Research On Grid Connection Of Doubly Fed Wind Power Generation And Power Compensation Control Strategy

The increasing penetration of doubly fed induction generator (DFIG) impacts thefrequency stability of power systems heavily. On the one hand, DFIG naturally does notprovide frequency response because of the decoupling between the output power andthe grid frequency; on the other hand, DFIG cannot regulate its active power tosupport the grid frequency because of the maximum power point tracking (MPPT)operation. Therefore, it is necessary to study the frequency control of DFIG, and designa controller to have a better response to frequency changing.This thesis introduces the control system of DFIG firstly, including wind turbinesystem, mathematic model of DFIG and the decoupled control. And, build the controlsystem model of DFIG in DIgSILENT.Secondly, the frequency response of different types of generator are comparedbased on the analysis of system frequency stability; and a virtual inertia control isestablished for DFIG. The DFIG can respond to the frequency drops of the powersystem, and show the inertial effect of DFIG to support the grid frequency and lower therate of frequency change.Then, a de-loading control is established for DFIG based on the analysis of thefrequency response of the power reserve. The reserved power can be stored in the DFIGall the real time and participate in the system frequency regulation through thefrequency control loop to improve the steady state characteristics of the systemfrequency.Finally, The simulation results demonstrate the effectiveness of the virtual inertiacontrol and power de-loading control, and decrease the initial rate of change and thesteady-state error of the system frequency based on the combination control.