Research On High And Low Voltage Crossing Technology Of Megawatt Doubly-fed Wind Turbine

With the rapid development of wind power,wind power in power system of more and more big,affect the stable operation of power system,with the national standards for wind turbine power grid fault voltage through the ability to release,need wind turbine needs to meet the requirements of low voltage across,high and low voltage through the reform demand based on the actual wind field as the background,chooses doubly-fed wind power generator for the model,in view of the grid at the high and low pressure rotor current and dc bus voltage is too high and cause the fan stop,for the sake of doubly-fed wind power generator in the power grid voltage failure through running smoothly,this paper carried out a research into the following:Firstly,in view of the fact that the previous doubly-fed wind turbine does not have the power grid voltage fault crossing capability,so the existing wind turbine cannot meet the published power grid voltage fault crossing requirements,this paper proposes to add additional hardware protection circuit and improve the control strategy of doubly-fed wind turbine.Second,for a grid voltage unbalance of single coordinate falls phase-locked loop testing phase and frequency is not accuracy,adopted double dq phase-locked loop,moves to the Crowbar protection circuit,the rotor side converter in the blocking state,Crowbar different resistance for doubly-fed fan fault output characteristic,the influence of the grid voltage failure can lead to dc bus voltage is too high,increase the Chopper protection circuit is presented to reduce voltage,for low power grid voltage unbalance voltage,stator flux linkage by increasing the current dynamic variable control strategy,effectively reduce the rotor current and dc bus voltage,For grid high voltage crossing,the dc bus voltage and rotor current are reduced by virtual impedance control strategy.Finally,the research on the overall system modeling and simulation in Matlab,respectively to different resistance Crowbar,presence of Chopper protection circuit,power grid low wear experiment was carried out,in unbalanced power grid,to take the increase of the stator flux current dynamicvariable low wear experiment,high voltage surge in power grid,increase the virtual damping in the rotor current feedback control,effectively reduce the dc bus voltage and rotor current.