688 / 2019-04-21 17:01:08

Input-Output Characteristics Based Fault Current Analysis of MMC-HVDC Transmission Systems

fault current analysis,input-output characteristics,MMC-HVDC,the operator approach

The modular multilevel converter (MMC) has been widely adopted in high voltage direct current (HVDC) transmission systems due to low switching frequency, no commutation failure, the ability of controlling active and reactive power, etc. However, the short-circuit current of MMC-HVDC raises rapidly after faults due to low damping of MMCs. This paper proposes an input-output characteristic-based fault current analysis method for MMC-HVDC. First, the operator approach is used to identify MMCs’ input-output characteristics. The MMC model is decomposed into a series combination of a linear and a nonlinear part, and simulation-based algorithms are proposed to make identifications. Second, the relationship between short circuit current and input-output characteristics of MMCs is constructed. The admittance matrix is used to illustrate the interactions between MMCs. The proposed method has good adaptability to the changes of system structures and operation conditions. Finally, time-domain simulations are performed to verify the efficacy of the proposed method.