US Patent 11165330 Elimination of commutation failure of LCC HVDC system

The disclosure relates to a line commutated converter, LCC, for a high-voltage direct current, HVDC, power converter. The LCC comprises at least one bridge circuit for connection to at least one terminal of a DC system. Each bridge circuit comprises at least two arms, and each arm is associated with a phase of an AC system. Each arm comprises one or more upper thyristor valves and one or more lower thyristor valves connected in series, and a branch extending from between the upper and lower thyristor valves. Each arm further comprises a parallel capacitor module comprising at least one parallel capacitor being connected in parallel between at least one pair of branches comprising a first branch and a second branch wherein during commutation of a flow of current in the first branch to a flow of current in the second branch, the at least one parallel capacitor is configured to discharge current in to the second branch in the same direction as the flow of current in the second branch.