Fault condition effects on the dynamic response of V-shaped offshore wind turbine

Offshore wind is an extensive renewable energy resource appropriate for fulfilling the increasing energy needs and increasing the security of energy supply. The issues related to the design of the support structure, installation, grid connection, operation, and maintenance in normal and fault conditions significantly influence the levelized cost of the produced energy. The feasibility of different concepts should be numerically calculated and assessed for all aforementioned issues. In this paper, the dynamic response of the V-shaped semisubmersible under different possible fault conditions is examined. Different response quantities of the floating wind turbine are compared for the case that the system operates under operational and fault conditions. The response quantities include motions of the platform in all six rigid-body degrees of freedom, mooring line tension, tower base-bending moment, and functionality of the wind turbine. A numerical model accounting for fully coupled dynamic analysis of the offshore wind turbine under different fault conditions has been developed. It is found that for the V-shaped semisubmersible, the mooring line tension is significantly affected by different fault conditions compared to the rest examined response quantities; the maximum value of the tension of the mooring lines is increased by a factor of 1.6 due to fault conditions. Among the different fault conditions, shutdown case seems to have the largest influence on the functionality and responses of the V-shaped floating wind turbine. For emergency shutdown fault conditions, backlash occurs that results in large variation of tower-bending moment.