Study On VIENNA Rectifier Based On Model Predictive Control

Power electronic devices are widely used in various fields such as transportation,communication,energy,national defense,industrial manufacturing,aerospace,environmental protection,and home appliances.While improving people's work and lifestyle,they also inject a large amount of harmonics and reactive power into the power grid,seriously pollute the power grid and affect the safe and reliable operation of other grid-connected devices,and reduce power quality.Among many power electronic devices,rectifiers account for the highest proportion.Therefore,it is necessary to study a rectifier with unity power factor operation and low harmonic content on the grid side to meet future high voltage and high power applications.VIENNA rectifier is a three-level rectifier with excellent performance.It has the advantages of simple structure,no bridge arm straight-through problem,low power switch and high power factor.It is deeply concerned by scholars.This paper will study and analyze the three-phase six-switch VIENNA rectifier.This paper firstly analyzes the topology and working principle of VIENNA rectifier.The operating characteristics of the rectifier under different power supply voltage polarities and switching states are discussed,and the corresponding equivalent switching model is designed.The mathematical model of VIENNA rectifiers in abc,??,dq three coordinate systems are derived by using Kirchhoff's law.The spatial voltage vector distribution of the VIENNA rectifier is analyzed according to the working mode.Then based on the instantaneous power theory,the direct power control strategy of VIENNA rectifier based on switch table and space voltage vector modulation is studied and analyzed.The hysteresis controller and switch vector lookup table are designed.The realization process of space vector modulation(SVPWM)is deduced,and the midpoint potential balance control strategy is designed.Aiming at the shortcomings of the two direct power control commonly used in VIENNA rectifiers,predictive control is combined with space vector modulation technology to design a model predictive direct power control strategy.The predictive control principle is analyzed and the power prediction model of VIENNA rectifier is established.In view of the problem of computational delay in predictive control,a delay compensation optimization prediction model is designed.The control effects of the three control strategies are compared by simulation,and the feasibility and superiority of the model for predicting direct power control are verified.It has the advantages of simple structure,easy control,fixed switching frequency,good dynamic steady state performance,high power factor and less harmonic content.Finally,the parameter design of the hardware circuit was completed,and the experimental prototype platform of the VIENNA rectifier was built and verified by experiments.The experimental results show that the output voltage of the three-phase VIENNA rectifier is stable at 700 V,achieving unit power factor operation,DC bus midpoint potential balance,and the current harmonic content of the network is lower than the national standard.The system has good static and dynamic performance,and the control effect is ideal.