Research On AC/DC Three-phase Rectifier With High Power Density Based On Vienna Structure

In the field of aviation power supply application,three-phase rectifier plays an important role in power factor correction at grid side,reducing the harmonic value of grid side current,stabilizing the voltage at DC side,at the same time,the power supply should have the characteristics of high power density and high efficiency.This thesis took the three-phase three-wire Vienna rectifier as the research object,analyzed its topological characteristics and operating principle,and focused on the LCL filter and its resonance damping method at the grid side,as well as the control and modulation method to improve the current waveform quality at the grid side.The specific research contents are as follows:1.The operating principle of Vienna rectifier and its mathematical model in d-q coordinate system and the double loop PI control method were analyzed.The sources of the grid side harmonics were analyzed,and the effect of the specific subharmonics suppression loop and repetitive control method for the grid side low frequency subharmonic suppression were analyzed.Their correctness was verified by simulation and experiment.2.The characteristics and causes of two kinds of current waveform zero crossing distortion were analyzed.The leading/lagging relationship between control voltage vector and current vector are the reasons for the wrong sector judgment,which leads to the wrong use of different small vectors.In order to solve this problem,this thesis presented a SVPWM modulation method which combines five segment modulation and seven segment modulation.In addition,this thesis focused on the analysis of the influence of the five segment SVPWM modulation strategy on the DC side neutral point potential and the common mode voltage of the rectifier,analyzed the condition of DC side neutral point potential stability and its impacts when the system adopted the five segment SVPWM modulation,and verified the correctness of the above modulation methods through simulation and experiment.3.The parameter selection method and active damping method of suppressing resonance of LCL filter on grid side were analyzed.The passive damping method was mainly studied.Finally,the R_d-C_d damping structure was selected,and the advantages of damping effect,low damping loss,and high frequency harmonic attenuation capability were analyzed.Finally,a R_d-C_d passive damping scheme with LC resonant structure in series was proposed.The damping loss was further reduced by removing the fundamental voltage component from the damping resistance.The method of selecting the parameters of damping branch was analyzed.The applicability was verified by simulation and experiment.