Uninterruptable Hierarchical Distributed Coordinated Control Scheme of Islanded AC/DC Microgrid Clusters Under Grid-Forming Converter Faults

Grid-forming converter faults in islanded hybrid AC/DC microgrid clusters could lead to voltage and frequency in-stability risk in the subgrid, thus threatening system operating safety. To solve this issue, this paper has proposed an uninter-ruptable hierarchical distributed coordinated control scheme of is-landed hybrid AC/DC microgrid clusters. Firstly, when grid-form-ing converter faults occur in a certain AC microgrid (ACMG), the interlinking converter connected with the faulty subgrid switches its control mode into grid-forming, providing stable voltage and frequency support for the faulty ACMG. Then, a two-layer coor-dinated control scheme is presented, where the first layer is de-signed for the remaining interlinking converters, and the second layer is designed for converters in normal subgrids and grid-fol-lowing converters in abnormal ACMG together with its interlink-ing converter. By the control mode switch of the IC and the two-layer coordinated control scheme, accurate power sharing can quickly fill the power deficit in the faulty subgrid, and the voltage and frequency of the microgrid clusters can remain stable. Verifi-cation results indicate that with the proposed scheme, the islanded AC/DC microgrid clusters can operate uninterruptedly under dif-ferent kinds of grid-forming converter faults.