Research On Pfc Convertors With Wide Input Frequency Range

Active PFC techniques have been widely used in electronics equipments owe to high power factor, high density and low total harmonic distortion (THD). However, the zero-crossing distortion of input current becomes more serious as the line frequency increases. There will be a big challenge for active PFC converters in future aircraft power system, whose line frequency is ranged in 360 to 800Hz. The causes of zero-crossing distortion in high line frequency application are analyzed, and some compentation methods are proposed.This thesis analyzes reasons of zero-crossing distortion on the basis of modeling Boost PFC converter, and points out the major causes are cusp distortions induced by the inductor and the phase displacement induced by the current loop and capacitors paralleled with rectifier. Two methods are proposed according to the two reasons and verified by simulation and experiments.To reduce the cusp distortion of the inductor current, this thesis analyzes the effects of the inductor value on the cusp distortion, damped factor, DCM operation, and proposes the optimum value of the inductor. According to the phase displacement between input current and input voltage, the compensation to the current loop and capacitor paralleled with rectifier is proposed in the thesis. A prototype with 115V, 360~800Hz input, 270V/ 500W output is designed and built in the lab.The causes of the zero-crossing distortion are verified by experiments. The experimental results show that Boost PFC converter with the proposed compensation to the current loop and capacitors paralleled with rectifier has lower input current harmonics and higher PF value than the Boost PFC converter with the compensation to the current loop only.