Research On Current Control Strategy Of Three-phase VIENNA Rectifier In Wide-range-Unbalanced Grid Conditions

The VIENNA rectifier is widely used in aviation power supplies,electric vehicles and other fields due to its small size,high power density and high reliability.However,the inherent topological property of VIENNA rectifier leads to the input current distortion.In practical applications,external interference factors such as grid faults and three-phase load asymmetry will cause unbalanced grids,which intensifies the input current distortion of the VIENNA rectifier.This paper studies the input current distortion of the VIENNA rectifier in wide-rangeunbalanced grids,and a current distortion suppression method is proposed to optimize the input current quality.Based on the working principle of VIENNA rectifier,the mathematical model of the VIENNA rectifier in unbalanced grids is established in this paper.Moreover,the expressions of input current references are derived and closed-loop control is realized.The static operating range is derived and analyzed according to the topology of the VIENNA rectifier.In widerange-unbalanced power grids,the VIENNA rectifier may operate outside the static operating range,which makes the modulation wave clamping method invalid in suppressing the currents distortion.In order to ensure the rectifier work normally in wide-range-unbalanced grids,a modulation wave clamping method based on current command adjustment is proposed in this paper.By introducing the negative sequence current adjustment coefficient k,the clamping scheme between the reference voltages and the reference currents is reduced,which avoids the reference voltage exceed the working range of the VIENNA rectifier.The system can maintain good currents quality by the suppression of input current distortion.Finally,a VIENNA rectifier experimental prototype is designed and built to verify the current distortion suppression method proposed in this paper.Simulation and experimental results show that this method can effectively suppress the current distortion,improve the quality of the grid-side current,and ensure the reliable operation of the VIENNA rectifier in widerange-unbalanced grids.