Study On Maintenance Strategy Of Offshore Wind Turbines Considering The Wake Effect

With the gradual urgency of fossil energy reserves and the increasingly severe environmental protection issues globally,the development and utilization of renewable energy has become an important project in many countries.Offshore wind power has become more and more important due to its significant advantages such as high wind speed,large single-unit capacity,and long annual utilization hours,and has entered a stage of rapid development.However,it also faces problems such as the impact of sea conditions,high construction costs,and short maintenance operating time.It is difficult to maintain the wind turbines.Simultaneously,subject to the footprint of the wind farm,the wake effect between wind turbines is significant,which will greatly affect the output power of the turbines and the formulation of maintenance strategies.Research on optimization methods of maintenance strategies for offshore wind turbines under complex sea conditions is of great significance for improving the offshore wind farm efficiency and reducing maintenance costs.Therefore,this paper has carried out the study on the maintenance strategy of offshore wind turbines considering the wake effect.The main contents are as follows:Aiming at the influence of the wake effect between wind turbines on the distribution of wind speed in the wind farm,a wake model is constructed using the kinetic energy conservation law of airflow per unit time.The model considers the effect of changing wind direction and turbine maintenance status on the wake distribution of the wind farm,and describes the aerodynamic coupling between the downstream wind turbine and multiple upstream turbines based on the aerodynamic coupling paths between the turbines during each period.Then,the input wind speed of the wind turbine can be analyzed in detail over the studied maintenance scheduling time horizon.And,the cases studies show that the effect of the varying wind direction on the wake effect between wind turbines can affect the output power of the offshore wind farm and the influence of the turbine in maintenance on the wake distribution in the wind farm cannot be ignored.The proposed wake model can accurately obtain the input wind speed of wind turbines to calculate output power in the scheduling period,which also lays a theoretical foundation for subsequent work.Considering the full utilization of offshore wind energy resources and ensuring the good economics of the maintenance scheduling,an optimization model for offshore wind farm maintenance scheduling is established with maximum power generation and minimum maintenance costs.The model takes into account the change of the wind direction and the turbine maintenance status during the maintenance scheduling period,and combines the aforementioned wake model to calculate the input wind speed of each turbine in the offshore wind farm.Simultaneously,in order to describe the arbitrariness and randomness of the offshore wind speed and direction,the scenario method is employed to obtain the set of scenarios for wind speed and direction prediction.The nonlinear part of the model is approximately described as a polyhedron to further transform it into a MILP model and the ?-constraint method is utilized to process the multi-objective function.Based on this,the model is solved to obtain the maintenance scheduling optimization scheme.The cases studies show that the proposed model can obtain the maintenance scheduling of offshore wind turbines with the best comprehensive economic benefits under the influence of wind conditions and provide decision support for turbine maintenance.Moreover,it can provide a reference for achieving reasonable economic evaluation.Besides,considering the impact of the complex marine environment on the wind turbine maintenance path,a maintenance routing stochastic programming model for offshore wind turbines considering the wake effect is constructed.The scenario sets are used to characterize the correlation and uncertainty of wind and waves in ocean weather.And the costs such as personnel,vessels,punishment,and loss of shutdown are comprehensively considered to establish an objective function that minimizes maintenance costs.Meanwhile,considering the influence of wind and waves on the vessel's sailing time and the window to the sea,relevant constraints are established.In addition,considering the maintenance condition will change the wake distribution between the turbines,the proposed wake model is combined to quantify the shutdown loss of the offshore wind farm finely.In order to improve the solve efficiency,a pre-evaluation strategy for the maximum number of maintainable turbines by per vessel in per day is introduced during the solution process,which effectively determines the search space for maintenance routing optimization and reduces the size of the calculation.The cases studies show that the obtained maintenance routing decision can better deal with the random marine weather environment and improve the adaptability of the routing decision result,as well as the maintenance routing decision result considering the wake effect is more economical.