An Approximated Analytical Model for Pole-to-Ground Faults in Symmetrical Monopole MMC-HVDC Systems

Developing pole-to-ground (PG) fault models for modular multilevel converters (MMCs) is not straightforward due to the asymmetry and converter switching concerning blocking characteristics. Various studies have been carried out regarding transient simulation of PG faults. However, there a lack analytical first stage fault. Therefore, this work proposes an approximated model faults in half-bridge MMCs. Closed-form expressions MMC contribution current are derived. We show that separating solutions different resonant frequencies represents system dynamics facilitates interpretation phenomena. When compared calculated by ordinary differential equations (ODEs), proposed provided good approximation wide range parameters. full PSCAD solution, was able precisely calculate peak value, which confirmed its validity.