AC transmission line fault current analysis in 220kV AC/DC hybrid system

This paper analyzes AC transmission line fault current in 220kV AC/DC hybrid system due to DC fast adjustment features. To illustrate the effect of DC response on AC fault current, a back-to-back HVDC system in 220kV hybrid system is exampled in the paper. After introducing basic principle and control method of HVDC system, the paper establishes simulation models of 220KV AC transmission system and 220KV AC/DC hybrid transmission system based on electromagnetic simulation software SIMULINK. Simulation results show that fault current in AC/DC hybrid system is different from the AC system, which will make AC transmission line protection mis-operate or mal-operate.