| It is fundamental for power system to analysis the eddy current field of electrical equipment.Studying the eddy current distribution of electrical equipment may improve its operational safety and extend its service life.Nowadays,China is facing the dilemma of containment in industrial software and the opportunity of the "digital twin" revolution in the electrical industry.The investigation of the 3-dimensional eddy current field numerical calculation and its reduced order algorithm is helpful for the development of industrial software in China and the innovation in the electrical industry.The numerical calculation of the 3-dimensional eddy current field is conducive to complementing the shortcomings of Chinese industrial software,and also meets the needs and development trends of the electrical industry.This thesis firstly introduces the current research on the simulation methods,application and development status of 3D eddy current field in detail.In this thesis,a timedomain finite element method is given for the three-dimensional eddy current field based on A,φ-A.An iterative method of nonlinear permeability in the ferromagnetic region is introduced at the same time.In order to make the mesh of the skin effect area in good shape,a hexahedral element is used in eddy current region with regular shape and a tetrahedral element in other regions.The post-processing methods for other variables in electromagnetic field and eddy current field base on A,φ-A.This thesis takes Model B of the TEAM benchmark problem 21 as an example and simulated this model based on the time-domain finite element method with Matlab.The solution of the method in this thesis is consistent with measurement and the solution of COMSOL.The effectiveness of the proposed method is verified.With the requirement of fast calculation for "Digital twin",This thesis proposes a POD order reduction algorithm of 3D eddy current field time-domain finite element method based on A,φ-A.Firstly,the fundamental and implementation steps of the POD method are introduced in detail.And then the order-reduced method is combined with the time-domain finite element method of 3D eddy current field.Similarly,Model B of the TEAM benchmark problem 21 is taken as an example.The field distribution of sinusoidal excitation and harmonic excitation was calculated by the POD order reduction method based on self-solution.The results show that the order reduction method obtains correct solution on the basis of saving calculation time.In addition,The field distribution of harmonic excitation was calculated by the POD order reduction method based on solution of sinusoidal excitation.In this situation,the computation time is further reduced with the satisfactory solution obtained.Finally,this thesis uses the proposed method to analyze the eddy current field distribution of a 400kVA,15kV/400V three-phase power transformer under two working conditions.The eddy current field distribution of the three-phase transformer in rated steady state operation is simulated by the time domain finite element method directly.The simulation results are consistent with the COMSOL results,which further verifies the validity of the proposed method to three-phase transformers.Besides,this thesis uses Simulink to simulate the phase current transient process of the three-phase transformer under load reduction process.Then the eddy current field distribution of the transformer under load reduction process is simulated by the time domain finite element method.In order to speed up the simulation,the POD method was used to reduce the order to analyze the transient process.The order reduction calculation employed the self-solution based sample and the experimental data based sample respectively.The order reduction method greatly reduces the calculation time and obtains the correct result. |
