Performance analysis of an HVDC link with a capacitor commutated inverter supplying a very weak AC system

Capacitor Commutated Converters (CCC) have been proposed for application in HVDC schemes with weak AC systems or long DC-cables. These types of converters rely on the voltage across series capacitors for the commutation of the converter thyristor valves and hence, are less influenced by depressions in the system voltage when compared with conventional converters. In this paper the technology of Capacitor Commutated Converters (CCC) is presented and the advantages of the CCC for high power transmission are shown. The steady-state as well as transient performance are presented using PSCAD/EMTDC. The system is derived from the first CIGRé HVDC Benchmark model. The results demonstrate the superior performance of a CCC link, when connected to a very weak AC system in terms of increased transmission capacity and improved stability of the AC network.