Research On Modeling And Optimal Control Of Wind Turbine

Wind energy,as a new type of renewable clean energy,has been paid of more and more attention.The importance of wind power is growing day by day.Due to the randomness of natural wind,the output power of wind turbine is random,which makes the quality of power output to the power grid decrease and has certain influence on the stability of the power grid.In this paper,based on the model of wind turbine and control system,the optimization of output power and its stability are studied.The main research contents include:Firstly,the mechanism model of the doubly-fed wind generator is established.In this paper,wind turbine is divided into four parts: wind turbine,transmission system,generator and frequency converter.Then the characteristics of each part are studied and the corresponding mathematical models are established respectively.Secondly,the control model of wind turbine is established.First,the operation process of the wind turbine is analyzed deeply,and the operation process of the unit is divided into four main operating regions.Then,according to the characteristics of each running region,establish the model of maximum power tracking control,pitch control,frequency control and grid control model,then the mechanism model and control model are made up of a complete closed-loop control system model,which lay the foundation for the improvement of control strategy.Thirdly,aiming at the shortcomings of the basic control strategy,a method to optimize the output power of wind turbine is proposed.In the pitch controller,speed control and power control are considered and the speed of rotation is first adjusted to slow down the wind speed mutation effect on output power.The torque controller is introduced in the torque compensator,so that the speed is higher than the rated speed,the torque response is more rapid,and by adding a torque reference value before the weighted average.And through the simulation,the control effect is compared before and after the improvement.The simulation results show that the output power of the unit is more stable and smoother after the improvement of the control strategy,which reduces the impact on the power grid.Finally,in order to ensure the improvement of control strategy does not affect the stability of the unit,the stability of wind turbine is analyzed and verified.The Lyapunov analysis method is used to analyze the stability of the unit without disturbance and perturbation.The simulation results show that the time required for the system to reach the equilibrium state in the absence of disturbance is short,but the system is stable with disturbance and no disturbance.