Research On Winding Over-voltage Of Permanent Magnet Wind Turbine Under Pulse Voltage And Its Countermeasures

As the core component of the wind power generation system,the generator plays an important role in the reliable operation of the wind turbine.With the continuous increase of wind turbine power and higher voltage levels,higher requirements are put forward on the insulation performance of generator windings,and the local overvoltage of the windings is the main reason for the deterioration of insulation performance.Since the wind turbine converter adopts the power electronic fast shut-off device,the output pulse voltage with steep rising and falling edges,spreading through the long cable will generate overvoltage at the generator end,and further act on the winding.The existence of the distributed parameters in the windings causes the overvoltage to be unevenly distributed between the windings.When it acts for a long time,it will cause partial discharges and deterioration of the insulation material in the windings,and even lead to insulation breakdown of the generator in severe cases.In view of the above problems,this thesis takes 1.5MW permanent magnet synchronous wind turbine as the research object,and the main work is as follows:Firstly,according to the structural characteristics of the stator winding,a single-slot winding model is established,and three distributed parameter modeling methods are compared,and the finite element method is preferred.On this basis,through finite element analysis(FEA)calculates the winding distribution parameters under the action of high-frequency pulse voltage,obtains the change law of the winding distribution parameters at different positions in the slot,and establishes the equivalent circuit model of the winding distribution parameters,which lays the foundation for the study of the generator winding overvoltage distribution.Secondly,analyze the influencing factors of generator winding overvoltage.According to the calculation results of the distributed parameters,the winding distribution parameter model is built in Matlab software,combined with the generator terminal overvoltage characteristics to analyze the uneven distribution of overvoltage between windings,analyze the position of the coils with overvoltage,and determine the insulation weak areas of the windings.The simulation verifies the influence of the distributed parameters on the overvoltage between turns of the generator windings,and also clarifies the conclusion that changing the distributed parameters can affect the overvoltage distribution.Finally,on the basis of the above analysis,study on the winding overvoltage countermeasures: according to its causes,filters are used to suppress the generator terminal overvoltage;for the uneven distribution of overvoltage in the windings,combined with the influence of the distribution parameters.It is proposed to reduce the distribution parameter value by changing the shape of the coil,the number of turns and the relative dielectric constant of the insulation.The simulation results show that these methods can effectively suppress the winding overvoltage under the pulse voltage and make it as evenly distributed as possible;The insulation fragility problem of the winding insulation is improved through the parameterized design of the winding insulation,and the insulation structure of the winding is improved,and the weak part is replaced with a better insulation material to achieve the optimization of the winding insulation performance.The method can effectively reduce the impact of overvoltage on winding insulation,avoid shortening the insulation life and premature failure,and improve the reliability of the operation of the wind turbine.