Analysis And Studies Of Influence Of System Parameters On Double Fed Induction Wind Power Generator When Low Voltage Ride-through

Presently, the doubly-fed induction generator (DFIG) accounts for the very greatproportion in the MW wind turbine generator system of variable speed and constantfrequency operation. With ceaseless increase of the unit capacity of the double fedinduction wind generator and wind power installed capacity, the interaction among thewind farm, wind power generator and the power system becomes more and moreimportant. It is a significance to study the transient stability of the double fed windpower generator when the power system fault and low voltage ride-through capabilityas well as the wind power system protective measures. This paper mainly concerns thetransient behavior of the doubly fed induction generator under grid fault. And the mainresearch content includes knowledge like the mathematical modeling, characteristics ofthe power decoupling control, low voltage ride-through technique standard of windturbine and the performance research of low voltage ride-through using crowbarprotection of DFIG wind power system.In order to have a better understanding of the basic principle and the powerdecoupling characteristics of the doubly-fed induction generator, this paper establishesthe mathematical models such as the doubly fed induction generator and the doublePWM converter. Basing on the basis of the mathematical model, the DFIG wind powersystem simulation model is established according to the active and reactive powerdecoupling vector control principle with the grid voltage orientation of the grid sideexcitation converter and stator flux oriented of motor side excitation converter takingthe advantage of MATLAB/Simulink simulation platform. Then the DFIG wind powersystem steady state power decoupling control characteristic is stimulatingly researched.What’s more, the thesis introduces the basic concept, realization principle of the lowvoltage ride-through technology of wind power generator; the low voltage ride-throughtechnology standards of the rest of the world related to wind power are also introduced.In the meanwhile, present various kinds of common technological means and protectionmeasures of low voltage ride-through are analyzed and compared. Moreover, thetransient simulation model using an active crowbar protection circuit of doubly fedinduction generator induction wind power system is established. Finally, thecharacteristics of transient current and electromagnetic torque of the double fedinduction wind generator are analyzed when three-phase symmetrical short-circuit grid has a fault. And the effect of different crowbar resistor to the transient transition processof the doubly fed induction generator uses an active crowbar protection circuit whengrid voltage sags is studied. The effect of the crowbar resistor and the motor parametersof the DFIG to the transient electromagnetic torque are also analyzed. In the meantime,the effect and relation of crowbar resistance with the electromagnetic torque of DFIG isbriefly analyzed when the asymmetric short circuit fault occurs in power grid.The conclusion of the study including the transient analysis of double fed inductionwind generator during a grid fault and the transient performance of double fed inductionwind generator using the active crowbar protection circuit in the low voltageride-through process will provide certain theoretical basis and decision support to thetransient stability analysis of the power system including large capacity wind turbinewith large capacity wind farm.