The Research On The Maximum Power Point Trackin Control Of Variable Speed Constant Frequency Generation System

With the reduction of the traditional energy such as oil and coal, the development of the renewable energy has become an important energy strategy in the world. In recent years, countries around the world use the renewable energy such as wind and solar as a main way to deal with the climate change. With the increasing of the wind turbines capacity, improving the turbines stability and reliability and tracking the maximum power point have become important parts to study. So the maximum of power point tracking control of the variable speed constant frequency (VSCF) has become a hot research.At first, this paper analyzes the modern status of the wind power generation system and points out the necessity and urgency for the study of the wind turbine's control technology. Then the modern existent implementations of the VSCF generation system are studied. The doubly fed indection generation (DFIG) system which has a simple structure, easy to control and converters system needs low capacity has been studied mostly and is widely used in the VSCF wind power generation system. After that the mathematical model and the operating power flow relationship of the DFIG are studied. All of these make a theoretical foundation for the later study of maximum power point tracking control.The existent metods of the maximum power point tracking control are analyzed. The tip speed ratio control algorithm is simple, however the detection of the wind speed is influenced by the environment, the application of this method is limited. The climbing research method is independent of the turbines parameters. However because of the inertia of the turbines, this method is only applied to small-capacity systems. An improving power singal feedback control is advanced in this paper.If the optimal tip speed ratio and the power characteristic curve are known. The speed of the wind turbine was measured first. According to the maximum power curve, the responding maximum output power is calculated. The result is the reference value of the wind turbine's output power. Control the speed of the wind turbine to achieve the maximum power point tracking control.This method doesn't need to detect the wind speed, which is a simple algorithm, and it has a good feasibility. According to the motor's vector control technology, the vector control of the DFIG is proposed in this paper which was based on the stator flux oriented. This vector control method is used to achieve the maximum power point tracking control.Using the MATLAB/simulink, the wind turbine model, the DFIG's S-function model and the vector control model are built. Then make a dynamic simulation study when the wind speed mutates for the maximum power point tracking control, which verifys that the maximum power point tracking control method is correct and practical.