Design and Optimization of a Highly Integrated Modular Filter Building Block for Three-Level Grid Tied Converters

With the advent of high power SiC devices, interleaving of converters offers benefits from high power density and efficiency point of view. One major advantage is low filter size requirement to meet THD and current harmonic levels compared to a single converter or hard paralleled converters. However, additional magnetic components are needed to mitigate the problem of circulating current between multiple converters which contribute to additional semiconductor and filter loss. In addition, there is a need for a modular filter architecture that can handle circulation and meet THD irrespective of the number of channels. Not to mention, the need for conducted emissions compliance, which is a key essence of modularity as the number of converters are scaled in parallel. Such an integrated filter block does not exist in current literature and is proposed in this paper. A detailed design and optimization procedure is presented to maximize efficiency and power density of this modular filter building block and the associated converter. A 5.8 kW/liter prototype of a three-channel interleaved 15 kW 3L-NPC converter is evaluated for up to three channels.