The Research On Modeling And Low Voltage Ride Through Control Strategy Of Doubly Fed Asynchronous Wind Power Generation System

Wind turbines are an indispensable power and source of clean energy,and the stability and reliability of wind power grid-connected control system are particularly important.Double-fed asynchronous wind turbines(DFIG,Doubly Fed Induction Generator)have the advantages of simple installation,lo w cost and high efficiency,so they have been widely used in the global wind power field.In the dual-fed asynchronous wind grid control system,the two-fed asynchronous turbine and the power grid via back-to-back AC,and the AC control strategy will directly affect the reliability,stability and the grid quality of the whole system,when the voltage of the grid fails,it will even break off the grid,causing the grid voltage again.In order to avoid double-fed asynchronous wind turbine units from the power grid failure and have good control performance,the control strategy of double-fed asynchronous wind turbine and low voltage crossing technology.Aiming at the control strategy and low voltage ride through technology(LVRT)of doubly fed asynchronous wind power generation grid connected system.The current situation of wind power generation technology,generator side and grid side control strategy in doubly fed asynchronous wind power generation grid connected system and low voltage ride through technology at home and abroad are analyzed;The mathematical models of doubly fed wind turbine,turbine side and grid side are established.The operation characteristics and output voltage equation based on three-phase electric back-to-back converter are studied.The working principle of wind energy maximum tracking control is given.The mathematical simulation model of wind turbine is built based on simulation software.In order to improve the control performance and grid quality of doubly fed asynchronous wind power generation grid connected control system,a model predictive current control(MPCC)scheme for generator side and grid side AC is proposed by using model predictive control(MPC)technology;Compared with the traditional proportional integral control,when the power grid voltage fluctuates,this scheme can make the system work reliably and stably,enhance the low-voltage ride through ability of the system and improve the power grid quality;Using the unit power factor and STATCOM exchange operation mode,a low-voltage ride through reactive power coordination control method is proposed,and its simulation model is built.The simulation results show that the low-voltage ride through control method based on STATCOM operation mode can ensure the stable and reliable operation of the system and meet the reactive power compensation requirements of the State Grid,And it can improve the low-voltage ride through capability and power grid quality.