Grey Prediction Control Of Variable Speed Constant Frequency Wind Turbines With Doubly Fed Induction Generator

During the process of wind power exploration, more and more attention has been paid to the research and utilization of Variable Speed Constant Frequency (VSCF) with Doubly-Fed Induction Generator (DFIG).Compared with other wind generators, the pitch control system of VSCF with DFIG can substantially track the change of wind speed and enhance the efficiency of wind energy extraction.Firstly , this dissertation generalizes the state of wind power development all over the world ;also , it gives a summary of the structures of different types of wind generators ,as well as the respective problems .Secondly , in order to deal with the complex wind speed and change rate ,this paper concentrates on the use of Grey System Theory ,which was invented by Professor Deng Ju long .To be more specific , I hope that we can put the grey prediction theory into the research of DFIG control system .Due to the excellent performance of GM(1,1) in the prediction of random data of a system ,this paper tries to build up the GM(1,1) dynamic model of wind speed for prediction ,which is implemented by the software of MATLAB for simulation .The results of simulation show that the GM(1,1) model can approximately track and predict the wind speed ,which can help to improve the control strategy of wind turbines .In addition , according to the motion equation of the rotor of DFIG, this paper obtains the formula of transfer function .Then the grey PID control method is applied to reduce the error of the rotor system ,thus advances the control precision and motion performance .The results of simulation show that grey estimation really can estimate the disturbance of a system effectively ,and supply the system with real-time and exact compensation .Consequently ,the total error of the system can be reduced to nearly zero .Obviously , this beforehand control method has a huge advantage over the traditional afterward control of PID .