A Survey of Active EMI Filters for Conducted EMI Noise Reduction in Power Electronic Converters

Wide bandgap devices enable high power density power converters. Despite the advantages of increased switching frequency, the passive components are still a major bottleneck toward enabling high power density. Among the passive components in the converter, the passive electromagnetic interference (EMI) filters are unavoidable to ensure compliance with conducted EMI standards. Active EMI filters (AEFs) help reduce the volume of the passive components and have been around for three decades now. The design and implementation of the AEFs depend upon the type of noise (common-mode or differential-mode) and power converter (ac-dc, dc-dc or inverter). This article presents a comprehensive survey of different AEFs and their implementations for different power converters presented in the literature. A comprehensive survey of noise-sensing, noise-processing, and noise-cancellation circuits is presented. Also, a comparison of attenuation provided by the AEFs for common-mode and differential-mode noises for different converters is carried out. Furthermore, other facets of AEFs such as the auxiliary power supply, power loss, and protection methods for the AEF are also summarized. This article is intended to be a useful reference for power converter designers in both industry and academia.