Analysis Of The Influence Of Low Voltage Ride Through On Early Fault Of Doubly Fed Wind Power Generator

Doubly fed wind power generator(DFIG)of interturn short-circuit and air gap flux density distortion,spindle eccentricity and bearing wear fault early in operation process,these faults although not directly caused significant harm or equipment downtime,but timely understanding of early fault degree and development trajectory,when necessary,stable operation of life with the power of the wind turbine itself are essential.At the same time,DFIG operating conditions are complex,including wind speed mutation,three-phase voltage imbalance,low pressure and normal operation.Among them,the low voltage crossing is that the wind turbine can guarantee the operation of the power grid when the grid fault causes the voltage sag of the wind turbine,and it should also be able to transmit reactive power to the power grid in order to ensure the stable operation of the power grid.Many factors contribute to the deterioration of the fault in the event of an early failure.Low voltage ride through capability is the inevitable requirement of grid connection of large wind turbine,without considering the environmental factors and other fault conditions,low voltage ride through conditions on the effect of early fault is very necessary.This paper carries on the analysis with doubly fed generator low voltage ride through capability of the theoretical basis and the mathematical model,based on the established DFIG grid model of the circuit with Crowbar 1.5MW using PSCAD software,and set the voltage drop caused by the fault of different degree,to achieve low voltage ride through the generator.Through simulation,the waveforms of stator current,stator voltage and speed with time are obtained.The simulation results show that the proposed scheme can achieve low voltage ride through.In order to study the electromagnetic field of the generator,the two-dimensional electromagnetic field theory and the finite element method and the transient magnetic field analysis theory are analyzed in this paper.The theoretical basis and effective doubly fed motor based on the data,a two-dimensional finite element model with the Ansoft software to establish the doubly fed induction generator,and the stator and rotor current under normal condition and low voltage obtained by the PSCAD simulation through the input generator as the excitation respectively in the finite element model of finite element analysis and postprocessing,the the normal and different degrees of low voltage ride through the magnetic field distribution inside the motor under the condition of different time and the air gap flux density curve.The simulation results are compared and analyzed in order to judge the influence of the low voltage traversing on the internal magnetic field of the motor,and whether it will cause the early fault.In order to determine the influence of the low voltage transmission on the inter turn short circuit,the factors that cause the insulation performance of the stator winding are analyzed,and several aging models are analyzed.Get the change of low pressure integrated PSCAD and Ansoft simulation of the process of crossing current,voltage,speed,magnetic field,air gap flux density and other physical quantities,and the heat generator iron and copper consumption reflects the different operating conditions of the core and winding of the aging model to determine whether the low voltage ride through the winding insulation performance effect,and then analyzed the influence to the interturn short circuit.The analysis results show that the low pressure crossing will cause the air gap flux density distortion of doubly fed wind power generator,and will have a bad effect on the winding insulation performance,most likely caused by generator interturn short circuit fault or the fault deterioration.