Research On Lvrt Of Direct Power Comtrol Strategy Of DFIG Wind Energy Conversion System Based On Stator Fluxlinkage Tracking

With the continuous decrease of limited energy resources such as oil and mineral materials on the earth,more and more people place their hopes for the future development of human society on renewable energy.Among them,due to its wide spread,clean and pollution-free,abundant storage and other advantages of wind resources,wind turbine has been widely concerned.Therefore,how to convert abundant wind energy into electricity efficiently and conveniently has become the focus of domestic and foreign experts and scholars.In modern wind power technology,because the doubly-fed Induction generator(Doubly Fed Induction Generator,DFIG)is easy to control and operation stability,therefore wind power system has been widely concerned.In this paper,the operation characteristics of the doubly-fed Induction generator in a variety of power grid conditions were studied,and for its control,a control strategy of the doubly-fed fan rotor-side converter based on SMC-DPC is proposed to improve the steady-state characteristics of DFIG.And,in order to solve the grid fault cases of doubly-fed Induction generator of low voltage ride through(LVRT),a low voltage DFIG control strategy based on stator flux tracking of direct power control strategy is proposed,this control method effectively solves the power grid failure during the DFIG wind power system converter operation state,and enhances the stability of the DFIG wind power system converter.The main research contents can be summarized as follows:Firstly,the mathematical model of the rotor side converter with instantaneous active and reactive power as state variables is established in the two-phase static coordinate system.And the control scheme of the rotor side converter based on direct power control is designed.The correctness of the proposed control scheme is verified by simulation.Under the condition of grid fault,the mathematic model of doubly-fed motor with active and reactive power as state variables is re-established,and the control scheme of rotor-side converter based on SMC-DPC is designed under the condition of unbalanced grid voltage.By analyzing the transient operation characteristics of the doubly-fed Induction generator in the case of grid voltage fault,the reactive power attenuation used to compensate is added.Expounds on the stator flux track power transient compensation principle,and then on symmetric power grid failure,this paper puts forward a low voltage DFIG control strategy based on stator flux tracking of direct power control strategy.This strategy improves the effective inhibition of the fault current,and the doubly-fed motor during the grid fault of low voltage crossing ability.Finally,through the measurement and control experiment platform of the dSPACE real-time simulation system for the doubly-fed Induction generator,several control schemes proposed in this paper are experimentally verified under ideal power grid and power grid fault conditions.The correctness and effectiveness of the proposed control strategy are proved.