Comparative study on DC line fault transient characteristics of four typical MMC-HVDC configurations

DC faults can cause serious problems such as power outage or even damaging the electrical equipment. The aim of this paper is to compare four DC fault clearance schemes in modular multilevel converter based high voltage direct current (MMC-HVDC) systems. Firstly, this paper summarizes four typical DC fault handling configurations including the DC circuit breaker (DCCB), the hybrid MMC with full bridge submodules and half bridge submodules (FHMMC), the LCC-MMC hybrid configuration with diode groups installed in the DC line close to the converters (LCCD-MMC) and the hybrid topology with an LCC and an MMC in series-connection. Then the basic structures and DC fault clearance schemes of the four configurations are discussed. Finally, a three-terminal simulation system is established to compare the DC line fault transient characteristics of the four MMC-HVDC configurations. The simulation result shows that the DCCBs perform the best DC fault clearance characteristics. Considering the cost efficiency and operation flexibility, the LCC-MMC hybrid topology has certain value of practical application in engineering.