A Novel Neutral Point-Based Active EMI Filter for Common Mode Noise Attenuation

This letter proposed a new configuration of neutral point-based common mode (CM) active electromagnetic interference (EMI) filter (NP-CM-AEF). It is achieved by setting the reference of filtering system to the neutral point of equipment under test. Therefore, CM noise could be sensed across neutral point and ground. Meanwhile, compensation signal could be built by op-amp and re-injected to cancel the initial CM noise. The main advantage of the proposed NP-CM-AEF lies in that no more noise separation such as bulky passive CM transformer is needed to get pure CM noise. The whole filter becomes smaller, lighter, and more compact compared with traditional CM AEF. Working principle is analyzed in details and hardware experimental tests are also performed. It shows that the proposed NP-CM-AEF has a good attenuation to CM noise and total size is pretty tiny.