Stability Analysis of Offshore Wind Power Transmission System via MMC based on HSS Theory

The stability problem of offshore wind power transmission systems via modular multilevel converter (MMC) is becoming more and more prominent worldwide, and there is an urgent need to analyze the mechanism of oscillations. Due to the existence of harmonic interactions within the MMC, new requirements on modelling methods have been put forward. Harmonic state space (HSS) modelling methods, which can consider multiple harmonic interactions, have drawn extensive attentions. However, the key eigenvalue screening problem in the eigenvalue analysis process of HSS models has not been solved yet. In this paper, an HSS eigenvalue screening method based on the comparison before and after downscaling is proposed to solve this problem. Eigenvalue analysis method is used to analyze the participation factor of system oscillation and control parameter damping sensitivity, and the key participation factor of oscillation and the adjustment direction of control parameter are obtained. Finally, the correctness of the analyzed results is proved by MATLAB/Simulink time-domain simulation.