Stability Analysis Of Doubly-Fed Induction Generator Unit With Stator Fault

With the wind power technology developing rapidly, the installed generator capacity of wind farms increased gradually, making the wind power penetration rate rising. Therefore, the stability of wind farms on power system will be more important. On one hand, the working condition of the wind turbine is bad, for the wind speed is intermittent and time variant. On the other hand, the incipient internal fault of the generator is difficult to detect, also there are examples showed that the generator would continue to run for some time with fault. So the stability of wind farm itself should be given appropriate attention. The research based on this, developed the model and simulation for the induction generator under the specific fault of stator winding inter-turn short circuit(SWITSC), then analyze the change of small signal stability of DFIG unit. This study has referenced significance to improve the stability of DFIG unit, even the grid stability contain large scale wind farms. The main research work are as follows:(1) Based on the multi-loop theory, the generator mathematical model with SWITSC fault is established.The model is written into a program by S function in MATLAB. The program of faulty generator is embed to replace the normal generator in the simulation model of doubly-fed wind power generation system.(2) The mathematical model of each part in the doubly-fed wind power generation system are developed, then the small signal model is derived including: wind turbine, shaft transmission parts, induction generator and control segment. In order to compare damping ratio, eigenvalues of the state matrix and its participation factors are calculated under normal and faulty conditions.(3) Based on Lyapunov theory, the eigenvalue analysis was completed to yield the loci of the dominant eigenvalues of DFIG unit by means of Matlab simulation. The key control parameter greatly influencing the stability of DFIG unit is also found out. Moreover, the effect of SWITSC fault on the stability of DFIG unit is revealed.The research results above are of reference and significance to improve the stability of grid-connected doubly-fed wind power system.