Research On VIENNA Rectifier Based On LCL Filter

With the continuous progress of power electronic technology and the need of social development, almost all electrical equipment need switching power supply. Switching power supply is a kind of power electronic device to provide communications, PC and other electronic equipment with DC power supply, has the advantages of small volume, high efficiency, high power density, occupies the leading position in the field of power, get more and more extensive application at present. But the network input power factor reduction because of this and Harmonic pollution is becoming more and more serious. Therefore, how to improve the power factor of the power electronic equipment(Power Factor, PF)and reduce THDi has become an important factor that influences its development and application. It forces the researchers in electronic technology field to propose effective solutions to such problems.In this paper, in view of the high power density, high efficiency and high reliability requirements of carrier-based power, VIENNA rectifier has the advantages of high power factor, low input THDi, small switch stress, less switching devices, and high reliability through the analysis and comparison of the advantages and disadvantages of different power topology and finally the VIENNA rectifier is selected as the main power topology. Then through the comparative study of several commonly used control methods and the analysis of the advantages and disadvantages of various control modes, Ultimately the control mode of Space Vector Pulse Width Modulation(SVPWM) is selected.Secondly, the design of VIENNA rectifier is carried out. In the understanding of its working principle, on the basis of L filter of traditional VIENNA rectifier and the application of this subject and its requirements,VIENNA rectifier with LCL filter is proposed and the parameters are calculated.The mathematical models of VIENNA rectifier are established in abc natural coordinates αβ two-phase stationary coordinates and dq rotating coordinates.Then study on the conventional three level SVPWM control strategy.Because of the need for judgments of sector and complex trigonometric operation in the application of SVPWM control strategy, This paper proposed a control strategy that turns the three level SVPWM into the two level SVPWM and the strategy is analyzed and studied. The rectifier output voltage is uncontrollable in the no-load, a method of soft start and load feedback is designed, which can effectively solve the problem of uncontrolled output voltagewithout load or light load. For the problem of unbalanced neutral point voltage potential, the influence of each vector to the midpoint potential is analyzed and the corresponding solution is put forward. Finally, the validity of the control strategy is verified through building simulation model.Again, the controller of VIENNA rectifier is designed and the feed forward decoupling and double loop control strategy are analyzed. PI parameters are calculated by L filter and LCL filter and the effect of LCL filter is better by simulation.Finally, according to the functional requirements and performance index of this thesis, the design scheme of the whole system is given, a 5k W experimental platform based on dsp F28069 is established by the previous research and detailed experiment is performed on the prototype according to the design in this paper.The analysis of results confirmed the validity and feasibility of the design.