Research on Improved Three Vectors Model Predictive Current Control of PWM Rectifier in Unbalanced Power System

When the grid voltage is unbalanced, the typical PI controller's double closed-loop control method is ineffective in suppressing the current distortion on the AC side and the second harmonic wave of the DC side voltage of a three-phase voltage rectifier of type PWM. Based on this, this research provides an enhancement of predictive current control by three vectors model based on the predictive current control by traditional two vectors model, which eliminates the need for multiple current loop PI regulators and decoupling control under positive and negative sequence, By using three basic voltage vectors in each sector to synthesize six expected voltage vectors of any amplitude and direction, and then online calculation of the interaction duration of the three voltage vectors. using the quadrature direct axis deadbeat method, the positive and negative sequence quadrature direct axis can be controlled rapidly and accurately at the same time, and the current ripple can be effectively reduced, which improves the dynamic and stable behavior of the system; In this study, the control approach of limiting negative sequence current from zero is used to lower the distortion rate and grid side current immunity; The simulation results display that the enhancement of predictive current control by three vectors model has fast response, small grid side current distortion and less harmonic content.