A new protection scheme for HVDC circuit based on MMC topology with controllable fault current

This paper proposes a new protection scheme for the HVDC circuit, which is based on the MMC topology with the double thyristor switches sub-modules. Although the MMC with double thyristor switches in each sub-module has the ability to clear the short circuit fault, the duration of AC and DC short circuit currents is not controllable. Former work solved the problem of the long duration of the AC short circuit current, the duration of the DC short circuit current still depends on the location of the fault, which could affect the restart of the MMC system. The new protection scheme can solve both problems and during normal operation the loss energy is less than that of the HVDC breaker topology in the former work. The advantages of HVDC breaker topology in the former work are still persisted in the new HVDC breaker topology. In order to verify the validity of the new protection scheme, a simulation has been used.