Research On Vienna Rectifier Based On Predictive Control Of Optimized Switching Sequence Model

As an important conversion interface for AC-DC power conversion in the power system,the three-phase Vienna rectifier has the advantages of low voltage stress of switching devices,high conversion efficiency,high power factor and high power quality,which can greatly improve the power conversion efficiency and current quality at the grid side.It has wide application prospect in industrial server power supply,aerospace power supply,uninterruptible power supply and other fields.In industrial applications,Vienna rectifier has good input current characteristics under both steady and dynamic operating conditions.However,the traditional control strategy has the problems of high switching loss,low efficiency and neutral point imbalance.Therefore,it is of great significance to study an improved control strategy with high efficiency,high power quality and neutral point potential balance ability.In this paper,the three-phase three-level Vienna rectifier is taken as the research object,and the control objective is optimized by establishing discrete prediction model,optimizing switching sequence and designing sliding mode controller.The main research contents of this paper are as follows:Firstly,the topology and working principle of the three-phase Vienna rectifier are introduced,and the basic idea and advantages of model predictive control are expounded.The mathematical model of the three-phase Vienna rectifier is derived in the abc,αβ and dq coordinate systems,and the discrete prediction model of the three-phase Vienna rectifier is established by the forward Euler method.In addition,this paper also introduces the sector division method of vector control,the calculation of vector operation time and the rule of reference vector synthesis.Secondly,this paper introduces the shortcomings of traditional model predictive control and traditional sliding mode control,and proposes a model predictive control based on optimized switching sequence by analyzing the function of basic vectors on neutral points.The proposed control strategy has the characteristics of high efficiency,good current quality and strong neutral point regulation ability.The proposed scheme eliminates the basic vectors with different polarity of voltage and current according to the polarity theory of voltage and current,and finds a group of redundant clamp modes in each small sector with opposite adjustment ability to the neutral point,and switches the appropriate clamp mode according to the offset direction of the neutral point potential,so as to realize the adjustment of the neutral point potential,and reduces the switching times and improves the efficiency of the system through voltage clamp.The outer ring sliding mode controller is used to realize fast DC voltage response.Finally,Matlab/Simulink software and the three-phase Vienna rectifier experiment platform are used to verify the proposed control strategy of the current inner loop sliding mode outer loop based on the optimized switch sequence.The results verify the correctness of the theoretical analysis and the effectiveness of the proposed scheme.