An Approach to Localize Circulating Current for Three Phase Interleaved AC-DC Converters

Majority of the interleaved converter applications require inter-channel coupled inductors to block circulating currents between converters. Primary advantages being smaller size and weight. However, a standalone filter (i.e. no interconnection between filters of parallel modules) such as LCL-DM and LCLC-CM filter is preferred due to fault tolerance and modularity compared to inter channel coupled inductors. The downside being bigger boost inductor and CM choke volume, to account for circulation. In order to utilize such a standalone filter to its full potential with interleaved systems, some of the key problems with direct use of LCL based filter topologies and variants with interleaved converters are identified. Analysis is limited to common mode (CM) circulation and the limitations of conventional CM filter topologies when used with interleaved operation are identified. Consequently, a novel scheme to localize CM circulation within the converter itself is proposed to improve loss density of CM choke. An experimental prototype is constructed for two channels to demonstrate the proposed concept.