Determination of Transient Overvoltages in a Bipolar MMC-HVDC Link with Metallic Return

This paper analyses transient system behaviour of a high-voltage direct current (HVDC) transmission link comprising mixed overhead-cable lines during IGBT blocking subsequent to a station internal dc fault. Based on time-domain simulations using PSCAD™IEMTDC™, occurring converter cell overvoltages as well as voltage stresses at the dc cable terminations are evaluated. The electromagnetic transients (EMT) study is performed for a bipolar MMC-HVDC link equipped with full-bridge (FB) submodules at various fault locations, fault impedances and pre-fault load flow set points.