Performance Analysis And Optimization Of The Space-Vector Modulation For Vienna Rectifier

The automobile has become an essential tool in the modern society,with the rapid growth of the number of automobile,the energy and enviromental problems caused by automobiles are also increasing.Electric vehicles haved been greatly developed in recent years because of the advantages of reduced fuel usage and greenhouse emissions compared with traditional cars.The demand for electric vehicle charging infrastructure increases dramatically as a result of increase in the number of electric cars.The three-phase three-level rectifier which is called the Vienna rectifier has been widely used in the high-power charging systems owing to several advantages including high efficiency,high power density,simple structure and high reliability.The characteristics of the Vienna rectifier are closely related to the modulation method.Space vector modulation method has the advantages of low current harmonics and high voltage utiliztion campared to other modulation method.In this paper,Vienna rectifier based on space vetor modulation method is studied from the following aspects.In section II,the working principle of the Vienna rectifier is described at first,and the mathematical model of the Vienna rectifier is established using state-space averaging technique.In addition,the simplified small-signal model of the Vienna rectifier in the synchronous rotating frame is derived,which is the basis for follow-up analysis.In section III,the space vector modulation strategy based on the nearest three vector principle for the Vienna rectifier is introduced,and two different ways of digital realization for SVM are described and compared in details.At Last,the correctness of two different digital realiazation methods are proved by both simulation and experiment.In section IV,the performance of space vector modulation for Vienna rectifier is analyzed and compared with other modulation methods in the aspects of current ripple and harmonics.And the mathematical relationship between the ripple of input current,the modulation ratio and the boost inductors is derived under the conditon of SVM method,which is useful for designing the boost inductors.In addition,this paper analyzes the cause of the current harmonics and compares the current harmonics in different modulation method.Aiming at the complexity and large computational complexity of the three-level vector modulation algorithm,a vector modulation implementation algorithm based on the principle of time-invariant of effective vector is proposed according to the basic principle of simplified three-level vector modulation.Compared with the traditional algorithm,this algorithm reduces the computational complexity and calculation error,which saves the time resources of the DSP.Finally,correctness and effectiveness of the algorithm is verified by both simulation and experiment.In section V,the cause of current distortion around zero-crossing point is analyzed,and then an improved space vector modulation method for Vienna rectifier is proposed.In order to avoid input current distortion,this method ensures that the voltage of the bridge-leg is clamped to zero level around zero-crossing point by the way of rearranging redundant vector in particular sectors.The performance of the proposed method is verified by both simulation and experiment.