PROJECT TITLE :

Fault Current Estimation in Multi-Terminal HVdc Grids Considering MMC Control

ABSTRACT:

For multi-terminal HVdc protection systems, DC faults are crucial events, and knowing the critical fault time is essential in the safeguards design. Critical fault time is studied using simulations or sophisticated analysis, which requires a substantial computer effort and is not resilient to parameter modifications in the literature. The usual technique relies on simple modular multilevel converter (MMC) models that ignore the dynamic influence of converter control loops. Node voltages and dc current measurements become progressively imprecise as one moves away from the fault location. For multi-terminal dc (MTdc) grids built on MMC, this study presents a method for estimating fault current that is more accurate than the existing differential equation-based approaches, including those used to model power and dc voltage controller dynamics. It is possible to analyse fault currents in different grid circumstances using the proposed method (e.g., fault resistance and limiting inductor value). For bipolar systems with pole-to-pole and pole-to-ground faults, this method can be applied, and it is tested using PSCAD simulations on the standard CIGRE MTdc grid.