High Performance Common-Differential Mode Chokes for High Efficient EMI Filters

Inhalt:
Converter operation of several 100 kHz in the lower kW power range requires very high filter attenuation for grid connected inverters, because of EMI standard limitations. Combined common-differential mode chokes can take advantage of attenuating both common and differential mode noise effectively. Therefore, these components can reduce the effort and the power loss of EMI filters. This paper will give an overview of different common-differential mode chokes including advantages and disadvantages of the different techniques. In order to enable a proper and quick design of such components a brief design guideline is given in the paper. An AC EMI filter for grid connected inverters is implemented and improved with common-differential mode components in order to highlight the advantages of this technique experimentally.