Investigation of protective devices for DC grids

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] The quick operability of the HVDC technology on the power transmission has allowed the integration of multiple energy sources such as distributed generations into the grid. However the consequent increase of the short-circuit fault current levels and the limitation of the DC breakers respect to the interruptible fault current lead to investigate new protection systems for the DC grids. This thesis investigates protective devices for DC grids. Firstly a multi-terminal DC grid for off-shore wind farms has been developed in Matlab/Simulink. The model consists of four converter stations connected in ring which exchange 90MW of power from wind turbines. Each converter station uses a symmetric monopole topology to transmit the power through the submarine cables. Subsequently a resistive-SFCL based on Bi2212 material is modeled. Afterwards a pole to ground fault and a pole to pole fault are created within the DC grid with and without resistive-SFCL. The simulations show a good performance of the resistive-SFCL against the faults. The fault peak current of the protected line is reduced from -47kA to -13kA in case of a pole to pole fault and from 10.37kA to 7.9kA in case of a phase to ground fault. However the temperature reached by the resistive-SFCL in case of a pole to pole fault is higher than 300K which damage the SFCL.