Studies of Commutation Failures in HVDC System Based on Hypersim

The study of commutation failures requires more detailed and accurate simulation of HVDC systems. Hypresim is an integrated digital simulator, which could provide reliable, extensible and high-speed electromagnetic transient simulation for power systems. Its special characteristics are introduced in this paper. A HVDC system is established based on Hypersim. Modeling details of the ac system, dc lines, dc converters and their control systems are presented. Commutation failures are triggered by external disturbances on the ac bus and internal faults on the thyristor valve; the dynamic behavior of the HVDC system is demonstrated; detailed analysis is also given. A protection method against commutation failures is proposed. Simulation result indicates that the probability of failure could be reduced.