Research On Optimal Control Strategy Of Direct Drive Wind Turbine Transmission System

As an important part of sustainable energy and the third source of power generation in China,the proportion of wind energy consumption in China is increasing year by year.Therefore,how to realize the efficient conversion of wind energy has become a hot issue both domestic and international.Wind turbines are the core equipment for wind energy conversion,and their efficiency is directly related to the ultimate utilization efficiency of wind energy.Direct-drive permanent magnet synchronous wind turbines have unique advantages in terms of potential reliability and efficiency compared to other types due to having no intermediate links such as gearboxes.In this paper,the direct-drive permanent magnet synchronous wind turbine is taken as the research object.Through the theoretical modeling and numerical simulation methods,the control strategies of several wind turbines are analyzed and compared,and an effective improved method is proposed to improve the wind energy conversion efficiency.First of all,the simulation model of direct drive wind power generation system is established by theoretical analysis and mathematical modeling of direct-drive wind turbines.Secondly,mathematical modeling and analysis of the grid-side converter and the machine-side converter are carried out to determine its control scheme.The proportional and integral coefficients of the controller are designed by the typical I system and the typical II system,and the controller is built,and its simulation model is verified according to the mathematical model.The two control strategies of tip speed ratio method and hill climbing algorithm are compared.The simulation results show that the hill climbing algorithm is better than the tip speed ratio method under a large change in wind speed.The adaptive step search method is proposed based on the analysis of the characteristics of the wind turbine and the principle of hill climbing algorithm.The simulation results show that the adaptive step search method can improve the stability and power of the wind power system.In order to further improve the performance of the wind power generation system,a fuzzy PI controller is introduced into the speed loop of the adaptive step search method and verified by simulation,and the simulation results show that the introduction of fuzzy PI can further improve the power and the response speed of the wind power generation system.Aiming at the shortcomings of the adaptive step search method,the fuzzy neural network algorithm is used to search the optimal speed based on the adaptive step search,and the simulation result is verified.The simulation results show that the fuzzy neural network algorithm can further improve the efficiency and stability of the wind power generation system,it solves the shortcomings of the adaptive step size search method and reduces the search error.The power of the fuzzy neural network compared to the power of classical fixed step and variable step hill climbing algorithm are increased by 6%and 6.82%,respectively.When the overall trend of wind speed fluctuates more frequently,the power of the fuzzy neural network compared to the power of classical fixed step and variable step hill climbing algorithm are increased by 16.37%and 16.8%,respectively.This paper provides a feasible scheme for wind turbine control.