A Novel Multiport Modular Multilevel Converter for AC-DC Hybrid Distribution Power System

The medium-voltage AC/DC (MVAC/MVDC) hybrid distribution network is progressively becoming a recent research focus with the massive access of distributed energy sources and electric vehicles. As the key enablers to connect MVAC and MVDC distribution girds, power-electronic-based stations usually adopt modular multilevel converter (MMC) due to its modularity and scalability. Unlike the conventional AC/DC converter with only one AC port, a multi-AC-port MMC (MACP-MMC) is proposed in this paper, in which multiple AC feeders can be interconnected via small-capacity interconnection ports. By means of coordinated control, the controllable and decoupling adjustment of active and reactive power on the lines can be realized. Besides, MACP-MMC also features simple structure, modularization, easy port expansion, low cost, and high power density. The operation principle, energy balance mechanism, and coordinated control strategies of the MACP-MMC are elaborated. Besides, its feasibility and effectiveness is verified by simulation results obtained from a 3-MVA model with three 10kV feeders.