Abstract: With the development trend of large-scale and ocean-going offshore wind farms, the demand for large-scale offshore converter stations will continue to increase, and their installation problems will gradually receive attention. In this paper, taking the SanXia Rudong offshore converter station as an example, a multi-body dynamic model is established by OrcaFlex software to numerically calculate the transportation and floatover installation process of the converter station, and the motion, acceleration and mooring line force of the barge and converter station in some stages are analyzed. The results show that during the transportation stage, when the significant wave height is the same, the motion amplitude and acceleration of the barge-converter station system increase correspondingly with the increase of the spectral peak period Tp (6~9s), but they are basically within the limit value. During the installation stage, the spectral peak period Tp = 8s at the same wave height will cause greater surge, sway, and yaw motion amplitudes than Tp = 6s and 10s, and more attention should be paid to such working conditions. In addition, head sea conditions are more conducive to the floatover operation. Besides, the risk research of the converter station transportation stage is carried out, and effective risk control measures are proposed to provide a certain reference for the actual large-scale offshore converter station installation operation.

Key words: offshore converter station, marine transportation, floatover installation, coupled hydrodynamic analysis, risk study