Research On Wideband Three-phase Input Buck PFC Converter And Its Control

Six-switch Buck PFC has the advantages of wide output voltage range,high reliability and small inrush current,and is widely used in airborne AC power supply system with wide voltage frequency.In order to achieve power factor correction and DC output voltage stability,this paper studies the topology,modulation mode and control strategy of six-switch Buck PFC converter.Firstly,the topology and working principle of the improved six-switch Buck PFC are analyzed,and its mathematical model in three-phase stationary coordinate system is established.Combined with the working mode,the influence of the common-mode filter composed of the DC-side common-mode capacitor and the DC-side inductor of the sixswitch Buck PFC on the input current harmonics is analyzed.The common-mode noise is suppressed and the input current quality is improved by cutting off the flow path of the high-frequency current.Secondly,according to the twelve-sector five-stage pulse width modulation strategy,the mathematical expressions of sector division,basic current vector synthesis sequence and vector action time are analyzed.A PWM signal modulation method is proposed to keep some power MOS tubes in the six-switch Buck PFC open by sector judgment,so as to reduce the switching times of power MOS tubes and reduce switching losses.Thirdly,the control loop of voltage and current double closed loop is designed.A reference value variable control technology under the combined action of input voltage and output current in the voltage loop is proposed,which avoids the over-modulation of six-switch Buck PFC and improves the dynamic response speed of output voltage.The phase relationship between input current and input voltage of indirect current control strategy in six-switch Buck PFC is analyzed.A power factor compensation method for delayed input voltage sampling signal is proposed to achieve high power factor in a wide input voltage frequency range.Finally,the hardware circuit and software program of the six-switch Buck PFC are designed.Based on the digital control chip,an experimental prototype with input voltage of 80 ～ 145 Vrms,frequency of 45 ～ 800 Hz and output of 200 V /270V/ 1500 W is developed.The full load efficiency of the prototype is 0.94 und er rated input conditions,and the PF value is greater than 0.98.Experiments verify the correctness and effectiveness of theoretical analysis,hardware parameter design and software program design.