Investigation on Conducted EMI for Single and Parallel Connected Inverters

Owing to increased penetration of sustainable energy sources, multiple converters are run in parallel to improve the power handling capacity in distributed generation systems. Paralleling of converters needs to be investigated carefully; and advantages in terms of semiconductor efficiency, power quality and conducted electromagnetic interference (EMI) should be evaluated. It can be ensured that paralleling results in increased efficiency, and better EMI performance by effectively controlling the type of coupling between passive components and interleaving angle amongst carriers. This article, at first, compares common mode (CM) and differential mode (DM) EMI generated by simple two-level voltage source and current source inverter (2L-VSI, 2L-CSI), using sinusoidal pulse width modulation (SPWM). A simple equivalent circuit model for the conducted noise has also been derived for both the topologies. Based on the preliminary results, CSI was down selected for further investigations, and effect of paralleling of CSIs on conducted noise has been studied. In the analysis, coupled inductors with different coupling configurations and coupling coefficients were considered and optimal combination is presented.