Research On Second Order Sliding Mode Control Strategy Based On Speed Sensorless Control Of Variable Speed Wind Turbine

As wind power plays an more and more important part in the field of energy,countries around the world have increasingly strict requirements on the safety,cost,quality and efficiency of wind power generation systems.Among them,the control strategy that ensures the safe,stable and efficient operation of wind turbines has gradually become the focus and hot-point of the control and engineering communities.Therefore,the in-depth study of wind power generation control technology for the optimization of wind turbine operation condition,wind turbine grid-connected operation technology,realizing the independent intellectual property right of wind turbine and enhancing market competitiveness is significant.In this paper,inevitable various situations and problems in the operation of wind power system due to randomness of wind,the strong non-linearity of wind power system,complexity and poor working environment are considered.The purpose of this study is to realize safe and reliable operation and maximum efficiency of wind energy capture under the control of wind power system.The main research content is as follows:Modeling and model analysis of wind turbine and permanent magnet synchronous generator are the basis of considered wind power system.First,the appropriate dynamic model is selected to establish the mechanical model of the turbine blade.Secondly,the electric power model of the permanent magnet synchronous generator is established.Under the reasonable assumption,the dynamic model of the wind turbine that meshes with the permanent magnet synchronous generator is established and simplified.In order to facilitate the design of the follow-up controller,it is necessary to analyze and deal with the dynamic model of the wind turbine generator.In the wind power generation system,the variable speed operation mode is an important method for optimal power tracking,i.e.,the change of the rotor speed is adjusted in time according to the change of the wind speed so as to achieve the best power tracking.Therefore,the rotor speed is an important variable in the wind power generation system.However,due to the fact that the speed sensor is susceptible to environmental influences,expensive,and maintenance difficulties,thus sensorless control in wind power generation system is particularly important.In this paper,an extended state observer is designed to replace the speed sensor to achieve the best torque estimation of the wind turbine.The estimated torque will be used as the torque reference of the outer-loop of the control link.Research on dual-loop control strategy for permanent magnet synchronous generator.The outer-loop of the system is an aerodynamic torque control loop.The control objective of the outer-loop is to calculate the control parameters required by the inner loop by tracking the maximum torque captured by the maximum wind force.The torque estimated by the extended state observer is applied in the torque control loop.The control objective of the inner-loop is to make the proportion of the useful power of the output power of the permanent magnet synchronous generator reach the maximum,and the AC power is efficiently converted into the DC power by adjusting the current.In the present control design,the control effect of the nonlinear control algorithm is obviously better than the traditional control strategy.The simulation results are confirmed to illustrate the effectiveness and robustness of the second order sliding mode controller based on extended state obsever,and the control effect of the controller is compared with a conventional PI controller.