Research On Different Core Structure Transformers' Magnetizing Characteristics Under DC-bias

When Geomagnetically Induced Currents(GIC) and the single polar earthing current of the HVDC project invade the grounded transformer neutrals, the large scale-transformer working at the rated state will partially be saturated, and its magnetic current will distorte accompanying with various of harmonic, increasing reactive power demand, noise, vibration and some other affiliated phenomenon. In order to quantitatively analyze the transient behavior of the saturation and various electrical variables, provide a basis for transformer design and selection, the non-linear transient model of different core structure transformer need to be study.First, the basic principles of J-A model are discussed in this paper. The relationship between parameters and the simulation results is discussed. The saturation characteristic is determined by Ms, a and the loss characteristic is determined byα, c, k. So the parameters are divided into two groups, and identified separately using genetic algorithm in MATLAB. Then, an equivalent model of different core structure transformer using duality principle is proposed in this paper. The model is established in PSCAD/EMTDC using Fortran and C. The model is fit for GIC problems. A detailed model of ODPFS-250000/500 transformer is established for calculation exciting current,reactive power lose and leakage flux. The simulation results are compared with the transformer factory test data and UMEC model simulation results, which demonstrate the validity of the method of J-A parameters identification and the duality model.