Design Considerations for a Modular 2-Stage LCLC Filter for Three Phase AC-DC Interleaved Converters

This paper presents the analysis and realization of a modular and scalable three phase CM-EMI filter that can be stacked as a standalone package under a single and multi-channel (parallel three phase converter blocks) configuration without significant loss of attenuation. A conventional two stage LCLC filter is selected for design and evaluation. Specifically, the impact of interleaving and PCC connection on component selection and CM filter volume is studied. The optimal switching frequency selection is based on achieving a balance between peak CM circulation and meeting CM conducted emissions compliance (as per EN-55011). Consequently, other aspects such as impact of asymmetry between channels, filter parasitic components and core material selection on emissions are examined. Experimental results are provided using SiC based 3L-NPC converters with up to three channels working under interleaved PWM scheme.