for verifying the effectiveness of the proposed control strategy. It is seen that more than 72% reduction in the amplitude of the double line frequency component can be achieved.