Modeling and Rekasius Substitution Stability Analysis of the Multi-terminal MMC-HVDC Cyber-physical System

Modular multilevel converters (MMCs) are favored in high voltage direct current (HVDC) systems because of their huge energy transmission capacity and few harmonics. However, the control-communication chain exerts a huge influence on the system dynamics by introducing the cyber delay. To find out the exact influence of the cyber delay and study this system, the multi-terminal MMC-HVDC cyber-physical model is established. For the stability investigation of multiple cyber delays inside the MMC-HVDC, the Rekasius substitution for multiple delays is proposed. Multiple methods including simulation methods and analytical methods are deployed to validate the model and Rekasius substitution. The verification shows the proposed method’s efficiency and practicability. The case results prove that the cyber delay affects the system stability and induces sub-synchronous oscillation when it’s over the margin.