Multilayer Modulation Scheme for a Single-Stage Dual-AC and Dual-DC Port Interlinking Converter in Hybrid Microgrids

Interlinking converters (ICs) are essential for hybrid microgrids to realize flexible power flow control among ac and dc subgrids. However, the conventional ICs with limited ports realize the connection of multiple ac/dc subgrids via the bus configuration, where separate converters are inevitably installed to match different bus voltage levels. Apart from the increased power conversion stages, communication demands among separate converters result in extra investment costs and communication burdens. Given this, this article proposes a dual-ac and dual-dc port IC (DDPIC) to achieve power exchange among multiple ac/dc subgrids in a single-stage power conversion. In the proposed topology, the power conversion efficiency is enhanced, and the communication burden is reduced due to the removal of separate converters. Besides, a port power-decoupled model of the DDPIC is built to simplify its modulation scheme design by considering the DDPIC as four virtual two-level converters. With the decoupled model, a multilayer space vector modulation (SVM) scheme, where each layer of the SVM regulates one virtual two-level converter, is proposed to simultaneously realize the ac voltage forming under unbalanced dc-port voltages and power distribution among subgrids. Finally, the effectiveness of the proposed topology and modulation scheme is verified by the experimental results.