A PROTECTION ARRANGEMENT FOR AN MMC-HVDC SUB-MODULE

摘要

In the field of voltage source converters for high voltage direct current (HVDC) power transmission there is provided a protection arrangement for a switching device. The protection arrangement comprises a thyristor that has main current-carrying terminals which in use are connected in reverse parallel with a switching device to be protected, whereby during normal operation of the switching device a reverse voltage is applied to the thyristor. The protection arrangement also includes a trigger circuit that is operatively connected with a gate control terminal of the thyristor. The trigger circuit is configured to apply a voltage to the gate control terminal of the thyristor when the reverse voltage applied to the thyristor reaches a safety threshold voltage whereby the thyristor fails and presents an irreversible short-circuit across the main current-carrying terminals of the switching device.