Research On Control Strategy Of Doubly Fed Induction Generator Under Fault Grid

To develop wind power is one of the important means to solve the energy shortage problem.Wind turbines based on doubly-fed induction generator become the main choice for large scale grid connected wind power.However,due to the structural of the double-fed induction motor connected to the power grid,it does not have a strong ability to pass through the power grid fault.Based on the above background,this paper takes the doubly-fed induction generator as the research object,mainly discusses the control technology of doubly-fed induction motor under disturbance fault(including negative-sequence voltage disturbance,harmonic distortion power grid)and three-phase voltage drop fault.First,the mathematical model of the doubly-fed induction machine under ideal and non-ideal conditions is given.The basic control principle of the brushless doubly-fed induction motor is briefly introduced.In addition,a phase-locked loop is designed suitable for non-ideal power grid conditions,which laid the foundation for subsequent research.Secondly,according to the different faults occurring in the power grid,the corresponding control methods are introduced to suppress the disturbances generated by the faults.In the case of unbalanced grid voltage,a complex vector resonant regulator is designed,the regulator can effectively suppress the negative-sequence disturbance component of the fault.This paper also studied repetitive controllers,in order to improve its stability,new parts is added based on its ideal expression,the characteristics of AC signals with different frequencies can be regulated at the same time to improve the waveform of the stator current under unbalanced harmonic distortion power grid.In order to deal with the three-phase light drop of the grid voltage,.A control method that can effectively suppress the free components of the rotor current,and for the case of deep drop,the resynchronization control strategy based on the rotor side converter and the switching technology of the Crowbar circuit are studied.Finally,the control method of this paper is simulated by MATLAB/Simulink and verified on the experimental platform.