Research On Multi-objective Pitch Control Of Large-Scale Wind Turbine

Under the goal of promoting "dual carbon" strategy and building a new power system,renewable energy mainly based on wind and solar has ushered in rapid development.As the key component of renewable energy,wind energy is making an important contribution to the zero-carbon society.At present,wind turbines are constantly developing towards large scale.Large-scale wind turbines not only mean higher power outputs,but also higher hub,more flexible blades and towers.In the long-term operation of wind shear,tower shadow and turbulent environment,higher requirements are put forward for wind turbines,such as stable power regulation,effective load reduction and fault tolerance control.When the wind speed exceeds the rated wind speed,effective pitch control can ensure the efficient and stable operation of the wind turbine,reduce the structural load and extend the service time of the wind turbine.In view of this,this paper will take the multi-objective pitch control of large wind turbines as the research content.The control strategy based on mechanism model and data model is adopted to solve the pitch control problem.The main research contents of this paper are as follows:(1)Based on the theory of multibody dynamics,a nonlinear mechanism model of wind turbine including wind speed,aerodynamics,transmission chain,generator,tower and pitch actuator of wind turbine is established.The main sources of nonlinearity for wind turbine are analyzed.At the same time,for different faults in the pitch actuators,the pitch actuators models under the different fault conditions are established,respectively.The step responses of the pitch actuators under various fault conditions are obtained.The model foundation for the design of subsequent controllers is established.(2)In order to solve the problem of nonlinear pitch control for wind turbine,the nonlinear model of wind turbine is linearized along the steady-state pitch trajectory to obtain a series of linearization models.With the help of OpenFAST software,the precise aerodynamic derivatives are calculated by differential method at steady-state pitch operating points.The gap metric theory is used to select the optimal local models.And a linear parameter varying model based on the grid is constructed.An adaptive model prediction collective pitch controller with time-varying Kalman filter is designed.Under gust,step and turbulent wind conditions,the effectiveness of the proposed model and controller is verified.(3)Aiming at the problem that the collective pitch cannot effectively reduce the imbalanced blade root load and the pitch actuator is prone to failure using individual pitch control,based on the feedback of blade root load data,a dual PI individual pitch control strategy of hub pitch and yaw bending moment is designed.Also,a model-free adaptive passive fault-tolerant control strategy with load error and actuator fault compensation factor are proposed.Finally,an individual pitch fault-tolerant control scheme based on blade root load feedback is formed.Under the conditions of fault-free,single fault and multiple faults of the actuators,it is verified that the proposed scheme can effectively reduce the imbalanced load of blade roots,and compensate the pitch output in time when the actuators fail,which ensures the safe operation of wind turbine.