Fast Search Method for AC / DC Cascading Failures based on Short Circuit Ratio Analysis

In China, multi in feed AC and DC hybrid power system has been formed. The AC system fault may lead to the failure of multi DC simultaneous commutation failure, and the cascading failure of avalanche type may occur. In this paper, a fast search method of AC fault region, which considers the interaction of AC and DC interaction and multi DC interaction, is considered, and the impact of single DC or multi DC commutation failure on AC power grid is evaluated, and the fast search for AC and DC cascading failures is realized. Firstly, based on the two port Devenan equivalent, the influence of AC fault on the node voltage of DC converter station is calculated quickly, and the AC failure criterion of DC commutation failure is derived according to the minimum turn off angle standard. Further considering the influence of DC commutation failure on other DC, from the fault bus, the node of commutation failure DC converter station and the adjacent converter station, the multi-port Devenan equivalent of the power grid is carried out to calculate the influence of reactive power impact on the bus voltage of other DC converter stations during the failure of DC commutation, and a comprehensive criterion for the commutation failure is derived. Then, the influence of DC commutation failure on AC power grid is quantitatively evaluated from two aspects of active power impact and reactive power impact. The actual power grid calculation shows that the proposed DC commutation failure judgment method is more accurate and comprehensive, and the construction method of AC and DC cascading fault sets is practical.