A Scalable Filter Topology for $N$-Parallel Modular Three-Phase AC–DC Converters by an Arrangement of Coupled Inductors

Modularity in hardware improves the manufacturability of power electronics systems and reduces maintenance costs. By paralleling modular ac–dc converters, the current capacity of SiC-based power conversion systems can be easily expanded. However, it is questionable which filter topology can be chosen for an arbitrary number of the converters ($N$). Considering interleaving, filters without any coupling may result in an overdesign. Meanwhile, filters that magnetically couple the paralleled converters may suffer from complexity in mechanical structure and $N-1$ redundancy. Based on these observations, this article proposes a filter structure that can be easily scaled to any number of converters. The proposed structure is comprised of a coupled inductor (CI) forming a loop of secondary windings, a single boost inductor on that loop, and a normally on normally closed (NONC) contactor per converter. Circulating currents are attenuated by the CI for any $N$. A single inductor rated for each channel realizes a boost inductor for a whole $N$-converters, which can bring a significant benefit on power density and cost. When one of the converter faults, the faulty converter can be easily isolated from the system by the NONC contactor, thus achieving $N-1$ redundancy. The proposed filter topology is experimentally verified with a 20-kW full-SiC modular ac–dc converter.