Reserch On Integral Switching Adapative Sliding Mode Control Strategy For Grid-connected Of Doubly-fed Wind Turbine

With the continuous innovation of science and technology,the consumption of fossil energy is increasing,but the excessive consumption of non-renewable energy,especially the excessive development and utilization of coal and petroleum energy,will not only cause a shortage of non-renewable resources,but also destroy the survival of human beings.Compared with other renewable energy sources,wind energy resources are rich and pollution-free,so they are highly valued by countries around the world.The wind turbine with constant speed and constant frequency control is gradually replaced by wind turbine with variable speed and constant frequency control,becoming the mainstream model in the wind power market.In this paper,the adaptive switching mode variable structure control strategy of integral switching is proposed to design the rotor side and grid side converters of wind power system,so that the doubly-fed wind power generator can meet the requirements of grid connection.This paper has done the following work:1)Analyze and study the wind speed model and the principle of maximum wind energy tracking in the doubly-fed wind power generation system.Use Matlab/Simulink simulation software to verify the correctness of the theory,and how to realize variable speed constant frequency control and three-phase static coordinates for doubly-fed wind power generation.And the mathematical model under the synchronous rotating coordinate system is elaborated.2)Based on the basic knowledge of sliding mode variable structure control theory,the concept,characteristics,definition,matching conditions and invariance of sliding mode variable structure are analyzed in detail.The adaptive function of the switching term of sliding mode variable structure controller is designed.The adaptive sliding mode variable structure control strategy is selected,and the Lyapunov function is selected to prove the stability of the improved controller.The correctness of the theory is further verified by an example.3)According to the control target of the machine-side converter,the variation of the grid excitation current of the doubly-fed wind turbine connected to the grid is analyzed,and the mathematical model of the rotor excitation current is obtained.Combined with the sliding mode variable structure control theory,the model is analyzed to satisfy the matching condition and invariance of the sliding mode variable structure.The proposed improved control strategy is applied to the rotor excitation current control of the doubly-fed wind turbine generator,and the Lyapunov function pair control is selected.Proof of stability andconvergence time.The simulation results show that the improved control strategy can effectively suppress the impact of stator current on the grid when grid-connected,and has strong robustness to system parameters and voltage drop.In order to further verify the effectiveness of the proposed control strategy,a real-time simulation system for doubly-fed wind power generation was built in the laboratory,and the real-time simulation results were consistent with the offline simulation results.4)Aiming at the control target of the grid-side converter,the proposed integral switching adaptive sliding mode control theory is applied to the network-side controller design respectively,and the stability and convergence time of the designed controller are proved.The simulation results show that compared with the traditional PI control strategy,the proposed control strategy can not only achieve the control objectives of the network-side converter,but also improve the control accuracy,response time and anti-interference ability of the system.