Control And Optimization Of The VIENNA Rectifier For Wide Variable Frequency Aviation Application

In recent years,in order to improve the performance of aircraft,reduce fuel consumption and carbon emissions,more/all electric aircraft(MEA/AEA)came into being.In an MEA/AEA,traditional mechanical equipment is replaced or partially replaced by electrical systems,and a new generation of high-voltage frequency conversion AC power supply system is adopted,thereinto,AC/DC rectifier is an important part,which is dominated by auto transformer rectifier unit(ATRU).However,with the development of technology,the demand for power quality and power density is increasing,so it is difficult for traditional ATRU to meet the needs of future development.Therefore,the three-phase VIENNA topology with outstanding advantages in power density,efficiency,EMI and so on is selected as the research object in this paper,and the research on its key control technology and optimization methods is carried out.Firstly,the principle of VIENNA rectifier is introduced,its equivalent mathematical model is also established and the key control parameters are designed.The basic law of three-level SVPWM to two-level SVPWM is analyzed in detail,and the time sequence and action time of basic vectors are deduced.Moreover,the control method based on redundant small vectors is studied for the unbalance of mid-point potential.Secondly,in view of the problem of zero-crossing distortion in VIENNA rectifier,the root cause of zero-crossing distortion is analyzed by using the new concept of non-shared vector.Starting with the three-phase inductance which leads to zero-crossing distortion,the relationship between inductance and current ripple is deduced and calculated,and an accurate design method for inductance is proposed.Three kinds of optimal SVPWM algorithm for zero-crossing distortion based on reactive power compensation,discontinuous PWM and hybrid PWM are presented,whose implementation process,advantages and disadvantages are discussed.In which,the law of vector combination in continuous and discontinuous control is explored and summarized to obtain the unified representation method of hybrid control,thus the control algorithm can be simplified.Thirdly,the fault-tolerant control of VIENNA rectifier is studied,including tolerant control under open-switch fault and parallel redundant control.The running state of the circuit under open-switch fault is analyzed,and a fast fault diagnosis method based on the characteristic of the input current is put forward,which is analyzed and designed in detail.The wrong substitution of vector is studied,on this basis,two software fault-tolerant control methods are proposed and the control process is deduced.To further improve the reliability of the system,a simple and easy-to-imple master-slave backup method is proposed,which combines software and hardware to realize continuous power supply to the rear stage.Finally,MATLAB/Simulink simulation model and a 1.5k W wide-variable-frequency VIENNA rectifier prototype based on traditional silicon devices are designed and built to verify the above control methods.In order to further improve the efficiency and power density,a same power grade VIENNA rectifier based on gallium nitride device is built.The efficiency and power density advantages of gallium nitride in high frequency situation are proved by loss calculation.