Investigations on the Active Reduction of Common Mode Noise with Opposing Noise Sources

Conventional filters needed for the electromagnetic compatibility lower the system power density by consuming additional space in power electronic setups. To increase the power density, alternatives for these filters are needed. If the power electronic setup offers the possibility to synchronize two opposing switching transitions, the common mode noise can be reduced without additional filters. In this case two opposing noise currents reduce one another by superimposition. For power electronic setups which do not offer the possibility to synchronize switching transitions, this paper presents an approach which uses additional half bridges as opposing noise sources connected to a replicated grounding impedance to create the opposing common mode noise. The main goal of the opposing noise source is to create similar potential changes as the power electronic setup over the replicated grounding impedance. The replicated grounding impedance emulates the grounding impedance of an ohmic inductive load with discrete elements. The achieved reduction of the common mode noise with this approach is evaluated with measurements.