Evaluation of Modular AC Filter Building Blocks for Full SiC based Grid-Tied Three Phase Converters

EMI filters in three-phase converters occupy about 40% of total converter volume. With interleaved operation, this volume requirement can be reduced on the grid side filters due to the absence of switching frequency harmonics. However, due to the presence of circulating current between channels, there is an additional requirement for filter components which outweigh the benefit from interleaving. This affects overall system power density and increases filter volume contribution. In addition, the existing filter topologies do not address modularity i.e. they cannot be used with any number of channels without affecting attenuation or performance. In this paper, a comprehensive study of existing and new modular filter topologies is performed to effectively attenuate circulation. These modular filter topologies are evaluated for power density and efficiency. The primary difference in loss between these topologies comes from the manner in which the circulating currents are attenuated. Some key differences in the coupled versions are discussed in particular. In the end, a brief summary is presented.