Research On Doubly-fed Induction Generator’s Synergetic Control Strategy And Stability Technology For High/low Voltage Ride Through

As the national puts forward the "14th Five-Year Plan" and the "2035Long-Term Plan",new energy power generation,especially wind power generation,will continue to develop rapidly.Among them,the Double Fed Induction Generator(DFIG)has technical advantages such as wide variable speed constant freq uency operation range,high power generation efficiency,and small converter capacity.It has become one of the main models of wind power generation.However,due to the special structure of the DFIG stator directly connected to the power grid via a transformer,the DFIG is very sensitive to voltage changes at the grid connection point.When the grid voltage suddenly rises/drops due to a f ault,it will cause overcurrent and overvoltage in the DFIG stator and rotor windings,which will threaten the safety of the unit.A large number of grid-connected wind turbines are disconnected from the grid to ensure their own safety,this will brings challenges to the stable operation of the power grid.Therefore,research on control strategies that can improve the voltage ride through(VRT)capability of DFIG has important engineering significance.Based on the DFIG’s mathematical model and synergetic control theory,this thesis proposes a synergetic control strategy that enables DFIG to have a strong voltage fault ride-through capability,and optimizes the control parameters of the synergetic controller.The main work completed and the main research res ults obtained in this thesis are as follows:(1)According to the synergetic control theory and DFIG ’s mathematical model,the synergetic control strategy of DFIG rotor side converter(RSC)and grid side converter(grid side convert,GSC)are proposed and the voltage ride-through performance of the synergetic control strategy is verified through simulation.(2)The nonlinear dynamics analysis of the proposed synergetic control strategy is given,and the DFIG’s synergetic control strategy is given to simultaneously satisfy the constraints of large-scale asymptotic stability during the high/low voltage fault ride-through process,a numerical solution is proposed that is approximately equivalent to the analytical method.(3)The DFIG’s dynamic performance that uses synergetic control strategy is verified through PSCAD/EMTDC.The synergetic control strategy can effectively reduce the overcurrent and overvoltage of the DFIG rotor during the fault period.At the same time,the validity of the proposed method for ju dging large scale stable values is verified.(4)Improve synergetic controller ’s dynamic performance by optimizing control parameters,and further optimize the dynamic characteristics of the DFIG during the fault ride-through period.And verify the robustness of the proposed synergetic control strategy by simulating DFIG units with different hardware parameters.