Common-Mode EMI Noise Reduction for Grid-Interface Converter in Low-Voltage DC Distribution System
Common-mode (CM) conducted EMI noise poses particular challenges to filter design in the grid-interface converter systems because the noise propagation paths are coupled between the dc and ac sides through the grounding capacitors. As shown in Fig. 1, the ac filter strucure not only reduces the leakage current on the dc-side, but also highly reduces the ac-side CM noise propagated into the single-phase utility. Thus, the total passive filter volume could be reduced. In addition, this ac filter strucure can also decouple the impact of the dc-side CM capacitors to ac-side CM noise level, which reduce the filter design process where both dc and ac-side EMI noise has to be attenuated.
As shown in Fig. 2, the investigated ac filter achieves a strong ac CM noise reduction compared to the typical ac filter strucure.