Research On VIENNA Rectifier Based On Sliding Mode Variable Structure Control

At present,various types of power electronic devices,such as rectifiers,are widely used in the field of power conversion.While serving the process of power conversion,they also cause severe harmonic pollution to the power grid.Rectifier is a common device in the field of electric energy conversion.Choosing a rectifier with low harmonic content and high power factor,combined with a scientific and reasonable control strategy,is helpful to alleviate the problem of harmonic pollution in the power grid,and enhance the safety of the power grid and improve the quality of power supply.Therefore,research on rectifiers and their control strategies has always been a hot topic in academic circles at home and abroad.The VIENNA rectifier has fewer built-in switch tubes,and the control circuit is relatively simple.There is no dead zone voltage in the bridge arm switch tube.In addition,the VIENNA rectifier shows the advantages of low current harmonic content and high power factor in the application,which makes it well received.With the attention of scholars at home and abroad,more and more researchers are committed to optimizing and improving the topology and control strategy of VIENNA rectifiers.VIENNA rectifiers have a typical three-level topology,further research on their control strategies,and continuous improvement of VIENNA rectifier performance indicators are of great significance for improving power conversion efficiency and maintaining power grid security.This paper systematically analyzes the control scheme of VIENNA rectifier under the condition of grid balance,and proposes new solutions to the key problems in the control scheme.The main content of this article is summarized as follows:(1)First,this article summarizes the current common control strategy of VIENNA rectifier,and analyzes its advantages and disadvantages.Then explored the working modes corresponding to the various switching states of VIENNA rectifier under the condition of different input current polarities,and constructed the mathematical model of VIENNA rectifier under the condition of grid balance.The mathematical model in lays the foundation for the application of the control strategy mentioned in this article(2)In view of the nonlinear characteristics of the three-phase rectifier,in order to further improve the system's starting response,steady-state characteristics and dynamic characteristics,on the basis of establishing a nonlinear mathematical model of the rectifier,this paper proposes a sliding mode based on the variable exponential reaching law Variable structure control strategy,and simulation analysis to verify that the proposed variable exponential approach law can better suppress the jitter existing in the sliding mode variable structure itself than the traditional exponential approach law.Then,the finite set model predictive control theory(FCS-MPC)and sliding mode variable structure control theory(SMC)are used to design the double closed-loop controller of the rectifier.In order to make the voltage overshoot of the voltage loop small and obtain a stable DC voltage,the voltage loop adopts sliding mode variable structure control(SMC)with good control performance for nonlinear systems to enhance the speed and robustness of the system;The current loop has better fast response.The current loop adopts no modulation unit,is easy to add constraints,and has strong anti-interference ability.The finite set model predictive control(FCS-MPC)can quickly stabilize the input current(3)In order to verify the feasibility of the system,a simulation model was established in the MATLAB/Simulink environment.The simulation results verified the correctness of the proposed scheme.The rectifier designed by the proposed control scheme has good dynamic characteristics and strong robustness.Strong anti-interference ability and other advantages.In addition,the software and hardware of the VIENNA rectifier system were designed,an experimental prototype with TMS320F28335 as the main controller was developed,and the experimental platform software and hardware were debugged to ensure the normal operation of the experimental prototype.Due to the special circumstances of the epidemic this year,the experiment was only completed The open loop experiment and the experimental part of the current inner loop closed loop are introduced.