Research On Response Signal Stationarity And Dynamic Characteristics Of Offshore Wind Turbine Under Operating Environment

With the vigorous development of offshore wind power,in order to reduce costs and improve power generation efficiency,offshore wind turbines are showing the development trend of large capacity,high towers,and long blades,which makes the structure"flexible"and the vibration problem is prominent.In-depth study of the power of large wind turbines The characteristics are of great significance to the safe and stable operation of the fan and design guidance.Operational Modal Analysis（OMA）is widely used in the identification of structural modal parameters of large civil engineering such as offshore wind turbines.This type of method assumes that the input is white noise.However,when the actual engineering structure excitation signal is difficult to meet this assumption,the recognition result will be uncertain.Therefore,realizing the smoothness inspection of structural vibration data has become an urgent research topic for the identification of engineering structural systems.Based on the stability response of offshore wind turbines in the operating environment,this paper studies the dynamic characteristics of wind turbine structures,using theoretical analysis,finite element simulation,and actual engineering verification methods to verify the feasibility and effectiveness of the new signal stability test method,and reveal the performance of offshore wind turbines in the operating environment.Vibration law and dynamic characteristics.This article mainly carried out the following work:A method that can quickly and objectively test the stationarity of a large number of data series samples is proposed.Based on the original vibration response data,construct the mean and autocovariance function stationarity test statistics,and then construct the hypothesis test problem,and use the method of statistical inference to determine whether the data sequence is stable.Through the verification of numerical simulation of stationary and non-stationary signals and the measured vibration signals of offshore wind turbines,it is verified that the signal stationarity test method can quickly and objectively test the stationarity of the signal,and can quickly perform stationarity test on a large number of data samples.Based on the complexity of the environment in which offshore wind turbines are located,we independently developed a long-term intelligent online monitoring system suitable for offshore wind turbines and in-depth study of the vibration changes of offshore wind turbines in the operating environment.Integrate the data of the offshore wind turbine’s long-term intelligent online monitoring system and the SCADA system and perform statistical analysis,in-depth study of the relationship between the wind turbine operating parameters,the wind turbine vibration characteristics under typical operating conditions,and the statistics of the wind turbine vibration laws under different operating conditions.Based on the data-driven random subspace method to identify the structural modal parameters of offshore wind turbines,and study the dynamic characteristics of offshore wind turbine structures in operating environments;describe the relationship between the natural frequencies of the offshore wind turbine structure and the rotation frequency of the impeller and the frequency of the propeller based on the Campbell diagram.After checking,the first-order frequency of the offshore wind turbine monitored in this paper falls within the frequency band.When the impeller speed is about 6.7 r/min,the amplitude is obviously strengthened and the structure resonates;it is proposed that the total damping of the offshore wind turbine in operation is determined by the wind turbine structure and aerodynamics.The estimated model of linear superposition of damping ignores the influence of aerodynamic damping at low wind speeds.The system damping of the wind turbine is mainly structural damping.The measured mean structural dampingξ_struc=0.42%in the main wind direction and structural dampingξ_struc=0.40%in the side wind direction.In the grid-connected power generation state,the average aerodynamic damping in the FA direction varies within the range of 2%to 4.5%,and the average aerodynamic damping in the SS direction is lower than 2%.The change in the total damping of wind turbines mainly comes from the change in aerodynamic damping.