Hybrid Series-connected HVDC System Faults Analysis

Multi-infeed cascaded hybrid series-connected DC transmission technology combines the advantages of line commutated converters and voltage sourced converters. Hybrid DC transmission is expected to play an important role in future power transmission systems. It is of great importance to understand the system's behavior under steady and transient states. This paper thoroughly examines the system's responses under different types of faults. The benefits of having such a hybrid system are also highlighted through the fault analysis. In order to cope with the AC system three-phase fault, based on the comparison, a new thyristor based DC energy dissipation device has been proposed. Simulation results show that this device could protect the VSCs from severe faults.