Offshore wind is an attractive source for renewable energy. However, the development and deployment of large scale (>2 MW) offshore wind turbines is hindered by a lack of
efficacious methods to develop a stable floating platform in ocean environments at depths greater than 100 m. A stable platform enables direct usage of large scale onshore wind turbines for offshore wind. In this paper, a system of three energy regenerative tuned mass dampers (TMD) is proposed as a means to both mitigate wave-induced structural motion of a floating platform of the DeepCwind 5 MW semisubmersible system and to harvest otherwise inaccessible ocean wave energy. Optimal tuning frequency and electrical damping of the TMD were obtained via the ?? norm optimization method. When the root mean square of the semisubmersible response was minimized, the TMD was shown to reduce the structural motion by more than 40%. Meanwhile, the harvested power was shown to reach 40~55 kW per significant wave height squared.