Interaction between inverters in the hybrid cascaded HVDC system under MMC converter transformer valve-side faults

Key Points

• Investigate the effects of valve-side faults on inrush current and voltage stability in hybrid HVDC systems.
• Adopted a hybrid submodule scheme to mitigate fault-induced inrush current.
• Analyzed impacts of voltage distortion on LCC inverter AC bus.
• Assessed the role of sympathetic inrush current in commutation failures.
• Fault-induced inrush current leads to significant voltage distortion on the LCC inverter AC bus.
• Primary commutation failures are aggravated by sympathetic inrush current.
• Blocking of current differential protection becomes incorrect due to enhanced sympathetic inrush current.

Abstract