Grid-Forming Interlinking Converter With Fault-Ride-Through Capability in Islanded Hybrid AC/DC Microgrids

With the expansion of hybrid AC/DC microgrids (MGs), the AC and DC subgrids should be able to maintain interconnection through interlinking converter (IC) under short-circuit faults to avoid the system instability caused by power mutation. Conventional IC control methods have given insights into the current restraining between two subgrids but neglect the transient voltage/frequency support requirement, especially under islanded operation mode. This paper proposes a grid-forming IC control with fault-ride-through (FRT) capability. An fn-Pic-Vdc control architecture is presented to regulate power exchanges among AC and DC subgrids with solid AC bus voltage supports under the premise of DC voltage stable. Additionally, the Lyapunov large disturbance stability equation is established, and the safe operating boundaries of key parameters are described based on the Takagi-Sugeno (TS) model criterion. It is revealed that within certain range, the proper DC voltage feedback control parameters in IC could enhance the system stability and the power support capability of DC subgrid to the AC side. Finally, comparative case studies are conducted to validate effectiveness of the proposed control strategy.