Research on Power-Factor-Correction Technique Based on Buck-Cascaded Buck-Boost (BUCBB) Converter

Abstract: Single-switch step-up/step-down converters, such as the buck-boost, SEPIC and Cuk, have relatively high voltage and current stresses on components compared to the buck or the boost converter. In this paper, we propose a two-switch topology, buck-cascaded buck-boost (BUCBB) converter. The BUCBB converter can work as a boost or as a buck converter depending on input-output conditions, and thus achieves lower stresses on components. BUCBB can offer significant performance improvements over single-switch buck-boost converters in PFC applications.BUCBB converter is selected as the main circuit of the APFC system. On account of the average current control chosen in the APFC system, a large signal dynamic BUCBB model is built and all the switching elements replaced by dependent sources. By this method, long computational times for obtaining switches simulation waveforms reduced. Based on the Simulink-Power System Block of Matlab, the simulation results indicate that the input current follows accurately the input voltage and the input current waveform is corrected.According to the buck situation will cause the input current discontinuity, a new improved elliptic-integral filter is added at input end of the APFC. The relation between output impedance of the input filter and input impedance of APFC circuit and its affection on APFC's stability are discussed. Also, the parameters of the input filter are selected.The paper presents an analysis of the BUCBB converter operation in PFC application, as well as design guidelines. At last BUCBB converter is demonstrated on an experimental 250-W, 200-V dc output, as a PFC rectifier…
Key words: Active power factor correction; Buck-cascaded Buck-Boost converter; Improved elliptic-integral filter; A large signal dynamic model

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