Interaction between damping characteristics and the initial-stage short-circuit current of MMC-HVDC transmission systems

This paper studies the interaction between the damping characteristics and the initial-stage short-circuit current of modular multilevel converter based high voltage direct current (MMC-HVDC) transmission system. First, the MMCs' input–output characteristics are obtained through the operator approach, and the influences of both linear part and nonlinear part are analysed. Second, an input–output characteristics based short-circuit current calculation method is proposed. Third, an eigenvalue-based comprehensive index is proposed to evaluate the damping characteristics of the MMC-HVDC transmission system. Finally, the interaction between the damping characteristics and the initial-stage DC short-circuit current is analysed under different system parameters and DC system structures. The analysis results show that there is a negative correlation between the system damping characteristics and the average rising rate of the short-circuit current. The proposed index G can effectively evaluate the short-circuit current of MMC-HVDC and can provide guidance for the planning of DC system structure, the selection of operation mode and system parameters.