Research On Pitch Control Strategy Of Spar-type Floating Wind Turbine Considering Wind-wave Coupling

There are a large territory and a huge amount of natural resources in China.However,as the development potential of onshore and offshore wind resources decreases,deep-sea floating offshore wind power is the main direction for new wind power installations in the future.Floating wind turbines are located in the deep sea area,and the changeable environment brings great challenges to the operation of wind turbines.Under the complex wind and wave coupling,the output power fluctuation of the floating wind turbine increases,the unbalanced load increases,and the vibration of the unit increases.This paper takes the Spar-type offshore floating wind turbine as the research object,and deeply studies the pitch control strategy of the floating wind turbine,aiming at improving the attitude stability,suppressing the power fluctuation of the floating turbine,and reducing the fatigue load of the key parts through the pitch control.The dynamic characteristics of floating wind turbines are deeply studied,and the dynamic response characteristics under external working conditions are analyzed.Considering the nonlinear strong coupling characteristics of the unit in complex and changeable environmental factors,the aerodynamic characteristics,hydrodynamic characteristics,mooring system characteristics and pitch control system characteristics of the unit are analyzed,and a sixfreedom Spar floating wind turbine is established.degree kinetic model.It lays a theoretical foundation for the pitch control strategy of floating wind turbines.Aiming at the attitude optimization problem of Spar-type floating wind turbine in complex deep sea environment,an independent pitch control strategy considering the attitude optimization of the unit is proposed.In this strategy,the azimuth angle of the blade is used as the feedback amount to optimize the attitude of the floating wind turbine,and the power fluctuation is used as the control target.The results of numerical example analysis show that,compared with the traditional pitch control,the proposed control strategy can effectively alleviate the displacement and acceleration of the top of the floating wind turbine tower,optimize the attitude of the unit,and stabilize the power output.Aiming at the problem of excessive load of Spar-type floating wind turbines in complex deep sea environment,an independent pitch control strategy considering the unbalanced load of the wind rotor is proposed.In this strategy,the blade root load is used as the feedback quantity,and the measured root load is converted into the pitch load and yaw load at the center of the hub by means of coordinate transformation,and two independent variable parameter PID controllers are used for independent pitch control.Then,the pitch angle signal of each blade is obtained by inverse coordinate transformation.In order to solve the nonlinear relationship between the pitch angle and the load and improve the control effect,the random inertia weight particle swarm algorithm is used to optimize the controller parameters,making it suitable for the load shedding control of offshore floating wind turbines.The numerical example analysis shows that the proposed control strategy can effectively alleviate the power fluctuation of the floating wind turbine and reduce the central load of the turbine hub.Based on the OC3-Hywind Spar floating foundation and the NREL 5MW unit,the cosimulation in Open FAST and Matlab/Simulink verifies the effectiveness and superiority of the proposed control strategy.The control effects such as unit power fluctuation and tower vibration are analyzed.The results show that the proposed floating unit control strategy can effectively alleviate the unit output power fluctuation,reduce the unit load and optimize the unit attitude.