Commutation Failures In Hvdc Schemes

Commutation failures are very frequent dynamic events in high voltage dc (HVDC) transmission systems. Commutation failure is mostly observed at the inverter side of HVDC links, where large firing angles are used. The minimum value of the extinction angle required for the proper operation of a valve is specified by the valve manufacturer; however, at the inverter side of HVDC systems the extinction angle is regulated to a value higher than the valve specifications to allow control adjustments and also leave an adequate safety margin for unforeseen events in the power system, such as faults. Sev…