Mobile QR Code QR CODE : The Korean Institute of Power Electronics
Title Suppression of Circulating Current in Parallel Operation of Three-Level AC/DC Converters
Authors Young-Kwang Son ; Seung-Jun Chee ; Younggii Lee ; Seung-Ki Sul
DOI 10.6113/TKPE/2016.21.4.312
Page pp.312-319
ISSN 1229-2214
Keywords Zero-sequence circulating current; Parallel converters; Circulating current suppression; Limit of linear modulation index; Voltage utilization rate
Abstract Zero-sequence Circulating Current (ZSCC) flows inevitably in parallel converters that share common DC and AC sources. The ZSCC commonly flowing in all converters increases loss and decreases the overall capacity of parallel converters. This paper proposes a simple and effective ZSCC suppression method based on the Space Vector PWM (SVPWM) with the ZSCC controller. The zero-sequence voltage for the proposed SVPWM is calculated on the basis of the grid voltage and not on the phase voltage references. The limit of the linear modulation region of the converters with the proposed method is analyzed and compared with other methods, thereby proving that the limit of the region can be extended with the proposed method. The effectiveness of the proposed method has been verified through the experimental setup comprising four parallel three-level converters. The ZSCC is confirmed to be well suppressed, and the linear modulation region is extended simultaneously with the proposed method. Moreover, the proposed control method does not require any communication between the converters to suppress the ZSCC unlike other conventional methods.