Coordinated control of single-point moored floating multi-wind turbines under fault events and shutdowns

Abstract The emergence of novel concepts aimed at the reduction of floating offshore wind energy cost is increasingly demanding new control approaches. This is the case of floating offshore multi-wind turbine assets (FOMWT), with two or more full wind turbines placed on the same floating platform. The strong dynamic interaction among the sub-components of such systems requires appropriate coordination of the commands driven by the individual wind turbine controllers. The impact of such coupling may increase depending on the asset confguration, as is the case of single-point distribution of mooring lines, commonly applied to FOMWTs. Among the most demanding situations are those under fault events and shutdowns, which may cause large uncontrolled platform rotation and put the system integrity at risk. To address this, a new coordinated control level, mastering the individual turbine controllers hierarchically, is proposed to govern the whole asset. The control concept proves to be effective under a reduced set of extreme load cases in accordance with standards for a two-wind turbine FOMWT. The simulations are performed with the multi-wind turbine simulation tool MUST, which accounts not only for the interaction among the two turbines and the platform, but also for the communication of the coordinated control and the individual turbine control levels.