Abstract

Due to the limit in current-rating of SiC MOSFETs, a number of SiC-based modular ac-dc converters needs to be paralleled to increase power capacity. The number of modular converters (N) may vary depending on the customer's requirement. On the other hand, paralleling diversifies paths of current, and complex filter topologies such as integrated inductors may complicate analysis. To enhance understanding of N-paralleled ac-dc converters and to provide an insight for filter design, four per-phase equivalent circuits are proposed. Any voltage on the frequency spectrum can be classified into four groups by two criteria; first, positive sequence and negative sequence versus zero sequence, and, second, circulating, versus in-phase. By extending symmetrical component theory to the parallel converters, the N-paralleled three-phase converters can be represented by four single-phase circuits for any N. Thanks to the simplicity, complex issues such as an impact of the magnetic integration or change of harmonic attenuation for different N can be easily understood for any N by single-phase equivalent circuits.