Research On Maximum Power Point Tracking Of Direct-drive Permanent Magnet Wind Power Generation System

The problem of environmental pollution is becoming more and more serious, and the sharp reduction of fossil energy on the earth makes it necessary for us to develop clean and renewable energy. Wind power has become the key field of energy industry because of its advantages of clean, pollution-free, short construction period, low operating cost and so on. In all wind power generation structure, direct drive permanent magnet wind power generation system has developed rapidly because of its high efficiency and low failure rate.First of all, this paper introduces the technical background and current development at home and abroad of wind power generation, and gives the structure of off grid direct drive permanent magnet wind power generation system. Then discusses the basic theory of wind power generation, and expounds the basic principle of coordinate transformation and the mathematical model of permanent magnet synchronous generator is given. The principle and characteristics of various chopper circuits are analyzed in detail. All of these lay the foundation for the analysis of the principle of maximum power tracking and the establishment of the model.Secondly, the principle of maximum power tracking of direct drive permanent magnet wind power generation system is studied and the relationship between maximum power tracking and duty cycle is given. In this paper, two kinds of adjusting methods of maximum power are introduced, and several commonly used maximum power tracking methods are compared. Then, this paper studies the hill-climbing search method based on BOOST circuit. In view of the shortcomings of the traditional hill climbing search method and the gradient step change hill climbing search method, an improved gradient step change hill climbing searchalgorithm is proposed.Finally, the maximum power simulation model of small type off grid direct drive permanent magnet wind power generation system and the combined wind speed simulation model are built in the MATLAB/Simulink platform. The output characteristic curve and wind speed curve of wind turbine are simulated. It can be seen from the combined wind speed curve that the wind speed has the characteristics of randomness, gradual change and sudden change.And the traditional and improved hill-climbing search methods are compared. The results show that the improved gradient variable step hill-climbing search method can not only track the maximum power point quickly, but also has high accuracy.