Directed Graph-Based Topology Derivation Method for Single-Stage Multiport Inverters

Single-stage multiport inverters (SSMIs) have been increasingly adopted in multisource systems, such as hybrid electric vehicles and renewable energy systems, due to their salient advantages of fewer power losses, passive filters, and higher system efficiency. Nowadays, SSMI topologies are mainly obtained by reforming existing multilevel converter topologies without dedicated derivation methods, potentially leading to redundant components and additional losses, which hinder the further development of SSMIs. To deal with this issue, a directed graph-based topology derivation method for SSMIs is proposed in this article. By modeling the SSMI topologies as directed graphs, the structural features and power flow characteristics are represented with graph language. Then the general configuration of directed graphs for SSMI is established from the perspective of power flow paths, and the topology derivation method by constructing new directed graphs following this configuration is proposed. With the proposed method, case studies are presented to show the specific process of topology derivation, resulting in a series of three-phase two/three source SSMI topologies with 30% and 39% fewer devices than those reformed from multilevel inverters. Finally, topology evaluation and experimental tests are carried out to verify the features and feasibility of derived topologies.