Research On Control Of VIENNA Rectifier Based On Carrier Phase Shifting Technology

The rapid development of electric vehicles have reduced the dependence of the automotive industry on fossil energy and reduced environmental pollution.However,the grid-connected charging of a large number of electric vehicles has made power quality problems such as harmonic pollution and voltage drift in the power grid more and more serious.VIENNA rectifiers are widely used in electric vehicle charging piles due to their high power factor and low current harmonic content.Reasonable control mode can not only improve the output of the rectifier,but also reduce the impact of the rectifier on the power quality of the grid.It is of far-reaching significance to study the VIENNA rectifier control to ensure its efficient operation.In this paper,the improved six-switch three-level VIENNA rectifier is taken as the research object,and its modulation technology and control strategy are studied.In term of rectifier modulation technology,the traditional carrier phase-shift modulation technology can not achieve the midpoint potential oscillation suppression of the rectifier.In this paper,the non-redundant and redundant vector components of the control pulse are decomposed,and the neutral point potential compensation coefficient D is calculated to adjust the decomposition ratio,in order to eliminate the influence of the two on the neutral point potential and ensure the stability of neutral point potential of the rectifier.The simulation result shows that the improved carrier phase shift modulation technique can effectively suppress the fluctuation of the midpoint potential of the rectifier,and the DC side output voltage and the grid side current harmonic content have been improved.In term of rectifier control strategy,in view of the poor dynamic performance of the traditional double closed-loop PI control strategy,this paper improves the dynamic response capability of the system by using the sliding mode controller instead of the PI controller in the voltage outer loop.In current control loop,feedforward decoupling is used to eliminate the interaction of d and q axis parameters.In voltage control loop,i_d and i_q are selected as output variables to determine the sliding mode surface,and choose the exponential approach law to design the sliding mode controller.The simulation result shows that the response speed and dynamic performance of the nonlinear control strategy based on sliding mode are improved,which is beneficial to the actual load change of the rectifier.Based on the theoretical analysis,this paper builds an experimental platform with TMS320F2812 digital processor as the main control chip to verify the practicality of the improved modulation technology and nonlinear control strategy proposed in this paper.