Research On Dynamic Opportunistic Grouping Maintenance Strategy Of Offshore Wind Turbine

China is abundant in offshore wind resources due to the long coastline.Offshore wind turbine is close to the power load center and access to power grid side,which is suitable for large-scale development and construction.Currently,the offshore wind industry in China has been developed from preliminary period to rapid development.China specialized in the area of design,manufacture and construction of offshore wind turbines,however,it is still a lack of systematic research on the operation and maintenance technology of offshore wind farms due to the high failure rate and difficulties of operation and maintenance tasks.As an important procedure of operation and maintenance technology research,maintenance strategy research can improve systematic reliability and maintenance accessibility,and play a role in improving the energy efficiency of offshore wind farms,which has important theoretical value and engineering practical significance in promoting the energy conservation and consumption reduction of offshore wind power industry.In this paper,the key technical problems of offshore wind turbine maintenance strategy was systematically studied,and the research contents are as follows.(1)The reliability analysis method of offshore wind turbine is studied.By analyzing the importance and limitation of fault data collection of offshore wind turbine,the fault prediction model of offshore wind turbine based on three-parameter Weibull distribution is constructed for the situation of limited turbine failure data,and the parameter estimation method of three parameter Weibull distribution model was studied.Based on the parameter estimation method of bi-linear regression,the concept of median is introduced to effectively avoid the problem of estimation distortion caused by the limited failure data.The constructed model was verified by an example,which indicated that the failure rate curve obtained by using the three-parameter Weibull distribution fault model is fitted to the actual failure rate of the wind turbine as compared to the two-parameter Weibull distribution fault model.It can be used as the technical basis for the research on the maintenance strategy of offshore wind turbine.(2)The weather window time for maintenance of offshore wind turbine was developed.Based on the offshore wind and wave data and the classification rules of maintenance tasks,the queuing theory was used to study the maintenance waiting time of the units.Based on the analysis of the forecast method of weather window with a factor,the error of the forecast of the weather window by subjective factors was reduced by introducing the maintenance task failure rate.The results illustrated that the prediction method proposed in this paper can utilize the potential functions of maintenance resources such as repairing ship,reasonably extend the maintenance weather window time,and provide a theoretical basis for the preparation of marine maintenance plans.(3)By introducing the weather window time inspection of offshore maintenance and considering the dependence of multi-component maintenance of offshore wind turbine,the dynamic opportunity grouping maintenance strategy of offshore wind turbine was proposed.The optimal maintenance interval and maintenance combination scheme in the preventive maintenance cycle were obtained through an practical example.The results show that the dynamic opportunity group maintenance strategy taking both economic and structural dependence into account can make full use of the offshore maintenance window time,further reduce the maintenance cost of the system,and thus increase availability and inaccessibility of the wind turbines.The comparative analysis on time and expense consuming under different structural coefficient indicated that a better performance can be seen on the precondition of higher dependence coefficient and more components involved of offshore wind turbine.(4)Based on the analysis of the energy efficiency of offshore wind farms,the dynamic opportunistic grouping maintenance model of offshore wind turbine was verified by an example.The paper analyzed the energy efficiency loss mechanism of offshore wind turbines and put forward various energy efficiency indicators.The impact of offshore maintenance inaccessibility on energy efficiency losses of the unit was studied.For the prediction method of offshore wind speed and wave height,the paper compared the Markov chain prediction method with the empirical formula derivation method,and verified the accuracy of the Markov chain prediction method under the prediction of wave height.Taking the offshore wind turbine group as the research object,the effectiveness of the maintenance mathematical model was verified by an offshore wind farm in Jiangsu province.The results showed that the annual average on-grid power of the offshore wind farm was increased by 5.09%,the number of downtime was reduced by 24.05%,and the maintenance cost was reduced by 9.04%.