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 (10; 100; 200; 300; 400; 600; 700) for a switching device (22; 122). The protection arrangement (10; 100; 200; 300; 400; 600; 700) comprises a thyristor (12) that has main current-carrying terminals which in use are connected in reverse parallel with a switching device (22; 122) to be protected, whereby during normal operation of the switching device (22; 122) a reverse voltage is applied to the thyristor (12). The protection arrangement (10; 100; 200; 300; 400; 600; 700) also includes a trigger circuit (38) that is operatively connected with a gate control terminal (40) of the thyristor (12). The trigger circuit (38) is configured to apply a voltage to the gate control terminal (40) of the thyristor (12) when the reverse voltage applied to the thyristor (12) reaches a safety threshold voltage (V 2 ) whereby the thyristor (12) fails and presents an irreversible short-circuit across the main current-carrying terminals of the switching device (22; 122).