Voltage Fluctuation And Flicker Emission Of DFIG, And Research On Mitigation Using STATCOM

The energy source and environment problem has become a pressing problem to besolved for human society’s surviving and developing nowadays, with the developingof human society. The renewable resource development and utilization have been paidmore attention to, due to the increasingly serious problem of the environment andresources. As a new and clean energy, wind power has been used widely. With thematurement of wind power technology and the expansion of the scale of wind farms,the influence brought by large wind farms connected to power systems has becomegreater and greater, which has become a great obstacle to large-scale wind powerdevelopment. One Problem with wind Power installations, is the influence of Powerquality at the Point of common coupling (PCC), mainly cause the voltage fluctuationand flicker. Thereby, studying the voltage fluctuation and flicker at system’s PCCwhich connect with wind farm and the influence of load characteristic become moreimportant.This paper discuss some problem that voltage flucation and flicker emissionof DFIG(Doubly-Fed Induction Generator) connect to the power system from thefollowing aspects:(1)The model of wind power model, OARS elongation control model and windspeed model are researched.The main type of wind turbine DFIG, the derivation ofdynamic equation and static equation in synchronous rotating coordinate system,establishing the mathematical model of DFIG.(2) Describes the concept of voltage fluctuation and flicker,and a flickermetermodel based on IEC standard is established in this thesis,in which an amendatoryblock is added.Introduces the constitutes of wind energy Power system and someimportant parameters, and find out four factors which closely in relation to theturbine’s flicker emission: the turbulent flow and wind speed. Besides, consider theinfluence of system’s capacity of short circuit at PCC, the ratio X/R of network. Onthe base of the simulation software PSCAD/EMTDC, the established complex loadmodel is used to carry out the simulation test on the standard wind energy system fordifferent PCC. The simulation results are compared with each other. The final analysisindicates that system parameters like the wind speed，turbulence intensity, the ratioX/R of network, system’s short circuit capacity ratio in PCC，have important influencefor the voltage fluctuation and flicker. (3)Analyzed the working principle of the STATCOM and established themathematical model and designed related parameters. Compared the direct currentcontrol and indirect current control methods, then introduces direct current controlwhich is superior performance, regulating with excellent effection.(4)DFIG connected grid running need to absorb lots of reactive power, therefore theexport of the wind farm required reactive power compensation, applied STATCOM forreactive power compensation, reduced voltage fluctuation and maintained steadyrunning of system take on important signification. Wind turbines connected gridcontaining STATCOM simulation, simulation results show that the STATCOMeffective damp voltage fluctuation and flicker in wind power connected grid.