Research On Beat Free Predictive Virtual Torque Control Of PWM Rectifier Under Unbalanced Power Network

PWM rectifiers are known as green energy converters due to their high power factor and two-way energy flow,and are widely used in high-voltage direct current transmission and new uninterruptible power supplies.The actual power grid is often unbalanced.If the control strategy designed under ideal power grid conditions is used,some problems will occur in the operating state of the PWM rectifier.Aiming at the problem of increased harmonics and serious distortion of the grid-side current of the PWM rectifier caused by the unbalanced power grid,this paper studies a deadbeat prediction virtual torque control scheme for the PWM rectifierFirst,the virtual torque can be calculated according to the grid-side current and virtual flux linkage of the PWM rectifier.This control method does not require positive and negative sequence extraction and synchronous rotation coordinate transformation,and the obtained current and voltage have the same asymmetry,namely When the resistance value of each phase is the same,the rectifier is equivalent to a pure resistive load to the power grid,which is more friendly to the power grid.Secondly,the deadbeat predictive control method is adopted based on the virtual torque variable,which eliminates the inner loop regulator,reduces the complexity of parameter debugging,and makes the implementation of the system easier.Finally,a 3kW PWM rectifier simulation model and physical platform were built respectively,and comparative simulation and experimental research were carried out.The results show that the proposed virtual torque control scheme for deadbeat prediction can be basically consistent with the imbalance control scheme of the PWM rectifier based on the virtual torque-based inner loop and the proportional resonant regulator in the goal of suppressing the grid-side current harmonics.The control effect verifies the correctness and effectiveness of the deadbeat prediction virtual torque control scheme of the PWM rectifier under the unbalanced power grid.