AC line fault characteristics of an HVDC link with line- and self-commutated converters in parallel operation

Inhalt:
The “dual” HVDC system consists of one line-commutated converter (LCC) and one self-commutated voltage source converter (VSC) at both ends of a point-to-point DC transmission line. While the operation of the pure VSC-HVDC and of the pure LCC-HVDC is well known, the behaviour of the two technologies in parallel connection has not yet attracted a lot of attention. The paper starts with a general introduction of the dual HVDC. Then, the operation principle and the control structure for a dual HVDC system for an example of an offshore wind farm grid connection will be presented. The normal operation of the dual HVDC will displayed in experiment. The main focus of the paper is on the fault ride-through capability of the dual HVDC in case of network-side grid events, which has been studied in simulation.