This paper provides a fault analysis of bipolar overhead line based HVDC grids using HB-MMC converters. The impacts of fault type and fault resistance are shown and the physical behaviour of the transient fault return current is explained.

The Failure Mode Effect Analysis (FMEA) is a technique used to investigate failures in a process or component and to identify the resultant effects of these failures on system operations. In this paper it is explained how the FMEA can be used to define and assess the impact of the failure modes (FM) of a protection strategy for High Voltage Direct Current (HVDC) grids.

This paper first analyzes the underlying instability issue attributed to the DC reactor by using a simplified converter station model, which reveals that the DC-link capacitor can compensate for the detrimental effect of the DC reactor and increase the stability margin. This capacitor, however, is usually avoided and distributed over the capacitors in sub-modules in the state-of-the-art Modular Multilevel Converters (MMCs).

In this paper the benefits of embedded VSC-HVDC links with supplementary controls for small-signal stability enhancement purposes using remote signals are studied and applied on the Nordic Grid.

This paper presents an application of the SCT to HVDC grids and proposes an implementation method for the resulting supervisors. The proposed method is capable of integrating decentralized and discrete-event controllers that interact with the continuous-time physical system. The language chosen for the implementation is C code, as it can be easily incorporated in power system simulation software, such as EMTP-RV. The method is validated by the simulation of the start-up of a point-to-point link in the EMTP-RV software.