Research On Double Closed Loop Control System Of Wind Power Grid-connected Inverter

The massive consumption of fossil fuels and environmental issues have prompted the vigorous development of clean and renewable energy power generation.As a renewable clean energy,wind energy provides a practical solution to alleviate the above problems.Permanent magnet direct-drive wind power generation system are widely used in wind power generation due to their high power generation efficiency and high reliability.Large-scale grid connection of wind turbines has an increasingly obvious impact on the power quality and stability of the grid.As an important element of connecting the wind power and the grid,wind power grid-connected inverters play an important role in ensuring power supply.Therefore,it is of certain significance to study the control strategy of the wind power grid-connected inverter.Firstly,from the background of the subject,this paper introduces the current development of the wind power industry,the current research status of the double closed loop control of wind power grid-connected inverters and active disturbance rejection control technology(ADRC).Secondly,the mathematical model of the wind power grid-connected inverter is introduced,which lays a theoretical foundation for the application of the traditional control strategy of the grid-connected inverter and the double closed loop structure based on linear active disturbance rejection control technology(LADRC).According to the mathematical model,the traditional double closed loop control structure of the grid-connected inverter is introduced,and the selection of the PI controller parameters of the traditional control strategy is analyzed.Then,the structure and design principle of the first-order LADRC are analyzed,and the indifference estimation of the second-order linear extended state observer(LESO),the stability,tracking and disturbance rejection of the first-order LADRC are theoretically proved,and then from the perspective of improving the dynamic performance of the DC bus voltage,a double closed loop structure based on LADRC is designed.The inner loop uses LADRC to improve the quality of grid-connected current,and the outer loop uses LADRC to improve the anti-interference performance of the DC bus voltage.Thirdly,in order to further improve the disturbance observation performance of LADRC,an improved LADRC with a proportional derivative controller added to the disturbance observation channel is designed.The stability,tracking and disturbance rejection of the improved LADRC in the frequency domain are proved.The improved LADRC is applied to the voltage outer loop to further improve the anti-interference performance of the DC bus voltage.Finally,the Simulink simulation software verifies the effectiveness of the designed double closed loop structure based on LADRC compared with the traditional PI double closed loop structure in improving the dynamic performance of the DC bus voltage in the case of a sudden change in the grid voltage.