The Research On Three-Phase Three-Level VIENNA Rectifier

With the rapid development of power electronic technology,the number of new power electronic equipment used in the field of electric energy conversion is increasing,which also causes problems such as grid pollution.The traditional rectifier circuit causes an increase in the harmonic content of the grid-side current due to its strong nonlinearity,resulting in a decrease in power quality.Therefore,how to improve the performance of the rectifier and reduce the impact of the rectifier on the grid-side power quality has become the focus of research by domestic and foreign scholars.VIENNA rectifiers are widely used in medium and high power fields such as direct-drive wind power generation,aviation power supply and electric vehicle charging piles because of its stable output voltage,unit power factor operation and low current harmonic content..This paper takes the three-phase VIENNA rectifier as the research object.Based on the topology and working principle of the three-level six-switch rectifier,the mathematical model of the VIENNA rectifier is established in the abc and dq coordinate systems;Design the main circuit parameters according to the circuit design index,adopt dual closed-loop PI control strategy and dual carrier modulation method,and add the method of midpoint potential balance control loop to control the rectifier.The system simulation model is built based on Matlab/Simulink.The simulation results show that the adopted control strategy reduces the harmonic content of the input current of the three-phase VIENNA rectifier,realizes the unit power factor operation of the rectifier and the control effect of the neutral point potential balance of the DC side.Aiming at the problems of complicated parameter setting,sudden load change and sudden change of the line voltage on the grid side when the voltage loop in the double closed-loop control system adopts the traditional PI control strategy,which causes that the system has poor robustness due to overshoot and oscillation of the DC voltage,the system adopts a single neuron adaptive control strategy based on fuzzy control.By building a Matlab/Simulink simulation model,comparing the DC output voltage simulation waveforms of the traditional PI controller and the single neuron adaptive controller based on fuzzy control in the three cases of load mutation,grid-side line voltage mutation,and simultaneous mutation of load and grid-side line voltage,It is verified that a single neuron adaptive control strategy based on fuzzy control can achieve automatic parameter optimization,so that the VIENNA rectifier has better anti-interference and robustness.Based on Matlab/Simulink,this paper completed the construction and simulation of the three-phase VIENNA rectifier control system simulation model.The results show that the designed VIENNA rectifier control strategy is correct and achieves the expected control effect,laying a foundation for the application of VIENNA rectifier in the engineering field.