Research On Control Strategy Of VIENNA Rectifier

Due to the rapid development of national industry,converter device has been widely used,and its big problem is the power grid pollution.A large number of reactive power and harmonic inject into the grid,making the power quality to reduce.So improving the quality of power problem becomes a major hot spot.VIENNA rectifier,as a typical topology,has received the widespread attention.As one of the three level topology structure,compared with the traditional two-level topology,VIENNA rectifier reduces the voltage dress of the switches.Each arm of VIENNA rectifier only requires one switch,which avoids the danger of upper and lower bridge arm conduction.It needn't consider the dead time,and the reduction of the switch makes the control algorithm easily to implement.Taking into account the economy and security,studying the control strategy of rectifier has a great use value.Firstly,this paper analyzes the principle of VIENNA rectifier,introduces the working status of each switch state.On this basis,analyze the VIENNA rectifier and its mathematical models which in abc natural coordinate system and dq rotating coordinate system,which lays the foundation for the research of the next modulation algorithm.Secondly,introduce the space vector modulation algorithm,as the traditional SVPWM control method requires a complex judgment of current sector,so propose a current sector judgment with the expected voltage auxiliary,which simplifies the control process.Aiming at the problem of the neutral-point voltage unbalanced,using the effect of small vector on neutral-point voltage,design the equalization module to adjust the balance of the neutral-point voltage.Thirdly,introduce the double closed loop control strategy.By analyzing the problem of poor dynamic response of the voltage loop during system starting and load changing,propose an optimized voltage outer loop control method and verified.By the comparison of the two methods,verify the feasibility of the optimized voltage outer loop control method.Finally,this paper sets up a system simulation of VIENNA rectifier based on Matlab/Simulink platform and verifies the control method.Build a 7.5kW electric car DC charging module experimental platform and introduce the software flow of the system.Verify the validity of the control strategy.