Research On Compound Control Of Three-level VIENNA Rectifier Based On SVPWM

Due to the strong non-linear characteristics of power electronic rectifier equipment,it will cause serious harmonic and reactive pollution to the power system.Therefore,research on PWM rectifiers with high power factor and low current harmonics has become a hot topic.As a three-level topology,compared with other traditional PWM rectifiers,three-level VIENNA rectifiers have the advantages of less switching stress,fewer switching devices,high power factor,and low current harmonics.Therefore,it is of great significance to study the control technology of three-level VIENNA rectifier.This article first analyzes the working principle of the three-level VIENNA rectifier in detail,and introduces the operation mode and current circulation path of the system in each switching state.On this basis,the mathematical model of the three-level VIENNA rectifier in the abc natural coordinate system is established,and the mathematical model in the abc natural coordinate system is converted to the dq two-phase rotating coordinate system through clark transformation and park transformation.Literary research lays a theoretical foundation.Then,based on the mathematical model in the dq coordinate,the control strategy of the voltage outer loop and current inner loop of the three-level VIENNA rectifier is designed.Aiming at the problem that the traditional current inner loop single PI control strategy has weak ability to suppress the current harmonics on the grid side,this paper uses a compound control strategy that combines PI control and repetitive control,and adds harmonic component feedforward control to the current inner loop,In order to improve the dynamic response speed of the system.At the same time,the fuzzy control technology is introduced in the current inner loop,and the proportional and integral coefficients of the PI control are adjusted in real time according to the size of the system current error to enhance the anti-interference ability of the system.A brief overview of the SVPWM modulation algorithm is provided.Aiming at the complex problem of the traditional SVPWM modulation algorithm,this article uses a two-level SVPWM modulation algorithm,and gives a specific derivation process.The cause of the midpoint potential imbalance is also analyzed,and the balance factor method is used to control the midpoint potential.Finally,the main circuit components of the system are calculated and selected,and a simulation platform is built on Matlab / Simulink.The simulation verifies the effectiveness of the three-level VIENNA rectifier control method and parameter design in this paper.A prototype of 4.225 kW three-level VIENNA rectifier is built and the hardware and software are designed.