Research On Winding Loss And Temperature Rise Characteristics Of Converter Transformer

As an important equipment in HVDC transmission system,the converter transformer is liable for the transformation and distribution for large scale power grids.With the increase of investment and technical support for HVDC transmission in our country and the increasing capacity of converter transformer,the local overheating caused by various losses becomes more prominent,and it will lead to a series of troubles such as the aging of transformer insulation.Therefore,it is urgent to restrain the local overheating of transformer.Firstly,the converter transformer with a model of ZZDFPZ-406000/500 is taken as the research object in this thesis,and the magnetic field,loss and temperature field are simulated.According to the actual structural parameters of the converter transformer,the finite element analysis software is used to establish the three-dimensional model of the converter transformer including the core,yoke,winding and oil tank,and the numerical simulation of its magnetic field is carried to obtain the magnetic flux density distribution nephogram of the core,winding and oil tank of the converter transformer.According to nephogram,the position of the maximum magnetic flux density of each structure is found,and distribution characteristic and formation reason of magnetic field in each structure is analyzed.Secondly,combined with the empirical formula and theoretical method of the converter transformer loss calculation,eddy current loss formula of grid element is derived.According to the magnetic flux density distribution,the loss distribution on the oil tank,winding and core of the converter transformer are calculated,which will be an excitation for the next fluid-solid-thermal coupling analysis.Finally,the temperature field analysis software is used to establish the threedimensional modeling of multi-physical field coupling analysis of converter transformer,and the heterogeneous grid structure mapping and interpolation method are used to accurately import the magnetic field loss into the corresponding temperature field simulation model.In this way,the fluid-solid-thermal multi-physical field coupling simulation calculation of the converter transformer is solved;the temperature field of the converter transformer and the transformer oil flow field are obtained;the highest temperature rise point is found;and the temperature distribution characteristic of the oil tank;winding and iron core is analyzed.The relationship between the temperature rise of the transformer oil and the flow rate are analyzed,and the feasibility of the calculation method is proved.In this thesis,based on the calculation of the magnetic field distribution and the loss distribution of each structure of the converter transformer,the temperature field and flow field of the converter transformer are simulated,which are more conformity with the actual conditions and improves the accuracy of the calculation model.Meanwhile,the research on the hot spot temperature and location has provided some guidance for the structure optimization and temperature monitoring of converter transformer.