A Novel Circulating Current Suppression for Paralleled Current Source Converter Based on Virtual Impedance Concept

• Published in: Energies (Basel) Vol. 15; no. 5; p. 1952
• Main Authors: Fu, Xiao, Wang, Huaibao, Guo, Xiaoqiang, Shi, Changli, Jia, Dongqiang, Chen, Chao, Guerrero, Josep M.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-03-2022
• Subjects: Communication; Control algorithms; Converters; Coordinate transformations; Current sharing; current source converter; Current sources; Impedance; mathematical model; Methods; paralleled operation; Power supply; suppression of circulating current; virtual impedance control
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en15051952

The circulating current is one of the important issues for parallel converters. It affects the system stable operation and degrades the power quality. In order to reduce the circulating current of the parallel converter and reduce the harmonic pollution to the power grid, a new circulating current suppression strategy is proposed for the parallel current source converter without any communication line. This strategy is able to realize the current sharing between parallel modules by changing the external characteristics of the parallel modules to thus suppress the circulating current among the parallel current source converters. The proposed control strategy adopts DC-side droop control and AC-side virtual impedance control. The DC-side droop control is used to generate the reference voltage of each parallel module, while the AC-side virtual impedance is used to the circulating current suppression. We performed a time domain test of the parallel converter, and the results show that the proposed control strategy reduced the RMS circulating current of the parallel converter by 50% and effectively reduced the grid-side current THD while ensuring the stable operation of the converter. The effectiveness of the proposed control strategy was, therefore, verified.