Joint external and internal opportunistic optimisation for wind turbine considering wind velocity. (October 2020) - Wang, Jinhe
Abstract: Wind farms are subject to unavoidable energy-production stoppage periods because of the stochastic behaviour of wind velocity; however, these periods provide additional opportunities for maintenance activities. In this research, we investigated a novel joint opportunistic maintenance strategy for wind turbines considering the stochastic wind velocity. Our strategy entailed considering two types of opportunities, namely, internal opportunities provided by the general degradation of wind turbines, and external opportunities generated by the weak wind-speed periods. An expected cost-rate model was formulated by utilising the semi-regenerative process theory based on all possible maintenance scenarios. In this model, all the maintenance activities at each decision point were determined in accordance with the maintenance requirement that is dictated by the state of deterioration of the wind turbines. Furthermore, a stationary probability density function was developed by derivation of the stationary law of the wind turbine condition, influenced by opportunistic maintenance. The maintenance activities and their corresponding probabilities were all derived on this basis. Finally, the applicability and correctness of the proposed approach were demonstrated by a case study and sensitivity analysis. The results of our study indicated that the maintenance policy we proposed could be of economic benefit to wind farms. Highlights: Novel joint opportunistic maintenance strategy for wind turbines. The opportunistic maintenance strategy considers the stochastic wind velocity. Long-term expected cost-rate model proposed to derive optimal maintenance policy. Economic benefits of proposed strategy compared with other maintenance strategies.