Point-to-point two-level converter system faults analysis

Voltage Source Converter (VSC) HVDC transmission is receiving significant attention as the UK is trying to meet its renewable energy targets. However, VSC-HVDC is more vulnerable to DC faults compared to more traditional CSCHVDC transmission techniques, due to the low DC side impedances and sensitive power electronics within the converters. This paper investigates the two-level converter system response under different fault scenarios, i.e., pole-to-pole and pole-to-ground faults. A point-to-point two-level VSC-HVDC system was developed in PSCAD/EMTDC to evaluate the system fault response and to verify the theoretical analysis. The study details the system response of the DC side and AC side to pole-to-pole and pole-to-ground faults. The paper details parameters which are considered to be fundamental in the design of a DC protection system. This work is sponsored by National Grid.