Impact of control system on small-signal stability of MMC-based MTDC transmission system

This paper studies influence of control system dynamics on the small-signal stability of modular multilevel converter (MMC) based multi-terminal DC (MTDC) transmission system. The small signal model is derived based on the state–space model of an MMC-based MTDC. Eigenvalue analysis and participation factor analysis are applied to study the inherent oscillatory modes of MMC-based MTDC transmission systems. The impacts of control system parameters on small-signal stability of the system are investigated through sensitivity analysis. The study shows that the control systems strongly affected the small signal stability of the MMC-based MTDC and the d-axis proportional gains in d–q decoupling main controllers have great impact on system stability, which needs to be properly selected for stability enhancement.