An experimental study and comparison of common mode and differential mode noise compensation characteristic for active EMI filter

Most of the many reported compensation schemes for active EMI filters (AEFs) use either voltage canceling or current canceling to deal with high frequency electromagnetic interference noise. The purpose of this paper is to investigate the compensation characteristics of these two kinds of AEFs under different type of noise source, i.e., common mode (CM) and differential mode (DM) noise source. This is examined by experimental identification and theoretically analysis of the insertion losses of AEF with voltage or current cancellation schemes. It is demonstrated that current canceling AEFs are effective to eliminate high impedance CM noise, while voltage canceling AEFs are good compensation solutions for low impedance DM noise source. The results reported in the paper enable the choice of optimized compensation schemes, from the above indicated aspects.