State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (North China Electric Power University), Beijing 102206, China

With the integration of high proportion of power electronic equipment and renewable energy, the future power system needs time-domain protection to deal with the complex fault characteristics of the system. System-level fault transient analysis is of great significance as the research basis of time-domain protection. In view of the controlled characteristics of inverter-interfaced generator (IIG), system-level fault transient analysis needs to deal with two challenges: dynamic phase conversion of output current of generation units and solving of high-order multi-generation system equations. A transient analysis method of system-level fault based on transient current back-substitution of IIG is proposed in this paper. By analyzing the dynamic relationship between the output power of generation unit and the terminal voltage phase, the dynamic phase conversion of IIG transient current to unified reference system is realized. The system equation is modified transiently to avoid high-order operation. On this basis, the transient voltage of the network nodes can be solved linearly by the transient current of each generation unit, and the time-domain accurate solution for the transient currents at the fault point and the whole network can be obtained. Simulation results show that the proposed method can achieve more accurate system-level fault transient analysis.