Research On Control Stratrgies Of The AC Exited VSCFWind Generation System

Recently,windenergyas arenewable,nopollutionenergyresource,is paidgreatattention by more and more countries. AC exited variable speed constant frequency(VSCF) wind generation system is an important subject in wind system. AC exitedgeneration can improve the stability of electric power system, have the ability toregulate the active and reactive power independently, and its rotor speed can bechanged, especiallycan enhance the availability of wind energyafter usingthe VSCFtechnology.The control strategies of the AC exited VSCF wind generation system is deeplyresearched. Firstly, the advantage of AC exited generation is introduced, the principleof double fed induction generator (DFIG) performed in the condition of VSCF isanalyzed, and the mathematic model of DFIG in three-phase standstill coordinatesystem is built. Through coordinatetransformation,themathematicmodel ofDFIG intwo-phase synchronous coordinate system is built, which lays a foundation for thefollowing research. Secondly, based on the mathematic model of DFIG in two-phasesynchronous coordinate system, using stator field oriented vector control technology,the grid-connection control principle of AC exited VSCF wind generation system isanalyzed, the scheme grid-connection control with no-load is built to realize"softgrid-connection". The grid-connection control with isolated-load is also researched.Thirdly, the principle of the maximum wind power tracing control is introduced, themaximum wind power capture scheme by the way of DFIG's active and reactivepower decoupled control is realized, DFIG's active and reactive decoupled controlstrategy is built. At last, the excited converter used in wind generation system isresearched. The advantage of dual PWM converter is introduced, the mathematicmodel of grid-side converter in three-phase standstill and two-phase synchronouscoordinate system is analyzed, and the control strategy of the grid-side converterbased on network voltage oriented vector control is built to control the input powerfactoratgrid-sideandDCbusvoltage.Simulation models due to grid-side converter control, grid connection controlwithno-loadandactiveandreactivepowerdecoupledcontrol strategyare built onthe platform of MATLAB/SIMULINK. The simulation results confirm the controlstrategies.