A General Interchanged Interleaving Carriers for Eliminating DC/Low-Frequency Circulating Currents in Multiparallel Three-Phase Power Converters
Zhiyong Zeng, Stefan M. Goetz
Abstract
This paper introduces a general interchanged interleaving scheme for multi-parallel converters. Our analysis identifies a common challenge to the multi-parallel converter using the existing interleaving scheme: the fixed interleaved angles introduce DC-bias/low-frequency intra-phase and zero-sequence circulating currents. These low-frequency and DC bias components present a significant challenge to the filter inductor designed to suppress switching-frequency-related circulating current. To address the challenge, the proposed interchanged interleaving carrier strategically adjusts the interleaved angles within each carrier period, achieving crucial symmetry over adjacent carrier periods. This symmetry ensues the zero average circulating current across the two adjacent carrier periods, shifting low-frequency/DC circulating currents closer to the switching frequency spectrum. The analytical and experimental results confirm that the proposed interchanged interleaving carrier effectively eliminates the low-frequency and DC-biased circulating currents that are inherent to the existing interleaving carrier, all while ensuring consistent output current quality, circulating current peak, and switching losses. The proposed scheme provides a general interleaving solution for multi-parallel converters.