Fault Ride-Through of Multiple Microgrid Clusters Based on Solid-State Transformers with Adaptive Current-Limiting Function

Multiple microgrid clusters (MMGCs) enable to more efficiently accommodate distributed renewable power generators and consume loads, and it can be regarded as an improved microgrid technology. Aiming at the imperative fault ride-through (FRT) issue of MMGCs, this paper proposes a method of applying solid-state transformers (SSTs) with an adaptive current-limiting (ACL) function. Firstly, the configuration structure and control scheme of the MMGCs with SSTs are presented. Then, the implementation of the ACL function in the SST and the equivalent fault features of the MMGCs are stated. The FRT strategy of the MMGCs in terms of the fault severity level is put forward. Using MATLAB, a detailed digital model of the MMGCs with SSTs is created. Multiple faults with different locations are imitated to validate the proposed FRT strategy's efficacy. From the simulations and comparisons, the SSTs with the ACL function can visibly suppress the fault currents of the MGs under the tolerable range, and alleviate the voltage dips to enhance the grid-connection ability of the MGs. Besides, the power angle changes and connecting line frequency variations of the MMGCs are restrained by the proposed method. Thus, the robustness of the MMGCs defending the faults is well increased, and the proposed method's feasibility is proven.