Research And Implementation Of Three-phase Buck Rectifier With High Power Factor And Low Input Current THD

The main problems of power quality are harmonics and power factor,and the research on methods of reducing harmonic content and improving power factor has attracted more and more attention for the industry.The PWM rectifier overcomes the shortcomings of high input harmonic content,poor controllability and low power factor.It is widely used in data centers,superconducting energy storage,new energy grid-connected power generation and induction heating.In order to meet the requirements of high power factor and low input current total harmonic distortion(THD)of the AC power supply system,it is necessary to reasonably design the filter parameters of the PWM rectifier and study methods to reduce the input current THD of the three-phase rectifier.Current-source pulse width modulation(PWM)rectifier is based on the buck topology,which has the characteristics of high reliability and adaptability to short-circuit conditions.This paper focuses on three-phase Buck rectifiers.Based on the three-phase stationary coordinate system,the mathematical model of the three-phase Buck rectifier is established,and the modulation strategy used in this paper is studied.Based on the current Space Vector Pulse Width Modulation(SVPWM)strategy,the on-time expression of the three-phase Buck rectifier switch is derived.According to the expression of current vector action time,two different calculation methods are proposed,and the advantages and disadvantages of the two vector action time calculation methods are analyzed.Experiments show that when the three-phase input voltage is balanced,both vector calculation methods can achieve high power factor and low input current THD of the three-phase Buck rectifier.However,when the three-phase input voltage is unbalanced,the method of dividing by the three-phase input voltage instantaneous value sum of squares can effectively suppress the harmonic content of the input current.Based on the twelve-sector five-segment modulation strategy,the modals of the traditional three-phase Buck rectifier are analyzed,and the disadvantages of the traditional three-phase Buck rectifier are analyzed.In order to improve the shortcomings of traditional three-phase Buck rectifiers,a three-phase Buck rectifier with a common-mode filter is studied.and the modal analysis of the three-phase Buck rectifier with common mode filter is also carried out.The inductive current ripple of traditional three-phase Buck rectifier and three-phase Buck finisher with common mode filter is compared and analyzed,and the influence of common mode filter on input current THD is analyzed.Experiments show that adding a common-mode filter can effectively reduce the input current THD of the three-phase Buck rectifier.The voltage and current stress of the bridge arm MOS tubes and diodes are calculated in detail,which provides a basis for their selection.The parameters of DC power inductor,DC output capacitor and common-mode filter are analyzed and designed.The parameters of the input side LC filter are designed on the premise of filtering out the current harmonics on the input side and achieving a high power factor.The three-phase Buck rectifier software system and experimental prototype are designed,and the correctness of the system parameter design and theoretical analysis are verified through experiments.