Research And Implementation Of Simplified-Mode SVPWM Control Strategy For VIENNA Rectifier

As a typical three-level rectifier topology,VIENNA rectifier has the advantages of low device voltage stresses and small input current harmonic distortion,compared with two-level rectifiers.In addition,there are fewer power devices,simple control circuits,and no dead time in this topology,all the superiorities of that make it the most promising topology among three-level rectifiers.At present,single-cycle control,average current control,and space vector pulse width modulation(SVPWM)are the control strategies mainly adopted by the VIENNA rectifier.However,the traditional three-level SVPWM control strategy has many shortcomings such as redundant small vectors and zero-crossing point distortion,which leads to increase the difficulty of analyses and reduce the efficiency of the algorithm execution.Hence,it is of importantly academic value and engineering significance to studying the three-level SVPWM control strategy.Aiming at the problem of existing the redundant small vectors in the traditional three-level SVPWM control strategy,this dissertation proposes a simplified-mode SVPWM control strategy by reducing original 12 small vectors to 6 small vectors in the three-level vector space to improve the efficiency of the algorithm execution.Meanwhile,in order to provide clearer guidance,detailed steps and specific codes are given for the design of the system hardware and software,and a VIENNA rectifier experimental prototype with a rated power of 4k W is built for the verifications.The following is completed works of this dissertation.Firstly,this dissertation analyzes the working process of the VIENNA rectifier and introduces the distribution of all 25 three-level space vectors by deriving its general mathematical model in a three-phase static coordinate system;the realization principle of the traditional three-level SVPWM algorithm based on the voltage-oriented control system is elaborated in detail.Secondly,it is proved by M-mode controllability theory that an 18-mode VIENNA rectifier is controllable and has three-level characteristics,and then this dissertation proposes an 18-mode SVPWM control strategy whose vector space is composed of 18 voltage vectors and 1 zero vector.Its simulation model is established in MATLAB/SIMULINK and the simulation results show that the 18-mode SVPWM control algorithm without the redundant small vectors has higher execution efficiency and no zero-crossing distortion.Then,TMS320F28335 is selected as the control core.The parameter calculation and selection of main power devices,the design of control circuits,the design of the program flow,the initial configuration of DSP peripheral resources and the realization of control algorithms for the VIENNA rectifier are introduced in detail.Finally,through drawing experimental comparisons with the traditional algorithm,it is verified that the 18-mode SVPWM control algorithm has higher execution efficiency and can be used as a kind of control strategy to achieve high power factor and efficiency operation of the VIENNA rectifier.