Studies On Grid-Connected Dfigwind Generation System Under Grid Fault

With constantly increasing of installed wind capacity, the proportion of wind power in power system gradually increase, the mutual influence between wind power and power system will be increasing. The transient performance of wind turbine generator system under grid fault will affect the safety and stability. It will also affect the stability of power system with large scale wind power integration. Therefore, researching on the transient performance of grid-connected wind generation system under grid fault has an important meaning. The researching work is a critical link to promote the technical progress of wind power.This thesis mainly focuses on the grid-connected doubly-fed induction generator (DFIG) wind generation system, and the transient operational performances under different grid faults are studied. The specific process is as follows. Firstly , the mathematical model of DFIG wind generation system has been established, which includes wind turbine,driven institutions,generator etc. Secondly, the maximum wind power tracking strategy of DFIG wind generation system has been proposed, on this basis, the control strategy has been established. The main control system is for the rotor-side converter and grid-side converter. Furthermore, this thesis analyzes common faults of power system and chooses two of the most serious fault type that influence the operation of grid-connected DFIG wind generation system. Then, the transient variable process of the generator flux and currents has been analyzed by the way of formula derivation. Finally, a simple simulation model of test system with DFIG wind generation system has been established, which is used to study the situations that mentioned above through MATLAB/Simulink.The correctness and effectiveness of the analysis achievement above has been proved through simulation study. Moreover, simulation results demonstrate that the transient operational process will be different under different faults, and protective devices will be needed if the fault is too serious to the safety of wind generation system...