Research On The Control Technology Of The VIENNA Topology Rectifier

Three phase VIENNA topology rectifier is a three-level voltage circuit which offers power devices lower voltage pressure and can achieve good power factor correction effect. The topology does not need dead time, so it can work under high switching frequency. Accordingly, The front-end passive filter can be smaller to get high power density in three-phase VIENNA topology rectifier. Based on all the advantages, this topology is currently widely used.Firstly, the modeling and analysis of the three-phase VIENNA topology rectifier is proposed in this paper. The rectifier can be divided into three-phase four-wire and three-phase three-wire according to its input connection method. The former one connects the forth input line with the midpoint of output capacitor and the system can be controlled individually; the latter circuit is not decoupling but its control is more flexible. Based on the three-phase four-wire VIENNA rectifier, LCL filter is introduced to increase the power density. According to the characteristics of the LCL filter, the traditional duty-ratio-feed forward control is corrected. Meanwhile, the digital delay effect on the stability of the system is analyzed under different current feedback position. Based on the digital delay, LCL parameters design method is proposed. Secondly, taking advantages of the Nyquist stability principle, a new active damping method is proposed based on the grid current feedback compensation, which does not require additional sensors, and the control is simple. This paper presents two kinds of current compensation transfer function via the analysis of all the possible methods on system active damping. Based on the three-phase three-wire VIENNA topology rectifier, this paper analyzes the space vector modulation mode, and the synthesis and functional time is given for each vector. A kind of phase compensation control is carried out to solve the input current spikes problem while changing sectors. Finally, the characteristics of VIENNA rectifier in the light load and empty-load are studied, the burst-mode control algorithm is introduced to ensure stable output voltage.All the algorithms and control method proposed are accomplished by simulation and experiment. Simulation is based on MATLAB S-Function block which can reduce the simulation errors by the use of the C programming language. Finally, all the algorithms are verified through the DSP control experiments.