The Last Circuit Breakers Identification in Hybrid AC/DC Power Grids Based on Improved Tarjan Algorithm

The last circuit breaker (LCB) protection is applied in hybrid AC/DC power grids to protect the AC/DC equipment from overvoltage threats caused by the unexpected tripping of LCBs. In this paper, an improved Tarjan algorithm is proposed to identify LCBs that correspond to the cut vertices on the path between any two vertices in the connected undirected graph. The proposed method can be applied to multiple converter valves to simultaneously identify the LCBs for each converter valve where all vertices in the connected undirected graph are traversed only once, which significantly improves the running efficiency. The real-time performance of the LCBs identification process was examined on a closed-loop simulation platform based on LabVIEW and MATLAB. The results reveal excellent capabilities of the proposed method for finding LCBs for all converter valves under various conditions of the AC field while exhibiting a lower and more stable runtime.